package library

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"slices"
	"testing"
	"time"

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

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

// TestScanner_FingerprintsOnlyNewOrChangedBytes_Integration pins WHEN the scan
// fingerprints. The cost of getting it wrong is asymmetric and invisible: a
// scan that re-fingerprints unchanged files still produces correct rows, just
// by decoding the entire library on every tag-repair pass.
//
// The fingerprinter is stubbed. CI has no real audio, and the tools' output is
// covered by the parser tests; this covers the scan's decisions.
func TestScanner_FingerprintsOnlyNewOrChangedBytes_Integration(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping scanner integration in -short mode")
	}
	dsn := os.Getenv("MINSTREL_TEST_DATABASE_URL")
	if dsn == "" {
		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
	}
	ctx := context.Background()
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))

	if err := db.Migrate(dsn, logger); err != nil {
		t.Fatalf("migrate: %v", err)
	}
	pool, err := pgxpool.New(ctx, dsn)
	if err != nil {
		t.Fatalf("pool: %v", err)
	}
	t.Cleanup(pool.Close)
	if _, err := pool.Exec(ctx, "TRUNCATE tracks, albums, artists RESTART IDENTITY CASCADE"); err != nil {
		t.Fatalf("truncate: %v", err)
	}

	root := t.TempDir()
	a := filepath.Join(root, "artist/album/01.mp3")
	b := filepath.Join(root, "artist/album/02.mp3")
	writeTestMP3(t, a, map[string]string{"TIT2": "One", "TPE1": "Artist", "TALB": "Album", "TRCK": "1"})
	writeTestMP3(t, b, map[string]string{"TIT2": "Two", "TPE1": "Artist", "TALB": "Album", "TRCK": "2"})

	sum := bytes.Repeat([]byte{0xAB}, 32)
	chroma := []int32{7, -7, 2147483647}
	result := fingerprintResult{streamSHA256: sum, chromaprint: chroma}
	calls := map[string]int{}

	scanner := New(pool, logger, []string{root})
	scanner.fingerprint = func(_ context.Context, path string) fingerprintResult {
		calls[path]++
		return result
	}

	scan := func(step string) Stats {
		t.Helper()
		st, err := scanner.Scan(ctx, nil)
		if err != nil {
			t.Fatalf("%s: scan: %v", step, err)
		}
		return st
	}
	type row struct {
		sha     []byte
		chroma  []int32
		version int16
	}
	stored := func(path string) (row, bool) {
		t.Helper()
		var r row
		err := pool.QueryRow(ctx, `
			SELECT f.audio_stream_sha256, f.chromaprint, f.fingerprint_version
			  FROM track_fingerprints f JOIN tracks t ON t.id = f.track_id
			 WHERE t.file_path = $1`, path).Scan(&r.sha, &r.chroma, &r.version)
		if errors.Is(err, pgx.ErrNoRows) {
			return row{}, false
		}
		if err != nil {
			t.Fatalf("read fingerprint for %s: %v", path, err)
		}
		return r, true
	}
	// A later step moves mtime forward past the row's updated_at, which is
	// what the scan reads as "these bytes changed".
	touch := func(path string, ahead time.Duration) {
		t.Helper()
		when := time.Now().Add(ahead)
		if err := os.Chtimes(path, when, when); err != nil {
			t.Fatalf("chtimes %s: %v", path, err)
		}
	}

	// 1. New files are fingerprinted, and stored at the current version.
	scan("first scan")
	if calls[a] != 1 || calls[b] != 1 {
		t.Fatalf("first scan fingerprint calls = %v, want one per file", calls)
	}
	got, ok := stored(a)
	if !ok {
		t.Fatal("first scan stored no fingerprint")
	}
	if !bytes.Equal(got.sha, sum) || !slices.Equal(got.chroma, chroma) || got.version != fingerprintVersion {
		t.Fatalf("stored %+v, want sha %x chromaprint %v version %d", got, sum, chroma, fingerprintVersion)
	}

	// 2. A tag-repair pass re-reads every unchanged file and must not
	// fingerprint any of them again.
	//
	// The Updated count is what makes this able to fail. Without it, a scan
	// that simply SKIPPED both files would also leave the call counts at one,
	// and the assertion would pass without the re-read path ever running.
	if _, err := pool.Exec(ctx, "UPDATE tracks SET duration_ms = 1000, tag_read_version = 0"); err != nil {
		t.Fatalf("force tag re-read: %v", err)
	}
	if st := scan("tag-repair scan"); st.Updated != 2 || st.Skipped != 0 {
		t.Fatalf("tag-repair scan stats = %+v, want both files re-read (Updated=2 Skipped=0)", st)
	}
	if calls[a] != 1 || calls[b] != 1 {
		t.Fatalf("tag-repair scan re-fingerprinted unchanged files: calls = %v", calls)
	}
	if _, ok := stored(a); !ok {
		t.Fatal("tag-repair scan dropped a stored fingerprint")
	}

	// 3. Bytes that changed are fingerprinted again, and only those.
	touch(a, time.Hour)
	scan("changed-file scan")
	if calls[a] != 2 || calls[b] != 1 {
		t.Fatalf("changed-file scan calls = %v, want a=2 b=1", calls)
	}

	// 4. A changed file whose attempt is inconclusive loses its old row: that
	// row describes the previous bytes, and a stall says nothing about the new
	// ones.
	result = fingerprintResult{streamSHA256: sum, printErr: fmt.Errorf("fpcalc: %w", errFingerprintTimeout)}
	touch(a, 2*time.Hour)
	scan("inconclusive scan")
	if _, ok := stored(a); ok {
		t.Fatal("inconclusive attempt left the previous bytes' fingerprint in place")
	}
	if _, ok := stored(b); !ok {
		t.Fatal("inconclusive attempt on one file removed another file's fingerprint")
	}

	// 5. A file the tools reject gets a row at the current version with both
	// halves NULL — a verdict, so the backfill does not retry it every boot.
	result = fingerprintResult{
		hashErr:  errors.New("ffmpeg exited 1"),
		printErr: errors.New("fpcalc exited 2"),
	}
	touch(a, 3*time.Hour)
	scan("rejected scan")
	got, ok = stored(a)
	if !ok {
		t.Fatal("a file the tools rejected got no row, so the backfill would retry it forever")
	}
	if got.sha != nil || got.chroma != nil || got.version != fingerprintVersion {
		t.Fatalf("rejected file stored %+v, want both halves NULL at version %d", got, fingerprintVersion)
	}
}