package library

import (
	"context"
	"errors"
	"io"
	"io/fs"
	"log/slog"
	"os"
	"path/filepath"
	"syscall"
	"testing"

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

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

func newPool(t *testing.T) *pgxpool.Pool {
	t.Helper()
	if testing.Short() {
		t.Skip("skipping integration test in -short mode")
	}
	dsn := os.Getenv("MINSTREL_TEST_DATABASE_URL")
	if dsn == "" {
		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
	}
	if err := db.Migrate(dsn, slog.New(slog.NewTextHandler(io.Discard, nil))); err != nil {
		t.Fatalf("migrate: %v", err)
	}
	pool, err := pgxpool.New(context.Background(), dsn)
	if err != nil {
		t.Fatalf("pool: %v", err)
	}
	t.Cleanup(pool.Close)
	dbtest.ResetDB(t, pool)
	return pool
}

func seedTrack(t *testing.T, pool *pgxpool.Pool, filePath string) (dbq.Track, dbq.Album, dbq.Artist) {
	t.Helper()
	q := dbq.New(pool)
	artist, err := q.UpsertArtist(context.Background(), dbq.UpsertArtistParams{
		Name: "Delete Test Artist", SortName: "Delete Test Artist",
	})
	if err != nil {
		t.Fatalf("artist: %v", err)
	}
	album, err := q.UpsertAlbum(context.Background(), dbq.UpsertAlbumParams{
		Title: "Delete Test Album", SortTitle: "Delete Test Album",
		ArtistID: artist.ID,
	})
	if err != nil {
		t.Fatalf("album: %v", err)
	}
	track, err := q.UpsertTrack(context.Background(), dbq.UpsertTrackParams{
		Title: "Delete Test Track", AlbumID: album.ID, ArtistID: artist.ID,
		DurationMs: 1000, FilePath: filePath, FileSize: 100, FileFormat: "mp3",
	})
	if err != nil {
		t.Fatalf("track: %v", err)
	}
	return track, album, artist
}

// stubRemoveFile makes file removal fail (or succeed) on demand for one test.
// See removeFile for why this is a seam rather than a chmod.
func stubRemoveFile(t *testing.T, fn func(string) error) {
	t.Helper()
	orig := removeFile
	removeFile = fn
	t.Cleanup(func() { removeFile = orig })
}

func TestDeleteTrackFile_HappyPath(t *testing.T) {
	pool := newPool(t)
	q := dbq.New(pool)

	dir := t.TempDir()
	path := filepath.Join(dir, "track.mp3")
	if err := os.WriteFile(path, []byte("payload"), 0o644); err != nil {
		t.Fatalf("write file: %v", err)
	}
	track, album, artist := seedTrack(t, pool, path)
	// A sibling keeps the album non-empty, so this case pins that the tidy-up
	// only removes an album the delete actually emptied.
	if _, err := q.UpsertTrack(context.Background(), dbq.UpsertTrackParams{
		Title: "Sibling", AlbumID: album.ID, ArtistID: artist.ID,
		DurationMs: 1000, FilePath: filepath.Join(dir, "sibling.mp3"), FileSize: 100, FileFormat: "mp3",
	}); err != nil {
		t.Fatalf("sibling: %v", err)
	}

	got, err := DeleteTrackFile(context.Background(), pool, nil, "", track.ID)
	if err != nil {
		t.Fatalf("DeleteTrackFile: %v", err)
	}

	if _, err := os.Stat(path); !errors.Is(err, os.ErrNotExist) {
		t.Errorf("file still exists: %v", err)
	}
	if _, err := q.GetTrackByID(context.Background(), track.ID); err == nil {
		t.Errorf("track row still exists")
	}
	if _, err := q.GetAlbumByID(context.Background(), album.ID); err != nil {
		t.Errorf("album with a remaining track vanished: %v", err)
	}
	if got.AlbumID != nil || got.ArtistID != nil {
		t.Errorf("reported tidy-up %+v for an album that still has a track", got)
	}
}

func TestDeleteTrackFile_EmptiedAlbumAndArtistGoToo(t *testing.T) {
	pool := newPool(t)
	q := dbq.New(pool)

	path := filepath.Join(t.TempDir(), "lone.mp3")
	if err := os.WriteFile(path, []byte("payload"), 0o644); err != nil {
		t.Fatalf("write file: %v", err)
	}
	track, album, artist := seedTrack(t, pool, path)

	got, err := DeleteTrackFile(context.Background(), pool, nil, "", track.ID)
	if err != nil {
		t.Fatalf("DeleteTrackFile: %v", err)
	}
	if got.AlbumID == nil || *got.AlbumID != album.ID {
		t.Errorf("AlbumID = %v, want %v", got.AlbumID, album.ID)
	}
	if got.ArtistID == nil || *got.ArtistID != artist.ID {
		t.Errorf("ArtistID = %v, want %v", got.ArtistID, artist.ID)
	}
	if _, err := q.GetAlbumByID(context.Background(), album.ID); err == nil {
		t.Errorf("emptied album row still exists")
	}
	if _, err := q.GetArtistByID(context.Background(), artist.ID); err == nil {
		t.Errorf("emptied artist row still exists")
	}
}

// The #3918 proof. A file that cannot be removed must leave EVERYTHING in place:
// the row is what carries likes, plays and playlist memberships, and the file
// surviving means the next scan would re-import it as a stranger.
func TestDeleteTrackFile_UnremovableFileDeletesNothing(t *testing.T) {
	cases := []struct {
		name        string
		errno       syscall.Errno
		notWritable bool
	}{
		{"read-only mount", syscall.EROFS, true},
		{"permission denied", syscall.EACCES, true},
		{"operation not permitted", syscall.EPERM, true},
		{"i/o error", syscall.EIO, false},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			pool := newPool(t)
			q := dbq.New(pool)

			dir := t.TempDir()
			path := filepath.Join(dir, "track.mp3")
			if err := os.WriteFile(path, []byte("payload"), 0o644); err != nil {
				t.Fatalf("write file: %v", err)
			}
			track, album, _ := seedTrack(t, pool, path)
			stubRemoveFile(t, func(name string) error {
				return &fs.PathError{Op: "remove", Path: name, Err: tc.errno}
			})

			_, err := DeleteTrackFile(context.Background(), pool, nil, "", track.ID)

			var fre *FileRemoveError
			if !errors.As(err, &fre) {
				t.Fatalf("err = %v, want a *FileRemoveError", err)
			}
			if fre.NotWritable() != tc.notWritable {
				t.Errorf("NotWritable = %v, want %v", fre.NotWritable(), tc.notWritable)
			}
			if fre.Dir() != dir {
				t.Errorf("Dir = %q, want the parent directory %q", fre.Dir(), dir)
			}
			if fre.Reason() != tc.errno.Error() {
				t.Errorf("Reason = %q, want %q", fre.Reason(), tc.errno.Error())
			}
			if fre.UID != os.Getuid() || fre.GID != os.Getgid() {
				t.Errorf("identity = %d:%d, want this process's %d:%d", fre.UID, fre.GID, os.Getuid(), os.Getgid())
			}
			if _, err := q.GetTrackByID(context.Background(), track.ID); err != nil {
				t.Errorf("track row was deleted although its file was not: %v", err)
			}
			if _, err := q.GetAlbumByID(context.Background(), album.ID); err != nil {
				t.Errorf("album row was deleted although the track's file was not: %v", err)
			}
			if _, err := os.Stat(path); err != nil {
				t.Errorf("file gone although removal was refused: %v", err)
			}
		})
	}
}

func TestDeleteTrackFile_FileAlreadyGoneSucceeds(t *testing.T) {
	pool := newPool(t)
	q := dbq.New(pool)

	track, _, _ := seedTrack(t, pool, "/no/such/file/anywhere.mp3")

	if _, err := DeleteTrackFile(context.Background(), pool, nil, "", track.ID); err != nil {
		t.Fatalf("DeleteTrackFile with missing file: %v", err)
	}
	if _, err := q.GetTrackByID(context.Background(), track.ID); err == nil {
		t.Errorf("track row still exists")
	}
}

func TestDeleteTrackFile_NotFoundReturnsErr(t *testing.T) {
	pool := newPool(t)

	var bogus pgtype.UUID
	bogus.Bytes = [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
	bogus.Valid = true

	_, err := DeleteTrackFile(context.Background(), pool, nil, "", bogus)
	if !errors.Is(err, ErrTrackNotFound) {
		t.Errorf("err = %v, want ErrTrackNotFound", err)
	}
}