package qbittorrent

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"os"
	"path"
	"path/filepath"
	"sync"
	"time"

	"git.kmsign.ru/royalcat/tstor/pkg/qbittorrent"
	"git.kmsign.ru/royalcat/tstor/pkg/rlog"
	"git.kmsign.ru/royalcat/tstor/src/config"
	"git.kmsign.ru/royalcat/tstor/src/logwrap"
	"git.kmsign.ru/royalcat/tstor/src/vfs"
	"github.com/anacrolix/torrent/metainfo"
	"github.com/anacrolix/torrent/types/infohash"
	infohash_v2 "github.com/anacrolix/torrent/types/infohash-v2"
	mapset "github.com/deckarep/golang-set/v2"
	"github.com/iceber/iouring-go"
	"github.com/royalcat/ctxio"
	"go.opentelemetry.io/otel"
)

var trace = otel.Tracer("git.kmsign.ru/royalcat/tstor/daemons/qbittorrent")

type Daemon struct {
	proc   *os.Process
	qb     qbittorrent.Client
	client *cacheClient

	sourceFilesMu sync.Mutex
	sourceFiles   map[string]string // [sourcePath]infohash

	registeredTorrents mapset.Set[string] // infohash list

	dataDir string
	ur      *iouring.IOURing
	log     *rlog.Logger
}

const defaultConf = `
[LegalNotice]
Accepted=true

[Preferences]
WebUI\LocalHostAuth=false
WebUI\Password_PBKDF2="@ByteArray(qef5I4wZBkDG+PP6/5mQwA==:LoTmorQM/QM5RHI4+dOiu6xfAz9xak6fhR4ZGpRtJF3JNCGG081Yrtva4G71kXz//ODUuWQKTLlrZPuIDvzqUQ==)"
`

func NewDaemon(conf config.QBittorrent) (*Daemon, error) {
	ctx := context.Background()
	log := rlog.Component("qbittorrent")

	binPath := conf.MetadataFolder + "/qbittorrent-nox"
	err := downloadLatestQbitRelease(ctx, binPath)
	if err != nil {
		return nil, err
	}

	daemonLog := log.WithComponent("process")
	outLog := logwrap.NewSlogWriter(ctx, slog.LevelInfo, daemonLog.Slog())
	errLog := logwrap.NewSlogWriter(ctx, slog.LevelError, daemonLog.Slog())

	_, err = os.Stat(conf.MetadataFolder + "/profile/qBittorrent/config/qBittorrent.conf")
	if errors.Is(err, os.ErrNotExist) {
		err = os.MkdirAll(conf.MetadataFolder+"/profile/qBittorrent/config", 0744)
		if err != nil {
			return nil, err
		}
		err = os.WriteFile(conf.MetadataFolder+"/profile/qBittorrent/config/qBittorrent.conf", []byte(defaultConf), 0644)
		if err != nil {
			return nil, err
		}
	}

	err = os.MkdirAll(conf.DataFolder, 0744)
	if err != nil {
		return nil, err
	}

	const port = 25436

	proc, err := runQBittorrent(binPath, conf.MetadataFolder+"/profile", port, outLog, errLog)
	if err != nil {
		return nil, err
	}

	time.Sleep(time.Second)

	qb, err := qbittorrent.NewClient(ctx, &qbittorrent.Config{
		Address: fmt.Sprintf("http://localhost:%d", port),
	})
	if err != nil {
		return nil, err
	}

	for { // wait for qbittorrent to start
		ver, err := qb.Application().Version(ctx)
		log.Info(ctx, "qbittorrent started", slog.String("version", ver))
		if err == nil {
			break
		}
		log.Warn(ctx, "waiting for qbittorrent to start", rlog.Error(err))
		time.Sleep(time.Second)
	}

	dataDir, err := filepath.Abs(conf.DataFolder)
	if err != nil {
		return nil, err
	}

	err = qb.Application().SetPreferences(ctx, &qbittorrent.Preferences{
		SavePath: dataDir,
	})
	if err != nil {
		return nil, err
	}

	ur, err := iouring.New(8, iouring.WithAsync())
	if err != nil {
		return nil, err
	}

	return &Daemon{
		qb:                 qb,
		proc:               proc,
		dataDir:            conf.DataFolder,
		ur:                 ur,
		sourceFiles:        make(map[string]string),
		registeredTorrents: mapset.NewSet[string](),
		client:             wrapClient(qb),
		log:                rlog.Component("qbittorrent"),
	}, nil
}

func (d *Daemon) Close(ctx context.Context) error {
	err := d.proc.Signal(os.Interrupt)
	if err != nil {
		return err
	}

	_, err = d.proc.Wait()
	if err != nil {
		return err
	}

	return nil
}

func torrentDataPath(dataDir string, ih string) (string, error) {
	return filepath.Abs(path.Join(dataDir, ih))
}

func (fs *Daemon) GetTorrentFS(ctx context.Context, sourcePath string, file vfs.File) (vfs.Filesystem, error) {
	ctx, span := trace.Start(ctx, "GetTorrentFS")
	defer span.End()

	stat, err := file.Info()
	if err != nil {
		return nil, err
	}

	log := fs.log.With(slog.String("file", file.Name()))

	ih, err := readInfoHash(ctx, file)
	if err != nil {
		return nil, err
	}
	log = log.With(slog.String("infohash", ih.HexString()))

	torrentPath, err := torrentDataPath(fs.dataDir, ih.HexString())
	if err != nil {
		return nil, fmt.Errorf("error getting torrent path: %w", err)
	}
	log = log.With(slog.String("torrentPath", torrentPath))

	log.Debug(ctx, "creating fs for torrent")

	err = fs.syncTorrentState(ctx, file, ih, torrentPath)
	if err != nil {
		return nil, fmt.Errorf("error syncing torrent state: %w", err)
	}

	fs.sourceFilesMu.Lock()
	fs.sourceFiles[sourcePath] = ih.HexString()
	fs.sourceFilesMu.Unlock()

	return newTorrentFS(ctx, fs.client, file.Name(), ih.HexString(), stat.ModTime(), torrentPath)
}

func (d *Daemon) syncTorrentState(ctx context.Context, file vfs.File, ih metainfo.Hash, torrentPath string) error {
	ctx, span := trace.Start(ctx, "syncTorrentState")
	defer span.End()
	log := d.log.With(slog.String("file", file.Name()), slog.String("infohash", ih.HexString()))

	info, err := d.client.getInfo(ctx, ih.HexString())
	if err != nil {
		return err
	}

	log = log.With(slog.String("torrentPath", torrentPath))

	if info == nil {
		_, err := file.Seek(0, io.SeekStart)
		if err != nil {
			return err
		}
		data, err := ctxio.ReadAll(ctx, file)
		if err != nil {
			return err
		}

		err = d.qb.Torrent().AddNewTorrent(ctx, &qbittorrent.TorrentAddOption{
			Torrents: []*qbittorrent.TorrentAddFileMetadata{
				{
					Data: data,
				},
			},
			SavePath: torrentPath,
			// SequentialDownload: "true",
			FirstLastPiecePrio: "true",
		})
		if err != nil {
			d.log.Error(ctx, "error adding torrent", rlog.Error(err))
			return fmt.Errorf("error adding torrent: %w", err)
		}

		var props *qbittorrent.TorrentProperties
		for {
			props, err = d.client.getProperties(ctx, ih.HexString())
			if err == nil {
				break
			}
			if errors.Is(err, context.DeadlineExceeded) {
				return err
			}
			log.Error(ctx, "waiting for torrent to be added", rlog.Error(err))
			time.Sleep(time.Millisecond * 15)
		}

		log.Info(ctx, "added torrent", slog.String("infohash", ih.HexString()))

		d.registeredTorrents.Add(props.Hash)

		return nil
	} else {
		// info := existing[0]
		props, err := d.client.getProperties(ctx, ih.HexString())
		if err != nil {
			return fmt.Errorf("error getting torrent properties: %w for infohash: %s", err, ih.HexString())
		}

		d.registeredTorrents.Add(props.Hash)

		if props.SavePath != torrentPath {
			log.Info(ctx, "moving torrent to correct location", slog.String("oldPath", props.SavePath))
			err = d.qb.Torrent().SetLocation(ctx, []string{ih.HexString()}, torrentPath)
			if err != nil {
				return fmt.Errorf("error moving torrent: %w", err)
			}
		}

		return nil
	}
}

// TODO caching
func readInfoHash(ctx context.Context, file vfs.File) (infohash.T, error) {
	mi, err := metainfo.Load(ctxio.IoReader(ctx, file))
	if err != nil {
		return infohash.T{}, err
	}
	info, err := mi.UnmarshalInfo()
	if err != nil {
		return infohash.T{}, err
	}

	if info.HasV2() {
		ih := infohash_v2.HashBytes(mi.InfoBytes)
		return *(&ih).ToShort(), nil
	}

	return infohash.HashBytes(mi.InfoBytes), nil
}