package sneklog

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"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
	closer    io.Closer
	formatter *Formatter
}

// 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
	}
	return w.formatter
}

// 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    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) {
	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 {
	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:      f.FormatTime(time.Now()),
		Level:     level.GetName(),
		Prefix:    prefix,
		Message:   s,
		Traceback: traceback,
	}

	buf := bytes.NewBuffer(nil)
	enc := json.NewEncoder(buf)
	enc.SetEscapeHTML(f.JSONEscapeHTML)
	if w.pretty {
		enc.SetIndent("", "  ")
	}

	err := enc.Encode(m)
	if err != nil {
		return err
	}
	data := buf.Bytes()
	if !newline {
		data = bytes.TrimSuffix(data, []byte("\n"))
	}
	_, err = w.writer.Write(data)
	if err != nil {
		return err
	}
	return nil
}

// Close closes the owned writer, if any.
func (w *LoggerJsonWriter) Close() error {
	if w.closer == nil {
		return nil
	}
	return w.closer.Close()
}

// CreateTextWriter wraps an external writer for text output without taking
// ownership of it.
func CreateTextWriter(w io.Writer) *LoggerTextWriter {
	writer := &LoggerTextWriter{
		writer: w,
	}
	return writer
}

// 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
	}
	file, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return nil, err
	}
	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 {
	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 {
		return nil, err
	}
	file, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return nil, err
	}
	writer := CreateJsonWriter(file, pretty)
	writer.closer = file
	return writer, nil
}