(new): add log level helpers and HTTP method levels

- 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

levels.go

@@ -0,0 +1,198 @@
+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
+	t string
+
+	fg    FgColor
+	fg256 FgColor256
+	fgRgb FgColorRGB
+
+	bg    BgColor
+	bg256 BgColor256
+	bgRgb BgColorRGB
+
+	attrs []Attribute
+}
+
+// NewLogLevel creates a log level without predefined colors.
+func NewLogLevel(index uint8, name string) LogLevel {
+	return NewLogLevelWithColors(index, name, 0, 0)
+}
+
+// NewLogLevelWithColors creates a log level with ANSI foreground and background colors.
+func NewLogLevelWithColors(index uint8, name string, fg FgColor, bg BgColor) LogLevel {
+	return LogLevel{n: index, t: name, fg: fg, bg: bg, attrs: []Attribute{}}
+}
+
+// NewInfoLogLevel creates an info-level log level without predefined colors.
+func NewInfoLogLevel(name string) LogLevel { return NewLogLevel(0, name) }
+
+// NewInfoLogLevelWithColors creates an info-level log level with ANSI colors.
+func NewInfoLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewLogLevelWithColors(0, name, fg, bg)
+}
+
+// NewWarnLogLevel creates a warn-level log level without predefined colors.
+func NewWarnLogLevel(name string) LogLevel { return NewLogLevel(1, name) }
+
+// NewWarnLogLevelWithColors creates a warn-level log level with ANSI colors.
+func NewWarnLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewLogLevelWithColors(1, name, fg, bg)
+}
+
+// NewErrorLogLevel creates an error-level log level without predefined colors.
+func NewErrorLogLevel(name string) LogLevel { return NewLogLevel(2, name) }
+
+// NewErrorLogLevelWithColors creates an error-level log level with ANSI colors.
+func NewErrorLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewLogLevelWithColors(2, name, fg, bg)
+}
+
+// NewFatalLogLevel creates a fatal-level log level without predefined colors.
+func NewFatalLogLevel(name string) LogLevel { return NewLogLevel(3, name) }
+
+// NewFatalLogLevelWithColors creates a fatal-level log level with ANSI colors.
+func NewFatalLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewLogLevelWithColors(3, name, fg, bg)
+}
+
+// NewDebugLogLevel creates a debug-level log level without predefined colors.
+func NewDebugLogLevel(name string) LogLevel { return NewLogLevel(4, name) }
+
+// NewDebugLogLevelWithColors creates a debug-level log level with ANSI colors.
+func NewDebugLogLevelWithColors(name string, fg FgColor, bg BgColor) LogLevel {
+	return NewLogLevelWithColors(4, 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
+}