package torrent

import (
	"bufio"
	"encoding/gob"
	"fmt"
	"hash/fnv"
	"math"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

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

const ALL_TORRENTS = "__all__"

type TorrentManager struct {
	DirectoryMap    cmap.ConcurrentMap[string, cmap.ConcurrentMap[string, *Torrent]] // directory -> accessKey -> Torrent
	checksum        string
	requiredVersion string
	cfg             config.ConfigInterface
	api             *realdebrid.RealDebrid
	antsPool        *ants.Pool
	log             *zap.SugaredLogger
	mu              *sync.Mutex
}

// 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) *TorrentManager {
	t := &TorrentManager{
		cfg:             cfg,
		DirectoryMap:    cmap.New[cmap.ConcurrentMap[string, *Torrent]](),
		requiredVersion: "18.11.2023",
		api:             api,
		antsPool:        p,
		log:             logutil.NewLogger().Named("manager"),
		mu:              &sync.Mutex{},
	}

	// create special directory
	t.DirectoryMap.Set("__all__", cmap.New[*Torrent]()) // key is AccessKey
	// create directory maps
	for _, directory := range cfg.GetDirectories() {
		t.DirectoryMap.Set(directory, cmap.New[*Torrent]())
	}

	newTorrents, _, err := t.api.GetTorrents(0)
	if err != nil {
		t.log.Fatalf("Cannot get torrents: %v\n", err)
	}

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

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

	anotherCt := 0
	allTorrents.IterCb(func(accessKey string, torrent *Torrent) {
		anotherCt++
		// get IDs
		var torrentIDs []string
		for _, instance := range torrent.Instances {
			torrentIDs = append(torrentIDs, instance.ID)
		}

		// get filenames
		filenames := torrent.SelectedFiles.Keys()
		// Map torrents to directories
		switch t.cfg.GetVersion() {
		case "v1":
			configV1 := t.cfg.(*config.ZurgConfigV1)
			for _, directories := range configV1.GetGroupMap() {
				for _, directory := range directories {
					if t.cfg.MeetsConditions(directory, torrent.AccessKey, torrentIDs, filenames) {
						torrents, _ := t.DirectoryMap.Get(directory)
						torrents.Set(accessKey, torrent)
						break
					}
				}
			}
		}
	})

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

	t.SetChecksum(t.getChecksum())

	if t.cfg.EnableRepair() {
		go t.repairAll()
	}
	go t.startRefreshJob()

	return t
}

func (t *TorrentManager) mergeToMain(t1, t2 *Torrent) *Torrent {
	mainTorrent := t1

	// Merge SelectedFiles - itercb accesses a different copy of the selectedfiles map
	t2.SelectedFiles.IterCb(func(key string, file *File) {
		// see if it already exists in the main torrent
		if mainFile, ok := mainTorrent.SelectedFiles.Get(key); !ok {
			mainTorrent.SelectedFiles.Set(key, file)
		} else if file.Link != "" && mainFile.Link == "" {
			// if it exists, but the link is empty, then we can update it
			mainTorrent.SelectedFiles.Set(key, file)
		}
	})

	// Merge Instances
	mainTorrent.Instances = append(t1.Instances, t2.Instances...)

	// LatestAdded
	if t1.LatestAdded < t2.LatestAdded {
		mainTorrent.LatestAdded = t2.LatestAdded
	}

	return mainTorrent
}

// proxy
func (t *TorrentManager) UnrestrictUntilOk(link string) *realdebrid.UnrestrictResponse {
	ret := t.api.UnrestrictUntilOk(link)
	return ret
}

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

func (t *TorrentManager) SetChecksum(checksum string) {
	t.mu.Lock()
	t.checksum = checksum
	t.mu.Unlock()
}

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

	// GetTorrents request
	go func() {
		torrents, totalCount, err := t.api.GetTorrents(1)
		if err != nil {
			errChan <- err
			return
		}
		torrentsChan <- torrentsResponse{torrents: torrents, totalCount: totalCount}
	}()

	// GetActiveTorrentCount request
	go func() {
		count, err := t.api.GetActiveTorrentCount()
		if err != nil {
			errChan <- err
			return
		}
		countChan <- count.DownloadingCount
	}()

	var torrents []realdebrid.Torrent
	var totalCount, count int

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

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

	checksum := fmt.Sprintf("%d%s%d", totalCount, torrents[0].ID, count)
	return checksum
}

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

		checksum := t.getChecksum()
		if checksum == t.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))

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

		noInfoCount := 0
		allTorrents, _ := t.DirectoryMap.Get(ALL_TORRENTS)
		retain := make(map[string]bool)
		for info := range torrentsChan {
			if info == nil {
				noInfoCount++
				continue
			}
			retain[info.AccessKey] = true
			if torrent, exists := allTorrents.Get(info.AccessKey); exists {
				mainTorrent := t.mergeToMain(torrent, info)
				allTorrents.Set(info.AccessKey, mainTorrent)
			} else {
				allTorrents.Set(info.AccessKey, info)
			}
		}

		allTorrents.IterCb(func(accessKey string, torrent *Torrent) {
			// get IDs
			var torrentIDs []string
			for _, instance := range torrent.Instances {
				torrentIDs = append(torrentIDs, instance.ID)
			}

			// get filenames
			var filenames []string
			torrent.SelectedFiles.IterCb(func(_ string, file *File) {
				filenames = append(filenames, file.Path)
			})

			// Map torrents to directories
			switch t.cfg.GetVersion() {
			case "v1":
				configV1 := t.cfg.(*config.ZurgConfigV1)
				for _, directories := range configV1.GetGroupMap() {
					for _, directory := range directories {
						if t.cfg.MeetsConditions(directory, torrent.AccessKey, torrentIDs, filenames) {
							torrents, _ := t.DirectoryMap.Get(directory)
							torrents.Set(accessKey, torrent)
							break
						}
					}
				}
			}
		})

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

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

		t.SetChecksum(t.getChecksum())

		if t.cfg.EnableRepair() {
			go t.repairAll()
		}
		go OnLibraryUpdateHook(t.cfg)
	}
}

// getMoreInfo gets original name, size and files for a torrent
func (t *TorrentManager) getMoreInfo(rdTorrent realdebrid.Torrent) *Torrent {
	var info *realdebrid.TorrentInfo
	var err error
	// file cache
	torrentFromFile := t.readFromFile(rdTorrent.ID)
	if torrentFromFile != nil && len(torrentFromFile.ID) > 0 && len(torrentFromFile.Links) == len(rdTorrent.Links) {
		if (len(torrentFromFile.Links) > 0 && torrentFromFile.Links[0] == rdTorrent.Links[0]) || len(torrentFromFile.Links) == 0 {
			// see if api data and file data still match
			// then it means data is still usable
			info = torrentFromFile
			info.Progress = rdTorrent.Progress
		}
	}
	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
	streamableCount := 0
	// if some Links are empty, we need to repair it
	for _, file := range info.Files {
		if isStreamable(file.Path) {
			streamableCount++
		}
		if file.Selected == 0 {
			continue
		}
		selectedFiles = append(selectedFiles, &File{
			File:   file,
			Added:  info.Added,
			Link:   "", // no link yet
			ZurgFS: hashStringToFh(file.Path + info.Hash),
		})
	}
	if len(selectedFiles) > len(info.Links) && info.Progress == 100 {
		// 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
		var isChaotic bool
		selectedFiles, isChaotic = t.organizeChaos(info.Links, selectedFiles)
		if isChaotic {
			t.log.Warnf("Torrent id=%s %s is unplayable; it is always returning a rar file (it will no longer show up in your directories)", info.ID, info.Name)
			// t.log.Debugf("You can try fixing it yourself magnet:?xt=urn:btih:%s", info.Hash)
			return nil
		} else if streamableCount == 1 {
			t.log.Warnf("Torrent id=%s %s is unplayable; the lone streamable link has expired (it will no longer show up in your directories)", info.ID, info.Name)
			// t.log.Debugf("You can try fixing it yourself magnet:?xt=urn:btih:%s", info.Hash)
			return nil
		}
	} 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.writeToFile(info) // only when there are selected files, else it's useless
	}
	return &torrent
}

func hashStringToFh(s string) (fh uint64) {
	hasher := fnv.New64a()
	_, _ = hasher.Write([]byte(s)) // Write the string to the hasher; ignoring error as it never returns an error
	return hasher.Sum64()          // Returns a 64-bit hash value
}

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

func (t *TorrentManager) writeToFile(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) readFromFile(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.UnrestrictResponse
	}

	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 workerPool to submit tasks
		err := t.antsPool.Submit(func() {
			defer wg.Done()
			resp := t.api.UnrestrictUntilOk(link)
			resultsChan <- Result{Response: resp}
		})
		if err != nil {
			t.log.Errorf("Error submitting task to workerPool: %v", err)
		}
	}

	go func() {
		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 {
				selectedFiles = append(selectedFiles, &File{
					File: realdebrid.File{
						ID:       math.MaxInt32,
						Path:     result.Response.Filename,
						Bytes:    result.Response.Filesize,
						Selected: 1,
					},
					Added:  time.Now().Format(time.RFC3339),
					Link:   result.Response.Link,
					ZurgFS: hashStringToFh(result.Response.Filename),
				})
			} else {
				isChaotic = true
			}
		}
	}

	return selectedFiles, isChaotic
}

func (t *TorrentManager) repairAll() {
	t.log.Info("Checking for torrents to repair")
	allTorrents, _ := t.DirectoryMap.Get(ALL_TORRENTS)
	allTorrents.IterCb(func(_ string, torrent *Torrent) {
		if torrent.InProgress() {
			t.log.Infof("Torrent %s is in progress, cannot repair", torrent.AccessKey)
			return
		}
		forRepair := false
		torrent.SelectedFiles.IterCb(func(_ string, file *File) {
			if file.Link == "" {
				forRepair = true
			}
		})
		if forRepair {
			t.Repair(torrent.AccessKey)
		}
	})
}

func (t *TorrentManager) Repair(accessKey string) {
	if !t.cfg.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(ALL_TORRENTS)
	torrent, _ := allTorrents.Get(accessKey)
	if torrent == nil {
		t.log.Warnf("Cannot find torrent %s anymore to repair it", accessKey)
		return
	}

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

	proceed := t.canCapacityHandle() // blocks for approx 45 minutes
	if !proceed {
		t.log.Error("Cannot add more torrents, ignoring repair request")
		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 links []string
	torrent.SelectedFiles.IterCb(func(_ string, file *File) {
		selectedFiles = append(selectedFiles, file)
		if file.Link != "" {
			links = append(links, file.Link)
		}
		file.Link = "" // empty the links = chaos!
	})
	selectedFiles, _ = t.organizeChaos(links, selectedFiles)
	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)
		}
	}

	// 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 file.Link == "" {
			missingFiles = append(missingFiles, *file)
		}
	})
	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)
		}
	}
}

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 file.Link == "" {
				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
		}

		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++
	}
}