package process

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os/exec"
	"strings"
	"sync"
	"time"

	"tuner/models"
)

// FFmpegManager manages an FFmpeg child process for IPTV relay.
type FFmpegManager struct {
	mu        sync.Mutex
	cmd       *exec.Cmd
	startTime time.Time
	lastError string
	streamURL string
	health    models.StreamHealth
}

// NewFFmpegManager creates a new FFmpeg process manager.
func NewFFmpegManager() *FFmpegManager {
	return &FFmpegManager{}
}

// Start spawns an FFmpeg process to pull from streamURL and push to MediaMTX.
// It kills any existing FFmpeg process first.
func (f *FFmpegManager) Start(streamURL string) error {
	f.mu.Lock()
	defer f.mu.Unlock()

	// Kill existing process if running
	f.stopLocked()

	f.cmd = exec.Command("ffmpeg",
		"-loglevel", "warning",
		"-progress", "pipe:1",
		"-reconnect", "1",
		"-reconnect_streamed", "1",
		"-reconnect_delay_max", "5",
		"-i", streamURL,
		"-c", "copy",
		"-f", "flv",
		"rtmp://localhost:1935/live/stream",
	)
	f.streamURL = streamURL
	f.lastError = ""
	f.health = models.StreamHealth{}

	// Capture stdout for progress stats, stderr for errors
	stdout, err := f.cmd.StdoutPipe()
	if err != nil {
		return fmt.Errorf("stdout pipe: %w", err)
	}
	stderr, err := f.cmd.StderrPipe()
	if err != nil {
		return fmt.Errorf("stderr pipe: %w", err)
	}

	if err := f.cmd.Start(); err != nil {
		f.lastError = err.Error()
		return fmt.Errorf("start ffmpeg: %w", err)
	}

	f.startTime = time.Now()
	log.Printf("[ffmpeg] started with pid %d, source: %s", f.cmd.Process.Pid, streamURL)

	// Pass cmd reference so goroutines can detect process replacement
	cmd := f.cmd
	go f.parseProgress(stdout)
	go f.logStderr(stderr)
	go f.monitor(cmd)

	return nil
}

// parseProgress reads FFmpeg -progress output and updates health stats.
func (f *FFmpegManager) parseProgress(r io.Reader) {
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()
		k, v, ok := strings.Cut(line, "=")
		if !ok {
			continue
		}
		f.mu.Lock()
		switch k {
		case "speed":
			f.health.Speed = v
		case "fps":
			f.health.FPS = v
		case "bitrate":
			f.health.Bitrate = v
		case "drop_frames":
			f.health.DropFrames = v
		case "dup_frames":
			f.health.DupFrames = v
		}
		f.mu.Unlock()
	}
}

func (f *FFmpegManager) logStderr(r io.Reader) {
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		log.Printf("[ffmpeg] %s", scanner.Text())
	}
}

func (f *FFmpegManager) monitor(cmd *exec.Cmd) {
	err := cmd.Wait()

	f.mu.Lock()
	defer f.mu.Unlock()

	// If the process was replaced by a new Start() call, don't touch state
	if f.cmd != cmd {
		return
	}

	if err != nil {
		f.lastError = err.Error()
		log.Printf("[ffmpeg] exited: %v", err)
	} else {
		log.Println("[ffmpeg] exited (status 0)")
	}

	f.cmd = nil
}

// Stop kills the FFmpeg process.
func (f *FFmpegManager) Stop() error {
	f.mu.Lock()
	defer f.mu.Unlock()
	return f.stopLocked()
}

func (f *FFmpegManager) stopLocked() error {
	if f.cmd == nil || f.cmd.Process == nil {
		return nil
	}

	if err := f.cmd.Process.Kill(); err != nil {
		return fmt.Errorf("kill ffmpeg: %w", err)
	}

	// Wait for the process to fully exit to avoid zombies
	_ = f.cmd.Wait()
	f.cmd = nil
	log.Println("[ffmpeg] killed")
	return nil
}

// Health returns the latest stream health stats from FFmpeg progress.
func (f *FFmpegManager) Health() *models.StreamHealth {
	f.mu.Lock()
	defer f.mu.Unlock()

	if f.cmd == nil || f.health.Speed == "" {
		return nil
	}

	h := f.health // copy
	return &h
}

// Status returns the current FFmpeg process status.
func (f *FFmpegManager) Status() models.ProcessInfo {
	f.mu.Lock()
	defer f.mu.Unlock()

	info := models.ProcessInfo{
		Error: f.lastError,
	}

	if f.cmd != nil && f.cmd.Process != nil {
		info.Running = true
		info.PID = f.cmd.Process.Pid
		info.Uptime = time.Since(f.startTime).Truncate(time.Second).String()
	}

	return info
}