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"
	"go.uber.org/zap"
)

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

	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
	// side note: 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
		}
		if instance.ForRepair {
			merged.ForRepair = true
		}
	}

	return merged
}

// proxy
func (t *TorrentManager) UnrestrictUntilOk(link string) *realdebrid.UnrestrictResponse {
	t.workerPool <- true
	ret := t.rd.UnrestrictUntilOk(link)
	<-t.workerPool
	return ret
}

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.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.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.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) {
				defer wg.Done()
				t.workerPool <- true
				torrentsChan <- t.getMoreInfo(newTorrents[idx])
				<-t.workerPool
			}(i)
		}

		// side note: 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.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
	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 {
		// 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 unfixable, it is 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.Warnf("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!
		// side note: 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(links []string, selectedFiles *orderedmap.OrderedMap[string, *File]) (*orderedmap.OrderedMap[string, *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)
		go func(lnk string) {
			defer wg.Done()
			t.workerPool <- true
			resp := t.rd.UnrestrictUntilOk(lnk)
			<-t.workerPool
			resultsChan <- Result{Response: resp}
		}(link)
	}

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

	isChaotic := false
	for result := range resultsChan {
		if result.Response == nil {
			continue
		}
		found := false
		// side note: 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() {
	// side note: 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
		}

		// do not repair if all files have links
		forRepair := false
		for el2 := torrent.SelectedFiles.Front(); el2 != nil; el2 = el2.Next() {
			file := el2.Value
			if file.Link == "" {
				forRepair = true
				break
			}
		}
		if !forRepair {
			// if it was marked for repair, unmark it
			torrent.ForRepair = false
			t.TorrentMap.Set(torrent.AccessKey, torrent)
			continue
		}

		// when getting info, we mark it for repair if it's missing some links
		if torrent.ForRepair {
			t.log.Infof("Found torrent for repair %s", torrent.AccessKey)
			t.Repair(torrent.AccessKey)
			break // only repair the first one for repair and then move on
		}
	}
}

func (t *TorrentManager) Repair(accessKey string) {
	if lastRepair, ok := t.repairMap.Get(accessKey); ok {
		if time.Since(lastRepair) < time.Duration(24*time.Hour) { // magic number: 24 hrs
			return
		}
	}
	t.repairMap.Set(accessKey, time.Now())

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

	torrent, _ := t.TorrentMap.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
	}

	// check if we can still add more downloads
	proceed := t.canCapacityHandle()
	if !proceed {
		t.log.Error("Cannot add more torrents, ignoring repair request")
		return
	}

	// make the file messy
	var links []string
	for el := torrent.SelectedFiles.Front(); el != nil; el = el.Next() {
		file := el.Value
		if file.Link != "" {
			links = append(links, file.Link)
		}
		file.Link = ""
	}
	selectedFiles, _ := t.organizeChaos(links, torrent.SelectedFiles)
	torrent.SelectedFiles = selectedFiles
	t.TorrentMap.Set(torrent.AccessKey, torrent)

	// 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
	for el := torrent.SelectedFiles.Front(); el != nil; el = el.Next() {
		file := el.Value
		if file.Link == "" {
			missingFiles = append(missingFiles, *file)
		}
	}
	if len(missingFiles) > 0 {
		t.log.Infof("Redownloading %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, look for missing files
	if missingFiles == "" {
		var tmpSelection string
		for el := torrent.SelectedFiles.Front(); el != nil; el = el.Next() {
			file := el.Value
			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.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.rd.SelectTorrentFiles(newTorrentID, missingFiles)
	if err != nil {
		t.log.Warnf("Cannot start redownloading: %v", err)
		t.rd.DeleteTorrent(newTorrentID)
		return false
	}
	time.Sleep(10 * time.Second)

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