package notify

import (
	"b612.me/stario"
	"bytes"
	"context"
	"errors"
	"io"
	"net"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

type serializedWriteTestConn struct {
	activeWrites int32
	concurrent   int32
	writeCount   int32
}

func (c *serializedWriteTestConn) Read([]byte) (int, error)         { return 0, net.ErrClosed }
func (c *serializedWriteTestConn) Close() error                     { return nil }
func (c *serializedWriteTestConn) LocalAddr() net.Addr              { return nil }
func (c *serializedWriteTestConn) RemoteAddr() net.Addr             { return nil }
func (c *serializedWriteTestConn) SetDeadline(time.Time) error      { return nil }
func (c *serializedWriteTestConn) SetReadDeadline(time.Time) error  { return nil }
func (c *serializedWriteTestConn) SetWriteDeadline(time.Time) error { return nil }

func (c *serializedWriteTestConn) Write(p []byte) (int, error) {
	if !atomic.CompareAndSwapInt32(&c.activeWrites, 0, 1) {
		atomic.StoreInt32(&c.concurrent, 1)
		return len(p), nil
	}
	time.Sleep(10 * time.Millisecond)
	atomic.AddInt32(&c.writeCount, 1)
	atomic.StoreInt32(&c.activeWrites, 0)
	return len(p), nil
}

func TestWriteFullToConnSerializesConcurrentWriters(t *testing.T) {
	conn := &serializedWriteTestConn{}
	payload := []byte("payload")

	var wg sync.WaitGroup
	for index := 0; index < 4; index++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			if err := writeFullToConn(conn, payload); err != nil {
				t.Errorf("writeFullToConn failed: %v", err)
			}
		}()
	}
	wg.Wait()

	if atomic.LoadInt32(&conn.concurrent) != 0 {
		t.Fatal("detected concurrent conn.Write execution")
	}
	if got, want := atomic.LoadInt32(&conn.writeCount), int32(4); got != want {
		t.Fatalf("write count = %d, want %d", got, want)
	}
}

func newTestBulkBatchSender(binding *transportBinding) *bulkBatchSender {
	return newTestBulkBatchSenderWithWriteTimeout(binding, nil)
}

func newTestBulkBatchSenderWithWriteTimeout(binding *transportBinding, writeTimeout func() time.Duration) *bulkBatchSender {
	return newBulkBatchSender(binding, bulkBatchCodec{
		encodeSingle: func(frame bulkFastFrame) ([]byte, func(), error) {
			return append([]byte(nil), frame.Payload...), nil, nil
		},
		encodeBatch: func(frames []bulkFastFrame) ([]byte, func(), error) {
			payload, err := encodeBulkFastBatchPlain(frames)
			return payload, nil, err
		},
	}, writeTimeout)
}

func newTestStreamBatchSender(binding *transportBinding, writeTimeout func() time.Duration) *streamBatchSender {
	return newStreamBatchSender(binding, streamBatchCodec{
		encodeSingle: func(frame streamFastDataFrame) ([]byte, error) {
			return encodeStreamFastFramePayload(frame)
		},
		encodeBatch: func(frames []streamFastDataFrame) ([]byte, error) {
			return encodeStreamFastBatchPlain(frames)
		},
	}, writeTimeout)
}

func TestBulkBatchSenderRespectsWriteDeadlineWhenReceiverStalls(t *testing.T) {
	left, right := net.Pipe()
	defer left.Close()
	defer right.Close()

	sender := newTestBulkBatchSenderWithWriteTimeout(newTransportBinding(left, stario.NewQueue()), func() time.Duration {
		return 50 * time.Millisecond
	})

	errCh := make(chan error, 1)
	go func() {
		errCh <- sender.submitData(context.Background(), 1, 1, bulkFastPathVersionV1, []byte("payload"))
	}()

	select {
	case err := <-errCh:
		if err == nil {
			t.Fatal("sender.submit should fail when receiver stalls")
		}
		if !isTimeoutLikeError(err) {
			t.Fatalf("sender.submit error = %v, want timeout-like error", err)
		}
	case <-time.After(time.Second):
		t.Fatal("sender.submit should not hang when receiver stalls")
	}
}

func TestStreamBatchSenderRespectsBindingWriteDeadlineWhenReceiverStalls(t *testing.T) {
	left, right := net.Pipe()
	defer left.Close()
	defer right.Close()

	sender := newTestStreamBatchSender(newTransportBinding(left, stario.NewQueue()), func() time.Duration {
		return 50 * time.Millisecond
	})

	errCh := make(chan error, 1)
	go func() {
		errCh <- sender.submitData(context.Background(), 1, 1, streamFastPathVersionV2, []byte("payload"))
	}()

	select {
	case err := <-errCh:
		if err == nil {
			t.Fatal("sender.submit should fail when receiver stalls")
		}
		if !isTimeoutLikeError(err) {
			t.Fatalf("sender.submit error = %v, want timeout-like error", err)
		}
	case <-time.After(time.Second):
		t.Fatal("sender.submit should not hang when receiver stalls")
	}
}

func TestControlBatchSenderRespectsWriteDeadlineWhenReceiverStalls(t *testing.T) {
	left, right := net.Pipe()
	defer left.Close()
	defer right.Close()

	sender := newControlBatchSender(newTransportBinding(left, stario.NewQueue()))
	deadline := time.Now().Add(50 * time.Millisecond)

	errCh := make(chan error, 1)
	go func() {
		errCh <- sender.submit([]byte("payload"), deadline)
	}()

	select {
	case err := <-errCh:
		if err == nil {
			t.Fatal("sender.submit should fail when receiver stalls")
		}
		if !isTimeoutLikeError(err) {
			t.Fatalf("sender.submit error = %v, want timeout-like error", err)
		}
	case <-time.After(time.Second):
		t.Fatal("sender.submit should not hang when receiver stalls")
	}
}

type blockingPacketWriteConn struct {
	startCh    chan struct{}
	unblockCh  chan struct{}
	writeCount atomic.Int32
}

func newBlockingPacketWriteConn() *blockingPacketWriteConn {
	return &blockingPacketWriteConn{
		startCh:   make(chan struct{}),
		unblockCh: make(chan struct{}),
	}
}

func (c *blockingPacketWriteConn) Read([]byte) (int, error) { return 0, net.ErrClosed }
func (c *blockingPacketWriteConn) Close() error             { return nil }
func (c *blockingPacketWriteConn) LocalAddr() net.Addr {
	return &net.UDPAddr{IP: net.IPv4zero, Port: 1}
}
func (c *blockingPacketWriteConn) RemoteAddr() net.Addr {
	return &net.UDPAddr{IP: net.IPv4(127, 0, 0, 1), Port: 2}
}
func (c *blockingPacketWriteConn) SetDeadline(time.Time) error      { return nil }
func (c *blockingPacketWriteConn) SetReadDeadline(time.Time) error  { return nil }
func (c *blockingPacketWriteConn) SetWriteDeadline(time.Time) error { return nil }

func (c *blockingPacketWriteConn) Write(p []byte) (int, error) {
	if c.writeCount.Add(1) == 1 {
		close(c.startCh)
		<-c.unblockCh
	}
	return len(p), nil
}

type vectoredShortWriteConn struct {
	steps  []int64
	idx    int
	buf    bytes.Buffer
	writes int
	writev int
}

func (c *vectoredShortWriteConn) Read([]byte) (int, error) { return 0, io.EOF }
func (c *vectoredShortWriteConn) Write(p []byte) (int, error) {
	c.writes++
	return c.buf.Write(p)
}
func (c *vectoredShortWriteConn) Close() error                     { return nil }
func (c *vectoredShortWriteConn) LocalAddr() net.Addr              { return nil }
func (c *vectoredShortWriteConn) RemoteAddr() net.Addr             { return nil }
func (c *vectoredShortWriteConn) SetDeadline(time.Time) error      { return nil }
func (c *vectoredShortWriteConn) SetReadDeadline(time.Time) error  { return nil }
func (c *vectoredShortWriteConn) SetWriteDeadline(time.Time) error { return nil }

func (c *vectoredShortWriteConn) WriteBuffers(bufs *net.Buffers) (int64, error) {
	c.writev++
	if c.idx >= len(c.steps) {
		return 0, io.ErrNoProgress
	}
	remaining := c.steps[c.idx]
	c.idx++
	written := int64(0)
	for len(*bufs) > 0 && remaining > 0 {
		part := (*bufs)[0]
		if len(part) == 0 {
			(*bufs)[0] = nil
			*bufs = (*bufs)[1:]
			continue
		}
		n := int64(len(part))
		if n > remaining {
			n = remaining
		}
		_, _ = c.buf.Write(part[:n])
		written += n
		remaining -= n
		if n == int64(len(part)) {
			(*bufs)[0] = nil
			*bufs = (*bufs)[1:]
			continue
		}
		(*bufs)[0] = part[n:]
		break
	}
	return written, nil
}

type unwrapVectoredConn struct {
	inner net.Conn
}

func (c *unwrapVectoredConn) Read(p []byte) (int, error)         { return c.inner.Read(p) }
func (c *unwrapVectoredConn) Write(p []byte) (int, error)        { return c.inner.Write(p) }
func (c *unwrapVectoredConn) Close() error                       { return c.inner.Close() }
func (c *unwrapVectoredConn) LocalAddr() net.Addr                { return c.inner.LocalAddr() }
func (c *unwrapVectoredConn) RemoteAddr() net.Addr               { return c.inner.RemoteAddr() }
func (c *unwrapVectoredConn) SetDeadline(t time.Time) error      { return c.inner.SetDeadline(t) }
func (c *unwrapVectoredConn) SetReadDeadline(t time.Time) error  { return c.inner.SetReadDeadline(t) }
func (c *unwrapVectoredConn) SetWriteDeadline(t time.Time) error { return c.inner.SetWriteDeadline(t) }
func (c *unwrapVectoredConn) UnwrapConn() net.Conn               { return c.inner }

func TestWriteNetBuffersFullUnlockedFallsBackToDirectWritesAfterFirstPartialVectoredWrite(t *testing.T) {
	conn := &vectoredShortWriteConn{steps: []int64{3}}
	header := []byte("head")
	payload := []byte("payload")
	if err := writeNetBuffersFullUnlocked(conn, net.Buffers{header, payload}); err != nil {
		t.Fatalf("writeNetBuffersFullUnlocked failed: %v", err)
	}
	if got, want := conn.writev, 1; got != want {
		t.Fatalf("vectored write calls = %d, want %d", got, want)
	}
	if got, want := conn.writes, 2; got != want {
		t.Fatalf("fallback direct writes = %d, want %d", got, want)
	}
	if got, want := conn.buf.String(), "headpayload"; got != want {
		t.Fatalf("written bytes = %q, want %q", got, want)
	}
}

func TestWriteNetBuffersFullUnlockedReturnsNoProgressWhenVectoredWriteDoesNotAdvance(t *testing.T) {
	conn := &vectoredShortWriteConn{steps: []int64{0}}
	err := writeNetBuffersFullUnlocked(conn, net.Buffers{[]byte("head"), []byte("payload")})
	if !errors.Is(err, io.ErrNoProgress) {
		t.Fatalf("writeNetBuffersFullUnlocked error = %v, want %v", err, io.ErrNoProgress)
	}
}

func TestWriteNetBuffersFullUnlockedUsesUnwrappedVectoredConn(t *testing.T) {
	inner := &vectoredShortWriteConn{steps: []int64{100}}
	conn := &unwrapVectoredConn{inner: inner}
	if err := writeNetBuffersFullUnlocked(conn, net.Buffers{[]byte("head"), []byte("payload")}); err != nil {
		t.Fatalf("writeNetBuffersFullUnlocked failed: %v", err)
	}
	if got, want := inner.writev, 1; got != want {
		t.Fatalf("unwrapped vectored write calls = %d, want %d", got, want)
	}
	if got := inner.writes; got != 0 {
		t.Fatalf("unexpected fallback direct writes = %d, want 0", got)
	}
}

func TestBulkBatchSenderSkipsQueuedCanceledRequest(t *testing.T) {
	conn := newBlockingPacketWriteConn()
	binding := newTransportBinding(conn, stario.NewQueue())
	sender := newTestBulkBatchSender(binding)
	defer sender.stop()

	firstErrCh := make(chan error, 1)
	go func() {
		firstErrCh <- sender.submitData(context.Background(), 1, 1, bulkFastPathVersionV1, []byte("first"))
	}()

	select {
	case <-conn.startCh:
	case <-time.After(time.Second):
		t.Fatal("first shared bulk write did not start")
	}

	ctx, cancel := context.WithCancel(context.Background())
	secondErrCh := make(chan error, 1)
	go func() {
		secondErrCh <- sender.submitData(ctx, 1, 2, bulkFastPathVersionV1, []byte("second"))
	}()
	time.Sleep(20 * time.Millisecond)
	cancel()

	select {
	case err := <-secondErrCh:
		if !errors.Is(err, context.Canceled) {
			t.Fatalf("second shared bulk submit error = %v, want %v", err, context.Canceled)
		}
	case <-time.After(time.Second):
		t.Fatal("second shared bulk submit did not return after cancel")
	}

	close(conn.unblockCh)

	select {
	case err := <-firstErrCh:
		if err != nil {
			t.Fatalf("first shared bulk submit failed: %v", err)
		}
	case <-time.After(time.Second):
		t.Fatal("first shared bulk submit did not finish")
	}

	time.Sleep(50 * time.Millisecond)
	if got, want := conn.writeCount.Load(), int32(1); got != want {
		t.Fatalf("shared bulk write count = %d, want %d", got, want)
	}
}

func TestBulkBatchSenderDoesNotDirectSubmitShareableV2Data(t *testing.T) {
	sender := &bulkBatchSender{}
	req := bulkBatchRequest{
		frames: []bulkFastFrame{{
			Type:    bulkFastPayloadTypeData,
			DataID:  1,
			Seq:     1,
			Payload: make([]byte, 256*1024),
		}},
		fastPathVersion: bulkFastPathVersionV2,
	}
	if sender.shouldDirectSubmit(req) {
		t.Fatal("shareable v2 shared bulk data should queue for super-batch instead of direct submit")
	}
}

func TestBulkBatchSenderDirectSubmitsUnbatchableRequest(t *testing.T) {
	sender := &bulkBatchSender{}
	req := bulkBatchRequest{
		frames: []bulkFastFrame{{
			Type:    bulkFastPayloadTypeRelease,
			DataID:  1,
			Seq:     0,
			Payload: []byte("rel"),
		}},
		fastPathVersion: bulkFastPathVersionV2,
	}
	if !sender.shouldDirectSubmit(req) {
		t.Fatal("unbatchable shared bulk control request should still direct submit")
	}
}

func TestBulkBatchSenderReturnsFlushResultAfterStartedContextCancel(t *testing.T) {
	conn := newBlockingPacketWriteConn()
	binding := newTransportBinding(conn, stario.NewQueue())
	sender := newTestBulkBatchSender(binding)
	defer sender.stop()

	ctx, cancel := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		errCh <- sender.submitData(ctx, 1, 1, bulkFastPathVersionV1, []byte("payload"))
	}()

	select {
	case <-conn.startCh:
	case <-time.After(time.Second):
		t.Fatal("shared bulk write did not start")
	}

	cancel()

	select {
	case err := <-errCh:
		t.Fatalf("sender.submit returned before flush completed: %v", err)
	case <-time.After(50 * time.Millisecond):
	}

	close(conn.unblockCh)

	select {
	case err := <-errCh:
		if err != nil {
			t.Fatalf("sender.submit failed after started flush: %v", err)
		}
	case <-time.After(time.Second):
		t.Fatal("sender.submit did not return after started flush completed")
	}
}

func TestTransportBindingStopBackgroundWorkersStopsSharedSender(t *testing.T) {
	binding := newTransportBinding(newBlockingPacketWriteConn(), stario.NewQueue())
	sender := binding.bulkBatchSenderSnapshotWithCodec(bulkBatchCodec{
		encodeSingle: func(frame bulkFastFrame) ([]byte, func(), error) {
			return append([]byte(nil), frame.Payload...), nil, nil
		},
		encodeBatch: func(frames []bulkFastFrame) ([]byte, func(), error) {
			payload, err := encodeBulkFastBatchPlain(frames)
			return payload, nil, err
		},
	}, nil)
	binding.stopBackgroundWorkers()

	err := sender.submitData(context.Background(), 1, 1, bulkFastPathVersionV1, []byte("payload"))
	if !errors.Is(err, errTransportDetached) {
		t.Fatalf("sender.submit after stop = %v, want %v", err, errTransportDetached)
	}
}

func TestTransportBindingStopBackgroundWorkersStopsControlSender(t *testing.T) {
	binding := newTransportBinding(&serializedWriteTestConn{}, stario.NewQueue())
	sender := binding.controlBatchSenderSnapshot()
	binding.stopBackgroundWorkers()

	err := sender.submit([]byte("payload"), time.Time{})
	if !errors.Is(err, errTransportDetached) {
		t.Fatalf("sender.submit after stop = %v, want %v", err, errTransportDetached)
	}
}