package ytsync

import (
	"bufio"
	"encoding/csv"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"os/exec"
	"os/signal"
	"sort"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/lbryio/lbry.go/errors"
	"github.com/lbryio/lbry.go/jsonrpc"
	"github.com/lbryio/lbry.go/stop"
	"github.com/lbryio/lbry.go/util"
	"github.com/lbryio/lbry.go/ytsync/redisdb"
	"github.com/lbryio/lbry.go/ytsync/sources"
	"github.com/mitchellh/go-ps"
	log "github.com/sirupsen/logrus"
	"google.golang.org/api/googleapi/transport"
	"google.golang.org/api/youtube/v3"
)

const (
	channelClaimAmount = 0.01
	publishAmount      = 0.01
)

type video interface {
	ID() string
	IDAndNum() string
	PlaylistPosition() int
	PublishedAt() time.Time
	Sync(*jsonrpc.Client, string, float64, string, int) (*sources.SyncSummary, error)
}

// sorting videos
type byPublishedAt []video

func (a byPublishedAt) Len() int           { return len(a) }
func (a byPublishedAt) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a byPublishedAt) Less(i, j int) bool { return a[i].PublishedAt().Before(a[j].PublishedAt()) }

// Sync stores the options that control how syncing happens
type Sync struct {
	YoutubeAPIKey           string
	YoutubeChannelID        string
	LbryChannelName         string
	StopOnError             bool
	MaxTries                int
	ConcurrentVideos        int
	TakeOverExistingChannel bool
	Refill                  int
	Manager                 *SyncManager

	daemon         *jsonrpc.Client
	claimAddress   string
	videoDirectory string
	db             *redisdb.DB
	syncedVideos   map[string]syncedVideo
	grp            *stop.Group

	mux   sync.Mutex
	wg    sync.WaitGroup
	queue chan video
}

// SendErrorToSlack Sends an error message to the default channel and to the process log.
func SendErrorToSlack(format string, a ...interface{}) error {
	message := format
	if len(a) > 0 {
		message = fmt.Sprintf(format, a...)
	}
	log.Errorln(message)
	return util.SendToSlack(":sos: " + message)
}

// SendInfoToSlack Sends an info message to the default channel and to the process log.
func SendInfoToSlack(format string, a ...interface{}) error {
	message := format
	if len(a) > 0 {
		message = fmt.Sprintf(format, a...)
	}
	log.Infoln(message)
	return util.SendToSlack(":information_source: " + message)
}

// IsInterrupted can be queried to discover if the sync process was interrupted manually
func (s *Sync) IsInterrupted() bool {
	select {
	case <-s.grp.Ch():
		return true
	default:
		return false
	}
}

func (s *Sync) FullCycle() (e error) {
	if os.Getenv("HOME") == "" {
		return errors.Err("no $HOME env var found")
	}
	if s.YoutubeChannelID == "" {
		return errors.Err("channel ID not provided")
	}
	syncedVideos, err := s.Manager.setChannelStatus(s.YoutubeChannelID, StatusSyncing)
	if err != nil {
		return err
	}

	defer func() {
		if e != nil {
			//conditions for which a channel shouldn't be marked as failed
			noFailConditions := []string{
				"this youtube channel is being managed by another server",
				"channel is already up to date",
			}
			if util.SubstringInSlice(e.Error(), noFailConditions) {
				return
			}
			_, err := s.Manager.setChannelStatus(s.YoutubeChannelID, StatusFailed)
			if err != nil {
				msg := fmt.Sprintf("Failed setting failed state for channel %s.", s.LbryChannelName)
				err = errors.Prefix(msg, err)
				e = errors.Prefix(err.Error(), e)
			}
		} else if !s.IsInterrupted() {
			_, err := s.Manager.setChannelStatus(s.YoutubeChannelID, StatusSynced)
			if err != nil {
				e = err
			}
		}
	}()

	defaultWalletDir := os.Getenv("HOME") + "/.lbryum/wallets/default_wallet"
	if os.Getenv("REGTEST") == "true" {
		defaultWalletDir = os.Getenv("HOME") + "/.lbryum_regtest/wallets/default_wallet"
	}
	walletBackupDir := os.Getenv("HOME") + "/wallets/" + strings.Replace(s.LbryChannelName, "@", "", 1)

	if _, err := os.Stat(defaultWalletDir); !os.IsNotExist(err) {
		return errors.Err("default_wallet already exists")
	}

	if _, err = os.Stat(walletBackupDir); !os.IsNotExist(err) {
		err = os.Rename(walletBackupDir, defaultWalletDir)
		if err != nil {
			return errors.Wrap(err, 0)
		}
		log.Println("Continuing previous upload")
	}

	defer func() {
		log.Printf("Stopping daemon")
		shutdownErr := stopDaemonViaSystemd()
		if shutdownErr != nil {
			logShutdownError(shutdownErr)
		} else {
			// the cli will return long before the daemon effectively stops. we must observe the processes running
			// before moving the wallet
			waitTimeout := 8 * time.Minute
			processDeathError := waitForDaemonProcess(waitTimeout)
			if processDeathError != nil {
				logShutdownError(processDeathError)
			} else {
				walletErr := os.Rename(defaultWalletDir, walletBackupDir)
				if walletErr != nil {
					log.Errorf("error moving wallet to backup dir: %v", walletErr)
				}
			}
		}
	}()

	s.videoDirectory, err = ioutil.TempDir("", "ytsync")
	if err != nil {
		return errors.Wrap(err, 0)
	}

	s.db = redisdb.New()
	s.syncedVideos = syncedVideos
	s.grp = stop.New()
	s.queue = make(chan video)

	interruptChan := make(chan os.Signal, 1)
	signal.Notify(interruptChan, os.Interrupt, syscall.SIGTERM)
	go func() {
		<-interruptChan
		log.Println("Got interrupt signal, shutting down (if publishing, will shut down after current publish)")
		s.grp.Stop()
	}()

	log.Printf("Starting daemon")
	err = startDaemonViaSystemd()
	if err != nil {
		return err
	}

	log.Infoln("Waiting for daemon to finish starting...")
	s.daemon = jsonrpc.NewClient("")
	s.daemon.SetRPCTimeout(40 * time.Minute)

WaitForDaemonStart:
	for {
		select {
		case <-s.grp.Ch():
			return nil
		default:
			_, err := s.daemon.WalletBalance()
			if err == nil {
				break WaitForDaemonStart
			}
			time.Sleep(5 * time.Second)
		}
	}

	err = s.doSync()
	if err != nil {
		return err
	} else {
		// wait for reflection to finish???
		wait := 15 * time.Second // should bump this up to a few min, but keeping it low for testing
		log.Println("Waiting " + wait.String() + " to finish reflecting everything")
		time.Sleep(wait)
	}

	return nil
}
func logShutdownError(shutdownErr error) {
	SendErrorToSlack("error shutting down daemon: %v", shutdownErr)
	SendErrorToSlack("WALLET HAS NOT BEEN MOVED TO THE WALLET BACKUP DIR")
}

func (s *Sync) doSync() error {
	var err error

	err = s.walletSetup()
	if err != nil {
		return errors.Prefix("Initial wallet setup failed! Manual Intervention is required.", err)
	}

	if s.StopOnError {
		log.Println("Will stop publishing if an error is detected")
	}

	for i := 0; i < s.ConcurrentVideos; i++ {
		go s.startWorker(i)
	}

	if s.LbryChannelName == "@UCBerkeley" {
		err = s.enqueueUCBVideos()
	} else {
		err = s.enqueueYoutubeVideos()
	}
	close(s.queue)
	s.wg.Wait()
	return err
}

func (s *Sync) startWorker(workerNum int) {
	s.wg.Add(1)
	defer s.wg.Done()

	var v video
	var more bool

	for {
		select {
		case <-s.grp.Ch():
			log.Printf("Stopping worker %d", workerNum)
			return
		default:
		}

		select {
		case v, more = <-s.queue:
			if !more {
				return
			}
		case <-s.grp.Ch():
			log.Printf("Stopping worker %d", workerNum)
			return
		}

		log.Println("================================================================================")

		tryCount := 0
		for {
			tryCount++
			err := s.processVideo(v)

			if err != nil {
				logMsg := fmt.Sprintf("error processing video: " + err.Error())
				log.Errorln(logMsg)
				fatalErrors := []string{
					":5279: read: connection reset by peer",
					"no space left on device",
					"NotEnoughFunds",
					"Cannot publish using channel",
				}
				if util.SubstringInSlice(err.Error(), fatalErrors) || s.StopOnError {
					s.grp.Stop()
				} else if s.MaxTries > 1 {
					errorsNoRetry := []string{
						"non 200 status code received",
						" reason: 'This video contains content from",
						"dont know which claim to update",
						"uploader has not made this video available in your country",
						"download error: AccessDenied: Access Denied",
						"Playback on other websites has been disabled by the video owner",
						"Error in daemon: Cannot publish empty file",
						"Error extracting sts from embedded url response",
						"Client.Timeout exceeded while awaiting headers)",
						"the video is too big to sync, skipping for now",
					}
					if util.SubstringInSlice(err.Error(), errorsNoRetry) {
						log.Println("This error should not be retried at all")
					} else if tryCount < s.MaxTries {
						if strings.Contains(err.Error(), "txn-mempool-conflict") ||
							strings.Contains(err.Error(), "failed: Not enough funds") ||
							strings.Contains(err.Error(), "Error in daemon: Insufficient funds, please deposit additional LBC") ||
							strings.Contains(err.Error(), "too-long-mempool-chain") {
							log.Println("waiting for a block and refilling addresses before retrying")
							err = s.walletSetup()
							if err != nil {
								s.grp.Stop()
								SendErrorToSlack("Failed to setup the wallet for a refill: %v", err)
								break
							}
						}
						log.Println("Retrying")
						continue
					}
					SendErrorToSlack("Video failed after %d retries, skipping. Stack: %s", tryCount, logMsg)
				}
				err = s.Manager.MarkVideoStatus(s.YoutubeChannelID, v.ID(), VideoStatusFailed, "", "", err.Error())
				if err != nil {
					SendErrorToSlack("Failed to mark video on the database: %s", err.Error())
				}
			}
			break
		}
	}
}

func (s *Sync) enqueueYoutubeVideos() error {
	client := &http.Client{
		Transport: &transport.APIKey{Key: s.YoutubeAPIKey},
	}

	service, err := youtube.New(client)
	if err != nil {
		return errors.Prefix("error creating YouTube service", err)
	}

	response, err := service.Channels.List("contentDetails").Id(s.YoutubeChannelID).Do()
	if err != nil {
		return errors.Prefix("error getting channels", err)
	}

	if len(response.Items) < 1 {
		return errors.Err("youtube channel not found")
	}

	if response.Items[0].ContentDetails.RelatedPlaylists == nil {
		return errors.Err("no related playlists")
	}

	playlistID := response.Items[0].ContentDetails.RelatedPlaylists.Uploads
	if playlistID == "" {
		return errors.Err("no channel playlist")
	}

	var videos []video

	nextPageToken := ""
	for {
		req := service.PlaylistItems.List("snippet").
			PlaylistId(playlistID).
			MaxResults(50).
			PageToken(nextPageToken)

		playlistResponse, err := req.Do()
		if err != nil {
			return errors.Prefix("error getting playlist items", err)
		}

		if len(playlistResponse.Items) < 1 {
			return errors.Err("playlist items not found")
		}

		for _, item := range playlistResponse.Items {
			// normally we'd send the video into the channel here, but youtube api doesn't have sorting
			// so we have to get ALL the videos, then sort them, then send them in
			videos = append(videos, sources.NewYoutubeVideo(s.videoDirectory, item.Snippet))
		}

		log.Infof("Got info for %d videos from youtube API", len(videos))

		nextPageToken = playlistResponse.NextPageToken
		if nextPageToken == "" {
			break
		}
	}

	sort.Sort(byPublishedAt(videos))
	//or sort.Sort(sort.Reverse(byPlaylistPosition(videos)))

Enqueue:
	for _, v := range videos {
		select {
		case <-s.grp.Ch():
			break Enqueue
		default:
		}

		select {
		case s.queue <- v:
		case <-s.grp.Ch():
			break Enqueue
		}
	}

	return nil
}

func (s *Sync) enqueueUCBVideos() error {
	var videos []video

	csvFile, err := os.Open("ucb.csv")
	if err != nil {
		return err
	}

	reader := csv.NewReader(bufio.NewReader(csvFile))
	for {
		line, err := reader.Read()
		if err == io.EOF {
			break
		} else if err != nil {
			return err
		}
		data := struct {
			PublishedAt string `json:"publishedAt"`
		}{}
		err = json.Unmarshal([]byte(line[4]), &data)
		if err != nil {
			return err
		}

		videos = append(videos, sources.NewUCBVideo(line[0], line[2], line[1], line[3], data.PublishedAt, s.videoDirectory))
	}

	log.Printf("Publishing %d videos\n", len(videos))

	sort.Sort(byPublishedAt(videos))

Enqueue:
	for _, v := range videos {
		select {
		case <-s.grp.Ch():
			break Enqueue
		default:
		}

		select {
		case s.queue <- v:
		case <-s.grp.Ch():
			break Enqueue
		}
	}

	return nil
}

func (s *Sync) processVideo(v video) (err error) {
	defer func() {
		if p := recover(); p != nil {
			var ok bool
			err, ok = p.(error)
			if !ok {
				err = errors.Err("%v", p)
			}
			err = errors.Wrap(p, 2)
		}
	}()

	log.Println("Processing " + v.IDAndNum())
	defer func(start time.Time) {
		log.Println(v.ID() + " took " + time.Since(start).String())
	}(time.Now())

	sv, ok := s.syncedVideos[v.ID()]
	alreadyPublished := ok && sv.Published

	neverRetryFailures := []string{
		"Error extracting sts from embedded url response",
		"the video is too big to sync, skipping for now",
	}
	if ok && !sv.Published && util.SubstringInSlice(sv.FailureReason, neverRetryFailures) {
		log.Println(v.ID() + " can't ever be published")
		return nil
	}

	//TODO: remove this after a few runs...
	alreadyPublishedOld, err := s.db.IsPublished(v.ID())
	if err != nil {
		return err
	}
	//TODO: remove this after a few runs...
	if alreadyPublishedOld && !alreadyPublished {
		//seems like something in the migration of blobs didn't go perfectly right so warn about it!
		SendInfoToSlack("A video that was previously published is on the local database but isn't on the remote db! fix it @Nikooo777! \nchannelID: %s, videoID: %s",
			s.YoutubeChannelID, v.ID())
		return nil
	}

	if alreadyPublished {
		log.Println(v.ID() + " already published")
		return nil
	}

	if v.PlaylistPosition() > s.Manager.VideosLimit {
		log.Println(v.ID() + " is old: skipping")
		return nil
	}
	summary, err := v.Sync(s.daemon, s.claimAddress, publishAmount, s.LbryChannelName, s.Manager.MaxVideoSize)
	if err != nil {
		return err
	}
	err = s.Manager.MarkVideoStatus(s.YoutubeChannelID, v.ID(), VideoStatusPublished, summary.ClaimID, summary.ClaimName, "")
	if err != nil {
		SendErrorToSlack("Failed to mark video on the database: %s", err.Error())
	}
	if err != nil {
		return err
	}

	return nil
}

func startDaemonViaSystemd() error {
	err := exec.Command("/usr/bin/sudo", "/bin/systemctl", "start", "lbrynet.service").Run()
	if err != nil {
		return errors.Err(err)
	}
	return nil
}

func stopDaemonViaSystemd() error {
	err := exec.Command("/usr/bin/sudo", "/bin/systemctl", "stop", "lbrynet.service").Run()
	if err != nil {
		return errors.Err(err)
	}
	return nil
}

// waitForDaemonProcess observes the running processes and returns when the process is no longer running or when the timeout is up
func waitForDaemonProcess(timeout time.Duration) error {
	processes, err := ps.Processes()
	if err != nil {
		return err
	}
	var daemonProcessId = -1
	for _, p := range processes {
		if p.Executable() == "lbrynet-daemon" {
			daemonProcessId = p.Pid()
			break
		}
	}
	if daemonProcessId == -1 {
		return nil
	}
	then := time.Now()
	stopTime := then.Add(time.Duration(timeout * time.Second))
	for !time.Now().After(stopTime) {
		wait := 10 * time.Second
		log.Println("the daemon is still running, waiting for it to exit")
		time.Sleep(wait)
		proc, err := os.FindProcess(daemonProcessId)
		if err != nil {
			// couldn't find the process, that means the daemon is stopped and can continue
			return nil
		}
		//double check if process is running and alive
		//by sending a signal 0
		//NOTE : syscall.Signal is not available in Windows
		err = proc.Signal(syscall.Signal(0))
		//the process doesn't exist anymore! we're free to go
		if err != nil && (err == syscall.ESRCH || err.Error() == "os: process already finished") {
			return nil
		}
	}
	return errors.Err("timeout reached")
}