package proto_socket_test

import (
	"encoding/binary"
	"errors"
	"net"
	"strings"
	"sync"
	"testing"
	"time"

	"google.golang.org/protobuf/proto"

	toki "git.toki-labs.com/toki/proto-socket/go"
	"git.toki-labs.com/toki/proto-socket/go/packets"
)

type fakeTransport struct {
	mu      sync.Mutex
	packets []*packets.PacketBase
}

func (f *fakeTransport) WritePacket(base *packets.PacketBase) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	f.packets = append(f.packets, base)
	return nil
}

func (f *fakeTransport) Close() error {
	return nil
}

func (f *fakeTransport) sent() []*packets.PacketBase {
	f.mu.Lock()
	defer f.mu.Unlock()
	return append([]*packets.PacketBase{}, f.packets...)
}

func testParserMap() toki.ParserMap {
	return toki.ParserMap{
		toki.TypeNameOf(&packets.TestData{}): func(b []byte) (proto.Message, error) {
			m := &packets.TestData{}
			return m, proto.Unmarshal(b, m)
		},
	}
}

func TestSendRequestTypeMismatch(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	defer communicator.Close()

	errCh := make(chan error, 1)
	go func() {
		_, err := toki.SendRequestTyped[*packets.TestData, *packets.TestData](
			communicator,
			&packets.TestData{Index: 1, Message: "hello"},
			time.Second,
		)
		errCh <- err
	}()

	var requestNonce int32
	for deadline := time.Now().Add(time.Second); time.Now().Before(deadline); {
		sent := transport.sent()
		if len(sent) == 1 {
			requestNonce = sent[0].GetNonce()
			break
		}
		time.Sleep(time.Millisecond)
	}
	if requestNonce == 0 {
		t.Fatal("request packet was not sent")
	}

	hb, err := proto.Marshal(&packets.HeartBeat{})
	if err != nil {
		t.Fatal(err)
	}
	communicator.OnReceivedData(toki.TypeNameOf(&packets.HeartBeat{}), hb, 0, requestNonce)

	err = <-errCh
	if err == nil {
		t.Fatal("expected response type mismatch error")
	}
}

func TestSendRequestTimeout(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	defer communicator.Close()

	_, err := toki.SendRequestTyped[*packets.TestData, *packets.TestData](
		communicator,
		&packets.TestData{Index: 1, Message: "no response"},
		25*time.Millisecond,
	)
	if err == nil {
		t.Fatal("expected request timeout error")
	}
	if !strings.Contains(err.Error(), "timeout") {
		t.Fatalf("expected timeout error, got %v", err)
	}
	if len(transport.sent()) != 1 {
		t.Fatalf("expected one request packet to be sent, got %d", len(transport.sent()))
	}
}

func TestListenerAndRequestListenerConflict(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	defer communicator.Close()

	toki.AddListenerTyped[*packets.TestData](communicator, func(*packets.TestData) {})

	defer func() {
		if recover() == nil {
			t.Fatal("expected panic")
		}
	}()
	toki.AddRequestListenerTyped[*packets.TestData, *packets.TestData](communicator, func(req *packets.TestData) (*packets.TestData, error) {
		return req, nil
	})
}

// TestInboundQueueFIFO: onReceivedData가 여러 메시지를 순서대로 전달한다.
func TestInboundQueueFIFO(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	defer communicator.Close()

	var mu sync.Mutex
	var received []int32

	toki.AddListenerTyped[*packets.TestData](communicator, func(m *packets.TestData) {
		mu.Lock()
		received = append(received, m.GetIndex())
		mu.Unlock()
	})

	for i := int32(1); i <= 5; i++ {
		data, _ := proto.Marshal(&packets.TestData{Index: i})
		communicator.OnReceivedData(toki.TypeNameOf(&packets.TestData{}), data, int32(i), 0)
	}

	deadline := time.Now().Add(time.Second)
	for time.Now().Before(deadline) {
		mu.Lock()
		n := len(received)
		mu.Unlock()
		if n == 5 {
			break
		}
		time.Sleep(time.Millisecond)
	}

	mu.Lock()
	defer mu.Unlock()
	if len(received) != 5 {
		t.Fatalf("expected 5 messages, got %d", len(received))
	}
	for i, idx := range received {
		if idx != int32(i+1) {
			t.Fatalf("FIFO violated: index %d at position %d", idx, i)
		}
	}
}

// TestSlowRequestHandlerResponseOrder: 느린 request handler라도 자동 응답이 FIFO를 보존한다.
func TestSlowRequestHandlerResponseOrder(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	defer communicator.Close()

	toki.AddRequestListenerTyped[*packets.TestData, *packets.TestData](communicator, func(req *packets.TestData) (*packets.TestData, error) {
		// 첫 번째 요청은 100ms 지연
		if req.GetIndex() == 1 {
			time.Sleep(100 * time.Millisecond)
		}
		return &packets.TestData{Index: req.GetIndex() + 100, Message: "echo"}, nil
	})

	data1, _ := proto.Marshal(&packets.TestData{Index: 1, Message: "first"})
	data2, _ := proto.Marshal(&packets.TestData{Index: 2, Message: "second"})
	communicator.OnReceivedData(toki.TypeNameOf(&packets.TestData{}), data1, 10, 0)
	communicator.OnReceivedData(toki.TypeNameOf(&packets.TestData{}), data2, 20, 0)

	// 두 응답이 전송될 때까지 대기
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if len(transport.sent()) >= 2 {
			break
		}
		time.Sleep(5 * time.Millisecond)
	}

	sent := transport.sent()
	if len(sent) < 2 {
		t.Fatalf("expected 2 responses, got %d", len(sent))
	}
	// 첫 번째 응답이 nonce=10에 대응, 두 번째가 nonce=20에 대응 (FIFO 순서)
	if sent[0].GetResponseNonce() != 10 {
		t.Errorf("expected first response for nonce 10, got %d", sent[0].GetResponseNonce())
	}
	if sent[1].GetResponseNonce() != 20 {
		t.Errorf("expected second response for nonce 20, got %d", sent[1].GetResponseNonce())
	}
}

// TestCloseCanelsPendingRequests: Close 시 pending sendRequest가 ErrNotConnected로 완료된다.
func TestCloseCancelsPendingRequests(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())

	errCh := make(chan error, 1)
	go func() {
		_, err := toki.SendRequestTyped[*packets.TestData, *packets.TestData](
			communicator,
			&packets.TestData{Index: 99, Message: "pending"},
			5*time.Second,
		)
		errCh <- err
	}()

	// 요청 패킷이 전송될 때까지 대기
	deadline := time.Now().Add(time.Second)
	for time.Now().Before(deadline) {
		if len(transport.sent()) == 1 {
			break
		}
		time.Sleep(time.Millisecond)
	}

	communicator.Close()

	select {
	case err := <-errCh:
		if !errors.Is(err, toki.ErrNotConnected) {
			t.Fatalf("expected ErrNotConnected, got %v", err)
		}
	case <-time.After(time.Second):
		t.Fatal("timed out waiting for pending request to be cancelled")
	}
}

type fakeGatewayItem struct {
	seq      int
	typeName string
	data     []byte
	nonce    int32
}

func TestWorkerGatewayReorderAndDispatch(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	defer communicator.Close()

	var mu sync.Mutex
	var received []int32

	toki.AddListenerTyped[*packets.TestData](communicator, func(m *packets.TestData) {
		mu.Lock()
		received = append(received, m.GetIndex())
		mu.Unlock()
	})

	// Fake gateway: out-of-order 아이템들을 seq 오름차순으로 정렬 후 coordinator로 밀어넣음
	items := []fakeGatewayItem{
		{seq: 2, typeName: toki.TypeNameOf(&packets.TestData{}), data: func() []byte { d, _ := proto.Marshal(&packets.TestData{Index: 2}); return d }(), nonce: 2},
		{seq: 1, typeName: toki.TypeNameOf(&packets.TestData{}), data: func() []byte { d, _ := proto.Marshal(&packets.TestData{Index: 1}); return d }(), nonce: 1},
	}

	// Reorder by seq
	for i := 0; i < len(items); i++ {
		for j := i + 1; j < len(items); j++ {
			if items[i].seq > items[j].seq {
				items[i], items[j] = items[j], items[i]
			}
		}
	}

	// Dispatch to coordinator in reordered sequence
	for _, item := range items {
		communicator.OnReceivedData(item.typeName, item.data, item.nonce, 0)
	}

	deadline := time.Now().Add(time.Second)
	for time.Now().Before(deadline) {
		mu.Lock()
		n := len(received)
		mu.Unlock()
		if n == 2 {
			break
		}
		time.Sleep(time.Millisecond)
	}

	mu.Lock()
	defer mu.Unlock()
	if len(received) != 2 {
		t.Fatalf("expected 2 messages, got %d", len(received))
	}
	if received[0] != 1 || received[1] != 2 {
		t.Fatalf("seq ordering was not preserved, got: %v", received)
	}
}

// TestInboundGatewayPreservesDispatchOrder: with the worker-pool gateway
// attached, a burst of raw frames decoded in parallel is still dispatched to the
// listener in input order, proving the coordinator keeps FIFO ownership.
func TestInboundGatewayPreservesDispatchOrder(t *testing.T) {
	transport := &fakeTransport{}
	communicator := toki.NewCommunicator(transport, testParserMap())
	communicator.EnableInboundGateway(4, 64)
	defer communicator.Close()

	var mu sync.Mutex
	var received []int32

	toki.AddListenerTyped[*packets.TestData](communicator, func(m *packets.TestData) {
		mu.Lock()
		received = append(received, m.GetIndex())
		mu.Unlock()
	})

	const total = 200
	typeName := toki.TypeNameOf(&packets.TestData{})
	for i := int32(1); i <= total; i++ {
		data, _ := proto.Marshal(&packets.TestData{Index: i})
		frame, err := proto.Marshal(&packets.PacketBase{TypeName: typeName, Nonce: i, Data: data})
		if err != nil {
			t.Fatal(err)
		}
		communicator.OnReceivedFrame(frame)
	}

	deadline := time.Now().Add(3 * time.Second)
	for time.Now().Before(deadline) {
		mu.Lock()
		n := len(received)
		mu.Unlock()
		if n == total {
			break
		}
		time.Sleep(time.Millisecond)
	}

	mu.Lock()
	defer mu.Unlock()
	if len(received) != total {
		t.Fatalf("expected %d messages, got %d", total, len(received))
	}
	for i, idx := range received {
		if idx != int32(i+1) {
			t.Fatalf("gateway dispatch order violated at position %d: got index %d", i, idx)
		}
	}
}

// frameTCP builds a TCP wire frame: 4-byte big-endian length prefix + PacketBase.
func frameTCP(t *testing.T, base *packets.PacketBase) []byte {
	t.Helper()
	b, err := proto.Marshal(base)
	if err != nil {
		t.Fatal(err)
	}
	out := make([]byte, 4+len(b))
	binary.BigEndian.PutUint32(out[:4], uint32(len(b)))
	copy(out[4:], b)
	return out
}

// countingGateway is a test InboundGateway that records every Submit and then
// forwards the decoded frame to the supplied sink. It lets a transport read-path
// test prove the read loop actually routes raw frames through the gateway rather
// than decoding inline and bypassing it.
type countingGateway struct {
	onSubmit func(toki.InboundFrame)
}

func (g *countingGateway) Submit(frame toki.InboundFrame) { g.onSubmit(frame) }
func (g *countingGateway) Close()                         {}

// TestTcpReadLoopRoutesThroughGateway: a real TcpClient.readLoop must hand raw
// frames to the attached gateway. The counting gateway fails the test if the
// read loop decodes inline and bypasses the gateway (the original wiring gap).
func TestTcpReadLoopRoutesThroughGateway(t *testing.T) {
	serverConn, clientConn := net.Pipe()
	// intervalSec=0 disables heartbeats, so the client never writes to the pipe.
	client := toki.NewTcpClient(clientConn, 0, 0, testParserMap())
	defer client.Close()

	var mu sync.Mutex
	var received []int32
	submitted := 0

	gw := &countingGateway{onSubmit: func(frame toki.InboundFrame) {
		mu.Lock()
		submitted++
		mu.Unlock()
		base := &packets.PacketBase{}
		if err := proto.Unmarshal(frame.Bytes, base); err != nil {
			return
		}
		client.OnReceivedData(base.GetTypeName(), base.GetData(), base.GetNonce(), base.GetResponseNonce())
	}}
	client.AttachInboundGateway(gw)

	toki.AddListenerTyped[*packets.TestData](&client.Communicator, func(m *packets.TestData) {
		mu.Lock()
		received = append(received, m.GetIndex())
		mu.Unlock()
	})

	const total = 20
	typeName := toki.TypeNameOf(&packets.TestData{})
	frames := make([][]byte, 0, total)
	for i := int32(1); i <= total; i++ {
		data, err := proto.Marshal(&packets.TestData{Index: i})
		if err != nil {
			t.Fatal(err)
		}
		frames = append(frames, frameTCP(t, &packets.PacketBase{TypeName: typeName, Nonce: i, Data: data}))
	}
	go func() {
		for _, f := range frames {
			if _, err := serverConn.Write(f); err != nil {
				return
			}
		}
	}()

	deadline := time.Now().Add(3 * time.Second)
	for time.Now().Before(deadline) {
		mu.Lock()
		n := len(received)
		mu.Unlock()
		if n == total {
			break
		}
		time.Sleep(time.Millisecond)
	}

	mu.Lock()
	defer mu.Unlock()
	if submitted != total {
		t.Fatalf("read loop bypassed gateway: submitted=%d, want %d", submitted, total)
	}
	if len(received) != total {
		t.Fatalf("expected %d messages, got %d", total, len(received))
	}
	for i, idx := range received {
		if idx != int32(i+1) {
			t.Fatalf("dispatch order violated at position %d: got index %d", i, idx)
		}
	}
}

// TestTcpReadLoopWorkerGatewayPreservesOrder: a real TcpClient.readLoop with the
// production worker-pool gateway (EnableInboundGateway) still dispatches frames
// to the listener in input order despite parallel decode.
func TestTcpReadLoopWorkerGatewayPreservesOrder(t *testing.T) {
	serverConn, clientConn := net.Pipe()
	client := toki.NewTcpClient(clientConn, 0, 0, testParserMap())
	defer client.Close()
	client.EnableInboundGateway(4, 64)

	var mu sync.Mutex
	var received []int32
	toki.AddListenerTyped[*packets.TestData](&client.Communicator, func(m *packets.TestData) {
		mu.Lock()
		received = append(received, m.GetIndex())
		mu.Unlock()
	})

	const total = 100
	typeName := toki.TypeNameOf(&packets.TestData{})
	frames := make([][]byte, 0, total)
	for i := int32(1); i <= total; i++ {
		data, err := proto.Marshal(&packets.TestData{Index: i})
		if err != nil {
			t.Fatal(err)
		}
		frames = append(frames, frameTCP(t, &packets.PacketBase{TypeName: typeName, Nonce: i, Data: data}))
	}
	go func() {
		for _, f := range frames {
			if _, err := serverConn.Write(f); err != nil {
				return
			}
		}
	}()

	deadline := time.Now().Add(3 * time.Second)
	for time.Now().Before(deadline) {
		mu.Lock()
		n := len(received)
		mu.Unlock()
		if n == total {
			break
		}
		time.Sleep(time.Millisecond)
	}

	mu.Lock()
	defer mu.Unlock()
	if len(received) != total {
		t.Fatalf("expected %d messages, got %d", total, len(received))
	}
	for i, idx := range received {
		if idx != int32(i+1) {
			t.Fatalf("dispatch order violated at position %d: got index %d", i, idx)
		}
	}
}

// TestTcpReadLoopParseErrorDisconnects: with no gateway, a malformed frame in
// the real read loop must still trigger the parse-error disconnect.
func TestTcpReadLoopParseErrorDisconnects(t *testing.T) {
	serverConn, clientConn := net.Pipe()
	client := toki.NewTcpClient(clientConn, 0, 0, testParserMap())
	defer client.Close()

	// length=3 prefix followed by bytes that are not valid protobuf wire format.
	bad := []byte{0, 0, 0, 3, 0xff, 0xff, 0xff}
	go func() { _, _ = serverConn.Write(bad) }()

	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if r := client.DisconnectInfo().Reason; r != toki.DisconnectReasonUnknown {
			break
		}
		time.Sleep(time.Millisecond)
	}

	info := client.DisconnectInfo()
	if info.Reason != toki.DisconnectReasonTCPPacketParse {
		t.Fatalf("expected %s disconnect, got %q", toki.DisconnectReasonTCPPacketParse, info.Reason)
	}
}

// TestTcpReadLoopGatewayParseErrorDisconnects: with the gateway attached, a
// malformed frame decoded off the read loop must still surface as the same
// parse-error disconnect via the gateway error path.
func TestTcpReadLoopGatewayParseErrorDisconnects(t *testing.T) {
	serverConn, clientConn := net.Pipe()
	client := toki.NewTcpClient(clientConn, 0, 0, testParserMap())
	defer client.Close()
	client.EnableInboundGateway(2, 16)

	// length=3 prefix followed by bytes that are not valid protobuf wire format.
	bad := []byte{0, 0, 0, 3, 0xff, 0xff, 0xff}
	go func() { _, _ = serverConn.Write(bad) }()

	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if r := client.DisconnectInfo().Reason; r != toki.DisconnectReasonUnknown {
			break
		}
		time.Sleep(time.Millisecond)
	}

	info := client.DisconnectInfo()
	if info.Reason != toki.DisconnectReasonTCPPacketParse {
		t.Fatalf("expected %s disconnect via gateway error path, got %q", toki.DisconnectReasonTCPPacketParse, info.Reason)
	}
}