(new): add threshold-based log level filtering and docs

- add threshold-aware LogLevel constructors - add Logger.SetThresholdMode and SameThreshold - preserve legacy SameLevel behavior for compatibility - extend tests for threshold mode and compatibility - update README and release notes for v2.2.0
(chore): document and test new LogLevel APIs
2026-04-28 09:45:40 +03:00 · 2026-04-27 17:04:41 +03:00 · 2026-04-27 16:36:30 +03:00 · 2026-04-27 15:42:24 +03:00 · 2026-04-27 10:24:53 +03:00 · 2026-04-27 09:56:46 +03:00
21 changed files with 3586 additions and 237 deletions
@@ -0,0 +1,12 @@
+name: Golang lint
+run-name: Linting code
+on: [push]
+
+jobs:
+  lint:
+    runs-on: go-latest
+    steps:
+      - name: Checkout repository code
+        uses: actions/checkout@v6
+      - name: Run golangci-lint
+        run: golangci-lint run
@@ -1,3 +1,5 @@
 .idea/
+.vscode/
+.codex
 test/
 *.log
@@ -0,0 +1,675 @@
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+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
+
@@ -1,2 +1,224 @@
-# ScuroLogger (slog)
+# SNekLog (ScuroNeko Logger)

+Small structured logger for Go with text and JSON output, multiple writers, and optional traceback metadata.
+
+Russian version: [README_ru.md](README_ru.md)
+
+## Features
+
+- Fan out the same record to multiple destinations.
+- Text and JSON writers.
+- `stdout`, files, and arbitrary external `io.Writer` values.
+- Optional timestamps for text output.
+- Compact traceback metadata for text writers and full traceback slices for JSON.
+- Message replacement for masking secrets or normalizing output.
+- Explicit ownership rules for writer closing.
+
+## Installation
+
+```bash
+go get git.scuroneko.dev/scuroneko/sneklog/v2
+```
+
+## Quick start
+
+```go
+package main
+
+import (
+	"log"
+
+	"git.scuroneko.dev/scuroneko/sneklog/v2"
+)
+
+func main() {
+	logger := sneklog.NewLogger().
+		SetName("API").
+		SetLevel(sneklog.DEBUG).
+		AddReplacer("SOME_SECRET", "<redacted>")
+
+	text := logger.CreateTextStdoutWriter()
+	jsonFile, err := logger.CreateJsonFileWriter("logs/app.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	logger.AddWriters(text, jsonFile)
+
+	logger.Infoln("service started")
+	logger.Warnln("cache miss")
+	logger.Errorln("request failed")
+	logger.Debugln("debug details")
+	logger.Infoln("token", "SOME_SECRET")
+
+	if err := logger.Close(); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+## Defaults
+
+`NewLogger()` starts with:
+
+- `Prefix("LOG")`
+- `Level(sneklog.FATAL)`
+- `JsonPretty(false)`
+- text formatter: `sneklog.DefaultTextFormatter`
+- JSON formatter: `sneklog.DefaultJsonFormatter`
+
+`CreateLogger()` is still available for backward compatibility.
+
+Important: with the current level ordering, `Level(sneklog.FATAL)` allows `INFO`, `WARN`, `ERROR`, and `FATAL`, but not `DEBUG`. Use `Level(sneklog.DEBUG)` to enable every level.
+
+If you want classic threshold filtering instead, call `SetThresholdMode(true)` and
+configure levels with `NewThresholdLogLevel(...)` or
+`NewThresholdLogLevelWithColors(...)`.
+
+## Writers and ownership
+
+`Logger.Close()` only closes writers created by the logger itself:
+
+- `CreateTextFileWriter(...)`
+- `CreateJsonFileWriter(...)`
+
+The following writers remain owned by the caller and are not closed by `Logger.Close()`:
+
+- `CreateTextWriter(existingWriter)`
+- `CreateJsonWriter(existingWriter)`
+- `CreateTextStdoutWriter()`
+- `CreateJsonStdoutWriter()`
+
+This makes it safe to plug in `bytes.Buffer`, network writers, and other externally managed resources.
+
+## Output formats
+
+Text writers render records like:
+
+```text
+2026-03-17T14:05:09+03:00 info API: service started
+```
+
+Use `SetFormatter` on a writer to customize timestamps, traceback fields, colors, and message layout.
+
+JSON writers emit objects with this shape:
+
+```json
+{
+  "time": "2026-03-17T14:05:09.123456789+03:00",
+  "level": "info",
+  "prefix": "API",
+  "message": "service started",
+  "traceback": [
+    {
+      "method": "main",
+      "filename": "main.go",
+      "line": 27,
+      "signature": "main.main",
+      "fullPath": "/path/to/main.go"
+    }
+  ]
+}
+```
+
+When `JsonPretty(true)` is enabled, JSON is indented.
+
+## Custom levels and colors
+
+You can define your own levels and assign ANSI, 256-color, or RGB colors, plus text attributes such as `Bold` or `Italic`.
+
+```go
+httpDelete := sneklog.NewLogLevel(0, "delete")
+httpDelete.SetBackgroundRGB(128, 0, 0)
+httpDelete.AddAttribute(sneklog.Italic).AddAttribute(sneklog.Bold)
+
+httpCache := sneklog.NewLogLevel(0, "cache")
+httpCache.SetForeground256Color(214)
+```
+
+Because `LogLevel` setters mutate the level in place, call them on a variable, not on a temporary value returned by `NewLogLevel(...)`.
+Short forms such as `SetFgColor` and `SetBgColor` remain available for backward compatibility.
+
+Common severities also have dedicated helpers:
+
+```go
+access := sneklog.NewInfoLogLevelWithColors("access", sneklog.FgCyan, sneklog.BgNone)
+audit := sneklog.NewWarnLogLevel("audit")
+```
+
+These helpers keep the legacy severity index for backward compatibility and also
+assign default threshold values:
+
+- `INFO`: `th=10`
+- `WARN`: `th=20`
+- `ERROR`: `th=30`
+- `FATAL`: `th=40`
+- `DEBUG`: `th=0`
+
+To define custom threshold-based levels explicitly:
+
+```go
+trace := sneklog.NewThresholdLogLevelWithColors(4, 5, "trace", sneklog.FgHiBlack, sneklog.BgNone)
+audit := sneklog.NewThresholdLogLevel(1, 25, "audit")
+
+logger := sneklog.NewLogger().
+	SetLevel(audit).
+	SetThresholdMode(true)
+
+logger.Print(trace, "verbose trace") // filtered out
+logger.Print(audit, "audit event")   // allowed
+```
+
+HTTP method-specific predefined levels are available out of the box:
+
+```go
+level := sneklog.LogLevelForMethod(http.MethodPost)
+logger.Print(level, "POST /users")
+```
+
+When comparing levels:
+
+- use `SameLevel` if only the legacy severity index matters;
+- use `SameThreshold` if only threshold filtering matters;
+- use `Equal` if the full configuration, including threshold, colors, and attributes, must match.
+
+## Message replacement
+
+`AddReplacer(old, new)` replaces matching text in every message before the
+record reaches any writer. Replacement rules are applied in the order they are
+added.
+
+```go
+logger := sneklog.CreateLogger().
+	Level(sneklog.DEBUG).
+	AddReplacer("SOME_SECRET", "<redacted>").
+	AddReplacer("user@example.com", "<email>")
+
+logger.Infoln("login token:", "SOME_SECRET")
+```
+
+This writes `<redacted>` instead of `SOME_SECRET` in both text and JSON output.
+An empty `old` value is ignored.
+
+## API summary
+
+- `Info`, `Warn`, `Error`, `Debug`, and `Fatal` accept a list of values.
+- `Infof`, `Warnf`, `Errorf`, `Debugf`, and `Fatalf` use `fmt.Sprintf`.
+- `Printf(level, format, args...)` formats a message for an explicit `LogLevel`.
+- The `*ln` methods preserve newline semantics, which is useful for `stdout`, Docker, and line-based collectors.
+- `Fatal`, `Fatalf`, and `Fatalln` call `os.Exit(1)` after writing the message.
+- `AddReplacer` masks or rewrites message text before records are sent to writers.
+
+## Traceback behavior
+
+- Text writers use the nearest user stack frame.
+- JSON writers receive the full traceback slice.
+- Internal `sneklog` frames and `runtime` frames are filtered out.
+
+## Repository example
+
+See [examples/main.go](examples/main.go).
+
+## License
+
+This project is licensed under GNU GPLv3. See [LICENSE](LICENSE).
@@ -0,0 +1,223 @@
+# SNekLog (ScuroNeko Logger)
+
+Небольшой структурированный логгер для Go с текстовым и JSON-выводом, несколькими writer'ами и настраиваемыми traceback-метаданными.
+
+English version: [README.md](README.md)
+
+## Возможности
+
+- Одновременная запись в несколько destinations.
+- Текстовый и JSON-форматы.
+- `stdout`, файлы и любые внешние `io.Writer`.
+- Опциональные timestamp'ы для текстового вывода.
+- Компактный traceback для текстовых writer'ов и полный traceback для JSON.
+- Замена текста в сообщениях для маскирования секретов или нормализации вывода.
+- Явные правила владения writer'ами при `Close()`.
+
+## Установка
+
+```bash
+go get git.scuroneko.dev/scuroneko/sneklog/v2
+```
+
+## Быстрый старт
+
+```go
+package main
+
+import (
+	"log"
+
+	"git.scuroneko.dev/scuroneko/sneklog/v2"
+)
+
+func main() {
+	logger := sneklog.NewLogger().
+		SetName("API").
+		SetLevel(sneklog.DEBUG).
+		AddReplacer("SOME_SECRET", "<redacted>")
+
+	text := logger.CreateTextStdoutWriter()
+	jsonFile, err := logger.CreateJsonFileWriter("logs/app.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	logger.AddWriters(text, jsonFile)
+
+	logger.Infoln("service started")
+	logger.Warnln("cache miss")
+	logger.Errorln("request failed")
+	logger.Debugln("debug details")
+	logger.Infoln("token", "SOME_SECRET")
+
+	if err := logger.Close(); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+## Значения по умолчанию
+
+`NewLogger()` создает логгер со следующими настройками:
+
+- `Prefix("LOG")`
+- `Level(sneklog.FATAL)`
+- `JsonPretty(false)`
+- текстовый formatter: `sneklog.DefaultTextFormatter`
+- JSON formatter: `sneklog.DefaultJsonFormatter`
+
+`CreateLogger()` по-прежнему доступен для обратной совместимости.
+
+Важно: в текущей модели уровней `Level(sneklog.FATAL)` пропускает `INFO`, `WARN`, `ERROR` и `FATAL`, но не `DEBUG`. Чтобы включить все сообщения, используйте `Level(sneklog.DEBUG)`.
+
+Если нужна классическая threshold-фильтрация, включите `SetThresholdMode(true)` и
+задавайте уровни через `NewThresholdLogLevel(...)` или
+`NewThresholdLogLevelWithColors(...)`.
+
+## Writer'ы и владение
+
+`Logger.Close()` закрывает только writer'ы, которые логгер создал сам:
+
+- `CreateTextFileWriter(...)`
+- `CreateJsonFileWriter(...)`
+
+Внешние writer'ы не закрываются:
+
+- `CreateTextWriter(existingWriter)`
+- `CreateJsonWriter(existingWriter)`
+- `CreateTextStdoutWriter()`
+- `CreateJsonStdoutWriter()`
+
+Это позволяет безопасно подключать `bytes.Buffer`, сетевые writer'ы и другие уже управляемые ресурсы.
+
+## Форматы вывода
+
+Текстовый writer формирует записи вида:
+
+```text
+2026-03-17T14:05:09+03:00 info API: service started
+```
+
+Используйте `SetFormatter` у writer'а, чтобы настроить timestamp'ы, traceback-поля, цвета и шаблон сообщения.
+
+JSON writer записывает объект со следующими полями:
+
+```json
+{
+  "time": "2026-03-17T14:05:09.123456789+03:00",
+  "level": "info",
+  "prefix": "API",
+  "message": "service started",
+  "traceback": [
+    {
+      "method": "main",
+      "filename": "main.go",
+      "line": 27,
+      "signature": "main.main",
+      "fullPath": "/path/to/main.go"
+    }
+  ]
+}
+```
+
+Если включен `JsonPretty(true)`, JSON выводится с отступами.
+
+## Кастомные уровни и цвета
+
+Можно создавать собственные уровни и назначать им ANSI, 256-color или RGB-цвета, а также текстовые атрибуты вроде `Bold` и `Italic`.
+
+```go
+httpDelete := sneklog.NewLogLevel(0, "delete")
+httpDelete.SetBackgroundRGB(128, 0, 0)
+httpDelete.AddAttribute(sneklog.Italic).AddAttribute(sneklog.Bold)
+
+httpCache := sneklog.NewLogLevel(0, "cache")
+httpCache.SetForeground256Color(214)
+```
+
+Так как setter'ы `LogLevel` изменяют уровень на месте, их нужно вызывать на переменной, а не на временном результате `NewLogLevel(...)`.
+Короткие формы вроде `SetFgColor` и `SetBgColor` сохранены для обратной совместимости.
+
+Для стандартных severity также есть отдельные helper'ы:
+
+```go
+access := sneklog.NewInfoLogLevelWithColors("access", sneklog.FgCyan, sneklog.BgNone)
+audit := sneklog.NewWarnLogLevel("audit")
+```
+
+Эти helper'ы сохраняют legacy severity index для обратной совместимости и
+одновременно выставляют значения threshold по умолчанию:
+
+- `INFO`: `th=10`
+- `WARN`: `th=20`
+- `ERROR`: `th=30`
+- `FATAL`: `th=40`
+- `DEBUG`: `th=0`
+
+Чтобы явно создавать уровни для threshold-режима:
+
+```go
+trace := sneklog.NewThresholdLogLevelWithColors(4, 5, "trace", sneklog.FgHiBlack, sneklog.BgNone)
+audit := sneklog.NewThresholdLogLevel(1, 25, "audit")
+
+logger := sneklog.NewLogger().
+	SetLevel(audit).
+	SetThresholdMode(true)
+
+logger.Print(trace, "verbose trace") // будет отфильтровано
+logger.Print(audit, "audit event")   // будет записано
+```
+
+Для HTTP-методов доступны готовые уровни:
+
+```go
+level := sneklog.LogLevelForMethod(http.MethodPost)
+logger.Print(level, "POST /users")
+```
+
+При сравнении уровней:
+
+- используйте `SameLevel`, если важен только legacy severity index;
+- используйте `SameThreshold`, если важна только threshold-фильтрация;
+- используйте `Equal`, если нужно полное совпадение конфигурации, включая threshold, цвета и атрибуты.
+
+## Замена сообщений
+
+`AddReplacer(old, new)` заменяет найденный текст в каждом сообщении до того,
+как запись попадет в writer'ы. Правила замены применяются в порядке добавления.
+
+```go
+logger := sneklog.CreateLogger().
+	Level(sneklog.DEBUG).
+	AddReplacer("SOME_SECRET", "<redacted>").
+	AddReplacer("user@example.com", "<email>")
+
+logger.Infoln("login token:", "SOME_SECRET")
+```
+
+В текстовом и JSON-выводе вместо `SOME_SECRET` будет записано `<redacted>`.
+Пустое значение `old` игнорируется.
+
+## API кратко
+
+- `Info`, `Warn`, `Error`, `Debug`, `Fatal` принимают список значений.
+- `Infof`, `Warnf`, `Errorf`, `Debugf`, `Fatalf` используют `fmt.Sprintf`.
+- `Printf(level, format, args...)` форматирует сообщение для явного `LogLevel`.
+- Методы `*ln` добавляют семантику перевода строки, что удобно для `stdout`, Docker и line-based collectors.
+- `Fatal`, `Fatalf` и `Fatalln` вызывают `os.Exit(1)` после записи сообщения.
+- `AddReplacer` маскирует или переписывает текст сообщений перед отправкой в writer'ы.
+
+## Поведение traceback
+
+- Текстовые writer'ы используют ближайший пользовательский stack frame.
+- JSON writer'ы получают полный traceback.
+- Внутренние frame'ы `sneklog` и `runtime` фильтруются из traceback.
+
+## Пример из репозитория
+
+См. [examples/main.go](examples/main.go).
+
+## Лицензия
+
+Проект распространяется под GNU GPLv3. См. [LICENSE](LICENSE).
@@ -0,0 +1,209 @@
+# Unreleased (planned v2.2.0)
+
+This release expands the public LogLevel API, adds optional threshold-based
+filtering alongside the legacy severity ordering, and improves documentation
+and test coverage.
+
+### Added
+
+- Added dedicated log level constructors:
+  - `NewInfoLogLevel`
+  - `NewInfoLogLevelWithColors`
+  - `NewWarnLogLevel`
+  - `NewWarnLogLevelWithColors`
+  - `NewErrorLogLevel`
+  - `NewErrorLogLevelWithColors`
+  - `NewFatalLogLevel`
+  - `NewFatalLogLevelWithColors`
+  - `NewDebugLogLevel`
+  - `NewDebugLogLevelWithColors`
+- Added threshold-aware log level constructors:
+  - `NewThresholdLogLevel`
+  - `NewThresholdLogLevelWithColors`
+- Added HTTP method-specific predefined log levels:
+  - `HTTPGetLevel`
+  - `HTTPHeadLevel`
+  - `HTTPPostLevel`
+  - `HTTPPutLevel`
+  - `HTTPPatchLevel`
+  - `HTTPDeleteLevel`
+  - `HTTPOptionsLevel`
+  - `HTTPConnectLevel`
+  - `HTTPTraceLevel`
+  - `HTTPUnknownLevel`
+- Added `LogLevelForMethod(method string) LogLevel` to map HTTP methods to predefined log levels.
+- Added `Logger.Printf(level, format, args...)` for formatted logging with an explicit log level.
+- Added `Logger.SetThresholdMode(bool)` to switch filtering from legacy severity-index ordering to threshold-based ordering.
+- Added `LogLevel.SameLevel`, `LogLevel.SameThreshold`, and `LogLevel.Equal` for severity-only, threshold-only, and full level comparisons.
+
+### Changed
+
+- Refactored log level definitions into a dedicated `levels.go` file.
+- Unified `Logger.Print` and `Logger.Println` through a shared internal implementation without changing their behavior.
+- Common helper constructors such as `NewInfoLogLevel` now also assign threshold values while preserving legacy severity indexes.
+- `LogLevel.Equal` now includes threshold configuration in full equality checks.
+- Expanded test coverage for `Logger.Printf`, HTTP level mapping, constructor behavior, threshold filtering, and backward compatibility.
+
+### Documentation
+
+- Improved GoDoc coverage for exported types, constructors, formatters, colors, HTTP helpers, and time layouts.
+- Documented threshold mode, threshold-aware constructors, level comparison helpers, and explicit-level formatted logging.
+- Expanded inline documentation for formatter tokens and default formatter behavior.
+- Updated English and Russian README files with threshold-mode examples and comparison guidance.
+
+### Compatibility
+
+- No breaking API changes.
+- Existing `Print`, `Println`, predefined levels, `Level/SetLevel`, and color APIs remain compatible.
+- Legacy severity ordering remains the default; threshold filtering is enabled only when `SetThresholdMode(true)` is called.
+- `SameLevel` remains severity-only for backward compatibility, even when levels carry threshold metadata.
+
+# v2.1.0
+
+This release expands sneklog color customization while preserving compatibility with the v2.0.1 API.
+
+## Added
+- custom LogLevel constructors with configurable colors
+- 256-color and RGB support for LogLevel
+- ANSI text attributes on LogLevel such as Bold and Italic
+- typed color helpers for foreground/background RGB and 256-color values
+- NewLogger, SetName, SetLevel, and SetJSONPretty as clearer preferred APIs
+
+## Improved
+- text and JSON writer handling of trailing newline semantics
+- formatter colorization logic for foreground, background, and attributes
+- GoDoc coverage across the public API
+- English and Russian README examples and API guidance
+
+## Compatibility
+- legacy APIs from v2.0.1 remain available as deprecated wrappers
+- legacy ColorStringBuilder method signatures were preserved for backward compatibility
+- deprecated methods now explicitly document their replacements and planned removal in v3
+
+## Fixed
+- extra separator/space issues in Println-style output
+- attribute slice handling and defensive copying for LogLevel
+- color mode precedence when switching between ANSI, 256-color, and RGB modes
+
+# v2.0.0
+
+## Highlights
+
+- Renamed the public Go package from `slog` to `sneklog` to avoid confusion with the standard library `log/slog` package.
+- Moved the module path to `git.scuroneko.dev/scuroneko/sneklog/v2` for Go module major-version compatibility.
+- Replaced fixed text writer settings with formatter-based output customization.
+- Added built-in ANSI color support and removed the external `github.com/fatih/color` dependency tree.
+- Formatters: a new way do display your logs!
+
+## Breaking Changes
+
+- Import paths must use the `/v2` module suffix:
+
+```go
+import "git.scuroneko.dev/scuroneko/sneklog/v2"
+```
+
+- Package references should use `sneklog` instead of `slog`.
+- Removed `Logger.PrintTime` and `Logger.PrintTraceback`; configure output through writer formatters instead.
+- Changed text writer constructors:
+  - `CreateTextWriter(w, printTraceback, printTime)` is now `CreateTextWriter(w)`.
+  - `CreateTextFileWriter(path, printTraceback, printTime)` is now `CreateTextFileWriter(path)`.
+  - `CreateTextStdoutWriter(printTraceback, printTime)` is now `CreateTextStdoutWriter()`.
+- Removed the old text formatting helpers: `BuildString`, `FormatTime`, `FormatTraceback`, and `FormatFullTraceback`.
+- JSON `time` values are now formatted through the configured formatter and stored as strings in `LoggerJsonMessage`.
+
+## Added
+
+- `Formatter` for configurable message layouts, timestamp layouts, traceback layouts, separators, and color behavior.
+- `DefaultTextFormatter` and `DefaultJsonFormatter` defaults for text and JSON writers.
+- `LoggerTextWriter.SetFormatter` and `LoggerJsonWriter.SetFormatter`.
+- Strftime-like timestamp format constants such as `RFC3339`, `Kitchen`, `DateTime`, `DateOnly`, and `TimeOnly`.
+- Built-in color types and helpers:
+  - `FgColor`, `BgColor`, and `Attribute`.
+  - `ColorStringBuilder`.
+  - Level color getters/setters on `LogLevel`.
+- Tests covering formatter defaults, empty traceback placeholders, literal `%` sequences in messages, color controls, and JSON newline semantics.
+
+## Changed
+
+- Text output defaults to `DefaultTextFormatter` instead of the old hard-coded string builder.
+- JSON output defaults to `DefaultJsonFormatter` and can now format the JSON `message` field through `Formatter`.
+- Newline semantics are normalized before text and JSON formatting, so trailing `\n` controls record termination without becoming part of the message.
+- Text color output is enabled by default only for stdout/stderr.
+- Example code now demonstrates custom formatters and color configuration.
+- Go dependencies were simplified by removing:
+  - `github.com/fatih/color`
+  - `github.com/mattn/go-colorable`
+  - `github.com/mattn/go-isatty`
+  - `golang.org/x/sys`
+
+## Fixed
+
+- `NewFormatter()` now returns a fresh copy instead of mutating `DefaultTextFormatter`.
+- `Formatter.FormatMessage` no longer panics when called with an empty traceback.
+- Placeholder-looking text inside log messages, such as `%L` or `%s`, is preserved literally.
+- `SetColorOutput(false)` disables color output.
+- `SetColorOnlyStdout(false)` allows color output for non-stdout writers.
+
+## Migration
+
+Before:
+
+```go
+import "git.scuroneko.dev/scuroneko/slog"
+
+logger := slog.CreateLogger().
+	Prefix("API").
+	Level(slog.DEBUG).
+	PrintTraceback(true)
+
+text := logger.CreateTextStdoutWriter()
+```
+
+After:
+
+```go
+import sneklog "git.scuroneko.dev/scuroneko/sneklog/v2"
+
+logger := sneklog.CreateLogger().
+	Prefix("API").
+	Level(sneklog.DEBUG)
+
+formatter := sneklog.NewFormatter().
+	SetFormat("%t [%L] %N: %m (%B)")
+
+text := logger.CreateTextStdoutWriter().
+	SetFormatter(formatter)
+```
+
+# v1.2.0
+
+## Highlights
+
+- Added message replacement with `Logger.AddReplacer(old, new)` for masking secrets or normalizing log output.
+- Preserved the existing `LoggerWriter.Print(...any)` contract, so custom writers do not need a signature update.
+- Improved JSON writer newline handling for messages that already end with `\n`.
+
+## Added
+
+- `Logger.AddReplacer(old, new)` appends a replacement rule that is applied before records are sent to writers.
+- README and package GoDoc now document message replacement and include usage examples.
+- Tests covering message type preservation for custom writers, JSON empty messages, and JSON trailing newline behavior.
+
+## Fixed
+
+- `LoggerJsonWriter.Print` no longer panics when called with no message arguments.
+- `LoggerJsonWriter.Print` now treats a trailing newline at the end of the last message as newline semantics and does not include that newline in the JSON `message` field.
+- Log messages keep their original argument types for custom writers when no replacement rules are configured.
+
+## Changed
+
+- Updated the example program to demonstrate `AddReplacer`.
+- Updated dependencies:
+  - `github.com/fatih/color` from `v1.18.0` to `v1.19.0`
+  - `github.com/mattn/go-isatty` from `v0.0.20` to `v0.0.21`
+  - `golang.org/x/sys` from `v0.42.0` to `v0.43.0`
+
+## Compatibility
+
+No breaking API changes are intended in this release. The public `LoggerWriter` interface continues to accept `messages ...any`.
@@ -0,0 +1,301 @@
+package sneklog
+
+import (
+	"fmt"
+	"strings"
+)
+
+// FgColor is a basic ANSI foreground color code.
+type FgColor uint8
+
+// BgColor is a basic ANSI background color code.
+type BgColor uint8
+
+// FgColor256 is an ANSI 256-color foreground value.
+type FgColor256 uint8
+
+// BgColor256 is an ANSI 256-color background value.
+type BgColor256 uint8
+
+// BgColorRGB is an ANSI truecolor background value encoded as RGB bytes.
+type BgColorRGB []uint8
+
+// FgColorRGB is an ANSI truecolor foreground value encoded as RGB bytes.
+type FgColorRGB []uint8
+
+// Attribute is an ANSI text attribute code.
+type Attribute uint8
+
+// NewBgColorRGB builds an RGB background color value.
+func NewBgColorRGB(r, g, b uint8) BgColorRGB {
+	return BgColorRGB{r, g, b}
+}
+
+// NewFgColorRGB builds an RGB foreground color value.
+func NewFgColorRGB(r, g, b uint8) FgColorRGB {
+	return FgColorRGB{r, g, b}
+}
+
+// Text attribute codes.
+const (
+	Reset Attribute = iota
+	Bold
+	Faint
+	Italic
+	Underline
+	BlinkSlow
+	BlinkRapid
+	Invert
+	Conceal
+	CrossedOut
+)
+
+// Additional text attribute codes.
+const (
+	DoubleUnderline Attribute = iota + 21 // Can be disable bold on some terminals
+	DisableBold
+	DisableItalic
+	DisableUnderline
+	DisableBlink
+	DisableInvert
+	DisableConceal
+	DisableCrossedOut
+)
+
+// Basic foreground color codes.
+const (
+	FgNone          = 0
+	FgBlack FgColor = iota + 30
+	FgRed
+	FgGreen
+	FgYellow
+	FgBlue
+	FgMagenta
+	FgCyan
+	FgWhite
+	FgDefault FgColor = 39
+)
+
+// Basic background color codes.
+const (
+	BgNone          = 0
+	BgBlack BgColor = iota + 40
+	BgRed
+	BgGreen
+	BgYellow
+	BgBlue
+	BgMagenta
+	BgCyan
+	BgWhite
+	BgDefault BgColor = 49
+)
+
+// High-intensity foreground color codes.
+const (
+	FgHiBlack FgColor = iota + 90
+	FgHiRed
+	FgHiGreen
+	FgHiYellow
+	FgHiBlue
+	FgHiMagenta
+	FgHiCyan
+	FgHiWhite
+)
+
+// High-intensity background color codes.
+const (
+	BgHiBlack BgColor = iota + 100
+	BgHiRed
+	BgHiGreen
+	BgHiYellow
+	BgHiBlue
+	BgHiMagenta
+	BgHiCyan
+	BgHiWhite
+)
+
+// Rarely used text attribute codes that are not supported by all terminals.
+const (
+	Border Attribute = iota + 51
+	Outline
+	Upperline
+	DisableBorderOutline
+	DisableUpperline
+)
+
+// ColorStringBuilder incrementally builds ANSI-colored strings.
+type ColorStringBuilder struct {
+	str string
+}
+
+// NewColorStringBuilder creates a builder for composing ANSI-colored strings.
+func NewColorStringBuilder() *ColorStringBuilder {
+	return &ColorStringBuilder{str: ""}
+}
+
+// AddAttribute appends an ANSI text attribute sequence.
+func (builder *ColorStringBuilder) AddAttribute(attr Attribute) *ColorStringBuilder {
+	builder.str += attr.String()
+	return builder
+}
+
+// AddFgColor appends a basic ANSI foreground color sequence.
+func (builder *ColorStringBuilder) AddFgColor(color FgColor) *ColorStringBuilder {
+	if color <= 0 {
+		return builder
+	}
+	builder.str += color.String()
+	return builder
+}
+
+// AddBgColor appends a basic ANSI background color sequence.
+func (builder *ColorStringBuilder) AddBgColor(color BgColor) *ColorStringBuilder {
+	if color <= 0 {
+		return builder
+	}
+	builder.str += color.String()
+	return builder
+}
+
+// AddForeground256Color appends a 256-color foreground sequence.
+func (builder *ColorStringBuilder) AddForeground256Color(color FgColor256) *ColorStringBuilder {
+	builder.str += color.String()
+	return builder
+}
+
+// AddColor256Fg appends a 256-color foreground sequence.
+// Deprecated: use AddForeground256Color. This method will be removed in v3.
+func (builder *ColorStringBuilder) AddColor256Fg(color uint8) *ColorStringBuilder {
+	return builder.AddForeground256Color(FgColor256(color))
+}
+
+// AddBackground256Color appends a 256-color background sequence.
+func (builder *ColorStringBuilder) AddBackground256Color(color BgColor256) *ColorStringBuilder {
+	builder.str += color.String()
+	return builder
+}
+
+// AddColor256Bg appends a 256-color background sequence.
+// Deprecated: use AddBackground256Color. This method will be removed in v3.
+func (builder *ColorStringBuilder) AddColor256Bg(color uint8) *ColorStringBuilder {
+	return builder.AddBackground256Color(BgColor256(color))
+}
+
+// AddForegroundRGB appends an RGB foreground sequence.
+func (builder *ColorStringBuilder) AddForegroundRGB(color FgColorRGB) *ColorStringBuilder {
+	builder.str += color.String()
+	return builder
+}
+
+// AddColorRgbFg appends an RGB foreground sequence.
+// Deprecated: use AddForegroundRGB. This method will be removed in v3.
+func (builder *ColorStringBuilder) AddColorRgbFg(r, g, b uint8) *ColorStringBuilder {
+	return builder.AddForegroundRGB(FgColorRGB{r, g, b})
+}
+
+// AddBackgroundRGB appends an RGB background sequence.
+func (builder *ColorStringBuilder) AddBackgroundRGB(color BgColorRGB) *ColorStringBuilder {
+	builder.str += color.String()
+	return builder
+}
+
+// AddColorRgbBg appends an RGB background sequence.
+// Deprecated: use AddBackgroundRGB. This method will be removed in v3.
+func (builder *ColorStringBuilder) AddColorRgbBg(r, g, b uint8) *ColorStringBuilder {
+	return builder.AddBackgroundRGB(BgColorRGB{r, g, b})
+}
+
+// AddReset appends the ANSI reset sequence.
+func (builder *ColorStringBuilder) AddReset() *ColorStringBuilder {
+	builder.str += "\x1b[0m"
+	return builder
+}
+
+// AddText appends plain text to the builder.
+func (builder *ColorStringBuilder) AddText(text string) *ColorStringBuilder {
+	builder.str += text
+	return builder
+}
+
+// String returns the built string and appends a reset sequence when needed.
+func (builder *ColorStringBuilder) String() string {
+	if strings.Contains(builder.str, "\x1b[") && !strings.HasSuffix(builder.str, "\x1b[0m") {
+		builder.AddReset()
+	}
+	return builder.str
+}
+
+// String returns the ANSI escape sequence for the attribute.
+func (a Attribute) String() string {
+	return fmt.Sprintf("\x1b[%dm", a)
+}
+
+// Uint8 returns the raw attribute value.
+func (a Attribute) Uint8() uint8 {
+	return uint8(a)
+}
+
+// Int returns the raw attribute value as int.
+func (a Attribute) Int() int {
+	return int(a)
+}
+
+// String returns the ANSI escape sequence for the foreground color.
+func (c FgColor) String() string {
+	return fmt.Sprintf("\x1b[%dm", c)
+}
+
+// Uint8 returns the raw foreground color value.
+func (c FgColor) Uint8() uint8 {
+	return uint8(c)
+}
+
+// Int returns the raw foreground color value as int.
+func (c FgColor) Int() int {
+	return int(c)
+}
+
+// String returns the ANSI escape sequence for the background color.
+func (c BgColor) String() string {
+	return fmt.Sprintf("\x1b[%dm", c)
+}
+
+// Uint8 returns the raw background color value.
+func (c BgColor) Uint8() uint8 {
+	return uint8(c)
+}
+
+// Int returns the raw background color value as int.
+func (c BgColor) Int() int {
+	return int(c)
+}
+
+// String returns the ANSI escape sequence for the 256-color foreground value.
+func (c FgColor256) String() string { return fmt.Sprintf("\u001B[38;5;%dm", c) }
+
+// Uint8 returns the raw 256-color foreground value.
+func (c FgColor256) Uint8() uint8 { return uint8(c) }
+
+// Int returns the raw 256-color foreground value as int.
+func (c FgColor256) Int() int { return int(c) }
+
+// String returns the ANSI escape sequence for the 256-color background value.
+func (c BgColor256) String() string { return fmt.Sprintf("\u001B[48;5;%dm", c) }
+
+// Uint8 returns the raw 256-color background value.
+func (c BgColor256) Uint8() uint8 { return uint8(c) }
+
+// Int returns the raw 256-color background value as int.
+func (c BgColor256) Int() int { return int(c) }
+
+// String returns the ANSI escape sequence for the RGB foreground value.
+func (c FgColorRGB) String() string { return fmt.Sprintf("\x1b[38;2;%d;%d;%dm", c[0], c[1], c[2]) }
+
+// Uint8 returns the raw RGB foreground components.
+func (c FgColorRGB) Uint8() []uint8 { return c }
+
+// String returns the ANSI escape sequence for the RGB background value.
+func (c BgColorRGB) String() string { return fmt.Sprintf("\x1b[48;2;%d;%d;%dm", c[0], c[1], c[2]) }
+
+// Uint8 returns the raw RGB background components.
+func (c BgColorRGB) Uint8() []uint8 { return c }
@@ -0,0 +1,53 @@
+// Package sneklog provides a small structured logger that can write the same
+// record to text and JSON outputs.
+//
+// A Logger can fan out records to stdout, files, or any external io.Writer.
+// Text writers can include timestamps and a compact traceback frame. JSON
+// writers always emit a structured traceback slice.
+//
+// CreateLogger uses the following defaults:
+//   - prefix: "LOG"
+//   - level: FATAL, which enables info, warn, error, and fatal records
+//   - pretty JSON: disabled
+//   - text formatter: DefaultTextFormatter
+//   - JSON formatter: DefaultJsonFormatter
+//
+// Call Level(DEBUG) to enable all records, including debug messages.
+// AddReplacer can be used to mask or normalize message text before records are
+// passed to writers. Call SetFormatter on a writer to customize timestamps,
+// traceback fields, colors, and message layout.
+//
+// The package also provides helper constructors for common severities such as
+// NewInfoLogLevel and NewErrorLogLevel, plus predefined HTTP method-specific
+// levels such as HTTPGetLevel and HTTPPostLevel. Use LogLevelForMethod to map
+// an HTTP method to one of those predefined levels.
+//
+// Basic usage:
+//
+//	logger := sneklog.CreateLogger().
+//		Prefix("API").
+//		Level(sneklog.DEBUG).
+//		AddReplacer("secret-token", "<redacted>")
+//
+//	text := logger.CreateTextStdoutWriter()
+//	jsonFile, err := logger.CreateJsonFileWriter("logs/app.json")
+//	if err != nil {
+//		panic(err)
+//	}
+//
+//	logger.AddWriters(text, jsonFile)
+//	logger.Infoln("service started", "secret-token")
+//
+//	if err := logger.Close(); err != nil {
+//		panic(err)
+//	}
+//
+// Writers created with CreateTextFileWriter or CreateJsonFileWriter are owned by
+// the logger and are closed by Logger.Close. Writers created from existing
+// io.Writer values through CreateTextWriter or CreateJsonWriter remain owned by
+// the caller and are not closed by the logger.
+//
+// LogLevel values can be compared with SameLevel when only the legacy severity
+// index matters, with SameThreshold when only threshold filtering matters, or
+// with Equal when the full level configuration must match.
+package sneklog
@@ -1,21 +1,88 @@
 package main

-import "git.nix13.pw/scuroneko/slog"
+import (
+	"bytes"
+
+	"git.scuroneko.dev/scuroneko/sneklog/v2"
+)

 func main() {
-	logger := slog.CreateLogger().JsonPretty(false)
-	defer logger.Close()
-	logger.AddWriter(logger.CreateTextStdoutWriter())
-	f, err := logger.CreateJsonFileWriter("main.log")
+	httpGet := sneklog.NewLogLevelWithColors(0, "get", sneklog.FgGreen, sneklog.BgNone)
+	httpPost := sneklog.NewLogLevelWithColors(0, "post", sneklog.FgBlue, sneklog.BgNone)
+	httpDelete := sneklog.NewLogLevel(0, "delete")
+	httpDelete.SetBackgroundRGB(128, 0, 0)
+	httpDelete.AddAttribute(sneklog.Italic).AddAttribute(sneklog.Bold)
+
+	logger := sneklog.NewLogger().
+		SetName("EXAMPLE").
+		SetLevel(sneklog.DEBUG).
+		SetJSONPretty(true).
+		AddReplacer("SOME_SECRET", "<Secret>")
+
+	sneklog.INFO.SetBgColor(sneklog.BgBlue).SetFgColor(sneklog.FgWhite)
+
+	textStdout := logger.CreateTextStdoutWriter()
+	jsonStdout := logger.CreateJsonStdoutWriter()
+
+	formatter := sneklog.NewFormatter().
+		SetFormat("[%t] [%L] [%N]: %m (%s)").
+		SetTimeStampFormat(sneklog.Kitchen).
+		SetTraceBackFormat("%s %f:%n %p")
+
+	jsonFormatter := sneklog.NewFormatter().
+		SetFormat("[%L] [%N] %m").
+		SetColorOutput(false).
+		SetTimeStampFormat(sneklog.Kitchen)
+
+	textStdout.SetFormatter(formatter)
+	jsonStdout.SetFormatter(jsonFormatter)
+
+	textFile, err := logger.CreateTextFileWriter("logs/text.log")
 	if err != nil {
+		_ = logger.Close()
 		panic(err)
 	}
-	logger.AddWriter(f)
-	logger.Infoln("Test")
-	logger.Warnln("Test")
-	logger.Errorln("Test")
-	logger.Debugln("Test") // No output
-	logger.Level(slog.DEBUG)
-	logger.Debugln("Test") // Now we have output
-	logger.Fatalln("Test") // Exit code 1
+
+	jsonFile, err := logger.CreateJsonFileWriter("logs/json.log")
+	if err != nil {
+		_ = logger.Close()
+		panic(err)
+	}
+
+	var externalBuffer bytes.Buffer
+	externalText := logger.CreateTextWriter(&externalBuffer)
+	externalJSON := logger.CreateJsonWriter(&externalBuffer)
+
+	logger.AddWriters(
+		textStdout,
+		jsonStdout,
+		textFile,
+		jsonFile,
+		externalText,
+		externalJSON,
+	)
+
+	logger.Infoln("service started")
+	logger.Warnln("cache miss")
+	logger.Errorln("request failed")
+	logger.Debugln("debug details")
+	logger.Infoln("sensitive info, SOME_SECRET")
+	logger.Println(httpGet, "this can be logging of http get request/response...")
+	logger.Println(httpPost, "...and this can be logging of http post request/response...")
+	logger.Println(httpDelete, "...but this logging of http delete request/response with highly customizable level!")
+
+	if err := logger.Close(); err != nil {
+		panic(err)
+	}
+
+	s := sneklog.NewColorStringBuilder().
+		AddBackgroundRGB(sneklog.NewBgColorRGB(31, 41, 40)).
+		AddForegroundRGB(sneklog.NewFgColorRGB(220, 215, 186)).
+		AddAttribute(sneklog.Italic).AddAttribute(sneklog.Bold).
+		AddText("Some Very very very cool stuff, themed in Kanagawa colors!").String()
+
+	println(s)
+
+	//fmt.Println("external buffer contents:")
+	//fmt.Println(externalBuffer.String())
 }
@@ -0,0 +1,221 @@
+package sneklog
+
+import (
+	"fmt"
+	"strings"
+	"time"
+)
+
+// Formatter configures how log records are rendered.
+//
+// Format tokens:
+//   - %t: time
+//   - %N: name
+//   - %l: level
+//   - %L: uppercase level
+//   - %b: first traceback frame
+//   - %B: full traceback
+//   - %m: message
+//   - %M: method
+//   - %f: filename
+//   - %n: line number
+//   - %s: method signature
+//   - %p: full path
+//
+// Example format: "%t [%l] %N: %m (%f:%n %s)"
+//
+// TimeStampFormat uses strftime-like directives such as %Y, %m, %d, %H, %M,
+// %S, %z, and %Z.
+//
+// TraceBackFormat supports the traceback-related tokens %M, %f, %n, %s, and %p.
+type Formatter struct {
+	Format           string
+	MessageSeparator string
+
+	// JSONTraceBackPath
+	// If true, in traceback will be path to file, otherwise only filename.
+	JSONTraceBackPath  bool
+	TimeStampFormat    string
+	TraceBackFormat    string
+	TraceBackSeparator string
+
+	ColorOutput     bool
+	ColorOnlyStdout bool
+}
+
+// DefaultTextFormatter is the default formatter used by text writers.
+var DefaultTextFormatter = &Formatter{
+	Format:             "%t %l %N: %m",
+	MessageSeparator:   " ",
+	TimeStampFormat:    RFC3339,
+	TraceBackFormat:    "%M (%f:%n %s)",
+	TraceBackSeparator: "->",
+	ColorOutput:        true,
+	ColorOnlyStdout:    true,
+}
+
+// DefaultJsonFormatter is the default formatter used by JSON writers.
+var DefaultJsonFormatter = &Formatter{
+	Format:           "%m",
+	MessageSeparator: " ",
+	TimeStampFormat:  RFC3339,
+	ColorOutput:      false,
+}
+
+// NewFormatter returns a copy of the default text formatter settings.
+func NewFormatter() *Formatter {
+	return &Formatter{
+		Format:             DefaultTextFormatter.Format,
+		MessageSeparator:   DefaultTextFormatter.MessageSeparator,
+		TimeStampFormat:    DefaultTextFormatter.TimeStampFormat,
+		TraceBackFormat:    DefaultTextFormatter.TraceBackFormat,
+		TraceBackSeparator: DefaultTextFormatter.TraceBackSeparator,
+		ColorOutput:        DefaultTextFormatter.ColorOutput,
+		ColorOnlyStdout:    DefaultTextFormatter.ColorOnlyStdout,
+	}
+}
+
+// SetFormat sets the formatter template used for text rendering.
+func (f *Formatter) SetFormat(format string) *Formatter {
+	f.Format = format
+	return f
+}
+
+// SetMessageSeparator sets the separator used to join message parts.
+func (f *Formatter) SetMessageSeparator(separator string) *Formatter {
+	f.MessageSeparator = separator
+	return f
+}
+
+// SetTimeStampFormat sets the strftime-like format used for timestamps.
+func (f *Formatter) SetTimeStampFormat(format string) *Formatter {
+	f.TimeStampFormat = format
+	return f
+}
+
+// SetTraceBackFormat sets the format used for a single traceback frame.
+func (f *Formatter) SetTraceBackFormat(format string) *Formatter {
+	f.TraceBackFormat = format
+	return f
+}
+
+// SetTraceBackSeparator sets the separator used between traceback frames.
+func (f *Formatter) SetTraceBackSeparator(separator string) *Formatter {
+	f.TraceBackSeparator = separator
+	return f
+}
+
+// SetColorOutput enables or disables colorized output.
+func (f *Formatter) SetColorOutput(color bool) *Formatter {
+	f.ColorOutput = color
+	return f
+}
+
+// SetColorOnlyStdout restricts colorized output to stdout and stderr when enabled.
+func (f *Formatter) SetColorOnlyStdout(only bool) *Formatter {
+	f.ColorOnlyStdout = only
+	return f
+}
+
+// FormatMessage applies the formatter template to the provided log record fields.
+func (f *Formatter) FormatMessage(level LogLevel, prefix string, tb []*MethodTraceback, messages ...any) string {
+	if f == nil {
+		return fmt.Sprint(messages...)
+	}
+	output := f.Format
+	output = strings.ReplaceAll(output, "%t", f.FormatTime(time.Now()))
+	output = strings.ReplaceAll(output, "%N", prefix)
+	output = strings.ReplaceAll(output, "%l", level.GetName())
+	output = strings.ReplaceAll(output, "%L", strings.ToUpper(level.GetName()))
+
+	if len(tb) > 0 {
+		formattedTraceback := f.FormatTraceback(tb[0])
+		output = strings.ReplaceAll(output, "%b", formattedTraceback)
+
+		formattedTraceback = f.FormatTracebacks(tb)
+		output = strings.ReplaceAll(output, "%B", formattedTraceback)
+	} else {
+		output = strings.ReplaceAll(output, "%b", "")
+		output = strings.ReplaceAll(output, "%B", "")
+	}
+
+	if len(tb) > 0 {
+		output = strings.ReplaceAll(output, "%M", tb[0].Method)
+		output = strings.ReplaceAll(output, "%f", tb[0].Filename)
+		output = strings.ReplaceAll(output, "%n", fmt.Sprintf("%d", tb[0].Line))
+		output = strings.ReplaceAll(output, "%s", tb[0].Signature)
+	} else {
+		output = strings.ReplaceAll(output, "%M", "")
+		output = strings.ReplaceAll(output, "%f", "")
+		output = strings.ReplaceAll(output, "%n", "")
+		output = strings.ReplaceAll(output, "%s", "")
+	}
+
+	if f.JSONTraceBackPath && len(tb) > 0 {
+		output = strings.ReplaceAll(output, "%p", tb[0].FullPath)
+	} else {
+		output = strings.ReplaceAll(output, "%p", "")
+	}
+
+	message := Map(messages, func(m any) string { return fmt.Sprint(m) })
+	output = strings.ReplaceAll(output, "%m", strings.Join(message, f.MessageSeparator))
+
+	return output
+}
+
+// ColorizeString wraps a string in the ANSI color sequences defined by the level.
+func (f *Formatter) ColorizeString(s string, level LogLevel) string {
+	builder := NewColorStringBuilder()
+	if level.fgRgb != nil {
+		builder.AddForegroundRGB(level.fgRgb)
+	} else if level.fg256 > 0 {
+		builder.AddForeground256Color(level.fg256)
+	} else {
+		builder.AddFgColor(level.fg)
+	}
+
+	if level.bgRgb != nil {
+		builder.AddBackgroundRGB(level.bgRgb)
+	} else if level.bg256 > 0 {
+		builder.AddBackground256Color(level.bg256)
+	} else {
+		builder.AddBgColor(level.bg)
+	}
+
+	for _, attr := range level.attrs {
+		builder.AddAttribute(attr)
+	}
+	return builder.AddText(s).AddReset().String()
+}
+
+// FormatTime formats a timestamp using the formatter timestamp layout.
+func (f *Formatter) FormatTime(t time.Time) string {
+	if f.TimeStampFormat == "" {
+		return t.Format(time.RFC3339)
+	}
+	return t.Format(StrftimeToGo(f.TimeStampFormat))
+}
+
+// FormatTraceback formats a single traceback frame.
+func (f *Formatter) FormatTraceback(traceback *MethodTraceback) string {
+	formattedTraceback := f.TraceBackFormat
+	if f.JSONTraceBackPath {
+		formattedTraceback = strings.ReplaceAll(formattedTraceback, "%p", traceback.FullPath)
+	} else {
+		formattedTraceback = strings.ReplaceAll(formattedTraceback, "%p", "")
+	}
+	formattedTraceback = strings.ReplaceAll(formattedTraceback, "%M", traceback.Method)
+	formattedTraceback = strings.ReplaceAll(formattedTraceback, "%f", traceback.Filename)
+	formattedTraceback = strings.ReplaceAll(formattedTraceback, "%n", fmt.Sprintf("%d", traceback.Line))
+	formattedTraceback = strings.ReplaceAll(formattedTraceback, "%s", traceback.Signature)
+	return formattedTraceback
+}
+
+// FormatTracebacks formats and joins multiple traceback frames.
+func (f *Formatter) FormatTracebacks(traceback []*MethodTraceback) string {
+	var formattedTraceback []string
+	for _, frame := range traceback {
+		formattedTraceback = append(formattedTraceback, f.FormatTraceback(frame))
+	}
+	return strings.Join(formattedTraceback, f.TraceBackSeparator)
+}
@@ -1,11 +1,3 @@
-module git.nix13.pw/scuroneko/slog
+module git.scuroneko.dev/scuroneko/sneklog/v2

-go 1.25
-
-require github.com/fatih/color v1.18.0
-
-require (
-	github.com/mattn/go-colorable v0.1.14 // indirect
-	github.com/mattn/go-isatty v0.0.20 // indirect
-	golang.org/x/sys v0.40.0 // indirect
-)
+go 1.26
@@ -1,9 +0,0 @@
-github.com/fatih/color v1.18.0 h1:S8gINlzdQ840/4pfAwic/ZE0djQEH3wM94VfqLTZcOM=
-github.com/fatih/color v1.18.0/go.mod h1:4FelSpRwEGDpQ12mAdzqdOukCy4u8WUtOY6lkT/6HfU=
-github.com/mattn/go-colorable v0.1.14 h1:9A9LHSqF/7dyVVX6g0U9cwm9pG3kP9gSzcuIPHPsaIE=
-github.com/mattn/go-colorable v0.1.14/go.mod h1:6LmQG8QLFO4G5z1gPvYEzlUgJ2wF+stgPZH1UqBm1s8=
-github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
-github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
-golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
-golang.org/x/sys v0.40.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
@@ -0,0 +1,47 @@
+package sneklog
+
+import "net/http"
+
+// HTTP method-specific log levels.
+var (
+	HTTPGetLevel    = NewInfoLogLevelWithColors("get", FgGreen, BgNone)
+	HTTPHeadLevel   = NewInfoLogLevelWithColors("head", FgCyan, BgNone)
+	HTTPPostLevel   = NewInfoLogLevelWithColors("post", FgBlue, BgNone)
+	HTTPPutLevel    = NewInfoLogLevelWithColors("put", FgYellow, BgNone)
+	HTTPPatchLevel  = NewInfoLogLevelWithColors("patch", FgMagenta, BgNone)
+	HTTPDeleteLevel = NewInfoLogLevelWithColors("delete", FgRed, BgNone)
+)
+
+// Additional HTTP method-specific log levels.
+var (
+	HTTPOptionsLevel = NewDebugLogLevelWithColors("options", FgWhite, BgNone)
+	HTTPConnectLevel = NewDebugLogLevelWithColors("connect", FgCyan, BgNone)
+	HTTPTraceLevel   = NewDebugLogLevelWithColors("trace", FgWhite, BgNone)
+	HTTPUnknownLevel = NewDebugLogLevelWithColors("http", FgWhite, BgNone)
+)
+
+// LogLevelForMethod returns the predefined log level associated with an HTTP method.
+func LogLevelForMethod(method string) LogLevel {
+	switch method {
+	case http.MethodGet:
+		return HTTPGetLevel
+	case http.MethodHead:
+		return HTTPHeadLevel
+	case http.MethodPost:
+		return HTTPPostLevel
+	case http.MethodPut:
+		return HTTPPutLevel
+	case http.MethodPatch:
+		return HTTPPatchLevel
+	case http.MethodDelete:
+		return HTTPDeleteLevel
+	case http.MethodOptions:
+		return HTTPOptionsLevel
+	case http.MethodConnect:
+		return HTTPConnectLevel
+	case http.MethodTrace:
+		return HTTPTraceLevel
+	default:
+		return HTTPUnknownLevel
+	}
+}
@@ -1,91 +1,130 @@
-package slog
+package sneklog

 import (
 	"fmt"
 	"os"
 )

+// Infof logs a formatted info message.
 func (l *Logger) Infof(format string, args ...any) {
-	l.print(INFO, fmt.Sprintf(format, args...))
+	l.Print(INFO, fmt.Sprintf(format, args...))
 }
+
+// Info logs an info message.
 func (l *Logger) Info(m ...any) {
-	l.print(INFO, m...)
+	l.Print(INFO, m...)
 }
+
+// Infoln logs an info message and appends a newline semantic for writers that need it.
 func (l *Logger) Infoln(m ...any) {
-	l.println(INFO, m...)
+	l.Println(INFO, m...)
 }

+// Warnf logs a formatted warning message.
 func (l *Logger) Warnf(format string, args ...any) {
-	l.print(WARN, fmt.Sprintf(format, args...))
+	l.Print(WARN, fmt.Sprintf(format, args...))
 }
+
+// Warn logs a warning message.
 func (l *Logger) Warn(m ...any) {
-	l.print(WARN, m...)
+	l.Print(WARN, m...)
 }
+
+// Warnln logs a warning message with newline semantic.
 func (l *Logger) Warnln(m ...any) {
-	l.println(WARN, m...)
+	l.Println(WARN, m...)
 }

+// Errorf logs a formatted error message.
 func (l *Logger) Errorf(format string, args ...any) {
-	l.print(ERROR, fmt.Sprintf(format, args...))
+	l.Print(ERROR, fmt.Sprintf(format, args...))
 }
+
+// Error logs an error message.
 func (l *Logger) Error(m ...any) {
-	l.print(ERROR, m...)
+	l.Print(ERROR, m...)
 }
+
+// Errorln logs an error message with newline semantic.
 func (l *Logger) Errorln(m ...any) {
-	l.println(ERROR, m...)
+	l.Println(ERROR, m...)
 }

+// Fatalf logs a formatted fatal message and exits the process with code 1.
 func (l *Logger) Fatalf(format string, args ...any) {
-	l.print(FATAL, fmt.Sprintf(format, args...))
+	l.Print(FATAL, fmt.Sprintf(format, args...))
 	os.Exit(1)
 }
+
+// Fatal logs a fatal message and exits the process with code 1.
 func (l *Logger) Fatal(m ...any) {
-	l.print(FATAL, m...)
+	l.Print(FATAL, m...)
 	os.Exit(1)
 }
+
+// Fatalln logs a fatal message with newline semantic and exits the process with code 1.
 func (l *Logger) Fatalln(m ...any) {
-	l.println(FATAL, m...)
+	l.Println(FATAL, m...)
 	os.Exit(1)
 }

+// Debugf logs a formatted debug message.
 func (l *Logger) Debugf(format string, args ...any) {
-	l.print(DEBUG, fmt.Sprintf(format, args...))
+	l.Print(DEBUG, fmt.Sprintf(format, args...))
 }
+
+// Debug logs a debug message.
 func (l *Logger) Debug(m ...any) {
-	l.print(DEBUG, m...)
+	l.Print(DEBUG, m...)
 }
+
+// Debugln logs a debug message with newline semantic.
 func (l *Logger) Debugln(m ...any) {
-	l.println(DEBUG, m...)
+	l.Println(DEBUG, m...)
 }

-// Write message without trailing "\n"
-// Good for database
-func (l *Logger) print(level LogLevel, m ...any) {
-	if l.level.n < level.n {
+func (l *Logger) print(level LogLevel, newline bool, m ...any) {
+	if l.threshold && l.level.th < level.th {
+		return
+	} else if l.level.n < level.n {
+		return
+	}
+	if len(l.writers) == 0 {
 		return
 	}

-	tb := getFullTraceback(0)
+	tb := getFullTraceback(1)
+	messages := l.replaceAll(m...)
+	if newline {
+		messages = append(messages, any("\n"))
+	}
 	for _, writer := range l.writers {
-		err := writer.Print(level, l.prefix, tb, m...)
+		if writer == nil {
+			continue
+		}
+		err := writer.Print(level, l.prefix, tb, messages...)
 		if err != nil {
-			l.Error(err)
+			l.reportWriterError(err)
 		}
 	}
 }

-// Docker requires "\n" at end to write to log.
-// print not work for docker, otherwise it will work and write into stdout
-func (l *Logger) println(level LogLevel, m ...any) {
-	if l.level.n < level.n {
+// Print logs a message without appending a trailing newline semantic.
+func (l *Logger) Print(level LogLevel, m ...any) { l.print(level, false, m...) }
+
+// Println logs a message and appends a trailing newline semantic for writers that need it.
+func (l *Logger) Println(level LogLevel, m ...any) { l.print(level, true, m...) }
+
+// Printf formats according to a format specifier and logs the resulting message.
+func (l *Logger) Printf(level LogLevel, format string, args ...any) {
+	l.print(level, false, fmt.Sprintf(format, args...))
+}
+
+// reportWriterError writes internal writer failures directly to stderr to avoid
+// re-entering the same logger path that just failed.
+func (l *Logger) reportWriterError(err error) {
+	if err == nil {
 		return
 	}
-
-	tb := getFullTraceback(0)
-	for _, writer := range l.writers {
-		err := writer.Print(level, l.prefix, tb, append(m, "\n")...)
-		if err != nil {
-			l.Error(err)
-		}
-	}
+	_, _ = fmt.Fprintf(os.Stderr, "[%s] logger writer error: %v\n", l.prefix, err)
 }
@@ -0,0 +1,269 @@
+package sneklog
+
+// Predefined log levels.
+var (
+	INFO  = NewInfoLogLevelWithColors("info", FgWhite, BgNone)
+	WARN  = NewWarnLogLevelWithColors("warn", FgHiYellow, BgNone)
+	ERROR = NewErrorLogLevelWithColors("error", FgHiRed, BgNone)
+	FATAL = NewFatalLogLevelWithColors("fatal", FgRed, BgNone)
+	DEBUG = NewDebugLogLevelWithColors("debug", FgGreen, BgNone)
+)
+
+// LogLevel describes a logging severity.
+type LogLevel struct {
+	n  uint8
+	th uint8
+	t  string
+
+	fg    FgColor
+	fg256 FgColor256
+	fgRgb FgColorRGB
+
+	bg    BgColor
+	bg256 BgColor256
+	bgRgb BgColorRGB
+
+	attrs []Attribute
+}
+
+// NewLogLevel creates a log level without predefined colors.
+// Deprecated: use NewThresholdLogLevel. This function will be removed in v3.
+func NewLogLevel(index uint8, name string) LogLevel {
+	return NewLogLevelWithColors(index, name, 0, 0)
+}
+
+// NewLogLevelWithColors creates a log level with ANSI foreground and background colors.
+// Deprecated: use NewThresholdLogLevelWithColors. This function will be removed in v3.
+func NewLogLevelWithColors(index uint8, name string, fg FgColor, bg BgColor) LogLevel {
+	return LogLevel{n: index, t: name, fg: fg, bg: bg, attrs: []Attribute{}}
+}
+
+// NewThresholdLogLevel creates a log level with both a legacy severity index and
+// a threshold value used when Logger.SetThresholdMode(true) is enabled.
+func NewThresholdLogLevel(index, th uint8, name string) LogLevel {
+	return NewThresholdLogLevelWithColors(index, th, name, FgNone, BgNone)
+}
+
+// NewThresholdLogLevelWithColors creates a log level with both a legacy
+// severity index and a threshold value, plus ANSI foreground and background
+// colors.
+func NewThresholdLogLevelWithColors(index, th uint8, name string, fg FgColor, bg BgColor) LogLevel {
+	return LogLevel{n: index, th: th, t: name, fg: fg, bg: bg, attrs: []Attribute{}}
+}
+
+// NewInfoLogLevel creates an info-level log level without predefined colors.
+func NewInfoLogLevel(name string) LogLevel { return NewThresholdLogLevel(0, 10, name) }
+
+// NewInfoLogLevelWithColors creates an info-level log level with ANSI colors.
+func NewInfoLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewThresholdLogLevelWithColors(0, 10, name, fg, bg)
+}
+
+// NewWarnLogLevel creates a warn-level log level without predefined colors.
+func NewWarnLogLevel(name string) LogLevel { return NewThresholdLogLevel(1, 20, name) }
+
+// NewWarnLogLevelWithColors creates a warn-level log level with ANSI colors.
+func NewWarnLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewThresholdLogLevelWithColors(1, 20, name, fg, bg)
+}
+
+// NewErrorLogLevel creates an error-level log level without predefined colors.
+func NewErrorLogLevel(name string) LogLevel { return NewThresholdLogLevel(2, 30, name) }
+
+// NewErrorLogLevelWithColors creates an error-level log level with ANSI colors.
+func NewErrorLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewThresholdLogLevelWithColors(2, 30, name, fg, bg)
+}
+
+// NewFatalLogLevel creates a fatal-level log level without predefined colors.
+func NewFatalLogLevel(name string) LogLevel { return NewThresholdLogLevel(3, 40, name) }
+
+// NewFatalLogLevelWithColors creates a fatal-level log level with ANSI colors.
+func NewFatalLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewThresholdLogLevelWithColors(3, 40, name, fg, bg)
+}
+
+// NewDebugLogLevel creates a debug-level log level without predefined colors.
+func NewDebugLogLevel(name string) LogLevel { return NewThresholdLogLevel(4, 0, name) }
+
+// NewDebugLogLevelWithColors creates a debug-level log level with ANSI colors.
+func NewDebugLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewThresholdLogLevelWithColors(4, 0, name, fg, bg)
+}
+
+// GetName returns the lowercase textual representation of the level.
+func (l *LogLevel) GetName() string { return l.t }
+
+// SetFgColor sets the ANSI foreground color and clears other foreground color modes.
+// Deprecated: use SetForegroundColor. This method will be removed in v3.
+func (l *LogLevel) SetFgColor(color FgColor) *LogLevel {
+	return l.SetForegroundColor(color)
+}
+
+// GetFgColor returns the ANSI foreground color for the level.
+// Deprecated: use GetForegroundColor. This method will be removed in v3.
+func (l *LogLevel) GetFgColor() FgColor { return l.GetForegroundColor() }
+
+// SetForegroundColor sets the ANSI foreground color and clears other foreground color modes.
+func (l *LogLevel) SetForegroundColor(color FgColor) *LogLevel {
+	l.fg = color
+	l.fg256 = 0
+	l.fgRgb = nil
+	return l
+}
+
+// GetForegroundColor returns the ANSI foreground color for the level.
+func (l *LogLevel) GetForegroundColor() FgColor { return l.fg }
+
+// SetForeground256Color sets the 256-color foreground and clears other foreground color modes.
+func (l *LogLevel) SetForeground256Color(color FgColor256) *LogLevel {
+	l.fg = 0
+	l.fg256 = color
+	l.fgRgb = nil
+	return l
+}
+
+// GetForeground256Color returns the configured 256-color foreground value.
+func (l *LogLevel) GetForeground256Color() FgColor256 { return l.fg256 }
+
+// SetForegroundRGB sets the RGB foreground color and clears other foreground color modes.
+func (l *LogLevel) SetForegroundRGB(r, g, b uint8) *LogLevel {
+	l.fg = 0
+	l.fg256 = 0
+	l.fgRgb = FgColorRGB{r, g, b}
+	return l
+}
+
+// GetForegroundRGB returns the configured RGB foreground value.
+func (l *LogLevel) GetForegroundRGB() FgColorRGB { return l.fgRgb }
+
+// SetBgColor sets the ANSI background color and clears other background color modes.
+// Deprecated: use SetBackgroundColor. This method will be removed in v3.
+func (l *LogLevel) SetBgColor(color BgColor) *LogLevel {
+	return l.SetBackgroundColor(color)
+}
+
+// GetBgColor returns the ANSI background color for the level.
+// Deprecated: use GetBackgroundColor. This method will be removed in v3.
+func (l *LogLevel) GetBgColor() BgColor { return l.GetBackgroundColor() }
+
+// SetBackgroundColor sets the ANSI background color and clears other background color modes.
+func (l *LogLevel) SetBackgroundColor(color BgColor) *LogLevel {
+	l.bg = color
+	l.bg256 = 0
+	l.bgRgb = nil
+	return l
+}
+
+// GetBackgroundColor returns the ANSI background color for the level.
+func (l *LogLevel) GetBackgroundColor() BgColor { return l.bg }
+
+// SetBackground256Color sets the 256-color background and clears other background color modes.
+func (l *LogLevel) SetBackground256Color(color BgColor256) *LogLevel {
+	l.bg = 0
+	l.bg256 = color
+	l.bgRgb = nil
+	return l
+}
+
+// GetBackground256Color returns the configured 256-color background value.
+func (l *LogLevel) GetBackground256Color() BgColor256 { return l.bg256 }
+
+// SetBackgroundRGB sets the RGB background color and clears other background color modes.
+func (l *LogLevel) SetBackgroundRGB(r, g, b uint8) *LogLevel {
+	l.bg = 0
+	l.bg256 = 0
+	l.bgRgb = BgColorRGB{r, g, b}
+	return l
+}
+
+// GetBackgroundRGB returns the configured RGB background value.
+func (l *LogLevel) GetBackgroundRGB() BgColorRGB { return l.bgRgb }
+
+// AddAttribute appends an ANSI text attribute to the level.
+func (l *LogLevel) AddAttribute(a Attribute) *LogLevel {
+	l.attrs = append(l.attrs, a)
+	return l
+}
+
+// RemoveAttribute removes all matching ANSI text attributes from the level.
+func (l *LogLevel) RemoveAttribute(a Attribute) *LogLevel {
+	attrs := make([]Attribute, 0)
+	for _, attr := range l.attrs {
+		if attr != a {
+			attrs = append(attrs, attr)
+		}
+	}
+	l.attrs = attrs
+	return l
+}
+
+// SetAttributes replaces the level attributes with a copy of the provided slice.
+func (l *LogLevel) SetAttributes(a []Attribute) *LogLevel {
+	attrs := make([]Attribute, len(a))
+	copy(attrs, a)
+	l.attrs = attrs
+	return l
+}
+
+// GetAttributes returns a copy of the configured ANSI text attributes.
+func (l *LogLevel) GetAttributes() []Attribute {
+	attrs := make([]Attribute, len(l.attrs))
+	copy(attrs, l.attrs)
+	return attrs
+}
+
+// SameLevel reports whether two log levels have the same severity index.
+// Deprecated: use SameThreshold for threshold-only comparisons or Equal for the
+// full level configuration. SameLevel remains severity-only for backward
+// compatibility and ignores threshold values.
+func (l *LogLevel) SameLevel(other LogLevel) bool {
+	return l.n == other.n
+}
+
+// SameThreshold reports whether two log levels have the same threshold value.
+func (l *LogLevel) SameThreshold(other LogLevel) bool {
+	return l.th == other.th
+}
+
+// Equal reports whether two log levels have identical configuration.
+func (l *LogLevel) Equal(other LogLevel) bool {
+	if l.t != other.t || l.n != other.n || l.th != other.th {
+		return false
+	}
+	if l.fg != other.fg || l.bg != other.bg {
+		return false
+	}
+
+	if l.fg256 != other.fg256 || l.bg256 != other.bg256 {
+		return false
+	}
+
+	if len(l.attrs) != len(other.attrs) {
+		return false
+	}
+	for i := range l.attrs {
+		if l.attrs[i] != other.attrs[i] {
+			return false
+		}
+	}
+
+	if len(l.fgRgb) != len(other.fgRgb) {
+		return false
+	}
+	for i := range l.fgRgb {
+		if l.fgRgb[i] != other.fgRgb[i] {
+			return false
+		}
+	}
+
+	if len(l.bgRgb) != len(other.bgRgb) {
+		return false
+	}
+	for i := range l.bgRgb {
+		if l.bgRgb[i] != other.bgRgb[i] {
+			return false
+		}
+	}
+	return true
+}
@@ -1,34 +1,13 @@
-package slog
+package sneklog

 import (
+	"errors"
 	"fmt"
 	"io"
 	"strings"
-	"time"
-
-	"github.com/fatih/color"
 )

-type Logger struct {
-	prefix  string
-	level   LogLevel
-	writers []LoggerWriter
-
-	printTraceback bool
-	printTime      bool
-	jsonPretty     bool
-}
-
-type LogLevel struct {
-	n uint8
-	t string
-	c color.Attribute
-}
-
-func (l *LogLevel) GetName() string {
-	return l.t
-}
-
+// MethodTraceback describes a single stack frame attached to a log entry.
 type MethodTraceback struct {
 	Method    string `json:"method"`
 	Filename  string `json:"filename"`
@@ -37,110 +16,170 @@ type MethodTraceback struct {
 	FullPath  string `json:"fullPath"`
 }

-var (
-	INFO  = LogLevel{n: 0, t: "info", c: color.FgWhite}
-	WARN  = LogLevel{n: 1, t: "warn", c: color.FgHiYellow}
-	ERROR = LogLevel{n: 2, t: "error", c: color.FgHiRed}
-	FATAL = LogLevel{n: 3, t: "fatal", c: color.FgRed}
-	DEBUG = LogLevel{n: 4, t: "debug", c: color.FgGreen}
-)
+// Logger routes log records to one or more configured writers.
+type Logger struct {
+	prefix string
+	level  LogLevel

+	writers   []LoggerWriter
+	replacers []replacer
+
+	jsonPretty bool
+	threshold  bool
+}
+
+// CreateLogger creates a logger with default settings.
+// Deprecated: use NewLogger. This method will be removed in v3.
 func CreateLogger() *Logger {
 	return &Logger{
 		prefix: "LOG",
 		level:  FATAL,
-		printTraceback: false,
-		printTime:      true,
 	}
 }

+// NewLogger creates a logger with default settings.
+func NewLogger() *Logger {
+	return &Logger{
+		prefix: "LOG",
+		level:  FATAL,
+	}
+}
+
+// Prefix sets the record prefix and returns the logger for chaining.
+// Deprecated: use SetName. This method will be removed in v3.
 func (l *Logger) Prefix(prefix string) *Logger {
 	l.prefix = prefix
 	return l
 }
+
+// SetName sets the record prefix and returns the logger for chaining.
+func (l *Logger) SetName(name string) *Logger {
+	l.prefix = name
+	return l
+}
+
+// Level sets the maximum enabled level and returns the logger for chaining.
+// Deprecated: use SetLevel. This method will be removed in v3.
 func (l *Logger) Level(level LogLevel) *Logger {
 	l.level = level
 	return l
 }
-func (l *Logger) PrintTraceback(b bool) *Logger {
-	l.printTraceback = b
-	return l
-}
-func (l *Logger) PrintTime(b bool) *Logger {
-	l.printTime = b
+
+// SetLevel sets the maximum enabled level and returns the logger for chaining.
+func (l *Logger) SetLevel(level LogLevel) *Logger {
+	l.level = level
 	return l
 }
+
+// JsonPretty enables or disables indented JSON output for JSON writers created by the logger.
+// Deprecated: use SetJSONPretty. This method will be removed in v3.
 func (l *Logger) JsonPretty(b bool) *Logger {
 	l.jsonPretty = b
 	return l
 }
+
+// SetJSONPretty enables or disables indented output for JSON writers created by the logger.
+func (l *Logger) SetJSONPretty(b bool) *Logger {
+	l.jsonPretty = b
+	return l
+}
+
+// SetThresholdMode switches Logger.Print filtering from legacy severity-index
+// ordering to LogLevel threshold ordering.
+func (l *Logger) SetThresholdMode(b bool) *Logger {
+	l.threshold = b
+	return l
+}
+
+// AddWriters appends multiple writers to the logger.
 func (l *Logger) AddWriters(writers ...LoggerWriter) *Logger {
 	l.writers = append(l.writers, writers...)
 	return l
 }
+
+// AddWriter appends a single writer to the logger.
+// Deprecated: use AddWriters. This method will be removed in v3.
 func (l *Logger) AddWriter(writer LoggerWriter) *Logger {
 	l.writers = append(l.writers, writer)
 	return l
 }
-func (l *Logger) Close() error {
-	for _, writer := range l.writers {
-		err := writer.Close()
-		if err != nil {
-			l.Error(err)
+
+// AddReplacer appends a message replacer and returns the logger for chaining.
+//
+// Replacement rules are applied before records are passed to writers. Empty old
+// values are ignored because replacing an empty string would insert the
+// replacement between every UTF-8 sequence.
+func (l *Logger) AddReplacer(old, new string) *Logger {
+	if old == "" {
+		return l
 	}
-	}
-	return nil
+	r := replacer{old: old, new: new}
+	l.replacers = append(l.replacers, r)
+	return l
 }

-func (l *Logger) CreateTextWriter(w io.Writer) *LoggerTextWriter {
-	return CreateTextWriter(w, l.printTraceback, l.printTime)
-}
-func (l *Logger) CreateTextStdoutWriter() *LoggerTextWriter {
-	return CreateTextStdoutWriter(l.printTraceback, l.printTime)
+// Close closes all owned writers and returns a joined error, if any.
+func (l *Logger) Close() error {
+	var errs []error
+	for _, writer := range l.writers {
+		if writer == nil {
+			continue
+		}
+		err := writer.Close()
+		if err != nil {
+			errs = append(errs, err)
+		}
+	}
+	l.writers = nil
+	return errors.Join(errs...)
 }
+
+// CreateTextWriter wraps an external writer with the logger text settings.
+func (l *Logger) CreateTextWriter(w io.Writer) *LoggerTextWriter { return CreateTextWriter(w) }
+
+// CreateTextStdoutWriter creates a non-owning text writer for os.Stdout.
+func (l *Logger) CreateTextStdoutWriter() *LoggerTextWriter { return CreateTextStdoutWriter() }
+
+// CreateTextFileWriter creates an owning text writer for a file.
 func (l *Logger) CreateTextFileWriter(filename string) (*LoggerTextWriter, error) {
-	return CreateTextFileWriter(filename, l.printTraceback, l.printTime)
+	return CreateTextFileWriter(filename)
 }
+
+// CreateJsonWriter wraps an external writer with the logger JSON settings.
 func (l *Logger) CreateJsonWriter(w io.Writer) *LoggerJsonWriter {
 	return CreateJsonWriter(w, l.jsonPretty)
 }
+
+// CreateJsonStdoutWriter creates a non-owning JSON writer for os.Stdout.
 func (l *Logger) CreateJsonStdoutWriter() *LoggerJsonWriter {
 	return CreateJsonStdoutWriter(l.jsonPretty)
 }
+
+// CreateJsonFileWriter creates an owning JSON writer for a file.
 func (l *Logger) CreateJsonFileWriter(filename string) (*LoggerJsonWriter, error) {
 	return CreateJsonFileWriter(filename, l.jsonPretty)
 }

-func FormatTime(t time.Time) string {
-	return fmt.Sprintf("%02d.%02d.%02d %02d:%02d:%02d", t.Day(), t.Month(), t.Year(), t.Hour(), t.Minute(), t.Second())
+type replacer struct {
+	old string
+	new string
 }
-func FormatTraceback(mt *MethodTraceback) string {
-	return fmt.Sprintf("%s:%s:%d", mt.Filename, mt.Method, mt.Line)
-}
-func FormatFullTraceback(tracebacks []*MethodTraceback) string {
-	formatted := make([]string, 0)
-	for _, tb := range tracebacks {
-		formatted = append(formatted, FormatTraceback(tb))
-	}
-	return strings.Join(formatted, "->")
-}
-func BuildString(level LogLevel, prefix string, printTime, printTraceback bool, m ...any) string {
-	args := []string{
-		fmt.Sprintf("[%s]", prefix),
-		fmt.Sprintf("[%s]", strings.ToUpper(level.t)),
-	}

-	if printTraceback {
-		args = append(args, fmt.Sprintf("[%s]", FormatTraceback(getTraceback())))
+func (r replacer) replace(s string) string { return strings.ReplaceAll(s, r.old, r.new) }
+func (l *Logger) replace(s string) string {
+	out := s
+	for _, repl := range l.replacers {
+		out = repl.replace(out)
 	}
-
-	if printTime {
-		args = append(args, fmt.Sprintf("[%s]", FormatTime(time.Now())))
+	return out
+}
+func (l *Logger) replaceAll(messages ...any) []any {
+	if len(l.replacers) == 0 {
+		return messages
 	}
-
-	msg := Map(m, func(el any) string {
-		return fmt.Sprintf("%v", el)
-	})
-	s := fmt.Sprintf("%s %s", strings.Join(args, " "), strings.Join(msg, " "))
-	return s
+	out := make([]any, len(messages))
+	for i, msg := range messages {
+		out[i] = l.replace(fmt.Sprint(msg))
+	}
+	return out
 }
@@ -0,0 +1,695 @@
+package sneklog
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"os"
+	"strings"
+	"testing"
+)
+
+type stubLoggerWriter struct {
+	printErr   error
+	closeErr   error
+	printCalls int
+	closeCalls int
+	messages   []any
+}
+
+func (w *stubLoggerWriter) Formatter() *Formatter {
+	return &Formatter{}
+}
+func (w *stubLoggerWriter) Close() error {
+	w.closeCalls++
+	return w.closeErr
+}
+
+func (w *stubLoggerWriter) Write(p []byte) (int, error) {
+	return len(p), nil
+}
+
+func (w *stubLoggerWriter) Print(_ LogLevel, _ string, _ []*MethodTraceback, messages ...any) error {
+	w.printCalls++
+	w.messages = append([]any(nil), messages...)
+	return w.printErr
+}
+
+func TestLoggerCloseReturnsJoinedErrorsWithoutRelogging(t *testing.T) {
+	firstErr := errors.New("first close failed")
+	secondErr := errors.New("second close failed")
+	first := &stubLoggerWriter{closeErr: firstErr}
+	second := &stubLoggerWriter{closeErr: secondErr}
+
+	logger := CreateLogger().AddWriters(first, second)
+	err := logger.Close()
+	if !errors.Is(err, firstErr) {
+		t.Fatalf("Close() error should include first writer error, got %v", err)
+	}
+	if !errors.Is(err, secondErr) {
+		t.Fatalf("Close() error should include second writer error, got %v", err)
+	}
+	if first.printCalls != 0 || second.printCalls != 0 {
+		t.Fatalf("Close() should not log through writers again, got print calls first=%d second=%d", first.printCalls, second.printCalls)
+	}
+	if first.closeCalls != 1 || second.closeCalls != 1 {
+		t.Fatalf("Close() should close each writer once, got close calls first=%d second=%d", first.closeCalls, second.closeCalls)
+	}
+	if err := logger.Close(); err != nil {
+		t.Fatalf("second Close() should be a no-op, got %v", err)
+	}
+}
+
+func TestLoggerPrintDoesNotRecurseOnWriterError(t *testing.T) {
+	oldStderr := os.Stderr
+	stderrFile, err := os.CreateTemp(t.TempDir(), "stderr")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	os.Stderr = stderrFile
+	t.Cleanup(func() {
+		os.Stderr = oldStderr
+		_ = stderrFile.Close()
+	})
+
+	bad := &stubLoggerWriter{printErr: errors.New("print failed")}
+	good := &stubLoggerWriter{}
+
+	logger := CreateLogger().AddWriters(bad, good)
+	logger.Error("boom")
+
+	if bad.printCalls != 1 {
+		t.Fatalf("bad writer should be called once, got %d", bad.printCalls)
+	}
+	if good.printCalls != 1 {
+		t.Fatalf("good writer should be called once, got %d", good.printCalls)
+	}
+}
+
+func TestLoggerPreservesMessageTypesWithoutReplacers(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().AddWriter(writer)
+
+	logger.Error("status", 500)
+
+	if len(writer.messages) != 2 {
+		t.Fatalf("writer should receive two messages, got %d", len(writer.messages))
+	}
+	if _, ok := writer.messages[1].(int); !ok {
+		t.Fatalf("writer should receive original int message type, got %T", writer.messages[1])
+	}
+}
+
+func TestLoggerPrintfFormatsMessage(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		SetLevel(DEBUG).
+		AddWriter(writer)
+
+	logger.Printf(INFO, "status=%d %s", 200, "ok")
+
+	if writer.printCalls != 1 {
+		t.Fatalf("Printf() should write once, got %d calls", writer.printCalls)
+	}
+	if len(writer.messages) != 1 {
+		t.Fatalf("Printf() should produce one formatted message, got %d parts", len(writer.messages))
+	}
+	if got, ok := writer.messages[0].(string); !ok || got != "status=200 ok" {
+		t.Fatalf("Printf() should format message, got %#v", writer.messages)
+	}
+}
+
+func TestLoggerUsesSeverityOrderingWhenThresholdModeIsDisabled(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		SetLevel(NewThresholdLogLevel(1, 0, "warn")).
+		AddWriter(writer)
+
+	logger.Print(NewThresholdLogLevel(0, 100, "info"))
+	logger.Print(NewThresholdLogLevel(2, 0, "error"))
+
+	if writer.printCalls != 1 {
+		t.Fatalf("severity mode should allow only lower-or-equal severity levels, got %d writes", writer.printCalls)
+	}
+}
+
+func TestLoggerUsesThresholdOrderingWhenThresholdModeIsEnabled(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		SetLevel(NewThresholdLogLevel(4, 20, "custom")).
+		SetThresholdMode(true).
+		AddWriter(writer)
+
+	logger.Print(NewThresholdLogLevel(4, 10, "debug"))
+	logger.Print(NewThresholdLogLevel(0, 30, "info"))
+
+	if writer.printCalls != 1 {
+		t.Fatalf("threshold mode should allow only entries at or below the configured threshold, got %d writes", writer.printCalls)
+	}
+}
+
+func TestDeprecatedLevelMethodKeepsLegacySeverityBehavior(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		Level(FATAL).
+		AddWriter(writer)
+
+	logger.Print(INFO, "info")
+	logger.Print(WARN, "warn")
+	logger.Print(ERROR, "error")
+	logger.Print(FATAL, "fatal")
+	logger.Print(DEBUG, "debug")
+
+	if writer.printCalls != 4 {
+		t.Fatalf("Level(FATAL) should keep legacy behavior and allow INFO/WARN/ERROR/FATAL only, got %d writes", writer.printCalls)
+	}
+}
+
+func TestSameLevelIgnoresThresholdDifferencesForCompatibility(t *testing.T) {
+	legacy := NewLogLevel(1, "warn")
+	threshold := NewThresholdLogLevel(1, 20, "warn")
+
+	if !legacy.SameLevel(threshold) {
+		t.Fatalf("SameLevel() should continue comparing only severity index")
+	}
+	if legacy.Equal(threshold) {
+		t.Fatalf("Equal() should distinguish levels with different threshold configuration")
+	}
+}
+
+func TestSameThresholdComparesOnlyThresholdValue(t *testing.T) {
+	first := NewThresholdLogLevel(1, 20, "warn")
+	second := NewThresholdLogLevel(9, 20, "custom")
+	third := NewThresholdLogLevel(1, 30, "warn")
+
+	if !first.SameThreshold(second) {
+		t.Fatalf("SameThreshold() should ignore severity and compare threshold only")
+	}
+	if first.SameThreshold(third) {
+		t.Fatalf("SameThreshold() should detect different threshold values")
+	}
+}
+
+func TestLogLevelForMethodReturnsExpectedLevels(t *testing.T) {
+	tests := []struct {
+		name   string
+		method string
+		want   LogLevel
+	}{
+		{name: "get", method: http.MethodGet, want: HTTPGetLevel},
+		{name: "head", method: http.MethodHead, want: HTTPHeadLevel},
+		{name: "post", method: http.MethodPost, want: HTTPPostLevel},
+		{name: "put", method: http.MethodPut, want: HTTPPutLevel},
+		{name: "patch", method: http.MethodPatch, want: HTTPPatchLevel},
+		{name: "delete", method: http.MethodDelete, want: HTTPDeleteLevel},
+		{name: "options", method: http.MethodOptions, want: HTTPOptionsLevel},
+		{name: "connect", method: http.MethodConnect, want: HTTPConnectLevel},
+		{name: "trace", method: http.MethodTrace, want: HTTPTraceLevel},
+		{name: "unknown", method: "PROPFIND", want: HTTPUnknownLevel},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := LogLevelForMethod(tt.method)
+			if got.n != tt.want.n || got.t != tt.want.t || got.fg != tt.want.fg || got.bg != tt.want.bg {
+				t.Fatalf("LogLevelForMethod(%q) = %#v, want %#v", tt.method, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestNewLevelConstructorsSetExpectedSeverity(t *testing.T) {
+	tests := []struct {
+		name   string
+		got    LogLevel
+		want   LogLevel
+		wantTh uint8
+	}{
+		{name: "info", got: NewInfoLogLevel("custom"), want: INFO, wantTh: 10},
+		{name: "warn", got: NewWarnLogLevel("custom"), want: WARN, wantTh: 20},
+		{name: "error", got: NewErrorLogLevel("custom"), want: ERROR, wantTh: 30},
+		{name: "fatal", got: NewFatalLogLevel("custom"), want: FATAL, wantTh: 40},
+		{name: "debug", got: NewDebugLogLevel("custom"), want: DEBUG, wantTh: 0},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.got.n != tt.want.n {
+				t.Fatalf("%s severity = %d, want %d", tt.name, tt.got.n, tt.want.n)
+			}
+			if tt.got.th != tt.wantTh {
+				t.Fatalf("%s threshold = %d, want %d", tt.name, tt.got.th, tt.wantTh)
+			}
+			if tt.got.GetName() != "custom" {
+				t.Fatalf("%s constructor should preserve name, got %q", tt.name, tt.got.GetName())
+			}
+		})
+	}
+}
+
+func TestNewLevelConstructorsWithColorsSetExpectedFields(t *testing.T) {
+	info := NewInfoLogLevelWithColors("info-custom", FgBlue, BgYellow)
+	if info.n != INFO.n || info.GetName() != "info-custom" || info.fg != FgBlue || info.bg != BgYellow {
+		t.Fatalf("NewInfoLogLevelWithColors() = %#v", info)
+	}
+
+	warn := NewWarnLogLevelWithColors("warn-custom", FgMagenta, BgCyan)
+	if warn.n != WARN.n || warn.GetName() != "warn-custom" || warn.fg != FgMagenta || warn.bg != BgCyan {
+		t.Fatalf("NewWarnLogLevelWithColors() = %#v", warn)
+	}
+
+	errLevel := NewErrorLogLevelWithColors("error-custom", FgRed, BgWhite)
+	if errLevel.n != ERROR.n || errLevel.GetName() != "error-custom" || errLevel.fg != FgRed || errLevel.bg != BgWhite {
+		t.Fatalf("NewErrorLogLevelWithColors() = %#v", errLevel)
+	}
+
+	fatal := NewFatalLogLevelWithColors("fatal-custom", FgHiRed, BgBlack)
+	if fatal.n != FATAL.n || fatal.GetName() != "fatal-custom" || fatal.fg != FgHiRed || fatal.bg != BgBlack {
+		t.Fatalf("NewFatalLogLevelWithColors() = %#v", fatal)
+	}
+
+	debug := NewDebugLogLevelWithColors("debug-custom", FgGreen, BgDefault)
+	if debug.n != DEBUG.n || debug.GetName() != "debug-custom" || debug.fg != FgGreen || debug.bg != BgDefault {
+		t.Fatalf("NewDebugLogLevelWithColors() = %#v", debug)
+	}
+}
+
+func TestCreateTextWriterCloseOnNonCloserIsNoOp(t *testing.T) {
+	writer := CreateTextWriter(&bytes.Buffer{})
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+}
+
+func TestCreateTextWriterDoesNotCloseExternalCloser(t *testing.T) {
+	file, err := os.CreateTemp(t.TempDir(), "text-writer")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	t.Cleanup(func() {
+		_ = file.Close()
+	})
+
+	writer := CreateTextWriter(file)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := file.WriteString("still open"); err != nil {
+		t.Fatalf("CreateTextWriter() should not close external writers, got %v", err)
+	}
+}
+
+func TestCreateJsonWriterCloseOnNonCloserIsNoOp(t *testing.T) {
+	writer := CreateJsonWriter(&bytes.Buffer{}, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+}
+
+func TestCreateJsonWriterDoesNotCloseExternalCloser(t *testing.T) {
+	file, err := os.CreateTemp(t.TempDir(), "json-writer")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	t.Cleanup(func() {
+		_ = file.Close()
+	})
+
+	writer := CreateJsonWriter(file, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := file.WriteString("still open"); err != nil {
+		t.Fatalf("CreateJsonWriter() should not close external writers, got %v", err)
+	}
+}
+
+func TestJsonWriterPrintAllowsEmptyMessages(t *testing.T) {
+	var buf bytes.Buffer
+	writer := CreateJsonWriter(&buf, false)
+
+	if err := writer.Print(INFO, "TEST", nil); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+
+	var message LoggerJsonMessage
+	if err := json.Unmarshal(buf.Bytes(), &message); err != nil {
+		t.Fatalf("json.Unmarshal() error = %v", err)
+	}
+	if message.Message != "" {
+		t.Fatalf("message should be empty, got %q", message.Message)
+	}
+}
+
+func TestJsonWriterPrintPreservesTrailingNewlineSemantic(t *testing.T) {
+	var buf bytes.Buffer
+	writer := CreateJsonWriter(&buf, false)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello\n"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+
+	data := buf.Bytes()
+	if !bytes.HasSuffix(data, []byte("\n")) {
+		t.Fatalf("JSON output should end with newline, got %q", data)
+	}
+
+	var message LoggerJsonMessage
+	if err := json.Unmarshal(bytes.TrimSuffix(data, []byte("\n")), &message); err != nil {
+		t.Fatalf("json.Unmarshal() error = %v", err)
+	}
+	if message.Message != "hello" {
+		t.Fatalf("message should not include trailing newline, got %q", message.Message)
+	}
+}
+
+func TestTextWriterPrintlnDoesNotLeaveTrailingMessageSeparator(t *testing.T) {
+	var buf bytes.Buffer
+	formatter := NewFormatter().
+		SetFormat("%m (%S)").
+		SetColorOutput(false)
+	writer := CreateTextWriter(&buf).SetFormatter(formatter)
+
+	if err := writer.Print(DEBUG, "TEST", nil, "debug details", "\n"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+
+	got := strings.TrimSuffix(buf.String(), "\n")
+	if got != "debug details (%S)" {
+		t.Fatalf("println newline marker should not leave trailing message separator, got %q", got)
+	}
+}
+
+func TestTextWriterPrintlnDoesNotLeaveTrailingMessageSeparatorAfterReplacement(t *testing.T) {
+	var buf bytes.Buffer
+	formatter := NewFormatter().
+		SetFormat("%m (%S)").
+		SetColorOutput(false)
+	writer := CreateTextWriter(&buf).SetFormatter(formatter)
+	logger := CreateLogger().
+		SetLevel(DEBUG).
+		AddWriter(writer).
+		AddReplacer("details", "details")
+
+	logger.Debugln("debug details")
+
+	got := strings.TrimSuffix(buf.String(), "\n")
+	if got != "debug details (%S)" {
+		t.Fatalf("println newline marker should not leave trailing message separator after replacements, got %q", got)
+	}
+}
+
+func TestJsonWriterPrintlnDoesNotLeaveTrailingMessageSeparator(t *testing.T) {
+	var buf bytes.Buffer
+	writer := CreateJsonWriter(&buf, false)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello", "\n"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+
+	var message LoggerJsonMessage
+	if err := json.Unmarshal(bytes.TrimSuffix(buf.Bytes(), []byte("\n")), &message); err != nil {
+		t.Fatalf("json.Unmarshal() error = %v", err)
+	}
+	if message.Message != "hello" {
+		t.Fatalf("message should not include trailing separator from newline marker, got %q", message.Message)
+	}
+}
+
+func TestLogLevelForegroundSettersOverridePreviousColorMode(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+	formatter := NewFormatter()
+
+	level.SetFgColor(FgRed)
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, FgRed.String()) {
+		t.Fatalf("expected plain foreground color prefix %q, got %q", FgRed.String(), got)
+	}
+
+	level.SetForeground256Color(FgColor256(123))
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, FgColor256(123).String()) {
+		t.Fatalf("expected 256-color foreground prefix %q, got %q", FgColor256(123).String(), got)
+	}
+
+	level.SetForegroundRGB(1, 2, 3)
+	expectedRGB := NewFgColorRGB(1, 2, 3).String()
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, expectedRGB) {
+		t.Fatalf("expected RGB foreground prefix %q, got %q", expectedRGB, got)
+	}
+
+	level.SetFgColor(FgBlue)
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, FgBlue.String()) {
+		t.Fatalf("expected last plain foreground color to win with prefix %q, got %q", FgBlue.String(), got)
+	}
+}
+
+func TestLogLevelBackgroundSettersOverridePreviousColorMode(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+	formatter := NewFormatter()
+
+	level.SetBgColor(BgRed)
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, BgRed.String()) {
+		t.Fatalf("expected plain background color prefix %q, got %q", BgRed.String(), got)
+	}
+
+	level.SetBackground256Color(BgColor256(123))
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, BgColor256(123).String()) {
+		t.Fatalf("expected 256-color background prefix %q, got %q", BgColor256(123).String(), got)
+	}
+
+	level.SetBackgroundRGB(1, 2, 3)
+	expectedRGB := NewBgColorRGB(1, 2, 3).String()
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, expectedRGB) {
+		t.Fatalf("expected RGB background prefix %q, got %q", expectedRGB, got)
+	}
+
+	level.SetBgColor(BgBlue)
+	if got := formatter.ColorizeString("x", level); !strings.HasPrefix(got, BgBlue.String()) {
+		t.Fatalf("expected last plain background color to win with prefix %q, got %q", BgBlue.String(), got)
+	}
+}
+
+func TestLogLevelAttributesAffectColorizedOutput(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+	level.AddAttribute(Italic).AddAttribute(Bold)
+
+	got := NewFormatter().ColorizeString("x", level)
+	if !strings.Contains(got, Italic.String()) {
+		t.Fatalf("expected italic attribute in colorized output, got %q", got)
+	}
+	if !strings.Contains(got, Bold.String()) {
+		t.Fatalf("expected bold attribute in colorized output, got %q", got)
+	}
+}
+
+func TestLogLevelRemoveAttributeRemovesAllMatches(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+	level.AddAttribute(Bold).AddAttribute(Italic).AddAttribute(Bold)
+
+	level.RemoveAttribute(Bold)
+
+	got := level.GetAttributes()
+	if len(got) != 1 || got[0] != Italic {
+		t.Fatalf("expected only italic attribute to remain, got %#v", got)
+	}
+}
+
+func TestLogLevelSetAttributesCopiesInputSlice(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+	attrs := []Attribute{Bold, Italic}
+
+	level.SetAttributes(attrs)
+	attrs[0] = Underline
+
+	got := level.GetAttributes()
+	if len(got) != 2 || got[0] != Bold || got[1] != Italic {
+		t.Fatalf("expected SetAttributes to copy input slice, got %#v", got)
+	}
+}
+
+func TestLogLevelGetAttributesReturnsCopy(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+	level.SetAttributes([]Attribute{Bold, Italic})
+
+	got := level.GetAttributes()
+	got[0] = Underline
+
+	again := level.GetAttributes()
+	if len(again) != 2 || again[0] != Bold || again[1] != Italic {
+		t.Fatalf("expected GetAttributes to return a copy, got %#v", again)
+	}
+}
+
+func TestLogLevelDeprecatedForegroundAccessorsRemainCompatible(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+
+	level.SetFgColor(FgBlue)
+	if got := level.GetFgColor(); got != FgBlue {
+		t.Fatalf("expected deprecated foreground accessors to round-trip %v, got %v", FgBlue, got)
+	}
+
+	level.SetForegroundColor(FgRed)
+	if got := level.GetFgColor(); got != FgRed {
+		t.Fatalf("expected deprecated getter to reflect new foreground setter, got %v", got)
+	}
+}
+
+func TestLogLevelDeprecatedBackgroundAccessorsRemainCompatible(t *testing.T) {
+	level := NewLogLevel(0, "custom")
+
+	level.SetBgColor(BgBlue)
+	if got := level.GetBgColor(); got != BgBlue {
+		t.Fatalf("expected deprecated background accessors to round-trip %v, got %v", BgBlue, got)
+	}
+
+	level.SetBackgroundColor(BgRed)
+	if got := level.GetBgColor(); got != BgRed {
+		t.Fatalf("expected deprecated getter to reflect new background setter, got %v", got)
+	}
+}
+
+func TestFormatterHandlesEmptyTracebackPlaceholders(t *testing.T) {
+	formatter := NewFormatter().
+		SetFormat("%m|%b|%B|%M|%f|%n|%s|%p")
+
+	got := formatter.FormatMessage(INFO, "TEST", nil, "hello")
+	if got != "hello|||||||" {
+		t.Fatalf("empty traceback placeholders should be empty, got %q", got)
+	}
+}
+
+func TestFormatterDoesNotInterpretPlaceholdersInsideMessages(t *testing.T) {
+	formatter := NewFormatter().
+		SetFormat("%L:%m")
+
+	message := "literal %L %s %p"
+	got := formatter.FormatMessage(INFO, "TEST", nil, message)
+	if got != "INFO:literal %L %s %p" {
+		t.Fatalf("message placeholder-looking text should stay literal, got %q", got)
+	}
+}
+
+func TestNewFormatterDoesNotMutateDefaultFormatter(t *testing.T) {
+	formatter := NewFormatter()
+	formatter.SetFormat("custom")
+
+	if DefaultTextFormatter.Format == "custom" {
+		t.Fatal("NewFormatter() should return a copy, not mutate DefaultTextFormatter")
+	}
+}
+
+func TestTextWriterColorOutputHonorsColorOnlyStdoutFalse(t *testing.T) {
+	var buf bytes.Buffer
+	formatter := NewFormatter().
+		SetFormat("%m").
+		SetColorOutput(true).
+		SetColorOnlyStdout(false)
+	writer := CreateTextWriter(&buf).SetFormatter(formatter)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+	if !strings.Contains(buf.String(), "\x1b[") {
+		t.Fatalf("ColorOnlyStdout(false) should allow color for external writers, got %q", buf.String())
+	}
+}
+
+func TestTextWriterColorOutputCanBeDisabled(t *testing.T) {
+	var buf bytes.Buffer
+	formatter := NewFormatter().
+		SetFormat("%m").
+		SetColorOutput(false).
+		SetColorOnlyStdout(false)
+	writer := CreateTextWriter(&buf).SetFormatter(formatter)
+
+	if err := writer.Print(INFO, "TEST", nil, "hello"); err != nil {
+		t.Fatalf("Print() error = %v", err)
+	}
+	if strings.Contains(buf.String(), "\x1b[") {
+		t.Fatalf("SetColorOutput(false) should disable color output, got %q", buf.String())
+	}
+}
+
+func TestCreateTextStdoutWriterDoesNotCloseStdout(t *testing.T) {
+	stdoutFile := swapStdout(t)
+
+	writer := CreateTextStdoutWriter()
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := stdoutFile.WriteString("still open"); err != nil {
+		t.Fatalf("stdout writer Close() should not close stdout, got %v", err)
+	}
+}
+
+func TestCreateJsonStdoutWriterDoesNotCloseStdout(t *testing.T) {
+	stdoutFile := swapStdout(t)
+
+	writer := CreateJsonStdoutWriter(false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := stdoutFile.WriteString("still open"); err != nil {
+		t.Fatalf("stdout writer Close() should not close stdout, got %v", err)
+	}
+}
+
+func TestGetFullTracebackSkipsRuntimeAndSneklogFrames(t *testing.T) {
+	tracebacks := captureTracebackForTest()
+	if len(tracebacks) == 0 {
+		t.Fatal("expected at least one traceback frame")
+	}
+
+	first := tracebacks[0]
+	if first.Method != "captureTracebackForTest" {
+		t.Fatalf("first frame should be the nearest user frame, got %s", first.Method)
+	}
+	for _, tb := range tracebacks {
+		if strings.HasPrefix(tb.Signature, "runtime.") {
+			t.Fatalf("runtime frame should be filtered out, got %s", tb.Signature)
+		}
+		if _, ok := internalTracebackMethods[tb.Method]; ok {
+			t.Fatalf("internal sneklog frame should be filtered out, got %s", tb.Signature)
+		}
+	}
+}
+
+func TestGetTracebackReturnsNearestUserFrame(t *testing.T) {
+	tb := captureSingleTracebackForTest()
+	if tb == nil {
+		t.Fatal("expected traceback frame")
+	}
+	if tb.Method != "captureSingleTracebackForTest" {
+		t.Fatalf("expected nearest user frame, got %s", tb.Method)
+	}
+	if strings.HasPrefix(tb.Signature, "runtime.") {
+		t.Fatalf("runtime frame should be filtered out, got %s", tb.Signature)
+	}
+	if _, ok := internalTracebackMethods[tb.Method]; ok {
+		t.Fatalf("internal sneklog frame should be filtered out, got %s", tb.Signature)
+	}
+}
+
+func swapStdout(t *testing.T) *os.File {
+	t.Helper()
+
+	oldStdout := os.Stdout
+	stdoutFile, err := os.CreateTemp(t.TempDir(), "stdout")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	os.Stdout = stdoutFile
+	t.Cleanup(func() {
+		os.Stdout = oldStdout
+		_ = stdoutFile.Close()
+	})
+	return stdoutFile
+}
+
+func captureTracebackForTest() []*MethodTraceback {
+	return getFullTraceback(0)
+}
+
+func captureSingleTracebackForTest() *MethodTraceback {
+	return getTraceback()
+}
@@ -0,0 +1,164 @@
+package sneklog
+
+import "strings"
+
+// Predefined strftime-like time layouts.
+const (
+	Layout   = "%m/%d %I:%M:%S%p '%y %z"
+	ANSIC    = "%a %b %e %H:%M:%S %Y"
+	UnixDate = "%a %b %e %H:%M:%S %Z %Y"
+	RubyDate = "%a %b %d %H:%M:%S %z %Y"
+
+	RFC822      = "%d %b %y %H:%M %Z"
+	RFC822Z     = "%d %b %y %H:%M %z"
+	RFC850      = "%A, %d-%b-%y %H:%M:%S %Z"
+	RFC1123     = "%a, %d %b %Y %H:%M:%S %Z"
+	RFC1123Z    = "%a, %d %b %Y %H:%M:%S %z"
+	RFC3339     = "%Y-%m-%dT%H:%M:%S%:z"
+	RFC3339Nano = "%Y-%m-%dT%H:%M:%S%#N%:z"
+	Kitchen     = "%-I:%M%p"
+
+	Stamp      = "%b %e %H:%M:%S"
+	StampMilli = "%b %e %H:%M:%S.%L"
+	StampMicro = "%b %e %H:%M:%S.%f"
+	StampNano  = "%b %e %H:%M:%S.%N"
+	DateTime   = "%Y-%m-%d %H:%M:%S"
+	DateOnly   = "%Y-%m-%d"
+	TimeOnly   = "%H:%M:%S"
+)
+
+type rule struct {
+	strf     string
+	goLayout string
+}
+
+var strftimeToGoRules = []rule{
+	// Long/special tokens first.
+	{"%::z", "Z07:00:00"},
+	{"%:::z", "Z07"},
+	{"%:z", "Z07:00"},
+
+	{"%#N", ".999999999"},
+	{"%#f", ".999999"},
+	{"%#L", ".999"},
+
+	{"%-m", "1"},
+	{"%#m", "1"},
+	{"%-d", "2"},
+	{"%#d", "2"},
+	{"%-H", "15"},
+	{"%#H", "15"},
+	{"%-I", "3"},
+	{"%#I", "3"},
+	{"%-M", "4"},
+	{"%#M", "4"},
+	{"%-S", "5"},
+	{"%#S", "5"},
+
+	{"%%", "%"},
+
+	{"%Y", "2006"},
+	{"%y", "06"},
+
+	{"%B", "January"},
+	{"%b", "Jan"},
+	{"%h", "Jan"},
+	{"%m", "01"},
+
+	{"%d", "02"},
+	{"%e", "_2"},
+
+	{"%A", "Monday"},
+	{"%a", "Mon"},
+
+	{"%H", "15"},
+	{"%I", "03"},
+	{"%M", "04"},
+	{"%S", "05"},
+
+	{"%p", "PM"},
+
+	{"%z", "-0700"},
+	{"%Z", "MST"},
+
+	{"%N", "000000000"},
+	{"%f", "000000"},
+	{"%L", "000"},
+
+	{"%F", "2006-01-02"},
+	{"%T", "15:04:05"},
+	{"%R", "15:04"},
+	{"%D", "01/02/06"},
+	{"%r", "03:04:05 PM"},
+}
+
+// StrftimeToGo converts a strftime-like layout into a Go time layout.
+func StrftimeToGo(format string) string {
+	var out strings.Builder
+
+	for i := 0; i < len(format); {
+		if format[i] != '%' {
+			out.WriteByte(format[i])
+			i++
+			continue
+		}
+
+		matched := false
+		for _, r := range strftimeToGoRules {
+			if strings.HasPrefix(format[i:], r.strf) {
+				out.WriteString(r.goLayout)
+				i += len(r.strf)
+				matched = true
+				break
+			}
+		}
+
+		if !matched {
+			// Можно заменить на ошибку, если хочешь strict mode.
+			out.WriteByte(format[i])
+			i++
+		}
+	}
+
+	return out.String()
+}
+
+// GoToStrftime converts a Go time layout into an approximate strftime-like layout.
+func GoToStrftime(format string) string {
+	format = strings.ReplaceAll(format, "2006", "%Y")
+	format = strings.ReplaceAll(format, "06", "%y")
+
+	format = strings.ReplaceAll(format, "15", "%H")
+	format = strings.ReplaceAll(format, "03", "%I")
+	format = strings.ReplaceAll(format, "3", "%-I")
+	format = strings.ReplaceAll(format, "3", "%#I")
+
+	format = strings.ReplaceAll(format, "January", "%B")
+	format = strings.ReplaceAll(format, "Jan", "%b")
+	format = strings.ReplaceAll(format, "01", "%m")
+	format = strings.ReplaceAll(format, "1", "%-m")
+
+	format = strings.ReplaceAll(format, "02", "%d")
+	format = strings.ReplaceAll(format, "_2", "%e")
+	format = strings.ReplaceAll(format, "2", "%-d")
+
+	format = strings.ReplaceAll(format, "Monday", "%A")
+	format = strings.ReplaceAll(format, "Mon", "%a")
+
+	format = strings.ReplaceAll(format, "04", "%M")
+	format = strings.ReplaceAll(format, "05", "%S")
+	format = strings.ReplaceAll(format, ".999999999", "%#N")
+	format = strings.ReplaceAll(format, "000000000", "%N")
+	format = strings.ReplaceAll(format, ".999999", "%#f")
+	format = strings.ReplaceAll(format, "000000", "%f")
+	format = strings.ReplaceAll(format, ".999", "%#L")
+	format = strings.ReplaceAll(format, "000", "%L")
+	format = strings.ReplaceAll(format, "PM", "%p")
+
+	format = strings.ReplaceAll(format, "-0700", "%z")
+	format = strings.ReplaceAll(format, "MST", "%Z")
+	format = strings.ReplaceAll(format, "Z07:00", "%:z")
+	format = strings.ReplaceAll(format, "Z07:00:00", "%::z")
+	format = strings.ReplaceAll(format, "Z07", "%:::z")
+	return format
+}
@@ -1,60 +1,84 @@
-package slog
+package sneklog

 import (
 	"runtime"
-	"sort"
 	"strings"
 )

-func getTraceback() *MethodTraceback {
-	caller, _, _, _ := runtime.Caller(5)
-	details := runtime.FuncForPC(caller)
-	signature := details.Name()
-	path, line := details.FileLine(caller)
-	splitPath := strings.Split(path, "/")
-
-	splitSignature := strings.Split(signature, ".")
-	method := splitSignature[len(splitSignature)-1]
-
-	tb := &MethodTraceback{
-		Filename:  splitPath[len(splitPath)-1],
-		FullPath:  path,
-		Line:      line,
-		Signature: signature,
-		Method:    method,
-	}
-
-	return tb
+var internalTracebackMethods = map[string]struct{}{
+	"Infof":             {},
+	"Info":              {},
+	"Infoln":            {},
+	"Warnf":             {},
+	"Warn":              {},
+	"Warnln":            {},
+	"Errorf":            {},
+	"Error":             {},
+	"Errorln":           {},
+	"Fatalf":            {},
+	"Fatal":             {},
+	"Fatalln":           {},
+	"Debugf":            {},
+	"Debug":             {},
+	"Debugln":           {},
+	"print":             {},
+	"println":           {},
+	"reportWriterError": {},
+	"getTraceback":      {},
+	"getFullTraceback":  {},
 }
+
+func getTraceback() *MethodTraceback {
+	tracebacks := getFullTraceback(0)
+	if len(tracebacks) == 0 {
+		return nil
+	}
+	return tracebacks[0]
+}
+
 func getFullTraceback(skip int) []*MethodTraceback {
 	pc := make([]uintptr, 15)
-	runtime.Callers(skip, pc)
+	n := runtime.Callers(skip+2, pc)
 	list := make([]*MethodTraceback, 0)
-	frames := runtime.CallersFrames(pc)
+	frames := runtime.CallersFrames(pc[:n])
 	for {
 		frame, more := frames.Next()
+		tb := buildMethodTraceback(frame.PC)
+		if tb != nil && !isInternalTraceback(tb) {
+			list = append(list, tb)
+		}
 		if !more {
 			break
 		}
-		details := runtime.FuncForPC(frame.PC)
-		signature := details.Name()
-		path, line := details.FileLine(frame.PC)
-		splitPath := strings.Split(path, "/")
+	}
+	return list
+}

+func buildMethodTraceback(pc uintptr) *MethodTraceback {
+	details := runtime.FuncForPC(pc)
+	if details == nil {
+		return nil
+	}
+
+	signature := details.Name()
+	path, line := details.FileLine(pc)
+	splitPath := strings.Split(path, "/")
 	splitSignature := strings.Split(signature, ".")
 	method := splitSignature[len(splitSignature)-1]

-		tb := &MethodTraceback{
+	return &MethodTraceback{
 		Filename:  splitPath[len(splitPath)-1],
 		FullPath:  path,
 		Line:      line,
 		Signature: signature,
 		Method:    method,
 	}
-		list = append(list, tb)
+}
+
+func isInternalTraceback(tb *MethodTraceback) bool {
+	if strings.HasPrefix(tb.Signature, "runtime.") {
+		return true
 	}
-	sort.Slice(list, func(i, j int) bool {
-		return j < i
-	})
-	return list
+	_, ok := internalTracebackMethods[tb.Method]
+	return ok
 }
@@ -1,5 +1,6 @@
-package slog
+package sneklog

+// Map applies f to each element of s and returns the resulting slice.
 func Map[T, R any](s []T, f func(T) R) []R {
 	out := make([]R, len(s))
 	for i, el := range s {
@@ -1,7 +1,6 @@
-package slog
+package sneklog

 import (
-	"bufio"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -11,67 +10,139 @@ import (
 	"time"
 )

+// LoggerWriter is the common sink interface used by Logger.
 type LoggerWriter interface {
 	Close() error
 	Write(p []byte) (n int, err error)
 	Print(level LogLevel, prefix string, traceback []*MethodTraceback, messages ...any) error
 }

+// PrepareMessages normalizes message parts and extracts a trailing newline marker.
+func PrepareMessages(messages ...any) (bool, []any) {
+	msg := Map(messages, func(el any) string { return fmt.Sprint(el) })
+	newline := false
+	if len(msg) > 0 && strings.HasSuffix(msg[len(msg)-1], "\n") {
+		newline = true
+		msg[len(msg)-1] = strings.TrimSuffix(msg[len(msg)-1], "\n")
+		if msg[len(msg)-1] == "" {
+			msg = msg[:len(msg)-1]
+		}
+	}
+	return newline, Map(msg, func(el string) any { return any(el) })
+}
+
+// LoggerTextWriter writes human-readable log records to an io.Writer.
 type LoggerTextWriter struct {
 	LoggerWriter
 	writer    io.Writer
-	printTraceback bool
-	printTime      bool
+	closer    io.Closer
+	formatter *Formatter
 }

-func (w *LoggerTextWriter) Write(p []byte) (n int, err error) {
-	n, err = w.writer.Write(p)
-	if err != nil {
-		return n, err
+// SetFormatter replaces the formatter used by the text writer.
+func (w *LoggerTextWriter) SetFormatter(formatter *Formatter) *LoggerTextWriter {
+	w.formatter = formatter
+	return w
+}
+
+// Formatter returns the effective formatter for the text writer.
+func (w *LoggerTextWriter) Formatter() *Formatter {
+	if w.formatter == nil {
+		return DefaultTextFormatter
 	}
-	err = bufio.NewWriter(w.writer).Flush()
-	return n, err
-}
-func (w *LoggerTextWriter) Print(level LogLevel, prefix string, _ []*MethodTraceback, messages ...any) error {
-	s := BuildString(level, prefix, w.printTime, w.printTraceback, messages...)
-	_, err := w.Write([]byte(s))
-	return err
-}
-func (w *LoggerTextWriter) Close() error {
-	return w.writer.(io.Closer).Close()
+	return w.formatter
 }

-// LoggerJsonWriter write into writer JSON
+// Write forwards raw bytes to the underlying writer.
+func (w *LoggerTextWriter) Write(p []byte) (n int, err error) {
+	return w.writer.Write(p)
+}
+
+// Print formats the provided record as text and writes it to the underlying writer.
+func (w *LoggerTextWriter) Print(level LogLevel, prefix string, traceback []*MethodTraceback, messages ...any) error {
+	newline, messages := PrepareMessages(messages...)
+
+	f := w.Formatter()
+	s := f.FormatMessage(level, prefix, traceback, messages...)
+	if f.ColorOutput && (!f.ColorOnlyStdout || w.writer == os.Stdout || w.writer == os.Stderr) {
+		s = f.ColorizeString(s, level)
+	}
+
+	_, err := w.Write([]byte(s))
+	if err != nil {
+		return err
+	}
+	if newline {
+		_, err = w.Write([]byte("\n"))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Close closes the owned writer, if any.
+func (w *LoggerTextWriter) Close() error {
+	if w.closer == nil {
+		return nil
+	}
+	return w.closer.Close()
+}
+
+// LoggerJsonWriter writes structured log records as JSON.
 type LoggerJsonWriter struct {
 	LoggerWriter
 	writer io.Writer
+	closer io.Closer
 	pretty bool
+
+	formatter *Formatter
 }
+
+// Formatter returns the effective formatter for the JSON writer.
+func (w *LoggerJsonWriter) Formatter() *Formatter {
+	if w.formatter == nil {
+		return DefaultJsonFormatter
+	}
+	return w.formatter
+}
+
+// SetFormatter replaces the formatter used by the JSON writer.
+func (w *LoggerJsonWriter) SetFormatter(f *Formatter) *LoggerJsonWriter {
+	w.formatter = f
+	return w
+}
+
+// LoggerJsonMessage is the JSON payload emitted by LoggerJsonWriter.
 type LoggerJsonMessage struct {
-	Time      time.Time          `json:"time"`
+	Time    string `json:"time"`
 	Level   string `json:"level"`
 	Prefix  string `json:"prefix"`
 	Message string `json:"message"`
+
 	Traceback []*MethodTraceback `json:"traceback"`
 }

+// Write forwards raw bytes to the underlying writer.
 func (w *LoggerJsonWriter) Write(data []byte) (int, error) {
-	n, err := w.writer.Write(data)
-	if err != nil {
-		return n, err
-	}
-	err = bufio.NewWriter(w.writer).Flush()
-	return n, err
+	return w.writer.Write(data)
 }
+
+// Print encodes the provided record as JSON and writes it to the underlying writer.
 func (w *LoggerJsonWriter) Print(level LogLevel, prefix string, traceback []*MethodTraceback, messages ...any) error {
-	msg := Map(messages, func(el any) string {
-		return fmt.Sprintf("%v", el)
-	})
+	newline, messages := PrepareMessages(messages...)
+
+	f := w.Formatter()
+	s := f.FormatMessage(level, prefix, traceback, messages...)
+	if f.ColorOutput && (!f.ColorOnlyStdout || w.writer == os.Stdout || w.writer == os.Stderr) {
+		s = f.ColorizeString(s, level)
+	}
+
 	m := LoggerJsonMessage{
-		Time:      time.Now(),
+		Time:      f.FormatTime(time.Now()),
 		Level:     level.GetName(),
 		Prefix:    prefix,
-		Message:   strings.Join(msg, " "),
+		Message:   s,
 		Traceback: traceback,
 	}
 	var data []byte
@@ -84,20 +155,33 @@ func (w *LoggerJsonWriter) Print(level LogLevel, prefix string, traceback []*Met
 	if err != nil {
 		return err
 	}
-	_, err = w.Write(append(data, []byte("\n")...))
+	if newline {
+		data = append(data, '\n')
+	}
+	_, err = w.Write(data)
 	return err
 }
+
+// Close closes the owned writer, if any.
 func (w *LoggerJsonWriter) Close() error {
-	return w.writer.(io.Closer).Close()
+	if w.closer == nil {
+		return nil
+	}
+	return w.closer.Close()
 }

-func CreateTextWriter(w io.Writer, printTraceback, printTime bool) *LoggerTextWriter {
+// CreateTextWriter wraps an external writer for text output without taking
+// ownership of it.
+func CreateTextWriter(w io.Writer) *LoggerTextWriter {
 	writer := &LoggerTextWriter{
-		writer: w, printTraceback: printTraceback, printTime: printTime,
+		writer: w,
 	}
 	return writer
 }
-func CreateTextFileWriter(path string, printTraceback, printTime bool) (*LoggerTextWriter, error) {
+
+// CreateTextFileWriter creates a text writer for path, creating parent
+// directories as needed. The returned writer owns the opened file.
+func CreateTextFileWriter(path string) (*LoggerTextWriter, error) {
 	err := os.MkdirAll(filepath.Dir(path), os.ModePerm)
 	if err != nil {
 		return nil, err
@@ -106,21 +190,38 @@ func CreateTextFileWriter(path string, printTraceback, printTime bool) (*LoggerT
 	if err != nil {
 		return nil, err
 	}
-	return CreateTextWriter(file, printTraceback, printTime), nil
-}
-func CreateTextStdoutWriter(printTraceback, printTime bool) *LoggerTextWriter {
-	return CreateTextWriter(os.Stdout, printTraceback, printTime)
+	writer := CreateTextWriter(file)
+	writer.closer = file
+	return writer, nil
 }

+// CreateTextStdoutWriter creates a text writer for os.Stdout without taking
+// ownership of stdout.
+func CreateTextStdoutWriter() *LoggerTextWriter {
+	writer := CreateTextWriter(os.Stdout)
+	writer.closer = nil
+	return writer
+}
+
+// CreateJsonWriter wraps an external writer for JSON output without taking
+// ownership of it.
 func CreateJsonWriter(w io.Writer, pretty bool) *LoggerJsonWriter {
 	writer := &LoggerJsonWriter{
 		writer: w, pretty: pretty,
 	}
 	return writer
 }
+
+// CreateJsonStdoutWriter creates a JSON writer for os.Stdout without taking
+// ownership of stdout.
 func CreateJsonStdoutWriter(pretty bool) *LoggerJsonWriter {
-	return CreateJsonWriter(os.Stdout, pretty)
+	writer := CreateJsonWriter(os.Stdout, pretty)
+	writer.closer = nil
+	return writer
 }
+
+// CreateJsonFileWriter creates a JSON writer for path, creating parent
+// directories as needed. The returned writer owns the opened file.
 func CreateJsonFileWriter(path string, pretty bool) (*LoggerJsonWriter, error) {
 	err := os.MkdirAll(filepath.Dir(path), os.ModePerm)
 	if err != nil {
@@ -130,5 +231,7 @@ func CreateJsonFileWriter(path string, pretty bool) (*LoggerJsonWriter, error) {
 	if err != nil {
 		return nil, err
 	}
-	return CreateJsonWriter(file, pretty), nil
+	writer := CreateJsonWriter(file, pretty)
+	writer.closer = file
+	return writer, nil
 }
Author	SHA1	Message	Date
ScuroNeko	e6d15b530f	(new): add threshold-based log level filtering and docs Golang lint / lint (push) Successful in 1m36s Details - add threshold-aware LogLevel constructors - add Logger.SetThresholdMode and SameThreshold - preserve legacy SameLevel behavior for compatibility - extend tests for threshold mode and compatibility - update README and release notes for v2.2.0	2026-04-28 09:45:40 +03:00
ScuroNeko	b7fa3f7606	(chore): document and test new LogLevel APIs Golang lint / lint (push) Successful in 47s Details - add godoc for SameLevel and Equal - update package docs and READMEs with new helpers - refresh unreleased release notes - add tests for Printf, HTTP method levels, and level constructors	2026-04-27 17:04:41 +03:00
ScuroNeko	812caed471	(new): add log level helpers and HTTP method levels Golang lint / lint (push) Successful in 42s Details - move LogLevel and predefined levels into levels.go - add level-specific constructors for info/warn/error/fatal/debug - add predefined HTTP method log levels and LogLevelForMethod - unify Logger Print/Println internals and add Printf - improve GoDoc coverage for exported APIs	2026-04-27 16:36:30 +03:00
ScuroNeko	3eac1851ec	(new): prepare v2.1.0 release Golang lint / lint (push) Successful in 24s Details - add custom LogLevel constructors and richer color configuration - support ANSI, 256-color, RGB, and text attributes on LogLevel - introduce clearer preferred APIs such as NewLogger and SetName - preserve backward compatibility with deprecated wrappers for v2.0.1 APIs - restore legacy ColorStringBuilder signatures as compatibility wrappers - fix newline separator handling in Println-style output - add tests for color precedence, deprecated aliases, and LogLevel attributes - update GoDoc and bilingual README documentation	2026-04-27 15:42:24 +03:00
ScuroNeko	b4c9203a79	(fix): lint error Golang lint / lint (push) Successful in 50s Details	2026-04-27 10:24:53 +03:00
ScuroNeko	19f8750d35	(fix): module declaration slog->sneklog Golang lint / lint (push) Failing after 48s Details	2026-04-27 09:56:46 +03:00
ScuroNeko	d534f92d48	(refactor): prepare breaking v2 API - rename package to sneklog and move module to /v2 - replace text output flags with writer formatters - remove external color dependencies - update migration notes and coverage	2026-04-24 15:43:14 +03:00
ScuroNeko	14b787710c	Merge branch 'main' of scuroneko.dev:ScuroNeko/slog	2026-04-20 18:11:30 +03:00
ScuroNeko	9268e222ab	feat: add message replacement for log records Add Logger.AddReplacer to mask or normalize message text before records reach writers. Document replacement behavior in README and package GoDoc, and update the example. Also fix JSON writer edge cases: - avoid panic on empty message lists - preserve newline semantics when the last message already ends with n - keep original message argument types for custom writers when no replacers are configured Update dependencies and add release notes for the next release.	2026-04-20 18:00:11 +03:00
ScuroNeko	6456d4d95d	update package name to new domain	2026-03-30 00:02:39 +03:00
ScuroNeko	5d96c6fbae	version bump	2026-03-17 15:41:00 +03:00
ScuroNeko	badee2c598	docs: add godoc and bilingual README	2026-03-17 15:33:11 +03:00
ScuroNeko	6112a707c7	fix: prevent logger close recursion and unsafe writer closing	2026-03-17 14:43:28 +03:00
ScuroNeko	956755fe82	license; v1.0.2	2026-01-29 11:56:48 +03:00
ScuroNeko	44ab702369	v1.0.1	2026-01-29 10:57:55 +03:00