package logrus

import (
	"bytes"
	"fmt"
	"sort"
	"strings"
	"time"
)

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

var (
	baseTimestamp          time.Time
	isTerminal             bool
	defaultTimestampFormat = time.RFC3339
)

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

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

type TextFormatter struct {
	// 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

	// Timestamp format to use for display, if 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 (f *TextFormatter) Format(entry *Entry) ([]byte, error) {
	var keys []string = 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)

	isColored := (f.ForceColors || isTerminal) && !f.DisableColors

	if f.TimestampFormat == "" {
		f.TimestampFormat = defaultTimestampFormat
	}
	if isColored {
		f.printColored(b, entry, keys)
	} else {
		if !f.DisableTimestamp {
			f.appendKeyValue(b, "time", entry.Time.Format(f.TimestampFormat))
		}
		f.appendKeyValue(b, "level", entry.Level.String())
		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 *Entry, keys []string) {
	var levelColor int
	switch entry.Level {
	case DebugLevel:
		levelColor = gray
	case WarnLevel:
		levelColor = yellow
	case ErrorLevel, FatalLevel, 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(f.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 false
		}
	}
	return true
}

func (f *TextFormatter) appendKeyValue(b *bytes.Buffer, key, value interface{}) {
	switch value.(type) {
	case string:
		if needsQuoting(value.(string)) {
			fmt.Fprintf(b, "%v=%s ", key, value)
		} else {
			fmt.Fprintf(b, "%v=%q ", key, value)
		}
	case error:
		if needsQuoting(value.(error).Error()) {
			fmt.Fprintf(b, "%v=%s ", key, value)
		} else {
			fmt.Fprintf(b, "%v=%q ", key, value)
		}
	default:
		fmt.Fprintf(b, "%v=%v ", key, value)
	}
}