package torrent

import (
	"fmt"
	"math"
	"strings"
	"time"
)

func (t *TorrentManager) RepairAll() {
	_ = t.repairWorker.Submit(func() {
		t.log.Info("Checking for torrents to repair")
		t.repairAll()
		t.log.Info("Finished checking for torrents to repair")
	})
}

func (t *TorrentManager) repairAll() {
	allTorrents, _ := t.DirectoryMap.Get(INT_ALL)
	var toRepair []*Torrent
	allTorrents.IterCb(func(_ string, torrent *Torrent) {
		if torrent.AnyInProgress() && torrent.ForRepair {
			t.log.Warnf("Skipping %s for repairs because it is in progress", torrent.AccessKey)
			return
		} else if torrent.ForRepair && !torrent.Unfixable {
			toRepair = append(toRepair, torrent)
		}
	})
	t.log.Debugf("Found %d torrents to repair", len(toRepair))
	for i := range toRepair {
		t.log.Infof("Repairing %s", toRepair[i].AccessKey)
		t.repair(toRepair[i])
	}
}

func (t *TorrentManager) Repair(torrent *Torrent) {
	_ = t.repairWorker.Submit(func() {
		t.log.Infof("Repairing torrent %s", torrent.AccessKey)
		t.repair(torrent)
		t.log.Infof("Finished repairing torrent %s", torrent.AccessKey)

		var updatedPaths []string
		t.assignedDirectoryCb(torrent, func(directory string) {
			updatedPaths = append(updatedPaths, fmt.Sprintf("%s/%s", directory, torrent.AccessKey))
		})
		t.TriggerHookOnLibraryUpdate(updatedPaths)
	})
}

func (t *TorrentManager) repair(torrent *Torrent) {
	if torrent.AnyInProgress() {
		t.log.Infof("Torrent %s is in progress, skipping repair until download is done", torrent.AccessKey)
		return
	}

	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
	}

	expiredLinkTolerance := 24 * time.Hour
	if torrent.OlderThanDuration(expiredLinkTolerance) {
		// first solution: reinsert with same selection
		if t.reinsertTorrent(torrent, "") {
			t.log.Infof("Successfully downloaded torrent %s to repair it", torrent.AccessKey)
			return
		} else {
			t.log.Warn("Failed to repair by reinserting torrent")
		}
	} else {
		t.log.Infof("Torrent %s is not older than %d hours to be repaired by reinsertion, skipping", torrent.AccessKey, expiredLinkTolerance.Hours())
	}

	// second solution: add only the missing 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 && torrent.SelectedFiles.Count() > 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 {
	oldTorrentIDs := make([]string, 0)
	// missing files means missing links
	// if missingFiles is not provided
	if missingFiles == "" {
		// only replace the torrent if we are reinserting all files
		oldTorrentIDs = torrent.DownloadedIDs.List()
		tmpSelection := ""
		torrent.SelectedFiles.IterCb(func(_ string, file *File) {
			tmpSelection += fmt.Sprintf("%d,", file.ID) // select all files
		})
		if tmpSelection == "" {
			return true // nothing to repair
		} else {
			missingFiles = tmpSelection[:len(tmpSelection)-1]
		}
	}

	// redownload torrent
	resp, err := t.Api.AddMagnetHash(torrent.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)
		for _, id := range oldTorrentIDs {
			t.Api.DeleteTorrent(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)
	for _, id := range oldTorrentIDs {
		t.Api.DeleteTorrent(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.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++
	}
}