package torrent

import (
	"bufio"
	"encoding/gob"
	"fmt"
	"math"
	"net/url"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/debridmediamanager/zurg/internal/config"
	"github.com/debridmediamanager/zurg/pkg/dav"
	"github.com/debridmediamanager/zurg/pkg/realdebrid"
	"github.com/debridmediamanager/zurg/pkg/utils"
	"github.com/dgraph-io/ristretto"
	cmap "github.com/orcaman/concurrent-map/v2"
	"github.com/panjf2000/ants/v2"
	"go.uber.org/zap"
)

const (
	INT_ALL        = "int__all__"
	INT_INFO_CACHE = "int__info__"
)

type TorrentManager struct {
	Config          config.ConfigInterface
	Api             *realdebrid.RealDebrid
	DirectoryMap    cmap.ConcurrentMap[string, cmap.ConcurrentMap[string, *Torrent]] // directory -> accessKey -> Torrent
	DownloadCache   cmap.ConcurrentMap[string, *realdebrid.Download]
	ResponseCache   *ristretto.Cache
	latestState     *LibraryState
	requiredVersion string
	workerPool      *ants.Pool
	log             *zap.SugaredLogger
}

// NewTorrentManager creates a new torrent manager
// it will fetch all torrents and their info in the background
// and store them in-memory and cached in files
func NewTorrentManager(cfg config.ConfigInterface, api *realdebrid.RealDebrid, p *ants.Pool, cache *ristretto.Cache, log *zap.SugaredLogger) *TorrentManager {
	initialSate := EmptyState()

	t := &TorrentManager{
		Config:          cfg,
		Api:             api,
		DirectoryMap:    cmap.New[cmap.ConcurrentMap[string, *Torrent]](),
		ResponseCache:   cache,
		latestState:     &initialSate,
		requiredVersion: "18.11.2023",
		workerPool:      p,
		log:             log,
	}

	// create internal directories
	t.DirectoryMap.Set(INT_ALL, cmap.New[*Torrent]())        // key is AccessKey
	t.DirectoryMap.Set(INT_INFO_CACHE, cmap.New[*Torrent]()) // key is Torrent ID
	// create directory maps
	for _, directory := range cfg.GetDirectories() {
		t.DirectoryMap.Set(directory, cmap.New[*Torrent]())
	}

	// Fetch downloads
	t.DownloadCache = cmap.New[*realdebrid.Download]()
	_ = t.workerPool.Submit(func() {
		page := 1
		offset := 0
		for {
			downloads, totalDownloads, err := t.Api.GetDownloads(page, offset)
			if err != nil {
				t.log.Fatalf("Cannot get downloads: %v\n", err)
			}
			for i := range downloads {
				if !t.DownloadCache.Has(downloads[i].Link) {
					t.DownloadCache.Set(downloads[i].Link, &downloads[i])
				}
			}
			offset += len(downloads)
			page++
			if offset >= totalDownloads {
				break
			}
		}
	})

	var newTorrents []realdebrid.Torrent
	var err error
	newTorrents, _, err = t.Api.GetTorrents(0)
	if err != nil {
		t.log.Fatalf("Cannot get torrents: %v\n", err)
	}

	t.log.Infof("Fetched %d downloads", t.DownloadCache.Count())

	torrentsChan := make(chan *Torrent, len(newTorrents))
	var wg sync.WaitGroup
	for i := range newTorrents {
		wg.Add(1)
		idx := i // capture the loop variable
		_ = t.workerPool.Submit(func() {
			defer wg.Done()
			torrentsChan <- t.getMoreInfo(newTorrents[idx])
		})
	}
	wg.Wait()
	close(torrentsChan)
	t.log.Infof("Fetched info for %d torrents", len(newTorrents))

	noInfoCount := 0
	allTorrents, _ := t.DirectoryMap.Get(INT_ALL)
	for tor := range torrentsChan {
		if tor == nil {
			noInfoCount++
			continue
		}
		if torrent, exists := allTorrents.Get(tor.AccessKey); !exists {
			allTorrents.Set(tor.AccessKey, tor)
		} else {
			mainTorrent := t.mergeToMain(torrent, tor)
			allTorrents.Set(tor.AccessKey, mainTorrent)
		}
	}

	allTorrents.IterCb(func(_ string, torrent *Torrent) {
		dav, html := t.buildTorrentResponses(torrent)
		t.AssignedDirectoryCb(torrent, func(directory string) {
			torrents, _ := t.DirectoryMap.Get(directory)
			torrents.Set(torrent.AccessKey, torrent)
			// torrent responses
			newHtml := strings.ReplaceAll(html, "$dir", directory)
			t.ResponseCache.Set(directory+"/"+torrent.AccessKey+".html", &newHtml, 1)
			newDav := strings.ReplaceAll(dav, "$dir", directory)
			t.ResponseCache.Set(directory+"/"+torrent.AccessKey+".dav", &newDav, 1)
		})
	})

	t.updateDirectoryResponsesCache()

	t.log.Infof("Compiled into %d torrents, %d were missing info", allTorrents.Count(), noInfoCount)

	t.SetNewLatestState(t.getCurrentState())

	if t.Config.EnableRepair() {
		t.log.Info("Checking for torrents to repair")
		t.repairAll()
		t.log.Info("Finished checking for torrents to repair")
	}

	_ = t.workerPool.Submit(func() {
		t.startRefreshJob()
	})

	t.log.Info("Finished initializing torrent manager")

	return t
}

func (t *TorrentManager) mergeToMain(mainTorrent, torrentToMerge *Torrent) *Torrent {
	// Merge SelectedFiles - itercb accesses a different copy of the selectedfiles map
	torrentToMerge.SelectedFiles.IterCb(func(filepath string, fileToMerge *File) {
		// see if it already exists in the main torrent
		if _, ok := mainTorrent.SelectedFiles.Get(filepath); !ok {
			// if it doesn't exist in the main torrent, add it
			mainTorrent.SelectedFiles.Set(filepath, fileToMerge)
		} else {
			// if it exists, compare the LatestAdded property and the link
			if mainTorrent.LatestAdded < torrentToMerge.LatestAdded && strings.HasPrefix(fileToMerge.Link, "http") {
				// if torrentToMerge is more recent and its file has a link, update the main torrent's file
				mainTorrent.SelectedFiles.Set(filepath, fileToMerge)
			}
			// else do nothing, the main torrent's file is more recent or has a valid link
		}
	})

	// Merge Instances
	mainTorrent.Instances = append(mainTorrent.Instances, torrentToMerge.Instances...)

	// LatestAdded
	if mainTorrent.LatestAdded < torrentToMerge.LatestAdded {
		mainTorrent.LatestAdded = torrentToMerge.LatestAdded
	}

	return mainTorrent
}

// proxy
func (t *TorrentManager) UnrestrictUntilOk(link string) *realdebrid.Download {
	retChan := make(chan *realdebrid.Download, 1)
	t.workerPool.Submit(func() {
		retChan <- t.Api.UnrestrictUntilOk(link, t.Config.ShouldServeFromRclone())
	})
	defer close(retChan)
	return <-retChan
	// return t.api.UnrestrictUntilOk(link, t.cfg.ShouldServeFromRclone())
}

func (t *TorrentManager) SetNewLatestState(checksum LibraryState) {
	t.latestState.DownloadingCount = checksum.DownloadingCount
	t.latestState.FirstTorrent = checksum.FirstTorrent
	t.latestState.TotalCount = checksum.TotalCount
}

func (t *TorrentManager) ScheduleForRefresh() {
	t.SetNewLatestState(EmptyState())
}

type torrentsResp struct {
	torrents   []realdebrid.Torrent
	totalCount int
}

// generates a checksum based on the number of torrents, the first torrent id and the number of active torrents
func (t *TorrentManager) getCurrentState() LibraryState {
	torrentsChan := make(chan torrentsResp, 1)
	countChan := make(chan int, 1)
	errChan := make(chan error, 2) // accommodate errors from both goroutines

	_ = t.workerPool.Submit(func() {
		torrents, totalCount, err := t.Api.GetTorrents(1)
		if err != nil {
			errChan <- err
			return
		}
		torrentsChan <- torrentsResp{torrents: torrents, totalCount: totalCount}
	})

	_ = t.workerPool.Submit(func() {
		count, err := t.Api.GetActiveTorrentCount()
		if err != nil {
			errChan <- err
			return
		}
		countChan <- count.DownloadingCount
	})

	// Existing goroutines for GetTorrents and GetActiveTorrentCount
	var torrents []realdebrid.Torrent
	var totalCount, count int

	for i := 0; i < 2; i++ {
		select {
		case resp := <-torrentsChan:
			torrents = resp.torrents
			totalCount = resp.totalCount
		case count = <-countChan:
		case err := <-errChan:
			t.log.Warnf("Checksum API Error: %v\n", err)
			return EmptyState()
		}
	}

	if len(torrents) == 0 {
		t.log.Error("Huh, no torrents returned")
		return EmptyState()
	}

	return LibraryState{
		TotalCount:       totalCount,
		FirstTorrent:     &torrents[0],
		DownloadingCount: count,
	}
}

// startRefreshJob periodically refreshes the torrents
func (t *TorrentManager) startRefreshJob() {
	t.log.Info("Starting periodic refresh")
	for {
		<-time.After(time.Duration(t.Config.GetRefreshEverySeconds()) * time.Second)

		checksum := t.getCurrentState()
		if t.latestState.equal(checksum) {
			continue
		}

		newTorrents, _, err := t.Api.GetTorrents(0)
		if err != nil {
			t.log.Warnf("Cannot get torrents: %v\n", err)
			continue
		}
		t.log.Infof("Detected changes! Refreshing %d torrents", len(newTorrents))

		// handle deleted torrents in info cache
		keep := make(map[string]bool)
		for _, torrent := range newTorrents {
			keep[torrent.ID] = true
		}
		var toDelete []string
		infoCache, _ := t.DirectoryMap.Get(INT_INFO_CACHE)
		infoCache.IterCb(func(torrentID string, torrent *Torrent) {
			if _, ok := keep[torrentID]; !ok {
				toDelete = append(toDelete, torrentID)
			}
		})
		for _, torrentID := range toDelete {
			infoCache.Remove(torrentID)
		}
		// end info cache cleanup

		torrentsChan := make(chan *Torrent, len(newTorrents))
		var wg sync.WaitGroup
		for i := range newTorrents {
			wg.Add(1)
			idx := i // capture the loop variable
			_ = t.workerPool.Submit(func() {
				defer wg.Done()
				torrentsChan <- t.getMoreInfo(newTorrents[idx])
			})
		}
		wg.Wait()
		close(torrentsChan)
		t.log.Infof("Fetched info for %d torrents", len(newTorrents))

		noInfoCount := 0
		oldTorrents, _ := t.DirectoryMap.Get(INT_ALL)
		newSet := cmap.New[*Torrent]()
		for info := range torrentsChan {
			if info == nil {
				noInfoCount++
				continue
			}
			if torrent, exists := oldTorrents.Get(info.AccessKey); !exists {
				oldTorrents.Set(info.AccessKey, info)
				newSet.Set(info.AccessKey, info)
			} else {
				mainTorrent := t.mergeToMain(torrent, info)
				oldTorrents.Set(info.AccessKey, mainTorrent)
				newSet.Set(info.AccessKey, mainTorrent)
			}
		}

		var updatedPaths []string

		newSet.IterCb(func(_ string, torrent *Torrent) {
			dav, html := t.buildTorrentResponses(torrent)
			t.AssignedDirectoryCb(torrent, func(directory string) {
				torrents, _ := t.DirectoryMap.Get(directory)
				torrents.Set(torrent.AccessKey, torrent)
				if torrent.LatestAdded > t.latestState.FirstTorrent.Added {
					updatedPaths = append(updatedPaths, fmt.Sprintf("%s/%s", directory, torrent.AccessKey))
				}
				// torrent responses
				cacheKey := directory + "/" + torrent.AccessKey
				newHtml := strings.ReplaceAll(html, "$dir", directory)
				t.ResponseCache.Set(cacheKey+".html", &newHtml, 1)
				newDav := strings.ReplaceAll(dav, "$dir", directory)
				t.ResponseCache.Set(cacheKey+".dav", &newDav, 1)
			})
		})

		// delete torrents that no longer exist
		oldAccessKeys := oldTorrents.Keys()
		for _, oldAccessKey := range oldAccessKeys {
			if _, ok := newSet.Get(oldAccessKey); !ok {
				t.DirectoryMap.IterCb(func(_ string, torrents cmap.ConcurrentMap[string, *Torrent]) {
					torrents.Remove(oldAccessKey)
				})
				t.log.Infof("Deleted torrent: %s\n", oldAccessKey)
			}
		}
		t.updateDirectoryResponsesCache()

		t.log.Infof("Compiled into %d torrents, %d were missing info", oldTorrents.Count(), noInfoCount)

		t.SetNewLatestState(t.getCurrentState())

		if t.Config.EnableRepair() {
			t.log.Info("Checking for torrents to repair")
			t.repairAll()
			t.log.Info("Finished checking for torrents to repair")
		} else {
			t.log.Info("Repair is disabled, skipping repair check")
		}
		_ = t.workerPool.Submit(func() {
			OnLibraryUpdateHook(updatedPaths, t.Config, t.log)
		})

		t.log.Info("Finished refreshing torrents")
	}
}

// getMoreInfo gets original name, size and files for a torrent
func (t *TorrentManager) getMoreInfo(rdTorrent realdebrid.Torrent) *Torrent {
	infoCache, _ := t.DirectoryMap.Get(INT_INFO_CACHE)
	if infoCache.Has(rdTorrent.ID) {
		tor, _ := infoCache.Get(rdTorrent.ID)
		return tor
	}

	var info *realdebrid.TorrentInfo
	var err error
	// file cache
	torrentFromFile := t.readTorrentFromFile(rdTorrent.ID)
	if torrentFromFile != nil && len(torrentFromFile.ID) > 0 && len(torrentFromFile.Links) > 0 && len(torrentFromFile.Links) == len(rdTorrent.Links) && torrentFromFile.Links[0] == rdTorrent.Links[0] {
		info = torrentFromFile
		info.Progress = rdTorrent.Progress
	} else {
		torrentFromFile = nil
	}
	if info == nil {
		info, err = t.Api.GetTorrentInfo(rdTorrent.ID)
		if err != nil {
			t.log.Warnf("Cannot get info for id=%s: %v\n", rdTorrent.ID, err)
			return nil
		}
	}
	// SelectedFiles is a subset of Files with only the selected ones
	// it also has a Link field, which can be empty
	// if it is empty, it means the file is no longer available
	// Files+Links together are the same as SelectedFiles
	var selectedFiles []*File
	// if some Links are empty, we need to repair it
	for _, file := range info.Files {
		if file.Selected == 0 {
			continue
		}
		selectedFiles = append(selectedFiles, &File{
			File:  file,
			Added: info.Added,
			Ended: info.Ended,
			Link:  "", // no link yet
		})
	}
	if len(selectedFiles) > len(info.Links) && info.Progress == 100 {
		t.log.Warnf("Torrent id=%s is partly expired, it has %d selected files but only %d links", info.ID, len(selectedFiles), len(info.Links))
	} else if len(selectedFiles) == len(info.Links) {
		// all links are still intact! good!
		for i, file := range selectedFiles {
			file.Link = info.Links[i]
			i++
		}
	}

	torrent := Torrent{
		AccessKey:   t.getName(info.Name, info.OriginalName),
		LatestAdded: info.Added,
		Instances:   []realdebrid.TorrentInfo{*info},
	}
	torrent.SelectedFiles = cmap.New[*File]()
	for _, file := range selectedFiles {
		torrent.SelectedFiles.Set(filepath.Base(file.Path), file)
	}

	if len(selectedFiles) > 0 && torrentFromFile == nil {
		t.writeTorrentToFile(info) // only when there are selected files, else it's useless
	}

	infoCache.Set(rdTorrent.ID, &torrent)

	return &torrent
}

func (t *TorrentManager) getName(name, originalName string) string {
	if t.Config.EnableRetainRDTorrentName() {
		return name
	}
	// drop the extension from the name
	if t.Config.EnableRetainFolderNameExtension() && strings.Contains(name, originalName) {
		return name
	} else {
		ret := strings.TrimSuffix(originalName, ".mp4")
		ret = strings.TrimSuffix(ret, ".mkv")
		return ret
	}
}

func (t *TorrentManager) writeTorrentToFile(torrent *realdebrid.TorrentInfo) error {
	filePath := "data/" + torrent.ID + ".bin"
	file, err := os.Create(filePath)
	if err != nil {
		return fmt.Errorf("failed creating file: %w", err)
	}
	defer file.Close()

	w := bufio.NewWriter(file)
	defer w.Flush()

	torrent.Version = t.requiredVersion
	dataEncoder := gob.NewEncoder(w)
	if err := dataEncoder.Encode(torrent); err != nil {
		return fmt.Errorf("failed encoding torrent: %w", err)
	}
	return nil
}

func (t *TorrentManager) readTorrentFromFile(torrentID string) *realdebrid.TorrentInfo {
	filePath := "data/" + torrentID + ".bin"
	file, err := os.Open(filePath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return nil
	}
	defer file.Close()

	r := bufio.NewReader(file)
	var torrent realdebrid.TorrentInfo
	dataDecoder := gob.NewDecoder(r)
	if err := dataDecoder.Decode(&torrent); err != nil {
		return nil
	}
	if torrent.Version != t.requiredVersion {
		return nil
	}
	return &torrent
}

func (t *TorrentManager) organizeChaos(links []string, selectedFiles []*File) ([]*File, bool) {
	type Result struct {
		Response *realdebrid.Download
	}

	resultsChan := make(chan Result, len(links))
	var wg sync.WaitGroup

	for _, link := range links {
		wg.Add(1)
		link := link // redeclare to avoid closure on loop variable
		// Use the existing worker pool to submit tasks
		_ = t.workerPool.Submit(func() {
			defer wg.Done()
			if t.DownloadCache.Has(link) {
				download, _ := t.DownloadCache.Get(link)
				resultsChan <- Result{Response: download}
				return
			}
			resp := t.Api.UnrestrictUntilOk(link, t.Config.ShouldServeFromRclone())
			resultsChan <- Result{Response: resp}
		})
	}

	wg.Wait()
	close(resultsChan)

	isChaotic := false
	for result := range resultsChan {
		if result.Response == nil {
			continue
		}
		found := false
		for _, file := range selectedFiles {
			if strings.Contains(file.Path, result.Response.Filename) {
				file.Link = result.Response.Link
				found = true
			}
		}
		if !found {
			if result.Response.Streamable == 1 {
				now := time.Now().Format(time.RFC3339)
				selectedFiles = append(selectedFiles, &File{
					File: realdebrid.File{
						ID:       math.MaxInt32,
						Path:     result.Response.Filename,
						Bytes:    result.Response.Filesize,
						Selected: 1,
					},
					Added: now,
					Ended: now,
					Link:  result.Response.Link,
				})
			} else {
				isChaotic = true
			}
		}
	}

	return selectedFiles, isChaotic
}

func (t *TorrentManager) repairAll() {
	proceed := t.canCapacityHandle() // blocks for approx 45 minutes if active torrents are full
	if !proceed {
		t.log.Error("Reached the max number of active torrents, cannot start repair")
		return
	}

	var toDelete []string
	allTorrents, _ := t.DirectoryMap.Get(INT_ALL)
	allTorrents.IterCb(func(_ string, torrent *Torrent) {
		if torrent.AnyInProgress() {
			t.log.Debugf("Skipping %s for repairs because it is in progress", torrent.AccessKey)
			return
		}
		forRepair := false
		unselected := 0
		torrent.SelectedFiles.IterCb(func(_ string, file *File) {
			if file.Link == "repair" && !forRepair {
				file.Link = "repairing"
				t.log.Debugf("Found a file to repair for torrent %s", torrent.AccessKey)
				forRepair = true
			}
			if file.Link == "unselect" {
				unselected++
			}
		})
		if forRepair {
			t.log.Infof("Repairing %s", torrent.AccessKey)
			t.Repair(torrent.AccessKey)
		}
		if unselected == torrent.SelectedFiles.Count() && unselected > 0 {
			t.log.Infof("Deleting %s", torrent.AccessKey)
			toDelete = append(toDelete, torrent.AccessKey)
		}
	})
	for _, accessKey := range toDelete {
		t.Delete(accessKey)
	}
}

func (t *TorrentManager) Delete(accessKey string) {
	infoCache, _ := t.DirectoryMap.Get(INT_INFO_CACHE)
	t.log.Infof("Deleting torrent %s", accessKey)
	allTorrents, _ := t.DirectoryMap.Get(INT_ALL)
	if torrent, ok := allTorrents.Get(accessKey); ok {
		for _, instance := range torrent.Instances {
			infoCache.Remove(instance.ID)
			t.Api.DeleteTorrent(instance.ID)
		}
	}
	t.DirectoryMap.IterCb(func(_ string, torrents cmap.ConcurrentMap[string, *Torrent]) {
		if _, ok := torrents.Get(accessKey); ok {
			torrents.Remove(accessKey)
		}
	})
}

func (t *TorrentManager) Repair(accessKey string) {
	if !t.Config.EnableRepair() {
		t.log.Warn("Repair is disabled; if you do not have other zurg instances running, you should enable repair")
		return
	}

	allTorrents, _ := t.DirectoryMap.Get(INT_ALL)
	torrent, _ := allTorrents.Get(accessKey)
	if torrent == nil {
		t.log.Warnf("Cannot find torrent %s anymore so we are not repairing it", accessKey)
		return
	}

	if torrent.AnyInProgress() {
		t.log.Infof("Torrent %s is in progress, cannot repair", torrent.AccessKey)
		return
	}

	// make the file messy
	t.log.Infof("Evaluating whole torrent to find the correct files for torrent: %s", torrent.AccessKey)

	var selectedFiles []*File
	var isChaotic bool
	var links []string
	streamableCount := 0
	torrent.SelectedFiles.IterCb(func(_ string, file *File) {
		if utils.IsStreamable(file.Path) {
			streamableCount++
		}
		fileCopy := &File{
			File:  file.File,
			Added: file.Added,
			Ended: file.Ended,
			Link:  file.Link,
		}
		selectedFiles = append(selectedFiles, fileCopy)
		if strings.HasPrefix(fileCopy.Link, "http") {
			links = append(links, fileCopy.Link)
		}
		fileCopy.Link = "" // empty the links = chaos!
	})
	// chaotic file means RD will not output the desired file selection
	// e.g. even if we select just a single mkv, it will output a rar
	selectedFiles, isChaotic = t.organizeChaos(links, selectedFiles)
	if isChaotic {
		t.log.Warnf("Torrent %s is always returning an unplayable rar file (it will no longer show up in your directories, zurg suggests you delete it)", torrent.AccessKey)
		t.DirectoryMap.IterCb(func(_ string, torrents cmap.ConcurrentMap[string, *Torrent]) {
			torrents.Remove(torrent.AccessKey)
		})
		t.ScheduleForRefresh()
		// t.log.Debugf("You can try fixing it yourself magnet:?xt=urn:btih:%s", info.Hash)
		return
	} else if streamableCount == 1 {
		t.log.Warnf("Torrent %s only file has expired (it will no longer show up in your directories, zurg suggests you delete it)", torrent.AccessKey)
		t.log.Debugf("You can try fixing it yourself magnet:?xt=urn:btih:%s", torrent.Instances[0].Hash)
		t.DirectoryMap.IterCb(func(_ string, torrents cmap.ConcurrentMap[string, *Torrent]) {
			torrents.Remove(torrent.AccessKey)
		})
		t.ScheduleForRefresh()
		return
	}
	// t.log.Debugf("Identified the expired files of torrent id=%s", info.ID)
	for _, newFile := range selectedFiles {
		if file, exists := torrent.SelectedFiles.Get(filepath.Base(newFile.Path)); exists {
			file.Link = newFile.Link
		} else {
			torrent.SelectedFiles.Set(filepath.Base(newFile.Path), newFile)
		}
	}

	proceed := t.canCapacityHandle() // blocks for approx 45 minutes if active torrents are full
	if !proceed {
		t.log.Error("Reached the max number of active torrents, cannot continue with the repair")
		return
	}

	// first solution: add the same selection, maybe it can be fixed by reinsertion?
	if t.reinsertTorrent(torrent, "") {
		t.log.Infof("Successfully downloaded torrent %s to repair it", torrent.AccessKey)
		return
	}

	// if all the selected files are missing but there are other streamable files
	var missingFiles []File
	torrent.SelectedFiles.IterCb(func(_ string, file *File) {
		if !strings.HasPrefix(file.Link, "http") {
			missingFiles = append(missingFiles, *file)
		}
	})

	// if we download a single file, it will be named differently
	// so we need to download 1 extra file to preserve the name
	// this is only relevant if we enable retain_rd_torrent_name
	if len(missingFiles) == 1 && streamableCount > 1 {
		// add the first file link encountered with a prefix of http
		for _, file := range torrent.SelectedFiles.Items() {
			if strings.HasPrefix(file.Link, "http") {
				missingFiles = append(missingFiles, *file)
				break
			}
		}
	}
	if len(missingFiles) > 0 {
		t.log.Infof("Redownloading in multiple batches the %d missing files for torrent %s", len(missingFiles), torrent.AccessKey)
		// if not, last resort: add only the missing files but do it in 2 batches
		half := len(missingFiles) / 2
		missingFiles1 := strings.Join(getFileIDs(missingFiles[:half]), ",")
		missingFiles2 := strings.Join(getFileIDs(missingFiles[half:]), ",")
		if missingFiles1 != "" {
			t.reinsertTorrent(torrent, missingFiles1)
		}
		if missingFiles2 != "" {
			t.reinsertTorrent(torrent, missingFiles2)
		}
	} else {
		t.log.Warnf("Torrent %s has no missing files to repair", torrent.AccessKey)
	}
}

func (t *TorrentManager) reinsertTorrent(torrent *Torrent, missingFiles string) bool {
	// if missingFiles is not provided, missing files means missing links
	if missingFiles == "" {
		tmpSelection := ""
		torrent.SelectedFiles.IterCb(func(_ string, file *File) {
			if !strings.HasPrefix(file.Link, "http") {
				tmpSelection += fmt.Sprintf("%d,", file.ID)
			}
		})
		if tmpSelection == "" {
			return false
		}
		if len(tmpSelection) > 0 {
			missingFiles = tmpSelection[:len(tmpSelection)-1]
		}
	}

	// redownload torrent
	resp, err := t.Api.AddMagnetHash(torrent.Instances[0].Hash)
	if err != nil {
		t.log.Warnf("Cannot redownload torrent: %v", err)
		return false
	}
	time.Sleep(1 * time.Second)

	// select files
	newTorrentID := resp.ID
	err = t.Api.SelectTorrentFiles(newTorrentID, missingFiles)
	if err != nil {
		t.log.Warnf("Cannot start redownloading: %v", err)
		t.Api.DeleteTorrent(newTorrentID)
		return false
	}
	time.Sleep(10 * time.Second)

	// see if the torrent is ready
	info, err := t.Api.GetTorrentInfo(newTorrentID)
	if err != nil {
		t.log.Warnf("Cannot get info on redownloaded torrent id=%s : %v", newTorrentID, err)
		t.Api.DeleteTorrent(newTorrentID)
		return false
	}

	if info.Status == "magnet_error" || info.Status == "error" || info.Status == "virus" || info.Status == "dead" {
		t.log.Warnf("The redownloaded torrent id=%s is in error state: %s", newTorrentID, info.Status)
		t.Api.DeleteTorrent(newTorrentID)
		return false
	}

	if info.Progress != 100 {
		t.log.Infof("Torrent id=%s is not cached anymore so we have to wait until completion (this should fix the issue already)", info.ID)
		return true
	}

	missingCount := len(strings.Split(missingFiles, ","))
	if len(info.Links) != missingCount {
		t.log.Infof("It did not fix the issue for id=%s, only got %d files but we need %d, undoing", info.ID, len(info.Links), missingCount)
		t.Api.DeleteTorrent(newTorrentID)
		return false
	}

	t.log.Infof("Repair successful id=%s", newTorrentID)
	return true
}

func (t *TorrentManager) canCapacityHandle() bool {
	// max waiting time is 45 minutes
	const maxRetries = 50
	const baseDelay = 1 * time.Second
	const maxDelay = 60 * time.Second
	retryCount := 0
	for {
		count, err := t.Api.GetActiveTorrentCount()
		if err != nil {
			t.log.Warnf("Cannot get active downloads count: %v", err)
			if retryCount >= maxRetries {
				t.log.Error("Max retries reached. Exiting.")
				return false
			}
			delay := time.Duration(math.Pow(2, float64(retryCount))) * baseDelay
			if delay > maxDelay {
				delay = maxDelay
			}
			time.Sleep(delay)
			retryCount++
			continue
		}

		if count.DownloadingCount < count.MaxNumberOfTorrents {
			// t.log.Infof("We can still add a new torrent, we have capacity for %d more", count.MaxNumberOfTorrents-count.DownloadingCount)
			return true
		}

		delay := time.Duration(math.Pow(2, float64(retryCount))) * baseDelay
		if delay > maxDelay {
			delay = maxDelay
		}
		t.log.Infof("We have reached the max number of active torrents, waiting for %s seconds before retrying", delay)

		if retryCount >= maxRetries {
			t.log.Error("Max retries reached, exiting")
			return false
		}

		time.Sleep(delay)
		retryCount++
	}
}

func (t *TorrentManager) updateDirectoryResponsesCache() {
	t.DirectoryMap.IterCb(func(directory string, torrents cmap.ConcurrentMap[string, *Torrent]) {
		allKeys := torrents.Keys()
		sort.Strings(allKeys)
		davRet := ""
		htmlRet := ""
		for _, accessKey := range allKeys {
			if tor, ok := torrents.Get(accessKey); ok {
				if tor.AnyInProgress() {
					continue
				}
				davRet += dav.Directory(tor.AccessKey, tor.LatestAdded)
				htmlRet += fmt.Sprintf("<li><a href=\"/http/%s/%s\">%s</a></li>", directory, tor.AccessKey, tor.AccessKey)
			}
		}

		cacheKey := directory
		davRet = "<?xml version=\"1.0\" encoding=\"utf-8\"?><d:multistatus xmlns:d=\"DAV:\">" + dav.BaseDirectory(directory, "") + dav.BaseDirectory(directory, "") + davRet + "</d:multistatus>"
		t.ResponseCache.Set(cacheKey+".dav", &davRet, 1)
		htmlRet = "<ol>" + htmlRet
		t.ResponseCache.Set(cacheKey+".html", &htmlRet, 1)
	})
}

func (t *TorrentManager) buildTorrentResponses(tor *Torrent) (string, string) {
	davRet := "<?xml version=\"1.0\" encoding=\"utf-8\"?><d:multistatus xmlns:d=\"DAV:\">" + dav.BaseDirectory(filepath.Join("$dir", tor.AccessKey), tor.LatestAdded)
	htmlRet := "<ol>"
	filenames := tor.SelectedFiles.Keys()
	sort.Strings(filenames)
	for _, filename := range filenames {
		file, _ := tor.SelectedFiles.Get(filename)
		if file == nil || !strings.HasPrefix(file.Link, "http") {
			// will be caught by torrent manager's repairAll
			// just skip it for now
			continue
		}

		davRet += dav.File(filename, file.Bytes, file.Ended)

		filePath := filepath.Join("$dir", tor.AccessKey, url.PathEscape(filename))
		htmlRet += fmt.Sprintf("<li><a href=\"%s\">%s</a></li>", filePath, filename)
	}
	davRet += "</d:multistatus>"

	return davRet, htmlRet
}

func (t *TorrentManager) AssignedDirectoryCb(tor *Torrent, cb func(string)) {
	var torrentIDs []string
	for _, instance := range tor.Instances {
		torrentIDs = append(torrentIDs, instance.ID)
	}
	// get filenames needed for directory conditions
	filenames := tor.SelectedFiles.Keys()
	// Map torrents to directories
	switch t.Config.GetVersion() {
	case "v1":
		configV1 := t.Config.(*config.ZurgConfigV1)
		for _, directories := range configV1.GetGroupMap() {
			for _, directory := range directories {
				if t.Config.MeetsConditions(directory, tor.AccessKey, torrentIDs, filenames) {
					cb(directory)
					break
				}
			}
		}
	}
}