package notify

import (
	"b612.me/stario"
	"context"
	"errors"
	"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 TestBulkBatchSenderRespectsWriteDeadlineWhenReceiverStalls(t *testing.T) {
	left, right := net.Pipe()
	defer left.Close()
	defer right.Close()

	sender := newBulkBatchSender(newTransportBinding(left, stario.NewQueue()))
	ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
	defer cancel()

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

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

	firstErrCh := make(chan error, 1)
	go func() {
		firstErrCh <- sender.submit(context.Background(), []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.submit(ctx, []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 TestBulkBatchSenderReturnsFlushResultAfterStartedContextCancel(t *testing.T) {
	conn := newBlockingPacketWriteConn()
	binding := newTransportBinding(conn, stario.NewQueue())
	sender := newBulkBatchSender(binding)
	defer sender.stop()

	ctx, cancel := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		errCh <- sender.submit(ctx, []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.bulkBatchSenderSnapshot()
	binding.stopBackgroundWorkers()

	err := sender.submit(context.Background(), []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)
	}
}