package torrent

import (
	"fmt"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/debridmediamanager/zurg/pkg/realdebrid"
	cmap "github.com/orcaman/concurrent-map/v2"
	"github.com/scylladb/go-set"
	"github.com/scylladb/go-set/strset"
)

func (t *TorrentManager) RefreshTorrents() []string {
	instances, _, err := t.Api.GetTorrents(0)
	if err != nil {
		t.log.Warnf("Cannot get torrents: %v\n", err)
		return nil
	}
	infoChan := make(chan *Torrent, len(instances))
	var wg sync.WaitGroup
	for i := range instances {
		wg.Add(1)
		idx := i // capture the loop variable
		_ = t.workerPool.Submit(func() {
			defer wg.Done()
			infoChan <- t.getMoreInfo(instances[idx])
		})
	}
	wg.Wait()
	close(infoChan)
	t.log.Infof("Fetched info for %d torrents", len(instances))

	freshKeys := set.NewStringSet()
	allTorrents, _ := t.DirectoryMap.Get(INT_ALL)
	noInfoCount := 0
	for info := range infoChan {
		if info == nil {
			noInfoCount++
			continue
		}
		freshKeys.Add(info.AccessKey)
		if torrent, exists := allTorrents.Get(info.AccessKey); !exists {
			t.allAccessKeys.Add(info.AccessKey)
			allTorrents.Set(info.AccessKey, info)
		} else if !strset.Difference(info.DownloadedIDs, torrent.DownloadedIDs).IsEmpty() {
			mainTorrent := t.mergeToMain(torrent, info)
			allTorrents.Set(info.AccessKey, &mainTorrent)
		}
	}
	t.log.Infof("Compiled into %d torrents, %d were missing info", allTorrents.Count(), noInfoCount)
	var updatedPaths []string
	// torrents yet to be assigned in a directory
	strset.Difference(freshKeys, t.allAccessKeys).Each(func(accessKey string) bool {
		// assign to directories
		tor, _ := allTorrents.Get(accessKey)
		t.assignedDirectoryCb(tor, func(directory string) {
			if strings.HasPrefix(directory, "int__") {
				return
			}
			torrents, _ := t.DirectoryMap.Get(directory)
			torrents.Set(accessKey, tor)
			updatedPaths = append(updatedPaths, fmt.Sprintf("%s/%s", directory, accessKey))
		})
		return true
	})
	// removed torrents
	strset.Difference(t.allAccessKeys, freshKeys).Each(func(accessKey string) bool {
		t.Delete(accessKey, false)
		return true
	})

	t.SetNewLatestState(t.getCurrentState())

	return updatedPaths
}

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

// 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
		}
		t.log.Infof("Detected changes! Refreshing %d torrents", checksum.TotalCount)

		updatedPaths := t.RefreshTorrents()
		t.log.Info("Finished refreshing torrents")

		t.TriggerHookOnLibraryUpdate(updatedPaths)

		if t.Config.EnableRepair() {
			t.RepairAll()
		} else {
			t.log.Info("Repair is disabled, skipping repair check")
		}
	}
}

// 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 tor, exists := infoCache.Get(rdTorrent.ID); exists && tor.SelectedFiles.Count() == len(rdTorrent.Links) {
		return tor
	}
	torrentFromFile := t.readTorrentFromFile(rdTorrent.ID)
	if torrentFromFile != nil && torrentFromFile.SelectedFiles.Count() == len(rdTorrent.Links) {
		infoCache.Set(rdTorrent.ID, torrentFromFile)
		return torrentFromFile
	}

	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
	}

	torrent := Torrent{
		AccessKey:   t.computeAccessKey(info.Name, info.OriginalName),
		LatestAdded: info.Added,
		Hash:        info.Hash,
	}
	// 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 {
		if len(info.Links) == 1 {
			// this usually is a rar file issue
			if t.Config.ShouldDeleteRarFiles() {
				t.log.Warnf("Torrent %s id=%s is a rar file, it cannot be repaired. Deleting...", info.Name, info.ID)
				t.Api.DeleteTorrent(info.ID)
			} else {
				t.log.Warnf("Torrent %s id=%s is a rar file, it cannot be repaired as it's a known Real-Debrid limitation. zurg recommends you delete this torrent or add auto_delete_rar_torrents: true in your config.yml", info.Name, info.ID)
				torrent.Unfixable = true
			}
			return nil
		} else {
			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))
			torrent.ForRepair = true
		}
	} else if len(selectedFiles) == len(info.Links) {
		// all links are still intact! good!
		for i, file := range selectedFiles {
			file.Link = info.Links[i]
		}
	}
	torrent.SelectedFiles = cmap.New[*File]()
	for _, file := range selectedFiles {
		// todo better handling of duplicate filenames
		if torrent.SelectedFiles.Has(filepath.Base(file.Path)) {
			oldName := filepath.Base(file.Path)
			ext := filepath.Ext(oldName)
			filename := strings.TrimSuffix(oldName, ext)
			newName := fmt.Sprintf("%s (%d)%s", filename, file.ID, ext)
			torrent.SelectedFiles.Set(newName, file)
		} else {
			torrent.SelectedFiles.Set(filepath.Base(file.Path), file)
		}
	}
	torrent.DownloadedIDs = strset.New()
	torrent.InProgressIDs = strset.New()
	if info.Progress == 100 {
		torrent.DownloadedIDs.Add(info.ID)
	} else {
		torrent.InProgressIDs.Add(info.ID)
	}

	t.writeTorrentToFile(rdTorrent.ID, &torrent)
	infoCache.Set(rdTorrent.ID, &torrent)

	return &torrent
}

func (t *TorrentManager) mergeToMain(existing, toMerge *Torrent) Torrent {
	mainTorrent := Torrent{}

	mainTorrent.AccessKey = existing.AccessKey
	mainTorrent.Hash = existing.Hash
	mainTorrent.DownloadedIDs = strset.New()
	mainTorrent.InProgressIDs = strset.New()

	// this function triggers only when we have a new DownloadedID
	strset.Difference(toMerge.DownloadedIDs, existing.DownloadedIDs).Each(func(id string) bool {
		mainTorrent.DownloadedIDs.Add(id)
		mainTorrent.InProgressIDs.Remove(id)
		return true
	})

	// the link can have the following values
	// 1. https://*** - the file is available
	// 2. repair - the file is available but we need to repair it
	// 3. repairing - the file is being repaired
	// 4. unselect - the file is deleted
	mainTorrent.SelectedFiles = existing.SelectedFiles
	toMerge.SelectedFiles.IterCb(func(filepath string, fileToMerge *File) {
		// see if it already exists in the main torrent
		if originalFile, ok := mainTorrent.SelectedFiles.Get(filepath); !ok || fileToMerge.Link == "unselect" {
			// if it doesn't exist in the main torrent, add it
			mainTorrent.SelectedFiles.Set(filepath, fileToMerge)
		} else if originalFile.Link != "unselect" {
			// if it exists, compare the LatestAdded property and the link
			if existing.LatestAdded < toMerge.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
		}
	})

	if existing.LatestAdded < toMerge.LatestAdded {
		mainTorrent.LatestAdded = toMerge.LatestAdded
	} else {
		mainTorrent.LatestAdded = existing.LatestAdded
	}

	return mainTorrent
}

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
	defer close(torrentsChan)
	defer close(countChan)
	defer close(errChan)

	_ = 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,
	}
}