// Command whep-client is a minimal Pion-based WHEP subscriber used for
// M1 end-to-end verification. It POSTs a recvonly SDP offer to a WHEP
// endpoint, applies the answer, then reports whether the video and
// audio tracks receive at least one RTP packet before a timeout.
//
// This is a test helper; it is NOT part of the Core binary.
package main

import (
	"bytes"
	"context"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"time"

	"github.com/pion/webrtc/v4"
)

func main() {
	var (
		whepURL = flag.String("url", "http://127.0.0.1:8787/whep/test", "WHEP endpoint URL")
		timeout = flag.Duration("timeout", 10*time.Second, "overall subscribe+receive timeout")
	)
	flag.Parse()

	ctx, cancel := context.WithTimeout(context.Background(), *timeout)
	defer cancel()

	if err := Subscribe(ctx, *whepURL); err != nil {
		log.Fatalf("subscribe failed: %v", err)
	}
	fmt.Println("OK: received video and audio RTP")
	os.Exit(0)
}

// Subscribe performs a full WHEP subscribe against whepURL and returns
// nil when both a video and an audio RTP packet have been observed
// before ctx expires. It is exported so tests can exercise it.
func Subscribe(ctx context.Context, whepURL string) error {
	me := &webrtc.MediaEngine{}
	if err := me.RegisterDefaultCodecs(); err != nil {
		return fmt.Errorf("register codecs: %w", err)
	}
	api := webrtc.NewAPI(webrtc.WithMediaEngine(me))

	pc, err := api.NewPeerConnection(webrtc.Configuration{})
	if err != nil {
		return fmt.Errorf("new peer connection: %w", err)
	}
	defer pc.Close()

	if _, err := pc.AddTransceiverFromKind(webrtc.RTPCodecTypeVideo,
		webrtc.RTPTransceiverInit{Direction: webrtc.RTPTransceiverDirectionRecvonly}); err != nil {
		return fmt.Errorf("add video transceiver: %w", err)
	}
	if _, err := pc.AddTransceiverFromKind(webrtc.RTPCodecTypeAudio,
		webrtc.RTPTransceiverInit{Direction: webrtc.RTPTransceiverDirectionRecvonly}); err != nil {
		return fmt.Errorf("add audio transceiver: %w", err)
	}

	videoDone := make(chan struct{})
	audioDone := make(chan struct{})
	pc.OnTrack(func(t *webrtc.TrackRemote, _ *webrtc.RTPReceiver) {
		kind := t.Kind()
		log.Printf("OnTrack: kind=%s codec=%s pt=%d", kind, t.Codec().MimeType, t.PayloadType())
		go func() {
			buf := make([]byte, 1500)
			// One successful ReadRTP is enough to prove egress.
			if _, _, err := t.Read(buf); err != nil {
				log.Printf("read %s: %v", kind, err)
				return
			}
			switch kind {
			case webrtc.RTPCodecTypeVideo:
				select {
				case <-videoDone:
				default:
					close(videoDone)
				}
			case webrtc.RTPCodecTypeAudio:
				select {
				case <-audioDone:
				default:
					close(audioDone)
				}
			}
		}()
	})

	offer, err := pc.CreateOffer(nil)
	if err != nil {
		return fmt.Errorf("create offer: %w", err)
	}
	gather := webrtc.GatheringCompletePromise(pc)
	if err := pc.SetLocalDescription(offer); err != nil {
		return fmt.Errorf("set local: %w", err)
	}
	select {
	case <-gather:
	case <-ctx.Done():
		return fmt.Errorf("ice gather: %w", ctx.Err())
	}

	answerSDP, err := postOffer(ctx, whepURL, pc.LocalDescription().SDP)
	if err != nil {
		return err
	}
	if err := pc.SetRemoteDescription(webrtc.SessionDescription{
		Type: webrtc.SDPTypeAnswer,
		SDP:  answerSDP,
	}); err != nil {
		return fmt.Errorf("set remote: %w", err)
	}

	// Wait for one RTP packet on each track or ctx timeout.
	select {
	case <-videoDone:
	case <-ctx.Done():
		return fmt.Errorf("waiting for video: %w", ctx.Err())
	}
	select {
	case <-audioDone:
	case <-ctx.Done():
		return fmt.Errorf("waiting for audio: %w", ctx.Err())
	}
	return nil
}

func postOffer(ctx context.Context, url, sdp string) (string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url,
		bytes.NewReader([]byte(sdp)))
	if err != nil {
		return "", fmt.Errorf("new request: %w", err)
	}
	req.Header.Set("Content-Type", "application/sdp")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("POST %s: %w", url, err)
	}
	defer resp.Body.Close()

	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode != http.StatusCreated {
		return "", fmt.Errorf("WHEP %s: %d %s", url, resp.StatusCode, string(body))
	}
	return string(body), nil
}