//go:build cgo

package capture

import (
	"bytes"
	"fmt"
	"image"
	"sync"

	x264 "github.com/gen2brain/x264-go"
)

var (
	h264Mu      sync.Mutex
	h264Enc     *x264.Encoder
	h264Buf     bytes.Buffer
	h264Width   int
	h264Height  int
	h264LastErr error
)

func encodeH264Frame(img *image.RGBA) ([]byte, error) {
	bounds := img.Bounds()
	width := bounds.Dx()
	height := bounds.Dy()

	h264Mu.Lock()
	defer h264Mu.Unlock()

	if err := ensureH264EncoderLocked(width, height); err != nil {
		h264LastErr = err
		return nil, err
	}

	h264Buf.Reset()
	if err := h264Enc.Encode(img); err != nil {
		h264LastErr = err
		return nil, err
	}
	h264LastErr = nil

	out := make([]byte, h264Buf.Len())
	copy(out, h264Buf.Bytes())
	return out, nil
}

func h264Available() bool {
	return true
}

func h264AvailabilityDetail() string {
	h264Mu.Lock()
	defer h264Mu.Unlock()
	if h264LastErr != nil {
		return fmt.Sprintf("x264 runtime error: %v", h264LastErr)
	}
	return "cgo build with x264-go"
}

func ensureH264EncoderLocked(width, height int) error {
	if h264Enc != nil && h264Width == width && h264Height == height {
		return nil
	}

	closeH264EncoderLocked()

	opts := &x264.Options{
		Width:        width,
		Height:       height,
		FrameRate:    120,
		Tune:         "zerolatency,fastdecode",
		Preset:       "ultrafast",
		Profile:      "baseline",
		RateControl:  "crf",
		RateConstant: 30,
		LogLevel:     x264.LogError,
	}

	enc, err := x264.NewEncoder(&h264Buf, opts)
	if err != nil {
		return err
	}

	h264Enc = enc
	h264Width = width
	h264Height = height
	return nil
}

func resetH264Encoder() {
	h264Mu.Lock()
	defer h264Mu.Unlock()
	closeH264EncoderLocked()
}

func closeH264EncoderLocked() {
	if h264Enc != nil {
		_ = h264Enc.Close()
		h264Enc = nil
	}
	h264Width = 0
	h264Height = 0
	h264Buf.Reset()
}