package gorrent

import (
	"errors"
	"fmt"
	"github.com/anacrolix/torrent"
	"github.com/anacrolix/torrent/storage"
	"golang.org/x/net/context"
	"net/http"
	"net/url"
	"os"
	"path"
	"strconv"
	"strings"
	"sync"
	"time"
)

const refreshSec = 3

type TorrentStatus struct {
	DownloadRate int64
	UploadRate   int64
	Seeds        int64
}
type FileStatus struct {
	Name     string
	Url      string
	Progress int64
	Length   int64
}

type Engine struct {
	fileIdx  int64
	settings *Settings
	torrCfg  *torrent.ClientConfig
	client   *torrent.Client
	torrent  *torrent.Torrent
	alive    bool
	srv      *http.Server
	srvWg    sync.WaitGroup
	ctx      context.Context
	shutdown context.CancelFunc
	msgs     chan string
	status   struct {
		lastBytesReadData    int64
		lastBytesWrittenData int64
		downRate             int64
		upRate               int64
		seeds                int64
	}
	fs FileStatus
}

func (o *Engine) IsAlive() bool {
	return o.alive
}
func (o *Engine) StartTorrent(idx int64) error {
	o.fileIdx = idx
	var err error
	o.torrCfg = torrent.NewDefaultClientConfig()
	o.torrCfg.ListenPort = o.settings.ListenPort
	o.torrCfg.DataDir = o.settings.DownloadPath
	o.torrCfg.Seed = o.settings.Seed
	o.torrCfg.AcceptPeerConnections = o.settings.AcceptPeerConnections
	o.torrCfg.DefaultStorage = storage.NewFileWithCompletion(o.settings.DownloadPath, storage.NewMapPieceCompletion())

	if o.settings.Proxy != "" {
		if u, err := url.Parse(o.settings.Proxy); err != nil {
			o.torrCfg.HTTPProxy = func(request *http.Request) (*url.URL, error) { return u, nil }
		}
	}
	o.client, err = torrent.NewClient(o.torrCfg)
	if err != nil {
		return fmt.Errorf(`create torrent client failed: %s`, err.Error())
	}
	o.debug(`got new client for torrent file: %s`, o.settings.TorrentPath)
	if o.torrent, err = o.client.AddTorrentFromFile(o.settings.TorrentPath); err != nil {
		o.error(`add torrent file failed: %s`, err.Error())
	}
	o.debug(`added torrent file: %s`, o.settings.TorrentPath)
	o.torrent.SetMaxEstablishedConns(o.settings.MaxConnections)
	o.debug(`set max connections: %d`, o.settings.MaxConnections)
	o.alive = true

	go func() {
		t := o.torrent
		<-t.GotInfo()

		o.setStaticFileStatusData(idx)

		file := o.torrent.Files()[idx]

		// отключаем загрузку всех файлов
		o.torrent.CancelPieces(0, o.torrent.NumPieces()-1)
		//

		firstPieceIndex := file.Offset() * int64(t.NumPieces()) / t.Length()
		endPieceIndex := (file.Offset() + file.Length()) * int64(t.NumPieces()) / t.Length()
		o.torrent.DownloadPieces(int(firstPieceIndex), int(endPieceIndex))

		go func() {
			ticker := time.NewTicker(time.Second * refreshSec)
			defer ticker.Stop()
			for {
				select {
				case <-o.ctx.Done():
					return
				case <-ticker.C:
					o.updateStats()
					o.debug(`update stats finished. down: %d KB/s up: %d KB/s seeds: %d`, o.status.downRate, o.status.upRate, o.status.seeds)
				}
			}
		}()

		o.srvWg.Add(1)
		go func() {
			defer o.srvWg.Done()

			router := http.NewServeMux()
			router.HandleFunc("/", o.GetFileHandler(file))

			o.srv = &http.Server{Addr: fmt.Sprintf(`%s:%d`, o.settings.HttpBindHost, o.settings.HttpBindPort), Handler: router}

			o.info(`starting http server on port: %d`, o.settings.HttpBindPort)
			err = o.srv.ListenAndServe()
			if err != nil && !errors.Is(err, http.ErrServerClosed) {
				o.error(`http listener exit with error: %s`, err.Error())
			}
			o.info(`http server stopped successfully`)
		}()
	}()

	return nil
}

func (o *Engine) setStaticFileStatusData(i int64) {
	o.fs = FileStatus{}
	file := o.torrent.Files()[i]

	pathParts := strings.Split(file.DisplayPath(), `/`)
	o.fs.Name = file.DisplayPath()
	for idx := range pathParts {
		pathParts[idx] = url.QueryEscape(pathParts[idx])
	}
	o.fs.Url = fmt.Sprintf(`http://%s:%d/files/%s`, o.settings.HttpBindHost, o.settings.HttpBindPort, strings.Join(pathParts, `/`))
	o.fs.Length = file.Length()
	if o.fs.Length < 0 {
		o.fs.Length *= -1
	}
}

func (o *Engine) updateStats() {
	stats := o.torrent.Stats()
	if o.status.lastBytesReadData == 0 {
		o.status.downRate = 0
	} else {
		o.status.downRate = (stats.BytesReadData.Int64() - o.status.lastBytesReadData) / 1024 / refreshSec
	}
	o.status.lastBytesReadData = stats.BytesReadData.Int64()
	if o.status.lastBytesWrittenData == 0 {
		o.status.upRate = 0
	} else {
		o.status.upRate = (stats.BytesWrittenData.Int64() - o.status.lastBytesWrittenData) / 1024 / refreshSec
	}
	o.status.lastBytesWrittenData = stats.BytesWrittenData.Int64()
	o.status.seeds = int64(stats.ConnectedSeeders)
}

func (o *Engine) Status() TorrentStatus {
	res := TorrentStatus{}
	res.DownloadRate = o.status.downRate
	res.UploadRate = o.status.upRate
	res.Seeds = o.status.seeds
	return res
}
func (o *Engine) FileStatus(i int) (FileStatus, error) {
	if i < 0 || i > len(o.torrent.Files())-1 {
		return o.fs, fmt.Errorf(`file index out of range: %d`, i)
	}
	file := o.torrent.Files()[i]
	o.fs.Progress = int64(float64(file.BytesCompleted()) / float64(file.Length()) * 100.0)
	if o.fs.Progress < 0 {
		o.fs.Progress *= -1
	}
	return o.fs, nil
}

func (o *Engine) Stop() {
	go func() {
		httpCtx, cancelHttp := context.WithTimeout(o.ctx, time.Second*5)
		defer cancelHttp()
		if err := o.srv.Shutdown(httpCtx); err != nil {
			o.error(`shutting down http server failed: %s`, err.Error())
		}

		o.srvWg.Wait()

		o.syncDebug(`dropping torrent`)
		o.torrent.Drop()
		o.syncDebug(`closing client`)
		o.client.Close()
		<-o.client.Closed()

		if !o.settings.KeepFiles {
			o.Clean()
		}

		o.syncDebug(`torrent engine stopped`)
		o.shutdown()
		close(o.msgs)
		o.alive = false
	}()
	return
}

func (o *Engine) GetMsg() string {
	select {
	case msg, ok := <-o.msgs:
		if ok {
			return msg
		} else {
			return "__CLOSED__"
		}
	default:
	}
	return "__NO_MSG__"
}
func (o *Engine) debug(tmpl string, args ...interface{}) {
	go o.syncDebug(tmpl, args...)
}
func (o *Engine) info(tmpl string, args ...interface{}) {
	go o.syncInfo(tmpl, args...)
}
func (o *Engine) error(tmpl string, args ...interface{}) {
	go o.syncError(tmpl, args...)
}
func (o *Engine) syncError(t string, a ...interface{}) {
	defer func() {
		if rec := recover(); rec != nil {
			fmt.Printf("recovered from panic: %v\n", rec)
		}
	}()
	var result string
	if len(a) > 0 {
		result = fmt.Sprintf(t, a...)
	} else {
		result = t
	}
	o.msgs <- fmt.Sprintf(`[ERROR] %s`, result)
}
func (o *Engine) syncDebug(t string, a ...interface{}) {
	if o.settings.Debug {
		defer func() {
			if rec := recover(); rec != nil {
				fmt.Printf("recovered from panic: %v\n", rec)
			}
		}()
		var result string
		if len(a) > 0 {
			result = fmt.Sprintf(t, a...)
		} else {
			result = t
		}
		o.msgs <- fmt.Sprintf(`[DEBUG] %s`, result)
	}
}
func (o *Engine) syncInfo(t string, a ...interface{}) {
	defer func() {
		if rec := recover(); rec != nil {
			fmt.Printf("recovered from panic: %v\n", rec)
		}
	}()
	var result string
	if len(a) > 0 {
		result = fmt.Sprintf(t, a...)
	} else {
		result = t
	}
	o.msgs <- fmt.Sprintf(`[INFO] %s`, result)
}

func (o *Engine) GetFileHandler(target *torrent.File) func(http.ResponseWriter, *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		entry := target.NewReader()

		defer func() {
			if err := entry.Close(); err != nil {
				o.error(`close torrent file in file handler failed: %s`, err.Error())
			}
		}()

		w.Header().Set("Content-Disposition", "attachment; filename="+strconv.Quote(target.DisplayPath()))
		http.ServeContent(w, r, target.DisplayPath(), time.Now(), entry)
	}
}

func (o *Engine) Clean() {
	fp := path.Join(o.settings.DownloadPath, o.torrent.Name())
	if err := os.RemoveAll(fp); err != nil {
		o.syncError(`remove downloaded data failed: %s`, err.Error())
	}
}