package broker

import (
	"bytes"
	"context"
	"errors"
	"io"
	"net"
	"strconv"
	"testing"
	"time"

	"git.asio.asia/nixevol/NixMsg/internal/app/port"
	"github.com/mochi-mqtt/server/v2/packets"
)

func TestPublishDownBackpressureWhenQueueFull(t *testing.T) {
	// 无缓冲 pipe：发送 goroutine 在客户端不读时堵住，队列才能填满。
	b, err := New(Options{Authenticator: AllowAuthenticator{}})
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = b.Close() }()
	r, w := net.Pipe()
	done := make(chan struct{})
	go func() {
		defer close(done)
		_ = b.AttachTCP(r)
	}()
	defer func() {
		_ = w.Close()
		select {
		case <-done:
		case <-time.After(3 * time.Second):
		}
	}()
	connectAndSubscribe(t, w, "ep-bp", 0)
	waitSession(t, b, "ep-bp")

	payload := bytes.Repeat([]byte("q"), 1024)
	var sawBP bool
	start := time.Now()
	// mochi outbound 缓冲 1024，发送 goroutine 要先填满它才会堵住，随后才轮到本地下行队列。
	for i := 0; i < 1024+downQueueMax+16; i++ {
		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
		err := b.PublishDown(ctx, "ep-bp", "", payload, port.PublishOpts{QoS: 1})
		cancel()
		if errors.Is(err, ErrBackpressure) {
			if time.Since(start) > 50*time.Millisecond && i == 0 {
				t.Fatalf("first backpressure took %s", time.Since(start))
			}
			sawBP = true
			break
		}
		if err != nil {
			t.Fatalf("publish %d: %v", i, err)
		}
	}
	if !sawBP {
		t.Fatal("expected ErrBackpressure")
	}
}

func TestSlowClientDoesNotBlockOtherPublishDown(t *testing.T) {
	b, err := New(Options{Authenticator: AllowAuthenticator{}})
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = b.Close() }()

	slowW, slowDone := acceptAndDial(t, b)
	fastW, fastDone := acceptAndDial(t, b)
	defer func() {
		_ = slowW.Close()
		_ = fastW.Close()
		select {
		case <-slowDone:
		case <-time.After(3 * time.Second):
		}
		select {
		case <-fastDone:
		case <-time.After(3 * time.Second):
		}
	}()

	writeConnect(t, slowW, "ep-slow", 30, 0)
	readExactPacket(t, slowW, packets.Connack, 3*time.Second)
	writeSubscribe(t, slowW, downTopic("ep-slow"))
	readExactPacket(t, slowW, packets.Suback, 3*time.Second)
	writeConnect(t, fastW, "ep-fast", 30, 0)
	readExactPacket(t, fastW, packets.Connack, 3*time.Second)
	writeSubscribe(t, fastW, downTopic("ep-fast"))
	readExactPacket(t, fastW, packets.Suback, 3*time.Second)
	waitSession(t, b, "ep-slow")
	waitSession(t, b, "ep-fast")

	big := bytes.Repeat([]byte("s"), 64*1024)
	for i := 0; i < 8; i++ {
		_ = b.PublishDown(context.Background(), "ep-slow", "", big, port.PublishOpts{QoS: 1})
	}

	small := []byte(`{"v":1,"type":"resp"}`)
	start := time.Now()
	if err := b.PublishDown(context.Background(), "ep-fast", "", small, port.PublishOpts{QoS: 1}); err != nil {
		t.Fatalf("fast publish: %v", err)
	}
	if time.Since(start) > 100*time.Millisecond {
		t.Fatalf("fast PublishDown took %s", time.Since(start))
	}
	got := readDownPayload(t, fastW, 2*time.Second)
	if !bytes.Equal(got, small) {
		t.Fatalf("fast got %q", got)
	}
}

func TestDownlinkFIFOOrder(t *testing.T) {
	b, w, done := startTCPClient(t, "ep-ord")
	defer func() { _ = b.Close() }()
	defer func() {
		_ = w.Close()
		select {
		case <-done:
		case <-time.After(3 * time.Second):
		}
	}()
	writeConnect(t, w, "ep-ord", 30, 0)
	readExactPacket(t, w, packets.Connack, 3*time.Second)
	writeSubscribe(t, w, downTopic("ep-ord"))
	readExactPacket(t, w, packets.Suback, 3*time.Second)
	waitSession(t, b, "ep-ord")

	const n = 64
	for i := 0; i < n; i++ {
		p := []byte(strconv.Itoa(i))
		if err := b.PublishDown(context.Background(), "ep-ord", "", p, port.PublishOpts{QoS: 1}); err != nil {
			t.Fatal(err)
		}
	}
	for i := 0; i < n; i++ {
		got := readDownPayload(t, w, 3*time.Second)
		want := []byte(strconv.Itoa(i))
		if !bytes.Equal(got, want) {
			t.Fatalf("order %d: got %s want %s", i, got, want)
		}
	}
}

func acceptAndDial(t *testing.T, b *Broker) (net.Conn, chan struct{}) {
	t.Helper()
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = ln.Close() })
	done := make(chan struct{})
	go func() {
		defer close(done)
		c, accErr := ln.Accept()
		if accErr != nil {
			return
		}
		_ = b.AttachTCP(c)
	}()
	w, err := net.Dial("tcp", ln.Addr().String())
	if err != nil {
		t.Fatal(err)
	}
	return w, done
}

func readDownPayload(t *testing.T, conn net.Conn, timeout time.Duration) []byte {
	t.Helper()
	deadline := time.Now().Add(timeout)
	for time.Now().Before(deadline) {
		_ = conn.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
		hdr := make([]byte, 1)
		if _, err := io.ReadFull(conn, hdr); err != nil {
			continue
		}
		rem, err := readRemainingLengthConn(conn)
		if err != nil {
			continue
		}
		body := make([]byte, rem)
		if _, err := io.ReadFull(conn, body); err != nil {
			continue
		}
		if hdr[0]>>4 != packets.Publish {
			continue
		}
		qos := (hdr[0] >> 1) & 0x3
		pk := new(packets.Packet)
		pk.ProtocolVersion = 5
		pk.FixedHeader = packets.FixedHeader{Type: packets.Publish, Remaining: rem, Qos: qos}
		if err := pk.PublishDecode(body); err != nil {
			t.Fatal(err)
		}
		if qos > 0 {
			ack := packets.Packet{
				FixedHeader:     packets.FixedHeader{Type: packets.Puback},
				ProtocolVersion: 5,
				PacketID:        pk.PacketID,
			}
			var ab bytes.Buffer
			_ = ack.PubackEncode(&ab)
			_, _ = conn.Write(ab.Bytes())
		}
		return pk.Payload
	}
	t.Fatal("timeout waiting publish")
	return nil
}