package adapter

import (
	"context"
	"testing"

	"github.com/sagernet/sing-box/log"
	"github.com/stretchr/testify/require"

	mDNS "github.com/miekg/dns"
)

type testDNSTransport struct {
	transportType string
	tag           string
}

func (t *testDNSTransport) Start(stage StartStage) error {
	return nil
}

func (t *testDNSTransport) Close() error {
	return nil
}

func (t *testDNSTransport) Type() string {
	return t.transportType
}

func (t *testDNSTransport) Tag() string {
	return t.tag
}

func (t *testDNSTransport) Dependencies() []string {
	return nil
}

func (t *testDNSTransport) Reset() {
}

func (t *testDNSTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
	return nil, nil
}

type testDNSTransportManager struct {
	transports      []DNSTransport
	transportByTag  map[string]DNSTransport
	fakeIPTransport FakeIPTransport
}

func newTestDNSTransportManager(transports ...DNSTransport) *testDNSTransportManager {
	manager := &testDNSTransportManager{
		transports:     transports,
		transportByTag: make(map[string]DNSTransport),
	}
	for _, transport := range transports {
		manager.transportByTag[transport.Tag()] = transport
	}
	return manager
}

func (m *testDNSTransportManager) Start(stage StartStage) error {
	return nil
}

func (m *testDNSTransportManager) Close() error {
	return nil
}

func (m *testDNSTransportManager) Transports() []DNSTransport {
	return m.transports
}

func (m *testDNSTransportManager) Transport(tag string) (DNSTransport, bool) {
	transport, loaded := m.transportByTag[tag]
	return transport, loaded
}

func (m *testDNSTransportManager) Default() DNSTransport {
	return nil
}

func (m *testDNSTransportManager) FakeIP() FakeIPTransport {
	return m.fakeIPTransport
}

func (m *testDNSTransportManager) Remove(tag string) error {
	return nil
}

func (m *testDNSTransportManager) Create(ctx context.Context, logger log.ContextLogger, tag string, outboundType string, options any) error {
	return nil
}

func TestLookupDNSTransportLocalAlias(t *testing.T) {
	t.Parallel()

	localTransport := &testDNSTransport{
		transportType: "local",
		tag:           "dns-local",
	}
	manager := newTestDNSTransportManager(localTransport)

	transport, loaded, ambiguous := LookupDNSTransport(manager, "local")
	require.True(t, loaded)
	require.False(t, ambiguous)
	require.Same(t, localTransport, transport)
}

func TestLookupDNSTransportExactTagPreferred(t *testing.T) {
	t.Parallel()

	localTransport := &testDNSTransport{
		transportType: "local",
		tag:           "local",
	}
	manager := newTestDNSTransportManager(localTransport)

	transport, loaded, ambiguous := LookupDNSTransport(manager, "local")
	require.True(t, loaded)
	require.False(t, ambiguous)
	require.Same(t, localTransport, transport)
}

func TestLookupDNSTransportLocalAliasAmbiguous(t *testing.T) {
	t.Parallel()

	manager := newTestDNSTransportManager(
		&testDNSTransport{transportType: "local", tag: "dns-local-a"},
		&testDNSTransport{transportType: "local", tag: "dns-local-b"},
	)

	transport, loaded, ambiguous := LookupDNSTransport(manager, "local")
	require.Nil(t, transport)
	require.False(t, loaded)
	require.True(t, ambiguous)
}