package library

import (
	"bytes"
	"context"
	"errors"
	"testing"

	"github.com/jackc/pgx/v5/pgtype"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

// fakeAdopter answers the audio-hash lookup only for the hash it holds, the way
// the real query does. A fake that returned its rows for any hash could not tell
// adoption by identity apart from adoption by coincidence.
type fakeAdopter struct {
	byMbid    []dbq.FindMissingTrackByMbidRow
	hash      []byte
	byHash    []dbq.FindMissingTrackByAudioHashRow
	mbidErr   error
	hashErr   error
	adoptErr  error
	adoptRows int64

	mbidQueried []string
	hashQueried [][]byte
	adopted     []dbq.AdoptTrackPathParams
}

func (f *fakeAdopter) FindMissingTrackByMbid(_ context.Context, mbid string) ([]dbq.FindMissingTrackByMbidRow, error) {
	f.mbidQueried = append(f.mbidQueried, mbid)
	return f.byMbid, f.mbidErr
}

func (f *fakeAdopter) FindMissingTrackByAudioHash(
	_ context.Context, audioStreamSha256 []byte,
) ([]dbq.FindMissingTrackByAudioHashRow, error) {
	f.hashQueried = append(f.hashQueried, audioStreamSha256)
	if f.hashErr != nil {
		return nil, f.hashErr
	}
	if !bytes.Equal(audioStreamSha256, f.hash) {
		return nil, nil
	}
	return f.byHash, nil
}

func (f *fakeAdopter) AdoptTrackPath(_ context.Context, arg dbq.AdoptTrackPathParams) (int64, error) {
	f.adopted = append(f.adopted, arg)
	if f.adoptErr != nil {
		return 0, f.adoptErr
	}
	return f.adoptRows, nil
}

// The narrowed interface must not drift from the real queries.
var _ trackAdopter = (*dbq.Queries)(nil)

func mbidRow(n byte, path string) dbq.FindMissingTrackByMbidRow {
	return dbq.FindMissingTrackByMbidRow{ID: testUUID(n), FilePath: path}
}

func hashRow(n byte, path string) dbq.FindMissingTrackByAudioHashRow {
	return dbq.FindMissingTrackByAudioHashRow{ID: testUUID(n), FilePath: path}
}

func audioHash(b byte) []byte { return bytes.Repeat([]byte{b}, 32) }

const (
	oldPath = "/music/Linkin Park/Minutes to Midnight/02 - Bleed It Out.mp3"
	newPath = "/music/Linkin Park/Minutes to Midnight/04 - Bleed It Out.mp3"
)

func TestAdoptMovedTrack_MatchesByMbid(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{byMbid: []dbq.FindMissingTrackByMbidRow{mbidRow(7, oldPath)}, adoptRows: 1}

	if !s.adoptMovedTrack(context.Background(), q, newPath, audioHash(1), "rec-mbid") {
		t.Fatal("expected the moved track to be adopted")
	}
	if len(q.adopted) != 1 || q.adopted[0].ID != testUUID(7) || q.adopted[0].FilePath != newPath {
		t.Fatalf("adopted = %+v, want row 7 at %q", q.adopted, newPath)
	}
	// MBID matched, so the weaker signal should not have been consulted.
	if len(q.hashQueried) != 0 {
		t.Errorf("queried the audio hash despite an MBID match")
	}
}

func TestAdoptMovedTrack_FallsBackToAudioHash(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{hash: audioHash(3), byHash: []dbq.FindMissingTrackByAudioHashRow{hashRow(3, oldPath)}, adoptRows: 1}

	// No MBID: an untagged file, which is exactly what the fallback is for.
	if !s.adoptMovedTrack(context.Background(), q, newPath, audioHash(3), "") {
		t.Fatal("expected adoption via the audio hash")
	}
	if len(q.mbidQueried) != 0 {
		t.Errorf("queried by MBID with no MBID available")
	}
	if len(q.hashQueried) != 1 || !bytes.Equal(q.hashQueried[0], audioHash(3)) {
		t.Fatalf("hash queried = %x, want exactly the file's hash", q.hashQueried)
	}
	if len(q.adopted) != 1 || q.adopted[0].ID != testUUID(3) {
		t.Errorf("adopted = %+v, want row 3", q.adopted)
	}
}

// The case the old (file_size, duration_ms) pair got wrong: an unrelated file
// that happens to share a size and a duration with a missing track. Size and
// duration are no longer inputs at all; only the audio itself can match, and a
// different recording has a different hash.
func TestAdoptMovedTrack_DifferentAudioIsNotAdopted(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{hash: audioHash(0xAA), byHash: []dbq.FindMissingTrackByAudioHashRow{hashRow(1, oldPath)}, adoptRows: 1}

	if s.adoptMovedTrack(context.Background(), q, newPath, audioHash(0xBB), "") {
		t.Fatal("adopted a missing track whose audio differs")
	}
	if len(q.adopted) != 0 {
		t.Errorf("adopted = %+v, want none", q.adopted)
	}
}

// Two missing rows carrying the same recording MBID means real duplicates.
// Adopting one arbitrarily would attach this file's future history to a coin
// flip, so it must insert fresh instead.
func TestAdoptMovedTrack_RefusesAmbiguousMbidMatch(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{byMbid: []dbq.FindMissingTrackByMbidRow{
		mbidRow(1, "/music/a.mp3"),
		mbidRow(2, "/music/b.mp3"),
	}, adoptRows: 1}

	if s.adoptMovedTrack(context.Background(), q, newPath, nil, "rec-mbid") {
		t.Fatal("expected refusal on an ambiguous MBID match")
	}
	if len(q.adopted) != 0 {
		t.Errorf("adopted despite ambiguity: %+v", q.adopted)
	}
}

// An ambiguous MBID may still be resolvable by the audio hash, which is a
// narrower signal — so falling through is allowed to succeed.
func TestAdoptMovedTrack_AmbiguousMbidFallsThroughToAudioHash(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{
		byMbid: []dbq.FindMissingTrackByMbidRow{
			mbidRow(1, "/music/a.mp3"),
			mbidRow(2, "/music/b.mp3"),
		},
		hash:      audioHash(2),
		byHash:    []dbq.FindMissingTrackByAudioHashRow{hashRow(2, "/music/b.mp3")},
		adoptRows: 1,
	}

	if !s.adoptMovedTrack(context.Background(), q, newPath, audioHash(2), "rec-mbid") {
		t.Fatal("expected the audio hash to disambiguate")
	}
	if len(q.adopted) != 1 || q.adopted[0].ID != testUUID(2) {
		t.Errorf("adopted = %+v, want row 2", q.adopted)
	}
}

// Two missing tracks with identical audio are duplicates of each other; a new
// file matching both cannot be assigned to either.
func TestAdoptMovedTrack_RefusesAmbiguousAudioHashMatch(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{hash: audioHash(5), byHash: []dbq.FindMissingTrackByAudioHashRow{
		hashRow(1, "/music/a.mp3"),
		hashRow(2, "/music/b.mp3"),
	}, adoptRows: 1}

	if s.adoptMovedTrack(context.Background(), q, newPath, audioHash(5), "") {
		t.Fatal("expected refusal on an ambiguous audio-hash match")
	}
	if len(q.adopted) != 0 {
		t.Errorf("adopted despite ambiguity: %+v", q.adopted)
	}
}

// No hash means it could not be taken. An empty hash must never be looked up:
// every unhashable file would pair with every other.
func TestAdoptMovedTrack_SkipsAudioHashWhenAbsent(t *testing.T) {
	for name, hash := range map[string][]byte{"nil": nil, "empty": {}} {
		t.Run(name, func(t *testing.T) {
			s := testScanner(t)
			q := &fakeAdopter{hash: hash, byHash: []dbq.FindMissingTrackByAudioHashRow{hashRow(1, oldPath)}, adoptRows: 1}
			if s.adoptMovedTrack(context.Background(), q, newPath, hash, "") {
				t.Error("adopted without an audio hash")
			}
			if len(q.hashQueried) != 0 {
				t.Error("looked up an absent audio hash")
			}
		})
	}
}

func TestAdoptMovedTrack_NoCandidates(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{adoptRows: 1}

	if s.adoptMovedTrack(context.Background(), q, newPath, audioHash(9), "rec-mbid") {
		t.Fatal("expected no adoption when nothing matches")
	}
	if len(q.adopted) != 0 {
		t.Errorf("adopted with no candidates: %+v", q.adopted)
	}
}

// The row's mark was cleared between lookup and update — another file adopted it
// first. AdoptTrackPath's `missing_since IS NOT NULL` predicate reports 0 rows.
func TestAdoptMovedTrack_LostRaceReportsNotAdopted(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{
		byMbid:    []dbq.FindMissingTrackByMbidRow{mbidRow(5, oldPath)},
		adoptRows: 0,
	}

	if s.adoptMovedTrack(context.Background(), q, newPath, audioHash(5), "rec-mbid") {
		t.Fatal("expected not-adopted when the update matched no rows")
	}
}

// Failing to detect a move must never fail the file: the caller falls back to
// inserting a fresh row, which is the pre-#2528 behaviour.
func TestAdoptMovedTrack_ToleratesQueryErrors(t *testing.T) {
	sentinel := errors.New("db down")
	tests := []struct {
		name string
		q    *fakeAdopter
	}{
		{"mbid lookup fails", &fakeAdopter{mbidErr: sentinel}},
		{"audio hash lookup fails", &fakeAdopter{hashErr: sentinel}},
		{"adopt fails", &fakeAdopter{
			byMbid:   []dbq.FindMissingTrackByMbidRow{mbidRow(1, oldPath)},
			adoptErr: sentinel,
		}},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			s := testScanner(t)
			if s.adoptMovedTrack(context.Background(), tc.q, newPath, audioHash(1), "rec-mbid") {
				t.Error("reported adoption despite a query error")
			}
		})
	}
}

// A failed MBID lookup must not stop the audio hash from being tried.
func TestAdoptMovedTrack_MbidErrorStillTriesAudioHash(t *testing.T) {
	s := testScanner(t)
	q := &fakeAdopter{
		mbidErr:   errors.New("db hiccup"),
		hash:      audioHash(9),
		byHash:    []dbq.FindMissingTrackByAudioHashRow{hashRow(9, oldPath)},
		adoptRows: 1,
	}

	if !s.adoptMovedTrack(context.Background(), q, newPath, audioHash(9), "rec-mbid") {
		t.Fatal("expected the audio hash to be tried after an MBID lookup error")
	}
	if len(q.adopted) != 1 || q.adopted[0].ID != testUUID(9) {
		t.Errorf("adopted = %+v, want row 9", q.adopted)
	}
}

func TestUniqueMatch(t *testing.T) {
	s := testScanner(t)
	if _, ok := s.uniqueMatch(nil, newPath, "mbid"); ok {
		t.Error("empty candidate set matched")
	}
	c, ok := s.uniqueMatch([]candidate{{id: testUUID(4), filePath: oldPath}}, newPath, "mbid")
	if !ok {
		t.Fatal("single candidate did not match")
	}
	if c.id != testUUID(4) || c.filePath != oldPath {
		t.Errorf("candidate = %+v, want id 4 at %q", c, oldPath)
	}
	if _, ok := s.uniqueMatch([]candidate{
		{id: testUUID(1)}, {id: testUUID(2)},
	}, newPath, "mbid"); ok {
		t.Error("multiple candidates matched")
	}
}

func TestRowConverters(t *testing.T) {
	got := rowsFromMbid([]dbq.FindMissingTrackByMbidRow{mbidRow(1, "/a"), mbidRow(2, "/b")})
	if len(got) != 2 || got[0].id != testUUID(1) || got[1].filePath != "/b" {
		t.Errorf("rowsFromMbid = %+v", got)
	}
	got = rowsFromAudioHash([]dbq.FindMissingTrackByAudioHashRow{hashRow(3, "/c")})
	if len(got) != 1 || got[0].id != testUUID(3) || got[0].filePath != "/c" {
		t.Errorf("rowsFromAudioHash = %+v", got)
	}
}

// pgtype.UUID zero value must not be mistaken for a real id.
func TestUniqueMatch_ZeroUUIDNotValid(t *testing.T) {
	var zero pgtype.UUID
	if zero.Valid {
		t.Fatal("zero pgtype.UUID should not be Valid")
	}
}