package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/teacat/pathx"

	"github.com/grafov/m3u8"
	"github.com/parnurzeal/gorequest"
	"github.com/urfave/cli"
)

// chaturbateURL is the base url of the website.
const chaturbateURL = "https://chaturbate.com/"

// retriesAfterOnlined tells the retries for stream when disconnected but not really offlined.
var retriesAfterOnlined = 0

// lastCheckOnline logs the last check time.
var lastCheckOnline = time.Now()

// buffer stores the media segments and wait for comsume.
var buffer = make(chan *m3u8.MediaSegment)

//
var bucket []string

//
var segmentIndex int

//
var (
	errInternal   = errors.New("err")
	errNoUsername = errors.New("chaturbate-dvr: channel username required with `-u [username]` argument")
)

// roomDossier is the struct to parse the HLS source from the content body.
type roomDossier struct {
	HLSSource string `json:"hls_source"`
}

// unescapeUnicode escapes the unicode from the content body.
func unescapeUnicode(raw string) string {
	str, err := strconv.Unquote(strings.Replace(strconv.Quote(string(raw)), `\\u`, `\u`, -1))
	if err != nil {
		panic(err)
	}
	return str
}

// getChannelURL returns the full channel url to the specified user.
func getChannelURL(username string) string {
	return fmt.Sprintf("%s%s", chaturbateURL, username)
}

// getBody gets the channel page content body.
func getBody(username string) string {
	_, body, _ := gorequest.New().Get(getChannelURL(username)).End()
	return body
}

// getOnlineStatus check if the user is currently online by checking the playlist exists in the content body or not.
func getOnlineStatus(username string) bool {
	return strings.Contains(getBody(username), "playlist.m3u8")
}

// getHLSSource extracts the playlist url from the room detail page body.
func getHLSSource(body string) (string, string) {
	//
	r := regexp.MustCompile(`window\.initialRoomDossier = "(.*?)"`)
	matches := r.FindAllStringSubmatch(body, -1)

	//
	var roomData roomDossier
	data := unescapeUnicode(matches[0][1])
	err := json.Unmarshal([]byte(data), &roomData)
	if err != nil {
		panic(err)
	}

	return roomData.HLSSource, strings.TrimRight(roomData.HLSSource, "playlist.m3u8")
}

// parseHLSSource parses the HLS table and return the maximum resolution m3u8 source.
func parseHLSSource(url string, baseURL string) string {
	_, body, _ := gorequest.New().Get(url).End()

	//
	p, listType, _ := m3u8.DecodeFrom(strings.NewReader(body), true)
	if listType != m3u8.MASTER {
		return ""
	}

	master := p.(*m3u8.MasterPlaylist)
	return fmt.Sprintf("%s%s", baseURL, master.Variants[len(master.Variants)-1].URI)
}

//
func parseM3U8Source(url string) (chunks []*m3u8.MediaSegment, wait float64, err error) {
	resp, body, errs := gorequest.New().Get(url).End()
	if len(errs) > 0 {
		return nil, 3, errInternal
	}
	if resp.StatusCode == http.StatusForbidden {
		return nil, 3, errInternal
	}

	//
	p, listType, _ := m3u8.DecodeFrom(strings.NewReader(body), true)
	if listType != m3u8.MEDIA {
		return nil, 0, errInternal
	}

	media := p.(*m3u8.MediaPlaylist)
	wait = media.TargetDuration / 1.5

	// Only fill with the real segments.
	for _, v := range media.Segments {
		if v == nil {
			continue
		}
		chunks = append(chunks, v)
	}
	return
}

// capture captures the specified channel streaming.
func capture(username string) {
	// Define the video filename by current time.
	filename := time.Now().String()
	// Get the channel page content body.
	body := getBody(username)
	// Get the master playlist URL from extracting the channel body.
	hlsSource, baseURL := getHLSSource(body)
	// Get the best resolution m3u8 by parsing the HLS source table.
	m3u8Source := parseHLSSource(hlsSource, baseURL)
	//
	f, err := os.OpenFile(filename+".ts", os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0777)
	if err != nil {
		panic(err)
	}

	// Keep fetching the stream chunks until the playlist cannot be accessed after retried x times (which means the channel is offlined).
	for {
		// Get the chunks.
		chunks, wait, err := parseM3U8Source(m3u8Source)
		//
		if err != nil {
			if retriesAfterOnlined > 10 {
				log.Printf("Failed to fetch the video segments after retried, %s might be offlined.", username)
				retriesAfterOnlined = 0
				break
			} else {
				log.Printf("Failed to fetch the video segments, will try again. (%d/10)", retriesAfterOnlined)
				//
				retriesAfterOnlined++
				// Wait to fetch the next playlist.
				<-time.After(time.Duration(wait*1000) * time.Millisecond)
				continue
			}
		}
		if retriesAfterOnlined != 0 {
			log.Printf("%s is backed online!", username)
			retriesAfterOnlined = 0
		}
		for _, v := range chunks {
			var ignore bool
			for _, j := range bucket {
				if v.URI[len(v.URI)-10:] == j {
					ignore = true
					break
				}
			}
			if ignore {
				continue
			}
			bucket = append(bucket, v.URI[len(v.URI)-10:])
			segmentIndex++
			go fetchSegment(f, v, baseURL, filename, segmentIndex)
		}
		<-time.After(time.Duration(wait*1000) * time.Millisecond)
	}
}

//
func fetchSegment(master *os.File, segment *m3u8.MediaSegment, baseURL string, filename string, index int) {
	_, body, _ := gorequest.New().Get(fmt.Sprintf("%s%s", baseURL, segment.URI)).EndBytes()
	fmt.Printf("GET %s, SIZE: %d\n", segment.URI, len(body))
	if len(body) == 0 {
		return
	}
	//
	f, err := os.OpenFile(fmt.Sprintf("%s~%d.ts", filename, index), os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0777)
	if err != nil {
		panic(err)
	}
	if _, err := f.Write(body); err != nil {
		panic(err)
	}
	//
	var retry int
	for {
		if !pathx.Exists(fmt.Sprintf("%s~%d.ts", filename, index-1)) && retry < 3 {
			retry++
			<-time.After(1 * time.Second)
		}
		break
	}
	//
	b, _ := ioutil.ReadFile(fmt.Sprintf("%s~%d.ts", filename, index-1))
	if _, err := master.Write(b); err != nil {
		panic(err)
	}
	//
	os.Remove(fmt.Sprintf("%s~%d.ts", filename, index-1))
}

// endpoint implements the application main function endpoint.
func endpoint(c *cli.Context) error {
	if c.String("username") == "" {
		log.Fatal(errNoUsername)
	}
	for {
		// Capture the stream if the user is currently online.
		if getOnlineStatus(c.String("username")) {
			capture(c.String("username"))
			continue
		}
		// Otherwise we keep checking the channel status until the user is online.
		log.Printf("%s is offlined, check again after 1 minutes...", c.String("username"))
		<-time.After(time.Minute * 1)
	}
	return nil
}

func main() {
	app := &cli.App{
		Flags: []cli.Flag{
			&cli.StringFlag{
				Name:    "username",
				Aliases: []string{"u"},
				Value:   "",
				Usage:   "channel username to watching",
			},
			&cli.StringFlag{
				Name:    "quality",
				Aliases: []string{"q"},
				Value:   "",
				Usage:   "video quality with `high`, `medium` and `low`",
			},
		},
		Name:   "chaturbate-dvr",
		Usage:  "watching a specified chaturbate channel and auto saved to local file",
		Action: endpoint,
	}
	err := app.Run(os.Args)
	if err != nil {
		log.Fatal(err)
	}
}