package formatter

import (
	"encoding/json"
	"fmt"
	"io"
	"text/template"
	"time"

	"gopkg.in/mcuadros/go-syslog.v2/format"
	"gopkg.in/mgo.v2/bson"
)

// Formatter is an interface, so that multiple implementations can exist
type Formatter func(format.LogParts) string

var tmplFuncs template.FuncMap
var syslogTmpl *template.Template

func init() {
	tmplFuncs := template.FuncMap{
		"dateFormat": func(dt time.Time, fmt string) string {
			return dt.Format(fmt)
		},
		"rfc822": func(dt time.Time) string {
			return dt.Format(time.RFC822)
		},
	}
	syslogTmpl = template.Must(template.New("syslog").Funcs(tmplFuncs).Parse(
		"{{rfc822 (index . \"timestamp\")}} {{index . \"hostname\"}} " +
			"{{index . \"app_name\"}}" +
			"{{ if (ne (index . \"proc_id\") \"-\")}}[{{index . \"proc_id\"}}]{{end}}: " +
			"{{index . \"message\"}}",
	))
}

type Format int

func (rf *Format) Set(v string) error {
	newvalue, err := parseFormat(v)
	if err != nil {
		return err
	}
	*rf = newvalue
	return nil
}

func (rf Format) String() string {
	switch rf {
	case FormatJSON:
		return "json"
	case FormatSyslog:
		return "syslog"
	case FormatBSON:
		return "bson"
	}
	return ""
}

func (rf Format) WriteFormatted(w io.Writer, msg format.LogParts) error {
	return WriteFormatted(w, rf, msg)
}

func parseFormat(s string) (Format, error) {
	switch s {
	case "json":
		return FormatJSON, nil
	case "syslog":
		return FormatSyslog, nil
	case "bson":
		return FormatBSON, nil
	default:
		return 0, fmt.Errorf("Undefined format `%s`", s)
	}
}

const (
	FormatSyslog = iota // 0
	FormatJSON   = iota
	FormatBSON   = iota
)

func WriteFormatted(w io.Writer, f Format, msg format.LogParts) error {
	switch f {
	case FormatSyslog:
		return syslogTmpl.Execute(w, msg)
	case FormatJSON:
		enc := json.NewEncoder(w)
		enc.SetIndent("", "  ")
		return enc.Encode(msg)
	case FormatBSON:
		enc, err := bson.Marshal(msg)
		if err != nil {
			return err
		}
		_, err = w.Write(enc)
		return err
	}
	return nil
}