package torrent

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

	"git.kmsign.ru/royalcat/tstor/pkg/rlog"
	"github.com/anacrolix/torrent"
	"github.com/anacrolix/torrent/metainfo"
	"github.com/anacrolix/torrent/storage"
)

// NewFileStorage creates a new ClientImplCloser that stores files using the OS native filesystem.
func NewFileStorage(baseDir string, pc storage.PieceCompletion) *fileStorage {
	return &fileStorage{
		client: storage.NewFileOpts(storage.NewFileClientOpts{
			ClientBaseDir:   baseDir,
			PieceCompletion: pc,
			TorrentDirMaker: func(baseDir string, info *metainfo.Info, infoHash metainfo.Hash) string {
				return torrentDir(baseDir, infoHash)
			},
			FilePathMaker: func(opts storage.FilePathMakerOpts) string {
				return filePath(*opts.File)
			},
		}),
		baseDir:         baseDir,
		pieceCompletion: pc,
		dupIndex:        newDupIndex(),
		log:             rlog.Component("daemon", "torrent"),
	}
}

// File-based storage for torrents, that isn't yet bound to a particular torrent.
type fileStorage struct {
	baseDir         string
	client          storage.ClientImplCloser
	pieceCompletion storage.PieceCompletion
	dupIndex        *dupIndex
	log             *rlog.Logger
}

var _ storage.ClientImplCloser = (*fileStorage)(nil)

func (me *fileStorage) Close() error {
	return errors.Join(
		me.client.Close(),
		me.pieceCompletion.Close(),
	)
}

func (fs *fileStorage) fullFilePath(infoHash metainfo.Hash, fileInfo metainfo.FileInfo) string {
	return filepath.Join(
		torrentDir(fs.baseDir, infoHash),
		filePath(fileInfo),
	)
}

func (fs *fileStorage) DeleteFile(file *torrent.File) error {
	infoHash := file.Torrent().InfoHash()
	torrentDir := torrentDir(fs.baseDir, infoHash)
	fileInfo := file.FileInfo()
	relFilePath := filePath(fileInfo)
	filePath := path.Join(torrentDir, relFilePath)
	for i := file.BeginPieceIndex(); i < file.EndPieceIndex(); i++ {
		pk := metainfo.PieceKey{InfoHash: infoHash, Index: i}
		err := fs.pieceCompletion.Set(pk, false)
		if err != nil {
			return err
		}
	}
	return os.Remove(filePath)
}

func (fs *fileStorage) CleanupDirs(ctx context.Context, expected []*Controller, dryRun bool) ([]string, error) {
	log := fs.log.With(slog.Int("expectedTorrents", len(expected)), slog.Bool("dryRun", dryRun))

	expectedEntries := []string{}
	for _, e := range expected {
		expectedEntries = append(expectedEntries, e.Torrent().InfoHash().HexString())
	}

	entries, err := os.ReadDir(fs.baseDir)
	if err != nil {
		return nil, err
	}

	toDelete := []string{}
	for _, v := range entries {
		if !slices.Contains(expectedEntries, v.Name()) {
			toDelete = append(toDelete, v.Name())
		}
	}

	if ctx.Err() != nil {
		return nil, ctx.Err()
	}

	log.Info(ctx, "deleting trash data", slog.Int("dirsCount", len(toDelete)))
	if !dryRun {
		for i, name := range toDelete {
			p := path.Join(fs.baseDir, name)
			log.Warn(ctx, "deleting trash data", slog.String("path", p))
			err := os.RemoveAll(p)
			if err != nil {
				return toDelete[:i], err
			}
		}
	}

	return toDelete, nil
}

func (s *fileStorage) CleanupFiles(ctx context.Context, expected []*Controller, dryRun bool) ([]string, error) {
	log := s.log.With(slog.Int("expectedTorrents", len(expected)), slog.Bool("dryRun", dryRun))

	expectedEntries := []string{}
	{
		for _, e := range expected {
			files, err := e.Files(ctx)
			if err != nil {
				return nil, err
			}

			for _, f := range files {
				expectedEntries = append(expectedEntries, s.fullFilePath(e.Torrent().InfoHash(), f.FileInfo()))
			}
		}
	}

	entries := []string{}
	err := filepath.WalkDir(s.baseDir,
		func(path string, info fs.DirEntry, err error) error {
			if err != nil {
				return err
			}
			if ctx.Err() != nil {
				return ctx.Err()
			}

			if info.IsDir() {
				return nil
			}
			entries = append(entries, path)
			return nil
		})
	if err != nil {
		return nil, err
	}

	toDelete := []string{}
	for _, v := range entries {
		if !slices.Contains(expectedEntries, v) {
			toDelete = append(toDelete, v)
		}
	}

	if ctx.Err() != nil {
		return toDelete, ctx.Err()
	}

	log.Info(ctx, "deleting trash data", slog.Int("filesCount", len(toDelete)))
	if !dryRun {
		for i, p := range toDelete {
			s.log.Warn(ctx, "deleting trash data", slog.String("path", p))
			err := os.Remove(p)
			if err != nil {
				return toDelete[i:], err
			}
		}
	}
	return toDelete, nil
}

func (s *fileStorage) iterFiles(ctx context.Context, iter func(ctx context.Context, path string, entry fs.FileInfo) error) error {
	return filepath.Walk(s.baseDir,
		func(path string, info fs.FileInfo, err error) error {
			if err != nil {
				return err
			}
			if ctx.Err() != nil {
				return ctx.Err()
			}

			if info.IsDir() {
				return nil
			}

			return iter(ctx, path, info)
		})
}