formatter.go

package logging

import (
	"fmt"
	"strings"
	"time"
)

// LogFormat is the name of a known formatting function.
type LogFormat string

// MINIMAL describes a formatter that just prints the message, replays are not indicated.
const MINIMAL LogFormat = "minimal"

// MINIMALTAGGED describes a formatter that just prints the level, tags and message, replays are not indicated.
const MINIMALTAGGED LogFormat = "minimaltagged"

// SIMPLE describes a formatter that just prints the date, level and message, replays are not indicated.
const SIMPLE LogFormat = "simple"

// FULL formats messages with the date to ms accuracy, the level, tags and message. Replayed messages have a special field added.
const FULL LogFormat = "full"

// FormatFromString converts a string name to a LogFormat. Valid
// arguemnts include full, simple, minimaltagged and minimal. An
// unknown string will be treated like simple.
func FormatFromString(formatName string) LogFormat {
	formatName = strings.ToLower(formatName)
	switch formatName {
	case "full":
		return FULL
	case "simple":
		return SIMPLE
	case "minimaltagged":
		return MINIMALTAGGED
	case "minimal":
		return MINIMAL
	default:
		return SIMPLE
	}
}

// GetFormatter returns the function associated with a named format.
func GetFormatter(formatName LogFormat) LogFormatter {
	switch formatName {
	case FULL:
		return fullFormat
	case SIMPLE:
		return simpleFormat
	case MINIMALTAGGED:
		return minimalWithTagsFormat
	case MINIMAL:
		return minimalFormat
	default:
		return simpleFormat
	}
}

// LogFormatter is a function type used to convert a log record into a string.
// Original time is provided times when the formatter has to construct a replayed message from the buffer.
type LogFormatter func(level LogLevel, tags []string, message string, t time.Time, original time.Time) string

var fullFormat = func(level LogLevel, tags []string, message string, t time.Time, original time.Time) string {

	if original != t {
		message = fmt.Sprintf("[replayed from %v] %v", original.Format(time.StampMilli), message)
	}

	if tags != nil && len(tags) > 0 {
		return fmt.Sprintf("[%v] [%v] %v %v", t.Format(time.StampMilli), level, tags, message)
	}
	return fmt.Sprintf("[%v] [%v] %v", t.Format(time.StampMilli), level, message)
}

var simpleFormat = func(level LogLevel, tags []string, message string, t time.Time, original time.Time) string {
	return fmt.Sprintf("[%v] [%v] %v", t.Format(time.Stamp), level, message)
}

var minimalFormat = func(level LogLevel, tags []string, message string, t time.Time, original time.Time) string {
	return message
}

var minimalWithTagsFormat = func(level LogLevel, tags []string, message string, t time.Time, original time.Time) string {
	if tags != nil && len(tags) > 0 {
		return fmt.Sprintf("[%v] %v %v", level, tags, message)
	}
	return fmt.Sprintf("[%v] %v", level, message)
}