package fabricvpn

import (
	"os"
	"testing"
)

func TestFabricRuntimeEndpointsPreferRouteBundle(t *testing.T) {
	cfg := runtimeConfig{
		Endpoints: []endpointConfig{{EndpointID: "legacy", Address: "quic://legacy.example:19131"}},
		RouteBundle: routeBundleConfig{
			EndpointCandidates: []endpointConfig{{EndpointID: "bundle", Address: "quic://bundle.example:19131"}},
		},
	}
	got := fabricRuntimeEndpoints(cfg)
	if len(got) != 1 || got[0].EndpointID != "bundle" {
		t.Fatalf("endpoints = %+v, want route bundle endpoint", got)
	}
}

func TestFabricRuntimeEndpointsPreferRouteLease(t *testing.T) {
	cfg := runtimeConfig{
		Endpoints: []endpointConfig{{EndpointID: "legacy", Address: "quic://legacy.example:19131"}},
		RouteBundle: routeBundleConfig{
			EndpointCandidates: []endpointConfig{{EndpointID: "bundle", Address: "quic://bundle.example:19131"}},
			RouteLease: routeLeaseConfig{
				SelectedTargetNode: "exit-1",
				PrimaryPath: routeLeasePath{
					TargetNodeID:       "exit-1",
					EndpointCandidates: []endpointConfig{{EndpointID: "lease-primary", Address: "quic://lease.example:19131"}},
				},
			},
		},
	}
	got := fabricRuntimeEndpoints(cfg)
	if len(got) != 1 || got[0].EndpointID != "lease-primary" {
		t.Fatalf("endpoints = %+v, want route lease primary endpoint", got)
	}
	if target := fabricRuntimeTargetNodeID(cfg); target != "exit-1" {
		t.Fatalf("target = %q, want exit-1", target)
	}
}

func TestFabricRuntimeEndpointsFallbackToLegacyEndpoints(t *testing.T) {
	cfg := runtimeConfig{
		Endpoints: []endpointConfig{{EndpointID: "legacy", Address: "quic://legacy.example:19131"}},
	}
	got := fabricRuntimeEndpoints(cfg)
	if len(got) != 1 || got[0].EndpointID != "legacy" {
		t.Fatalf("endpoints = %+v, want legacy endpoint fallback", got)
	}
}

func TestLiveFabricVPNRuntimeStartsFromRouteLease(t *testing.T) {
	raw := os.Getenv("RAP_LIVE_FABRICVPN_CONFIG")
	if raw == "" {
		t.Skip("RAP_LIVE_FABRICVPN_CONFIG is not set")
	}
	manager := NewManager()
	if err := manager.Start(raw); err != nil {
		t.Fatalf("start live fabric vpn runtime: %v", err)
	}
	defer manager.Stop()
	if snapshot := manager.SnapshotJSON(); snapshot == "" {
		t.Fatal("empty live fabric vpn snapshot")
	}
	if os.Getenv("RAP_LIVE_FABRICVPN_PACKET_PROBE") == "" {
		return
	}
	if err := manager.SendPacket(testDNSIPv4Packet()); err != nil {
		t.Fatalf("send live dns packet: %v", err)
	}
	for i := 0; i < 20; i++ {
		packet, err := manager.ReceivePacket(500)
		if err != nil {
			t.Fatalf("receive live dns packet: %v", err)
		}
		if len(packet) > 0 {
			if packet[9] != 17 || packet[12] != 1 || packet[13] != 1 || packet[14] != 1 || packet[15] != 1 {
				t.Fatalf("unexpected response packet header: %v", packet[:min(20, len(packet))])
			}
			return
		}
	}
	t.Fatal("timed out waiting for live dns response through fabric vpn")
}

func testDNSIPv4Packet() []byte {
	dns := []byte{
		0x12, 0x34, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x07, 'e', 'x', 'a',
		'm', 'p', 'l', 'e', 0x03, 'c', 'o', 'm', 0x00,
		0x00, 0x01, 0x00, 0x01,
	}
	udpLen := 8 + len(dns)
	totalLen := 20 + udpLen
	packet := make([]byte, totalLen)
	packet[0] = 0x45
	packet[2] = byte(totalLen >> 8)
	packet[3] = byte(totalLen)
	packet[8] = 64
	packet[9] = 17
	copy(packet[12:16], []byte{10, 77, 0, 2})
	copy(packet[16:20], []byte{1, 1, 1, 1})
	packet[20] = 0xcf
	packet[21] = 0x08
	packet[22] = 0x00
	packet[23] = 0x35
	packet[24] = byte(udpLen >> 8)
	packet[25] = byte(udpLen)
	copy(packet[28:], dns)
	sum := ipv4HeaderChecksum(packet[:20])
	packet[10] = byte(sum >> 8)
	packet[11] = byte(sum)
	return packet
}

func ipv4HeaderChecksum(header []byte) uint16 {
	var sum uint32
	for i := 0; i+1 < len(header); i += 2 {
		if i == 10 {
			continue
		}
		sum += uint32(header[i])<<8 | uint32(header[i+1])
	}
	for sum > 0xffff {
		sum = (sum & 0xffff) + (sum >> 16)
	}
	return ^uint16(sum)
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}