// Command teleportfling is a standalone sender for the Teleport protocol.
//
// M1 milestone: protocol proof-of-life. It streams a synthetic test pattern
// (colour bars with a moving box) plus a silent stereo 48 kHz audio tone over
// TCP and announces itself on the LAN multicast group, so an OBS instance
// with the obs-teleport plugin can discover and decode the stream.
//
// Usage:
//
//	teleportfling [--name NAME] [--port PORT] [--width W] [--height H]
//	             [--fps N] [--quality 1..100] [--duration SECONDS]
//
// M2+ replaces the synthetic sources with real PipeWire screen/audio capture.
package main

import (
	"flag"
	"image"
	"image/color"
	"log"
	"os"
	"os/signal"
	"strconv"
	"sync/atomic"
	"syscall"
	"time"

	"teleportfling/internal/discovery"
	"teleportfling/internal/output"
	"teleportfling/internal/protocol"
)

func main() {
	var (
		name     = flag.String("name", "", "announce name (default: hostname)")
		port     = flag.Int("port", 9756, "TCP listening port")
		width    = flag.Int("width", 1920, "frame width")
		height   = flag.Int("height", 1080, "frame height")
		fps      = flag.Int("fps", 30, "video frames per second")
		quality  = flag.Int("quality", 80, "JPEG quality 1..100")
		duration = flag.Duration("duration", 0, "stream duration (0 = run until interrupted)")
	)
	flag.Parse()

	// Build the sender: TCP listener + multicast announcer.
	sender := output.New()
	p, err := sender.Listen(addr(*port))
	if err != nil {
		log.Fatalf("output: listen: %v", err)
	}
	announcer := discovery.Start(*name, p)
	log.Printf("teleportfling: advertising on %d, capturing %dx%d @ %d fps", p, *width, *height, *fps)

	// Pipeline state.
	var (
		totalFrames   atomic.Int64
		encoder       = mustNewEncoder()
		frameInterval = time.Second / time.Duration(*fps)
		audioInterval = 100 * time.Millisecond
		sampleRate    = 48000
		speakers      = 2
		start         = time.Now()
		audioStart    time.Time
		deadline      time.Time
		stop          = make(chan struct{})
	)

	if *duration > 0 {
		deadline = start.Add(*duration)
	}

	// Interrupt / SIGTERM handling.
	sigc := make(chan os.Signal, 1)
	signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)

	// — Audio goroutine: ~100 ms chunks of a silent stereo float32 tone —
	// A silent master tone keeps OBS's audio pipeline alive without needing
	// a mic. M2 will replace this with real captured audio.
	audioDone := make(chan struct{})
	go func() {
		defer close(audioDone)
		audioStart = time.Now()
		tick := time.NewTicker(audioInterval)
		defer tick.Stop()

		framesPerChunk := int32(float64(sampleRate) * audioInterval.Seconds())
		pcm := make([]byte, 0, framesPerChunk*int32(speakers)*4)

		sendAudio := func(ts uint64, chunkFrames int32) {
			// Right = left = 0 → digital silence.
			pcm = pcm[:0]
			for f := 0; f < int(chunkFrames); f++ {
				pcm = append(pcm, 0, 0, 0, 0, 0, 0, 0, 0)
			}
			packet, err := protocol.BuildWavePacket(ts, protocol.AudioFormatF32, int32(sampleRate), int32(speakers), chunkFrames, pcm)
			if err != nil {
				log.Printf("teleportfling: wave: %v", err)
				return
			}
			sender.Send(packet)
		}

		for {
			select {
			case now := <-tick.C:
				ts := uint64(now.Sub(audioStart))
				// Compute frames elapsed since audioStart so timestamps are a
				// continuous stream (not aligned to tick boundaries).
				elapsedFrames := int64(now.Sub(audioStart) / (time.Second / time.Duration(sampleRate)))
				// Cumulative frames sent so far.
				sendAudio(ts, framesPerChunk)
				_ = elapsedFrames
			case <-stop:
				return
			}
		}
	}()

	// — Video loop —
	videoDone := make(chan struct{})
	go func() {
		defer close(videoDone)
		ticker := time.NewTicker(frameInterval)
		defer ticker.Stop()

		var frameNum int64
		for {
			select {
			case now := <-ticker.C:
				ts := uint64(now.Sub(start))
				img := testPattern(*width, *height, int(frameNum))
				frameNum++

				frameStart := time.Now()
				buf, err := encoder.Encode(img, *quality)
				if err != nil {
					log.Printf("teleportfling: jpeg: %v", err)
					continue
				}
				encodeDur := time.Since(frameStart)

				packet, err := protocol.WritePacket(
					protocol.Header{Type: protocol.VideoType, Timestamp: ts, Size: int32(len(buf))},
					ptr(protocol.DefaultBT709Full()),
					nil,
					buf,
				)
				if err != nil {
					log.Printf("teleportfling: packet: %v", err)
					continue
				}
				sender.Send(packet)
				totalFrames.Add(1)

				_ = encodeDur // stats below
			case <-stop:
				return
			}
		}
	}()

	// — Stats ticker —
	statsDone := make(chan struct{})
	go func() {
		defer close(statsDone)
		tick := time.NewTicker(5 * time.Second)
		defer tick.Stop()
		for {
			select {
			case <-tick.C:
				log.Printf("stats: %d frames, %d conns",
					totalFrames.Load(), sender.NumConns())
			case <-stop:
				return
			}
		}
	}()

	// — Wait for interrupt/duration —
	select {
	case <-sigc:
		log.Printf("teleportfling: stopping…")
	case <-func() <-chan struct{} {
		if *duration > 0 {
			ch := make(chan struct{})
			time.AfterFunc(time.Until(deadline), func() { close(ch) })
			return ch
		}
		return nil
	}():
		log.Printf("teleportfling: duration reached")
	}

	close(stop)
	<-audioDone
	<-videoDone
	<-statsDone

	announcer.Stop()
	sender.Close()
	encoder.Close()
	log.Printf("teleportfling: stopped after %s", time.Since(start).Round(time.Millisecond))
}

// mustNewEncoder creates a JPEG encoder or panics.
func mustNewEncoder() *protocol.JPEGEncoder {
	enc, err := protocol.NewJPEGEncoder()
	if err != nil {
		log.Fatal(err)
	}
	return enc
}

// ptr returns a pointer to v, for passing headers to WritePacket.
func ptr[T any](v T) *T { return &v }

// addr formats a port as a listen address.
func addr(port int) string {
	return ":" + strconv.Itoa(port)
}

// testPattern renders a standard SMPTE colour bar with a moving white box at
// the given frame index. The result is a *image.YCbCr 4:2:0 image so the
// encoder uses the YUV path — closest to what real PipeWire capture will
// produce in M2.
func testPattern(w, h, frame int) *image.YCbCr {
	img := image.NewYCbCr(image.Rect(0, 0, w, h), image.YCbCrSubsampleRatio420)

	// 7 vertical colour bars (grey, yellow, cyan, green, magenta, red, blue).
	bars := []color.RGBA{
		{R: 191, G: 191, B: 191}, // 75% grey
		{R: 191, G: 191, B: 0},   // yellow
		{R: 0, G: 191, B: 191},   // cyan
		{R: 0, G: 191, B: 0},     // green
		{R: 191, G: 0, B: 191},   // magenta
		{R: 191, G: 0, B: 0},     // red
		{R: 0, G: 0, B: 191},     // blue
	}

	const barCount = 7
	barW := w / barCount
	const boxSize = 80

	// Moving white box sweeps left→right across the lower black block.
	boxMinX := (frame*(w+boxSize)/120)%(w+boxSize) - boxSize/2

	buf := make([]color.RGBA, w*h)
	for by := 0; by < h; by++ {
		rowIsBars := by < h*2/3
		for bx := 0; bx < w; bx++ {
			var c color.RGBA
			switch {
			case rowIsBars:
				idx := bx / barW
				if idx >= barCount {
					idx = barCount - 1
				}
				c = bars[idx]
			case by%8 < 4 && bx > w/3 && bx < w*2/3:
				// Periodic white band across the lower black block for motion.
				c = color.RGBA{R: 255, G: 255, B: 255, A: 255}
			default:
				c = color.RGBA{}
			}
			// Overlay the moving box on the bottom band.
			if bx >= boxMinX && bx < boxMinX+boxSize && by >= h*2/3 {
				c = color.RGBA{R: 255, G: 255, B: 255, A: 255}
			}
			buf[by*w+bx] = c
		}
	}

	// Chroma planes: average each 2x2 RGB block, then convert to Cb/Cr.
	for by := 0; by < h; by += 2 {
		for bx := 0; bx < w; bx += 2 {
			var rSum, gSum, bSum uint32
			n := uint32(0)
			for dy := 0; dy < 2; dy++ {
				for dx := 0; dx < 2; dx++ {
					xx, yy := bx+dx, by+dy
					if xx >= w || yy >= h {
						continue
					}
					px := buf[yy*w+xx]
					rSum += uint32(px.R)
					gSum += uint32(px.G)
					bSum += uint32(px.B)
					n++
				}
			}
			_, cb, cr := color.RGBToYCbCr(uint8(rSum/n), uint8(gSum/n), uint8(bSum/n))
			img.Cb[(by/2)*img.CStride+bx/2] = cb
			img.Cr[(by/2)*img.CStride+bx/2] = cr
		}
	}

	// Luma plane: Y = YCbCr luma of every pixel.
	for by := 0; by < h; by++ {
		for bx := 0; bx < w; bx++ {
			px := buf[by*w+bx]
			y, _, _ := color.RGBToYCbCr(px.R, px.G, px.B)
			img.Y[by*img.YStride+bx] = y
		}
	}

	return img
}