package mesh

import (
	"context"
	"crypto/rand"
	"crypto/rsa"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"math/big"
	"testing"
	"time"

	"github.com/example/remote-access-platform/agents/rap-node-agent/internal/fabricproto"
	"github.com/quic-go/quic-go"
)

func TestQUICFabricTransportPingPong(t *testing.T) {
	listener := startQUICFabricEchoServer(t)
	defer listener.Close()

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	transport := NewQUICFabricTransport(&quic.Config{EnableDatagrams: true})
	session, err := transport.Connect(ctx, FabricTransportTarget{
		Endpoint: listener.Addr().String(),
		TLSConfig: &tls.Config{
			InsecureSkipVerify: true,
			NextProtos:         []string{fabricQUICNextProto},
		},
		Timeout:       time.Second,
		InboundBuffer: 4,
		ErrorBuffer:   4,
	})
	if err != nil {
		t.Fatalf("connect quic fabric: %v", err)
	}
	defer session.Close()

	if err := session.Send(ctx, fabricproto.Frame{Type: fabricproto.FramePing, Sequence: 42, Payload: []byte("quic")}); err != nil {
		t.Fatalf("send ping: %v", err)
	}
	select {
	case frame := <-session.Frames():
		if frame.Type != fabricproto.FramePong || frame.Sequence != 42 || string(frame.Payload) != "quic" {
			t.Fatalf("frame = %+v", frame)
		}
	case err := <-session.Errors():
		t.Fatalf("session error: %v", err)
	case <-ctx.Done():
		t.Fatal(ctx.Err())
	}
}

func TestQUICFabricTransportDataAck(t *testing.T) {
	listener := startQUICFabricEchoServer(t)
	defer listener.Close()

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	session, err := NewQUICFabricTransport(nil).Connect(ctx, FabricTransportTarget{
		Endpoint: listener.Addr().String(),
		TLSConfig: &tls.Config{
			InsecureSkipVerify: true,
			NextProtos:         []string{fabricQUICNextProto},
		},
		Timeout:       time.Second,
		InboundBuffer: 4,
		ErrorBuffer:   4,
	})
	if err != nil {
		t.Fatalf("connect quic fabric: %v", err)
	}
	defer session.Close()

	if err := session.Send(ctx, fabricproto.Frame{
		Type:         fabricproto.FrameOpenStream,
		StreamID:     9,
		TrafficClass: fabricproto.TrafficClassInteractive,
	}); err != nil {
		t.Fatalf("open stream: %v", err)
	}
	if err := session.Send(ctx, fabricproto.Frame{
		Type:         fabricproto.FrameData,
		StreamID:     9,
		Sequence:     7,
		TrafficClass: fabricproto.TrafficClassInteractive,
		Payload:      []byte("packet"),
	}); err != nil {
		t.Fatalf("send data: %v", err)
	}
	select {
	case frame := <-session.Frames():
		if frame.Type != fabricproto.FrameAck || frame.StreamID != 9 || frame.Sequence != 7 {
			t.Fatalf("frame = %+v", frame)
		}
	case err := <-session.Errors():
		t.Fatalf("session error: %v", err)
	case <-ctx.Done():
		t.Fatal(ctx.Err())
	}
}

func startQUICFabricEchoServer(t *testing.T) *quic.Listener {
	t.Helper()
	listener, err := quic.ListenAddr("127.0.0.1:0", testQUICTLSConfig(t), &quic.Config{EnableDatagrams: true})
	if err != nil {
		t.Fatalf("listen quic: %v", err)
	}
	go func() {
		conn, err := listener.Accept(context.Background())
		if err != nil {
			return
		}
		stream, err := conn.AcceptStream(context.Background())
		if err != nil {
			_ = conn.CloseWithError(1, "accept stream failed")
			return
		}
		session := fabricproto.NewSession(fabricproto.SessionConfig{})
		for {
			frame, err := fabricproto.ReadFrame(stream, fabricproto.DefaultMaxPayload)
			if err != nil {
				_ = conn.CloseWithError(0, "closed")
				return
			}
			_, responses, err := session.HandleFrame(frame)
			if err != nil {
				_ = conn.CloseWithError(2, err.Error())
				return
			}
			for _, response := range responses {
				if err := fabricproto.WriteFrame(stream, response); err != nil {
					_ = conn.CloseWithError(3, err.Error())
					return
				}
			}
		}
	}()
	return listener
}

func testQUICTLSConfig(t *testing.T) *tls.Config {
	t.Helper()
	key, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		t.Fatalf("generate key: %v", err)
	}
	template := x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject:      pkix.Name{CommonName: "rap-fabric-test"},
		NotBefore:    time.Now().Add(-time.Minute),
		NotAfter:     time.Now().Add(time.Hour),
		KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		DNSNames:     []string{"localhost"},
	}
	certDER, err := x509.CreateCertificate(rand.Reader, &template, &template, &key.PublicKey, key)
	if err != nil {
		t.Fatalf("create certificate: %v", err)
	}
	keyDER := x509.MarshalPKCS1PrivateKey(key)
	cert, err := tls.X509KeyPair(
		pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certDER}),
		pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: keyDER}),
	)
	if err != nil {
		t.Fatalf("key pair: %v", err)
	}
	return &tls.Config{
		Certificates: []tls.Certificate{cert},
		NextProtos:   []string{fabricQUICNextProto},
	}
}