minstrel/internal/library/duplicate_survivor_test.go

package library

import (
	"testing"
	"time"
)

func TestProposeSurvivor(t *testing.T) {
	older := time.Date(2025, 1, 1, 0, 0, 0, 0, time.UTC)
	newer := older.Add(24 * time.Hour)
	cases := []struct {
		name       string
		cands      []SurvivorCandidate
		wantID     string
		wantReason string
	}{
		{
			// Lossless wins even against a much larger lossy file, and even
			// when the lossy copy has been in the library longer.
			name: "lossless beats larger and older",
			cands: []SurvivorCandidate{
				{TrackID: "mp3", FileFormat: "mp3", FileSize: 90_000_000, AddedAt: older},
				{TrackID: "flac", FileFormat: "FLAC", FileSize: 30_000_000, AddedAt: newer},
			},
			wantID: "flac", wantReason: "lossless (flac)",
		},
		{
			// m4a may be AAC; it must not outrank an mp3 just for being m4a.
			name: "m4a is not treated as lossless",
			cands: []SurvivorCandidate{
				{TrackID: "m4a", FileFormat: "m4a", FileSize: 5_000_000, AddedAt: older},
				{TrackID: "mp3", FileFormat: "mp3", FileSize: 9_000_000, AddedAt: newer},
			},
			wantID: "mp3", wantReason: "largest file",
		},
		{
			name: "larger file wins among lossy copies",
			cands: []SurvivorCandidate{
				{TrackID: "128k", FileFormat: "mp3", FileSize: 3_400_000, AddedAt: older},
				{TrackID: "320k", FileFormat: "mp3", FileSize: 8_600_000, AddedAt: newer},
			},
			wantID: "320k", wantReason: "largest file",
		},
		{
			// The #3885 pair: identical audio, sizes equal but for the tags.
			name: "the longest-standing copy wins when size ties",
			cands: []SurvivorCandidate{
				{TrackID: "www-02", FileFormat: "mp3", FileSize: 6_900_000, AddedAt: newer},
				{TrackID: "www-01", FileFormat: "mp3", FileSize: 6_900_000, AddedAt: older},
			},
			wantID: "www-01", wantReason: "in the library longest",
		},
		{
			name: "a full tie falls back to the lowest id, stably",
			cands: []SurvivorCandidate{
				{TrackID: "b", FileFormat: "mp3", FileSize: 1, AddedAt: older},
				{TrackID: "a", FileFormat: "mp3", FileSize: 1, AddedAt: older},
			},
			wantID: "a", wantReason: "copies are otherwise identical",
		},
		{
			name:   "one copy",
			cands:  []SurvivorCandidate{{TrackID: "only", FileFormat: "mp3", FileSize: 1, AddedAt: older}},
			wantID: "only", wantReason: "the only copy",
		},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			id, reason := ProposeSurvivor(tc.cands)
			if id != tc.wantID || reason != tc.wantReason {
				t.Fatalf("ProposeSurvivor = (%q, %q), want (%q, %q)", id, reason, tc.wantID, tc.wantReason)
			}
		})
	}
}

// The reason must name the rule that decided. Across three copies that is the
// comparison between first and second place, not the first rule any pair
// differs on: here the lossy copy differs from the others by format, but the
// two FLACs are separated by size.
func TestProposeSurvivor_ReasonIsTheDecidingRule(t *testing.T) {
	at := time.Date(2025, 1, 1, 0, 0, 0, 0, time.UTC)
	id, reason := ProposeSurvivor([]SurvivorCandidate{
		{TrackID: "mp3", FileFormat: "mp3", FileSize: 99_000_000, AddedAt: at},
		{TrackID: "flac-small", FileFormat: "flac", FileSize: 20_000_000, AddedAt: at},
		{TrackID: "flac-big", FileFormat: "flac", FileSize: 40_000_000, AddedAt: at},
	})
	if id != "flac-big" || reason != "largest file" {
		t.Fatalf("got (%q, %q), want (flac-big, largest file)", id, reason)
	}
}

// M498 #5436: the copy whose tags fit the album outranks every quality rule but
// lossless, which decides first: a deleted FLAC cannot be recovered, and on
// 2026-10-20 five went for mp3s whose only edge was a recording MBID. Each tag
// fit case is built so file size would choose the other copy.
func TestProposeSurvivor_LosslessThenTagFit(t *testing.T) {
	at := time.Date(2025, 1, 1, 0, 0, 0, 0, time.UTC)
	cases := []struct {
		name       string
		cands      []SurvivorCandidate
		wantID     string
		wantReason string
	}{
		{
			name: "lossless beats tag fit",
			cands: []SurvivorCandidate{
				{TrackID: "fits", FileFormat: "mp3", FileSize: 5_000_000, AddedAt: at, TagFit: 3},
				{TrackID: "flac", FileFormat: "flac", FileSize: 40_000_000, AddedAt: at, TagFit: 1},
			},
			wantID: "flac", wantReason: "lossless (flac)",
		},
		{
			name: "tag fit beats a larger file",
			cands: []SurvivorCandidate{
				{TrackID: "big", FileFormat: "mp3", FileSize: 9_000_000, AddedAt: at, TagFit: 1},
				{TrackID: "fits", FileFormat: "m4a", FileSize: 5_000_000, AddedAt: at, TagFit: 3},
			},
			wantID: "fits", wantReason: "tags fit the album",
		},
		{
			// The Humanz shape: two rips a few bytes apart, one carrying a
			// video marker and clashing with another track's position.
			name: "tag fit beats a few bytes",
			cands: []SurvivorCandidate{
				{TrackID: "rip", FileFormat: "mp3", FileSize: 5_104_498, AddedAt: at, TagFit: 1},
				{TrackID: "clean", FileFormat: "mp3", FileSize: 5_104_492, AddedAt: at, TagFit: 3},
			},
			wantID: "clean", wantReason: "tags fit the album",
		},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			id, reason := ProposeSurvivor(tc.cands)
			if id != tc.wantID || reason != tc.wantReason {
				t.Fatalf("ProposeSurvivor = (%q, %q), want (%q, %q)", id, reason, tc.wantID, tc.wantReason)
			}
		})
	}
}

func TestTagFitScore(t *testing.T) {
	cases := []struct {
		name           string
		hasTrackNumber bool
		clash          bool
		path           string
		hasMBID        bool
		want           int
	}{
		{"clean, numbered, identified", true, false, "/music/A/B/A - B - 01 - Song.flac", true, 3},
		{"position taken by another track", true, true, "/music/A/B/A - B - 01 - Song.flac", true, 2},
		{"no track number", false, false, "/music/A/B/Song.flac", true, 2},
		{"video rip", true, false, "/music/A/B/A - B - 01 - Song (Official Video).mp3", true, 2},
		{"rip with nothing else", false, false, "/music/A/B/Song (Official Video).mp3", false, 0},
	}
	for _, tc := range cases {
		if got := TagFitScore(tc.hasTrackNumber, tc.clash, tc.path, tc.hasMBID); got != tc.want {
			t.Errorf("%s: TagFitScore = %d, want %d", tc.name, got, tc.want)
		}
	}
}