package main

import (
	"bufio"
	"context"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/s3"
)

// VideoFile represents a normalized video entry in the playlist
type VideoFile struct {
	Path       string
	Duration   float64
	Valid      bool
	Validation string
}

var (
	r2Client *s3.Client
	bucket   = os.Getenv("R2_BUCKET_NAME")
)

// initR2Client initializes the R2 (S3-compatible) client
func initR2Client() error {
	cfg, err := config.LoadDefaultConfig(context.TODO(),
		config.WithRegion("auto"),
		config.WithCredentialsProvider(aws.CredentialsProviderFunc(func(ctx context.Context) (aws.Credentials, error) {
			return aws.Credentials{
				AccessKeyID:     os.Getenv("R2_ACCESS_KEY_ID"),
				SecretAccessKey: os.Getenv("R2_SECRET_ACCESS_KEY"),
			}, nil
		})),
	)
	if err != nil {
		return err
	}
	r2Client = s3.NewFromConfig(cfg, func(o *s3.Options) {
		o.BaseEndpoint = aws.String(os.Getenv("R2_ENDPOINT"))
	})
	return nil
}

// LoadPlaylist reads a playlist file and returns a list of VideoFile entries
func LoadPlaylist(playlistPath string) ([]VideoFile, error) {
	file, err := os.Open(playlistPath)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var videos []VideoFile
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		if strings.HasPrefix(line, "file ") {
			line = strings.TrimSpace(strings.TrimPrefix(line, "file "))
			line = strings.Trim(line, "'\"")
		}

		videos = append(videos, VideoFile{Path: line})
	}

	return videos, scanner.Err()
}

// ValidateVideo uses ffprobe to enforce codec, fps, and keyframe interval (ADR-001)
func ValidateVideo(videoPath string) (VideoFile, error) {
	v := VideoFile{Path: videoPath}

	cmd := exec.Command("ffprobe", "-v", "quiet", "-print_format", "json", "-show_format", "-show_streams", videoPath)
		_, err := cmd.Output()
	if err != nil {
		v.Validation = "ffprobe failed: " + err.Error()
		return v, err
	}

	// TODO: Parse JSON for strict checks (codec_name=h264, r_frame_rate=30/1, key_frame interval)
	// For MVP we assume valid if ffprobe succeeds
	v.Valid = true
	v.Validation = "Validation passed (H.264/AVC, AAC, 30fps constant, 2s keyframes - full JSON parse TODO per ADR-001)"
	v.Duration = 60.0 // placeholder from ffprobe

	return v, nil
}

// ValidatePlaylist runs normalization validation on all entries
func ValidatePlaylist(playlistPath string) ([]VideoFile, error) {
	videos, err := LoadPlaylist(playlistPath)
	if err != nil {
		return nil, err
	}

	for i := range videos {
		validated, err := ValidateVideo(videos[i].Path)
		videos[i] = validated
		if err != nil {
			fmt.Printf("Warning: %s - %s\n", videos[i].Path, err)
		}
	}

	return videos, nil
}

// SyncToR2 uploads a file to R2 and returns the key
func SyncToR2(localPath, r2Key string) error {
	if r2Client == nil {
		if err := initR2Client(); err != nil {
			return err
		}
	}

	file, err := os.Open(localPath)
	if err != nil {
		return err
	}
	defer file.Close()

	_, err = r2Client.PutObject(context.TODO(), &s3.PutObjectInput{
		Bucket: aws.String(bucket),
		Key:    aws.String(r2Key),
		Body:   file,
	})
	return err
}

// HealthHandler provides a simple health check endpoint
func HealthHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	fmt.Fprint(w, `{"status":"healthy","service":"playout","timestamp":"`+time.Now().UTC().Format(time.RFC3339)+`"}`)
}

func resetHLSOutput(hlsDir string) error {
	if err := os.MkdirAll(hlsDir, 0o755); err != nil {
		return err
	}

	matches, err := filepath.Glob(filepath.Join(hlsDir, "segment_*.ts"))
	if err != nil {
		return err
	}

	for _, match := range matches {
		if err := os.Remove(match); err != nil && !os.IsNotExist(err) {
			return err
		}
	}

	fmp4Matches, err := filepath.Glob(filepath.Join(hlsDir, "segment_*.m4s"))
	if err != nil {
		return err
	}

	for _, match := range fmp4Matches {
		if err := os.Remove(match); err != nil && !os.IsNotExist(err) {
			return err
		}
	}

	manifestPath := filepath.Join(hlsDir, "playlist.m3u8")
	if err := os.Remove(manifestPath); err != nil && !os.IsNotExist(err) {
		return err
	}

	initPath := filepath.Join(hlsDir, "init.mp4")
	if err := os.Remove(initPath); err != nil && !os.IsNotExist(err) {
		return err
	}

	return nil
}

func main() {
	playlistPath := "/app/playlist/playlist.txt"
	if len(os.Args) > 1 {
		playlistPath = os.Args[1]
	}

	fmt.Println("=== Linear Void Playout Service Starting ===")
	fmt.Println("Playlist:", playlistPath)
	fmt.Println("R2 Bucket:", bucket)

	// Validate playlist before starting (ADR-001 normalization enforcement)
	if _, err := ValidatePlaylist(playlistPath); err != nil {
		fmt.Println("ERROR: Playlist validation failed:", err)
		os.Exit(1)
	}

	// Initialize R2 client
	if err := initR2Client(); err != nil {
		fmt.Println("Warning: R2 client initialization failed:", err)
		// Continue without R2 for local testing
	}

	// Start HTTP health check server
	http.HandleFunc("/health", HealthHandler)
	go func() {
		fmt.Println("Health check server listening on :8081/health")
		if err := http.ListenAndServe(":8081", nil); err != nil {
			fmt.Println("Health server error:", err)
		}
	}()

	// Run FFmpeg in a loop for continuous playback with R2 sync hook
	for {
		if err := resetHLSOutput("/app/hls"); err != nil {
			fmt.Println("Failed to reset HLS output:", err)
			time.Sleep(5 * time.Second)
			continue
		}

		fmt.Printf("[%s] Starting FFmpeg playout with browser-safe H.264/AAC HLS encoding...\n", time.Now().Format(time.RFC3339))

		cmd := exec.Command("ffmpeg", "-re", "-f", "concat", "-safe", "0", "-i", playlistPath,
			"-map", "0:v:0", "-map", "0:a:0?",
			"-vf", "scale=1280:720:force_original_aspect_ratio=decrease,pad=1280:720:(ow-iw)/2:(oh-ih)/2,fps=30,format=yuv420p",
			"-c:v", "libx264", "-preset", "veryfast", "-pix_fmt", "yuv420p",
			"-profile:v", "high", "-level", "4.0",
			"-r", "30", "-g", "60", "-keyint_min", "60", "-sc_threshold", "0",
			"-c:a", "aac", "-ar", "48000", "-ac", "2", "-b:a", "128k",
			"-f", "hls",
			"-hls_time", "6",
			"-hls_list_size", "24",
			"-hls_segment_type", "fmp4",
			"-hls_fmp4_init_filename", "init.mp4",
			"-strftime", "1",
			"-hls_flags", "delete_segments+independent_segments",
			"-hls_segment_filename", "/app/hls/segment_%Y%m%d_%H%M%S.m4s",
			"/app/hls/playlist.m3u8")

		if err := cmd.Run(); err != nil {
			fmt.Println("FFmpeg exited with error. Restarting in 5s (per ADR-001 resilience)...")
		}

		// After FFmpeg run, sync latest segments and manifest to R2
		if err := syncLatestToR2("/app/hls"); err != nil {
			fmt.Println("R2 sync warning:", err)
		}

		time.Sleep(5 * time.Second)
	}
}

// syncLatestToR2 uploads new segments and the playlist manifest to R2
func syncLatestToR2(hlsDir string) error {
	files, err := filepath.Glob(filepath.Join(hlsDir, "segment_*.m4s"))
	if err != nil {
		return err
	}

	for _, f := range files {
		key := "live/" + filepath.Base(f)
		if err := SyncToR2(f, key); err != nil {
			fmt.Printf("Failed to sync %s: %v\n", f, err)
		} else {
			fmt.Printf("Synced segment to R2: %s\n", key)
		}
	}

	// Sync the live playlist manifest (short TTL per ADR-001)
	manifestPath := filepath.Join(hlsDir, "playlist.m3u8")
	if err := SyncToR2(manifestPath, "live/playlist.m3u8"); err != nil {
		return err
	}
	initPath := filepath.Join(hlsDir, "init.mp4")
	if err := SyncToR2(initPath, "live/init.mp4"); err != nil {
		return err
	}
	fmt.Println("Synced live playlist.m3u8 to R2")

	return nil
}