// NextNVR v0.3.3 — FFmpeg stream recorder
// Records 5-minute segments with rec_ prefix and second-level timestamps.
// Output: /mnt/recordings/{cam-name}/rec_{YYYY-MM-DD-HH-MM-SS}.mp4
package main

import (
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"time"
)

// RecorderManager manages FFmpeg recording processes for all cameras.
type RecorderManager struct {
	mu        sync.Mutex
	processes map[string]*recorderProcess
	config    StorageConfig
}

type recorderProcess struct {
	camera CameraConfig
	cmd    *exec.Cmd
	done   chan struct{}
}

// NewRecorderManager creates a new recorder manager.
func NewRecorderManager(cfg StorageConfig) *RecorderManager {
	return &RecorderManager{
		processes: make(map[string]*recorderProcess),
		config:    cfg,
	}
}

// StartAll launches recording goroutines for all enabled cameras.
// Cameras are started with a 500ms stagger to avoid I/O and CPU spikes.
func (rm *RecorderManager) StartAll(cameras []CameraConfig) {
	for _, cam := range cameras {
		if !cam.Enabled || !cam.Record {
			log.Printf("recorder: skipping camera %s (enabled=%v, record=%v)", cam.ID, cam.Enabled, cam.Record)
			continue
		}
		go rm.startRecorder(cam)
		time.Sleep(500 * time.Millisecond) // staggered startup
	}
	log.Printf("recorder: all cameras launched")
}

// StopAll terminates all recording processes.
func (rm *RecorderManager) StopAll() {
	rm.mu.Lock()
	defer rm.mu.Unlock()

	for id, proc := range rm.processes {
		log.Printf("recorder: stopping camera %s", id)
		close(proc.done)
		if proc.cmd != nil && proc.cmd.Process != nil {
			proc.cmd.Process.Signal(os.Interrupt)
		}
	}
	log.Println("recorder: all processes stopped")
}

// startRecorder runs the per-segment recording loop for a single camera.
//
// Architecture:
//   1. Build RTSP URL from camera config.
//   2. Create output directory: /mnt/recordings/{cam-name}/
//   3. LOOP:
//      a. Compute filename: YYYY-MM-DD-HH-MM.part.mp4 (start-of-segment timestamp)
//      b. Launch ffmpeg -t 300 -i {rtsp} -c copy → .part.mp4
//      c. On success: atomic rename .part.mp4 → .mp4
//      d. On failure: .part file stays (picked up by cleaner), wait 5s, retry
//
// Each segment is exactly 5 minutes. Gaps between segments are ~1-2s
// (FFmpeg restart overhead). The -t 300 flag provides a hard timeout
// preventing hung FFmpeg processes.
func (rm *RecorderManager) startRecorder(cam CameraConfig) {
	rtspURL := cam.RTSPMain
	if rtspURL == "" {
		rtspURL = fmt.Sprintf("rtsp://%s:%s@%s:554/Streaming/Channels/101",
			cam.Username, cam.Password, cam.IP)
	}

	log.Printf("recorder: starting %s → %s", cam.ID, rtspURL)

	rm.mu.Lock()
	proc := &recorderProcess{
		camera: cam,
		done:   make(chan struct{}),
	}
	rm.processes[cam.ID] = proc
	rm.mu.Unlock()

	// Use camera name for the directory (human-readable).
	// Fall back to cam ID if name is empty.
	camDirName := cam.Name
	if camDirName == "" {
		camDirName = cam.ID
	}

	outDir := filepath.Join(rm.config.RecordingsPath, camDirName)
	if err := os.MkdirAll(outDir, 0755); err != nil {
		log.Printf("recorder: %s — mkdir %s failed: %v", cam.ID, outDir, err)
		return
	}

	for {
		select {
		case <-proc.done:
			log.Printf("recorder: %s — shutdown signal received", cam.ID)
			return
		default:
		}

		// Generate filename: rec_{YYYY-MM-DD-HH-MM-SS}.mp4
		now := time.Now()
		timeStr := now.Format("2006-01-02-15-04-05")
		partFile := filepath.Join(outDir, "rec_"+timeStr+".part.mp4")
		finalFile := filepath.Join(outDir, "rec_"+timeStr+".mp4")

		// Build FFmpeg command with hard 5-minute timeout.
		cmd := exec.Command("ffmpeg",
			"-hide_banner", "-loglevel", "error",
			"-rtsp_transport", "tcp",
			"-i", rtspURL,
			"-an",              // drop audio (pcm_mulaw not supported in MP4)
			"-c:v", "copy",     // stream-copy video: zero transcoding, near-zero CPU
			"-t", "300",        // hard stop after 300 seconds (5 minutes)
			"-y",               // overwrite output without asking
			partFile,
		)

		// Silence FFmpeg by default; uncomment for debugging.
		// cmd.Stdout = os.Stdout
		// cmd.Stderr = os.Stderr

		startTime := time.Now()
		if err := cmd.Start(); err != nil {
			log.Printf("recorder: %s — FFmpeg start failed: %v", cam.ID, err)
			time.Sleep(5 * time.Second)
			continue
		}

		proc.cmd = cmd
		log.Printf("recorder: %s — segment %s (PID %d)", cam.ID, timeStr, cmd.Process.Pid)

		err := cmd.Wait()
		proc.cmd = nil
		elapsed := time.Since(startTime)

		if err != nil {
			// FFmpeg exited with error or was killed.
			// .part file remains — will be cleaned up later.
			if strings.Contains(err.Error(), "signal: killed") || strings.Contains(err.Error(), "signal: interrupt") {
				log.Printf("recorder: %s — segment %s killed after %v (shutdown)", cam.ID, timeStr, elapsed.Round(time.Second))
				return
			}
			log.Printf("recorder: %s — segment %s failed after %v: %v — retrying in 5s", cam.ID, timeStr, elapsed.Round(time.Second), err)
			// Remove partial file on error so it doesn't accumulate.
			os.Remove(partFile)
			time.Sleep(5 * time.Second)
			continue
		}

		// Segment completed successfully — atomic rename.
		if err := os.Rename(partFile, finalFile); err != nil {
			log.Printf("recorder: %s — rename %s → %s failed: %v", cam.ID, partFile, finalFile, err)
		} else {
			log.Printf("recorder: %s — segment %s complete (%v, %d bytes)",
				cam.ID, timeStr, elapsed.Round(time.Second), fileSize(finalFile))
		}

		// Immediate loop — next segment starts with current timestamp.
	}
}

// fileSize returns the size of a file in bytes, or 0 on error.
func fileSize(path string) int64 {
	info, err := os.Stat(path)
	if err != nil {
		return 0
	}
	return info.Size()
}