logger.go

// Credit to logrus project. Much of the code here is modified from the TextFormatter

package canoe

import (
	"bytes"
	"fmt"
	"github.com/Sirupsen/logrus"
	"os"
	"runtime"
	"sort"
	"strings"
	"time"
)

// DefaultLogger gives a default logger for canoe
var DefaultLogger = &logrus.Logger{
	Out: os.Stderr,
	Formatter: &textFormatter{
		Prefix:        "canoe",
		FullTimestamp: true,
	},
	Level: logrus.InfoLevel,
}

const (
	nocolor = 0
	red     = 31
	green   = 32
	yellow  = 33
	blue    = 34
	gray    = 37
)

var (
	baseTimestamp time.Time
	isTerminal    bool
)

func init() {
	baseTimestamp = time.Now()
	isTerminal = logrus.IsTerminal()
}

func miniTS() int {
	return int(time.Since(baseTimestamp) / time.Second)
}

//
type textFormatter struct {
	// String that all logs are prefixed with
	Prefix string

	// Set to true to bypass checking for a TTY before outputting colors.
	ForceColors bool

	// Force disabling colors.
	DisableColors bool

	// Disable timestamp logging. useful when output is redirected to logging
	// system that already adds timestamps.
	DisableTimestamp bool

	// Enable logging the full timestamp when a TTY is attached instead of just
	// the time passed since beginning of execution.
	FullTimestamp bool

	// TimestampFormat to use for display when a full timestamp is printed
	TimestampFormat string

	// The fields are sorted by default for a consistent output. For applications
	// that log extremely frequently and don't use the JSON formatter this may not
	// be desired.
	DisableSorting bool
}

func prefixFieldClashes(data logrus.Fields) {
	if t, ok := data["time"]; ok {
		data["fields.time"] = t
	}

	if m, ok := data["msg"]; ok {
		data["fields.msg"] = m
	}

	if l, ok := data["level"]; ok {
		data["fields.level"] = l
	}
}
func (f *textFormatter) Format(entry *logrus.Entry) ([]byte, error) {
	var keys = make([]string, 0, len(entry.Data))
	for k := range entry.Data {
		keys = append(keys, k)
	}

	if !f.DisableSorting {
		sort.Strings(keys)
	}

	b := &bytes.Buffer{}

	prefixFieldClashes(entry.Data)

	isColorTerminal := isTerminal && (runtime.GOOS != "windows")
	isColored := (f.ForceColors || isColorTerminal) && !f.DisableColors

	b.WriteString(f.Prefix)

	timestampFormat := f.TimestampFormat
	if timestampFormat == "" {
		timestampFormat = logrus.DefaultTimestampFormat
	}
	if isColored {
		f.printColored(b, entry, keys, timestampFormat)
	} else {
		if !f.DisableTimestamp {
			f.appendKeyValue(b, "time", entry.Time.Format(timestampFormat))
		}
		f.appendKeyValue(b, "level", entry.Level.String())
		if entry.Message != "" {
			f.appendKeyValue(b, "msg", entry.Message)
		}
		for _, key := range keys {
			f.appendKeyValue(b, key, entry.Data[key])
		}
	}

	b.WriteByte('\n')
	return b.Bytes(), nil
}

func (f *textFormatter) printColored(b *bytes.Buffer, entry *logrus.Entry, keys []string, timestampFormat string) {
	var levelColor int
	switch entry.Level {
	case logrus.DebugLevel:
		levelColor = gray
	case logrus.WarnLevel:
		levelColor = yellow
	case logrus.ErrorLevel, logrus.FatalLevel, logrus.PanicLevel:
		levelColor = red
	default:
		levelColor = blue
	}

	levelText := strings.ToUpper(entry.Level.String())[0:4]

	if !f.FullTimestamp {
		fmt.Fprintf(b, "\x1b[%dm%s\x1b[0m[%04d] %-44s ", levelColor, levelText, miniTS(), entry.Message)
	} else {
		fmt.Fprintf(b, "\x1b[%dm%s\x1b[0m[%s] %-44s ", levelColor, levelText, entry.Time.Format(timestampFormat), entry.Message)
	}
	for _, k := range keys {
		v := entry.Data[k]
		fmt.Fprintf(b, " \x1b[%dm%s\x1b[0m=%+v", levelColor, k, v)
	}
}

func needsQuoting(text string) bool {
	for _, ch := range text {
		if !((ch >= 'a' && ch <= 'z') ||
			(ch >= 'A' && ch <= 'Z') ||
			(ch >= '0' && ch <= '9') ||
			ch == '-' || ch == '.') {
			return true
		}
	}
	return false
}

func (f *textFormatter) appendKeyValue(b *bytes.Buffer, key string, value interface{}) {

	b.WriteString(key)
	b.WriteByte('=')

	switch value := value.(type) {
	case string:
		if !needsQuoting(value) {
			b.WriteString(value)
		} else {
			fmt.Fprintf(b, "%q", value)
		}
	case error:
		errmsg := value.Error()
		if !needsQuoting(errmsg) {
			b.WriteString(errmsg)
		} else {
			fmt.Fprintf(b, "%q", value)
		}
	default:
		fmt.Fprint(b, value)
	}

	b.WriteByte(' ')
}