minstrel/internal/release/version.go

package release

import "strings"

// TitleVersion is the version of a recording a release group's title names
// in its qualifier: the words in brackets, or after a dash. MusicBrainz
// does not always type such a group: My Chemical Romance's "Common People
// (Recorded For BBC Radio 1)" is a plain Single (#5573). Typ is the
// MusicBrainz secondary type the version is, or "" for one no type names
// (an acoustic or instrumental version); Word is the word that said so.
type TitleVersion struct {
	Word string
	What string
	Typ  string
}

// titleVersions are the qualifier words that name a version, in the order
// they are looked for: "rough mix" is a demo before "mix" is a remix.
var titleVersions = []struct {
	words []string
	what  string
	typ   string
}{
	{[]string{"demo", "demos", "outtake", "outtakes", "rehearsal", "rough mix"}, "demo recordings", "Demo"},
	{[]string{"live", "bootleg", "bbc", "session", "sessions", "unplugged", "recorded for", "in concert"}, "a live recording", "Live"},
	{[]string{"remix", "remixes", "remixed", "rmx", "mix", "mixes"}, "a remix", "Remix"},
	{[]string{"instrumental", "instrumentals", "acoustic", "karaoke", "acapella", "acappella", "a cappella",
		"drumless", "nightcore", "slowed", "sped up"}, "another version", ""},
	{[]string{"commentary", "interview", "interviews"}, "commentary or interviews", "Interview"},
}

// VersionInTitle reads a release group's title for the version it names,
// if any. Only the qualifier counts, so "Live Through This" and "Live
// Forever" name no version.
func VersionInTitle(title string) (TitleVersion, bool) {
	for _, q := range qualifiers(title) {
		tokens := Tokens(q)
		for _, v := range titleVersions {
			for _, w := range v.words {
				if contains(tokens, strings.Fields(w)) {
					return TitleVersion{Word: w, What: v.what, Typ: v.typ}, true
				}
			}
		}
	}
	return TitleVersion{}, false
}

// qualifiers are the parts of a title in brackets, and what follows a
// spaced dash.
func qualifiers(title string) []string {
	var out []string
	depth, start := 0, 0
	for i, c := range title {
		switch c {
		case '(', '[', '{':
			if depth == 0 {
				start = i + 1
			}
			depth++
		case ')', ']', '}':
			if depth > 0 {
				depth--
				if depth == 0 {
					out = append(out, title[start:i])
				}
			}
		}
	}
	if depth > 0 {
		out = append(out, title[start:])
	}
	for _, dash := range []string{" - ", " – ", " — "} {
		if i := strings.Index(title, dash); i >= 0 {
			out = append(out, title[i+len(dash):])
		}
	}
	return out
}