package main

import (
	"fmt"
	"log"

	"github.com/bogem/id3v2"
)

func main() {
	// Open file and parse tag in it.
	tag, err := id3v2.Open("file.mp3", id3v2.Options{Parse: true})
	if err != nil {
 		log.Fatal("Error while opening mp3 file: ", err)
 	}
	defer tag.Close()

	// Read frames.
	fmt.Println(tag.Artist())
	fmt.Println(tag.Title())

	// Set simple text frames.
	tag.SetArtist("New artist")
	tag.SetTitle("New title")

	// Set comment frame.
	comment := id3v2.CommentFrame{
		Encoding:    id3v2.EncodingUTF8,
		Language:    "eng",
		Description: "My opinion",
		Text:        "Very good song",
	}
	tag.AddCommentFrame(comment)

	// Write it to file.
	if err = tag.Save(); err != nil {
		log.Fatal("Error while saving a tag: ", err)
	}
}

pictures := tag.GetFrames(tag.CommonID("Attached picture"))
for _, f := range pictures {
	pic, ok := f.(id3v2.PictureFrame)
	if !ok {
		log.Fatal("Couldn't assert picture frame")
	}

	// Do something with picture frame.
	// For example, print the description:
	fmt.Println(pic.Description)
}

// Options influence on processing the tag.
type Options struct {
	// Parse defines, if tag will be parsed.
	Parse bool

	// ParseFrames defines, that frames do you only want to parse. For example,
	// `ParseFrames: []string{"Artist", "Title"}` will only parse artist
	// and title frames. You can specify IDs ("TPE1", "TIT2") as well as
	// descriptions ("Artist", "Title"). If ParseFrame is blank or nil,
	// id3v2 will parse all frames in tag. It works only if Parse is true.
	//
	// It's very useful for performance, so for example
	// if you want to get only some text frames,
	// id3v2 will not parse huge picture or unknown frames.
	ParseFrames []string
}

tag := id3v2.NewEmptyTag()
comment := id3v2.CommentFrame{
	Encoding:    id3v2.EncodingUTF16,
	Language:    "ger",
	Description: "Tier",
	Text:        "Der Löwe",
}
tag.AddCommentFrame(comment)

_, err := tag.WriteTo(w)
if err != nil {
	log.Fatal(err)
}