package generator

import (
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"segmenta/pkg/handler"
	"strings"
	"sync"

	"gopkg.in/fsnotify.v1"
)

const AppName = "segmenta"
const DefaultPlaylistFilename = "playlist.m3u8"

// Generator generates assets for a given stream. The default implementation
// segments using FFMPEG.
type FFMPEGGenerator struct {
	name     string
	src      io.Reader
	handlers map[handler.Handler]bool
}

func NewFFMPEGGenerator(name string, src io.Reader) *FFMPEGGenerator {
	return &FFMPEGGenerator{
		name:     name,
		src:      src,
		handlers: make(map[handler.Handler]bool),
	}
}

func (g *FFMPEGGenerator) Generate() error {
	// first, create a temporary directory.
	prefix := fmt.Sprintf("%s-%s", AppName, g.name)
	tmpdir, err := ioutil.TempDir("", prefix)
	if err != nil {
		return fmt.Errorf("ffmpeg: error initializing TempDir: %v", tmpdir)
	}
	defer os.RemoveAll(tmpdir)

	playlist := filepath.Join(tmpdir, DefaultPlaylistFilename)

	// FIXME: Better concurrency management is needed here. We should expect doMMPEG to run
	// indefinitely, and its eventual closure (successful or otherwise) to trigger closure
	// of this main process, including other goroutines.
	// one instance of doWatch should be running at all times until the FFMPEG goroutine is
	// closed. If it is interrupted for some reason before doFFMPEG has terminated, then
	// this is a bug. It should be restarted.
	var wg sync.WaitGroup

	go g.doFFMPEG(&wg, playlist)
	go g.doWatch(&wg, tmpdir)

	wg.Add(2)
	wg.Wait()

	return nil
}

func (g *FFMPEGGenerator) AddHandler(h handler.Handler) {
	g.handlers[h] = true
}

func (g *FFMPEGGenerator) RemoveHandler(h handler.Handler) {
	delete(g.handlers, h)
}

// TODO should wg be passed in a Context?
func (g *FFMPEGGenerator) doFFMPEG(wg *sync.WaitGroup, dest string) {
	defer wg.Done()

	cmd := exec.Command("ffmpeg", "-re", "-i", "-", "-f", "hls", "-hls_flags", "delete_segments", dest)
	cmd.Stdin = g.src

	if err := cmd.Run(); err != nil {
		// TODO: error handling
		log.Fatalf("ffmpeg: error running cmd: %v", err)
	}

	fmt.Println("ffmpeg: exited")
}

func (g *FFMPEGGenerator) doWatch(wg *sync.WaitGroup, srcDir string) {
	defer wg.Done()

	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		// TODO: error handling
		log.Fatal(err)
	}
	defer watcher.Close()

	err = watcher.Add(srcDir)
	if err != nil {
		log.Fatal(err)
	}

	for {
		select {
		case event, ok := <-watcher.Events:
			if !ok {
				return
			}
			key := filepath.Join(g.name, filepath.Base(event.Name))
			if event.Op&fsnotify.Create == fsnotify.Create && strings.HasSuffix(event.Name, ".m3u8") {
				asset := handler.Asset{
					Key:         key,
					Type:        handler.MediaPlaylist,
					ContentType: "vnd.apple.mpegURL",
					Path:        event.Name,
				}
				for h, _ := range g.handlers {
					h.AssetAdded(asset)
				}
			}
			if event.Op&fsnotify.Write == fsnotify.Write && strings.HasSuffix(event.Name, ".ts") {
				asset := handler.Asset{
					Key:         key,
					Type:        handler.Segment,
					ContentType: "video/MP2T",
					Path:        event.Name,
				}
				for h, _ := range g.handlers {
					h.AssetAdded(asset)
				}
			}
			if event.Op&fsnotify.Remove == fsnotify.Remove && strings.HasSuffix(event.Name, ".ts") {
				asset := handler.Asset{
					Key:         key,
					Type:        handler.Segment,
					ContentType: "video/MP2T",
					Path:        event.Name,
				}
				for h, _ := range g.handlers {
					h.AssetRemoved(asset)
				}
			}
		case err, ok := <-watcher.Errors:
			if !ok {
				return
			}
			log.Println("Got error:", err)
		}
	}

	fmt.Println("watch: exited")
}