package vpnruntime

import (
	"context"
	"sync"
	"testing"
	"time"
)

type recordingGatewayTransport struct {
	mu      sync.Mutex
	batches [][][]byte
}

func (t *recordingGatewayTransport) SendGatewayPacketBatch(ctx context.Context, packets [][]byte) error {
	copied := make([][]byte, len(packets))
	for i, packet := range packets {
		copied[i] = append([]byte(nil), packet...)
	}
	t.mu.Lock()
	t.batches = append(t.batches, copied)
	t.mu.Unlock()
	return nil
}

func (t *recordingGatewayTransport) ReceiveGatewayPacketBatch(ctx context.Context, timeout time.Duration) ([][]byte, error) {
	return nil, ctx.Err()
}

func (t *recordingGatewayTransport) firstBatch() [][]byte {
	t.mu.Lock()
	defer t.mu.Unlock()
	if len(t.batches) == 0 {
		return nil
	}
	return t.batches[0]
}

func TestGatewayUploadPrioritizesTCPControlPackets(t *testing.T) {
	transport := &recordingGatewayTransport{}
	gateway := &Gateway{Transport: transport, VPNConnectionID: "vpn-1"}
	priorityPackets := make(chan []byte, 1)
	packets := make(chan []byte, 1)

	normal := testIPv4TCPPacket([4]byte{101, 32, 118, 25}, [4]byte{10, 77, 0, 2}, 443, 37566)
	priority := testIPv4TCPPacket([4]byte{192, 168, 200, 95}, [4]byte{10, 77, 0, 2}, 3389, 51000)
	priority[33] = 0x12

	packets <- normal
	priorityPackets <- priority

	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() {
		done <- gateway.uploadGatewayPackets(ctx, priorityPackets, packets)
	}()
	defer func() {
		cancel()
		<-done
	}()

	deadline := time.After(time.Second)
	for {
		if batch := transport.firstBatch(); len(batch) == 1 {
			if string(batch[0]) != string(priority) {
				t.Fatalf("first uploaded packet = %#v, want priority packet", batch[0])
			}
			return
		}
		select {
		case <-deadline:
			t.Fatal("timed out waiting for first gateway upload batch")
		default:
			time.Sleep(time.Millisecond)
		}
	}
}

func TestIsTCPControlPacket(t *testing.T) {
	packet := testIPv4TCPPacket([4]byte{192, 168, 200, 95}, [4]byte{10, 77, 0, 2}, 3389, 51000)
	if isTCPControlPacket(packet) {
		t.Fatal("packet without control flags was classified as control")
	}
	packet[33] = 0x12
	if !isTCPControlPacket(packet) {
		t.Fatal("tcp syn-ack was not classified as control")
	}
	packet[9] = 17
	if isTCPControlPacket(packet) {
		t.Fatal("udp packet was classified as tcp control")
	}
}