package torrent

import (
	"encoding/gob"
	"fmt"
	"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"
	"github.com/elliotchance/orderedmap/v2"
	"github.com/nutsdb/nutsdb"
	"go.uber.org/zap"
)

type TorrentManager struct {
	TorrentMap      *orderedmap.OrderedMap[string, *Torrent] // accessKey -> Torrent
	requiredVersion string
	rd              *realdebrid.RealDebrid
	checksum        string
	config          config.ConfigInterface
	db              *nutsdb.DB
	workerPool      chan bool
	mu              *sync.Mutex
	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(config config.ConfigInterface, db *nutsdb.DB) *TorrentManager {
	t := &TorrentManager{
		TorrentMap:      orderedmap.NewOrderedMap[string, *Torrent](),
		requiredVersion: "10.11.2023",
		rd:              realdebrid.NewRealDebrid(config.GetToken(), logutil.NewLogger().Named("realdebrid")),
		config:          config,
		db:              db,
		workerPool:      make(chan bool, config.GetNumOfWorkers()),
		mu:              &sync.Mutex{},
		log:             logutil.NewLogger().Named("manager"),
	}

	// start with a clean slate
	t.mu.Lock()

	newTorrents, _, err := t.rd.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) {
			defer wg.Done()
			t.workerPool <- true
			torrentsChan <- t.getMoreInfo(newTorrents[idx])
			<-t.workerPool
		}(i)
	}
	t.log.Infof("Got %d torrents", len(newTorrents))
	wg.Wait()
	close(torrentsChan)
	for newTorrent := range torrentsChan {
		if newTorrent == nil {
			continue
		}
		torrent, _ := t.TorrentMap.Get(newTorrent.AccessKey)
		if torrent != nil {
			t.TorrentMap.Set(newTorrent.AccessKey, t.mergeToMain(torrent, newTorrent))
		} else {
			t.TorrentMap.Set(newTorrent.AccessKey, newTorrent)
		}
	}
	t.checksum = t.getChecksum()
	t.mu.Unlock()

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

	return t
}

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

	// Merge SelectedFiles
	// iteration works!
	for el := t2.SelectedFiles.Front(); el != nil; el = el.Next() {
		if _, ok := merged.SelectedFiles.Get(el.Key); !ok {
			merged.SelectedFiles.Set(el.Key, el.Value)
		}
	}

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

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

	// InProgress - if one of the instances is in progress, then the whole torrent is in progress
	for _, instance := range merged.Instances {
		if instance.Progress != 100 {
			merged.InProgress = true
			break
		}
	}

	return merged
}

// proxy
func (t *TorrentManager) UnrestrictUntilOk(link string) *realdebrid.UnrestrictResponse {
	return t.rd.UnrestrictUntilOk(link)
}

type torrentsResponse 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) 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.rd.GetTorrents(1)
		if err != nil {
			errChan <- err
			return
		}
		torrentsChan <- torrentsResponse{torrents: torrents, totalCount: totalCount}
	}()

	// GetActiveTorrentCount request
	go func() {
		count, err := t.rd.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.Errorf("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.config.GetRefreshEverySeconds()) * time.Second)

		checksum := t.getChecksum()
		if checksum == t.checksum {
			continue
		}

		t.mu.Lock()

		newTorrents, _, err := t.rd.GetTorrents(0)
		if err != nil {
			t.log.Errorf("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) {
				defer wg.Done()
				t.workerPool <- true
				torrentsChan <- t.getMoreInfo(newTorrents[idx])
				<-t.workerPool
			}(i)
		}

		// iteration works!
		var toDelete []string
		for el := t.TorrentMap.Front(); el != nil; el = el.Next() {
			found := false
			for _, newTorrent := range newTorrents {
				if newTorrent.ID == el.Value.AccessKey {
					found = true
					break
				}
			}
			if !found {
				toDelete = append(toDelete, el.Key)
			}
		}
		for _, accessKey := range toDelete {
			t.TorrentMap.Delete(accessKey)
		}

		wg.Wait()
		close(torrentsChan)
		for newTorrent := range torrentsChan {
			if newTorrent == nil {
				continue
			}
			torrent, _ := t.TorrentMap.Get(newTorrent.AccessKey)
			if torrent != nil {
				t.TorrentMap.Set(newTorrent.AccessKey, t.mergeToMain(torrent, newTorrent))
			} else {
				t.TorrentMap.Set(newTorrent.AccessKey, newTorrent)
			}
		}
		t.checksum = t.getChecksum()
		t.mu.Unlock()

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

// 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) {
		// see if api data and file data still match
		// then it means data is still usable
		info = torrentFromFile
	}
	if info == nil {
		info, err = t.rd.GetTorrentInfo(rdTorrent.ID)
		if err != nil {
			t.log.Errorf("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
	selectedFiles := orderedmap.NewOrderedMap[string, *File]()
	streamableCount := 0
	// if some Links are empty, we need to repair it
	forRepair := false
	for _, file := range info.Files {
		if isStreamable(file.Path) {
			streamableCount++
		}
		if file.Selected == 0 {
			continue
		}
		selectedFiles.Set(filepath.Base(file.Path), &File{
			File: file,
			Link: "", // no link yet
		})
	}
	if selectedFiles.Len() > len(info.Links) && info.Progress == 100 {
		t.log.Debugf("%d links has expired for %s %s", selectedFiles.Len()-len(info.Links), info.ID, info.Name)
		// 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(&rdTorrent, selectedFiles)
		if isChaotic {
			t.log.Errorf("Torrent id=%s %s is unfixable, it's always returning an unstreamable link (it is no longer shown 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 {
				// case for repair 1: it's missing some links (or all links)
				// if we download it as is, we might get the same file over and over again
				// so we need to redownload it with other files selected
				// that is why we check if there are other streamable files
				t.log.Infof("Torrent id=%s %s marked for repair", info.ID, info.Name)
				forRepair = true
			} else {
				t.log.Errorf("Torrent id=%s %s is unfixable, the lone streamable link has expired (it is no longer shown 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 selectedFiles.Len() == len(info.Links) {
		// all links are still intact! good!
		// iteration works!
		i := 0
		for el := selectedFiles.Front(); el != nil; el = el.Next() {
			if i < len(info.Links) {
				file := el.Value
				file.Link = info.Links[i] // verified working!
				selectedFiles.Set(el.Key, file)
				i++
			}
		}
	}

	info.ForRepair = forRepair
	torrent := Torrent{
		AccessKey:     t.getName(info.Name, info.OriginalName),
		SelectedFiles: selectedFiles,
		Directories:   t.getDirectories(info),
		LatestAdded:   info.Added,
		InProgress:    info.Progress != 100,
		Instances:     []realdebrid.TorrentInfo{*info},
	}
	if selectedFiles.Len() > 0 && torrentFromFile == nil {
		t.writeToFile(info) // only when there are selected files, else it's useless
	}
	return &torrent
}

func (t *TorrentManager) getName(name, originalName string) string {
	// 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) getDirectories(torrent *realdebrid.TorrentInfo) []string {
	var ret []string
	// Map torrents to directories
	switch t.config.GetVersion() {
	case "v1":
		configV1 := t.config.(*config.ZurgConfigV1)
		groupMap := configV1.GetGroupMap()
		// for every group, iterate over every torrent
		// and then sprinkle/distribute the torrents to the directories of the group
		for _, directories := range groupMap {
			for _, directory := range directories {
				var filenames []string
				for _, file := range torrent.Files {
					if file.Selected == 0 {
						continue
					}
					filenames = append(filenames, file.Path)
				}
				accessKey := t.getName(torrent.Name, torrent.OriginalName)
				if configV1.MeetsConditions(directory, torrent.ID, accessKey, filenames) {
					ret = append(ret, directory)
					break // we found a directory for this torrent for this group, so we can stop looking for more
				}
			}
		}
	default:
		t.log.Error("Unknown config version")
	}
	return ret
}

func (t *TorrentManager) writeToFile(torrent *realdebrid.TorrentInfo) {
	filePath := fmt.Sprintf("data/%s.bin", torrent.ID)
	file, err := os.Create(filePath)
	if err != nil {
		t.log.Fatalf("Failed creating file: %s", err)
		return
	}
	defer file.Close()

	torrent.Version = t.requiredVersion
	dataEncoder := gob.NewEncoder(file)
	dataEncoder.Encode(torrent)
}

func (t *TorrentManager) readFromFile(torrentID string) *realdebrid.TorrentInfo {
	filePath := fmt.Sprintf("data/%s.bin", torrentID)
	fileInfo, err := os.Stat(filePath)
	if err != nil {
		return nil
	}

	if time.Since(fileInfo.ModTime()) > time.Duration(t.config.GetCacheTimeHours())*time.Hour {
		return nil
	}

	file, err := os.Open(filePath)
	if err != nil {
		return nil
	}
	defer file.Close()

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

func (t *TorrentManager) organizeChaos(info *realdebrid.Torrent, selectedFiles *orderedmap.OrderedMap[string, *File]) (*orderedmap.OrderedMap[string, *File], bool) {
	type Result struct {
		Response *realdebrid.UnrestrictResponse
	}

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

	// Limit concurrency
	sem := make(chan bool, t.config.GetNumOfWorkers())

	for _, link := range info.Links {
		wg.Add(1)
		sem <- true
		go func(lnk string) {
			defer wg.Done()
			defer func() { <-sem }()
			resp := t.rd.UnrestrictUntilOk(lnk)
			resultsChan <- Result{Response: resp}
		}(link)
	}

	go func() {
		wg.Wait()
		close(sem)
		close(resultsChan)
	}()

	isChaotic := false
	for result := range resultsChan {
		if result.Response == nil {
			continue
		}
		found := false
		// iteration works!
		for el := selectedFiles.Front(); el != nil; el = el.Next() {
			if file, _ := selectedFiles.Get(el.Key); strings.Contains(file.Path, result.Response.Filename) {
				file.Link = result.Response.Link
				found = true
			}
		}
		if !found {
			if result.Response.Streamable == 1 {
				selectedFiles.Set(filepath.Base(result.Response.Filename), &File{
					File: realdebrid.File{
						ID:       math.MaxInt32,
						Path:     result.Response.Filename,
						Bytes:    result.Response.Filesize,
						Selected: 1,
					},
					Link: result.Response.Link,
				})
			} else {
				isChaotic = true
			}
		}
	}

	return selectedFiles, isChaotic
}

func (t *TorrentManager) repairAll() {
	// iteration works!
	for el := t.TorrentMap.Front(); el != nil; el = el.Next() {
		torrent := el.Value
		// do not repair if in progress
		if torrent.InProgress {
			continue
		}

		var missingFiles []File
		for el2 := torrent.SelectedFiles.Front(); el2 != nil; el2 = el2.Next() {
			file, ok := torrent.SelectedFiles.Get(el2.Key)
			if !ok {
				continue
			}
			// check for case of repairs like
			// case 1: missing links
			// case 2: unrestrictable links TODO
			if file.Link == "" {
				missingFiles = append(missingFiles, *file)
			}
		}
		if len(missingFiles) == 0 {
			continue
		}

		for _, info := range torrent.Instances {
			if info.ForRepair {
				t.log.Infof("There were less links than was expected on %s %s; fixing...", info.ID, info.Name)
				// t.repair(&info, true)
				break // only repair the first one for repair and then move on
			}
		}
	}
}

// func (t *TorrentManager) repair(info *realdebrid.TorrentInfo, tryReinsertionFirst bool) {
// 	// file.Link == "" should be repaired
// 	// then we repair it!
// 	t.log.Infof("Repairing torrent id=%s", info.ID)
// 	// check if we can still add more downloads
// 	proceed := t.canCapacityHandle()
// 	if !proceed {
// 		t.log.Error("Cannot add more torrents, exiting")
// 		return
// 	}

// 	// first solution: add the same selection, maybe it can be fixed by reinsertion?
// 	success := false
// 	if tryReinsertionFirst {
// 		success = t.reinsertTorrent(info, "", true)
// 	}
// 	if !success {
// 		// if all the selected files are missing but there are other streamable files
// 		var otherStreamableFileIDs []int
// 		for _, file := range info.Files {
// 			found := false
// 			for el := selectedFiles.Front(); el != nil; el = el.Next() {

// 			}
// 			for _, selectedFile := range selectedFiles {
// 				if selectedFile.ID == file.ID {
// 					found = true
// 					break
// 				}
// 			}
// 			if !found && isStreamable(file.Path) {
// 				otherStreamableFileIDs = append(otherStreamableFileIDs, file.ID)
// 			}
// 		}
// 		if (len(missingFiles) == len(selectedFiles) || len(missingFiles) == 1) && len(otherStreamableFileIDs) > 0 {
// 			// we will download 1 extra streamable file to force a redownload of the missing files
// 			// or if there's only 1 missing file, we will download 1 more to prevent a rename
// 			missingFilesPlus1 := strings.Join(getFileIDs(missingFiles), ",")
// 			t.log.Infof("Redownloading %d missing files", len(missingFiles))
// 			t.reinsertTorrent(info, missingFilesPlus1, false)
// 		} else if len(selectedFiles) > 1 {
// 			// 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.log.Infof("Redownloading %d missing files; batch 1 of 2", len(missingFiles1))
// 				t.reinsertTorrent(info, missingFiles1, false)
// 			}
// 			if missingFiles2 != "" {
// 				t.log.Infof("Redownloading %d missing files; batch 2 of 2", len(missingFiles2))
// 				t.reinsertTorrent(info, missingFiles2, false)
// 			} else {
// 				t.log.Info("No other missing files left to reinsert")
// 			}
// 		} else {
// 			t.log.Infof("Torrent id=%s is unfixable as the only link cached in RD is already broken (it is no longer shown in your directories)", info.ID)
// 			t.log.Debugf("You can try fixing it yourself magnet:?xt=urn:btih:%s", info.Hash)
// 			return
// 		}
// 		t.log.Info("Waiting for downloads to finish")
// 	}
// }

// func (t *TorrentManager) reinsertTorrent(torrent *realdebrid.TorrentInfo, missingFiles string, deleteIfFailed bool) bool {
// 	// if missingFiles is not provided, look for missing files
// 	if missingFiles == "" {
// 		var tmpSelection string
// 		for _, file := range torrent.Files {
// 			if file.Selected == 0 {
// 				continue
// 			}
// 			tmpSelection += fmt.Sprintf("%d,", file.ID)
// 		}
// 		if tmpSelection == "" {
// 			return false
// 		}
// 		if len(tmpSelection) > 0 {
// 			missingFiles = tmpSelection[:len(tmpSelection)-1]
// 		}
// 	}

// 	// redownload torrent
// 	resp, err := t.rd.AddMagnetHash(torrent.Hash)
// 	if err != nil {
// 		t.log.Errorf("Cannot redownload torrent: %v", err)
// 		return false
// 	}
// 	newTorrentID := resp.ID
// 	err = t.rd.SelectTorrentFiles(newTorrentID, missingFiles)
// 	if err != nil {
// 		t.log.Errorf("Cannot start redownloading: %v", err)
// 	}

// 	if deleteIfFailed {
// 		if err != nil {
// 			t.rd.DeleteTorrent(newTorrentID)
// 			return false
// 		}
// 		time.Sleep(1 * time.Second)
// 		// see if the torrent is ready
// 		info, err := t.rd.GetTorrentInfo(newTorrentID)
// 		if err != nil {
// 			t.log.Errorf("Cannot get info on redownloaded torrent id=%s : %v", newTorrentID, err)
// 			if deleteIfFailed {
// 				t.rd.DeleteTorrent(newTorrentID)
// 			}
// 			return false
// 		}
// 		time.Sleep(1 * time.Second)

// 		if info.Progress != 100 {
// 			t.log.Infof("Torrent id=%s is not cached anymore so we have to wait until completion, currently %d%%", info.ID, info.Progress)
// 			t.rd.DeleteTorrent(newTorrentID)
// 			return false
// 		}

// 		missingCount := len(strings.Split(missingFiles, ","))
// 		if len(info.Links) != missingCount {
// 			t.log.Infof("It didn't fix the issue for id=%s, only got %d files but we need %d, undoing", info.ID, len(info.Links), missingCount)
// 			t.rd.DeleteTorrent(newTorrentID)
// 			return false
// 		}
// 		t.log.Infof("Redownload successful id=%s, deleting old torrent id=%s", newTorrentID, torrent.ID)
// 		t.rd.DeleteTorrent(torrent.ID)
// 	}
// 	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.rd.GetActiveTorrentCount()
// 		if err != nil {
// 			t.log.Errorf("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++
// 	}
// }