package broker

import (
	"bytes"
	"context"
	"io"
	"net"
	"sync"
	"testing"
	"time"

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

func TestLargeFrameQuotaReleasedOnPuback(t *testing.T) {
	b, w, done := startTCPClient(t, "ep-large-ack")
	defer func() { _ = b.Close() }()
	defer func() {
		_ = w.Close()
		select {
		case <-done:
		case <-time.After(3 * time.Second):
		}
	}()

	writeConnect(t, w, "ep-large-ack", 30, 0)
	readExactPacket(t, w, packets.Connack, 3*time.Second)
	writeSubscribe(t, w, downTopic("ep-large-ack"))
	readExactPacket(t, w, packets.Suback, 3*time.Second)
	waitSession(t, b, "ep-large-ack")

	stop := make(chan struct{})
	defer close(stop)
	var writeMu sync.Mutex
	go autoPuback(w, stop, &writeMu)

	payload := bytes.Repeat([]byte("x"), 70*1024)
	for i := 0; i < 65; i++ {
		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
		err := b.PublishDown(ctx, "ep-large-ack", "", payload, port.PublishOpts{QoS: 1})
		cancel()
		if err != nil {
			t.Fatalf("publish %d: %v", i+1, err)
		}
	}
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if len(b.largeSem) == 0 {
			return
		}
		time.Sleep(10 * time.Millisecond)
	}
	t.Fatalf("slots still held: %d", len(b.largeSem))
}

func TestLargeFrameQuotaReleasedOnDisconnect(t *testing.T) {
	b, w, done := startTCPClient(t, "ep-large-disc")
	defer func() { _ = b.Close() }()

	writeConnect(t, w, "ep-large-disc", 30, 0)
	readExactPacket(t, w, packets.Connack, 3*time.Second)
	writeSubscribe(t, w, downTopic("ep-large-disc"))
	readExactPacket(t, w, packets.Suback, 3*time.Second)
	waitSession(t, b, "ep-large-disc")

	go func() {
		buf := make([]byte, 32*1024)
		for {
			_, err := w.Read(buf)
			if err != nil {
				return
			}
		}
	}()

	payload := bytes.Repeat([]byte("y"), 70*1024)
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	if err := b.PublishDown(ctx, "ep-large-disc", "", payload, port.PublishOpts{QoS: 1}); err != nil {
		cancel()
		t.Fatal(err)
	}
	cancel()
	if len(b.largeSem) == 0 {
		t.Fatal("expected a held large slot before disconnect")
	}
	_ = w.Close()
	select {
	case <-done:
	case <-time.After(3 * time.Second):
		t.Fatal("client attach did not return")
	}
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if len(b.largeSem) == 0 {
			return
		}
		time.Sleep(10 * time.Millisecond)
	}
	t.Fatalf("slots after disconnect: %d", len(b.largeSem))
}

func TestLargeFrameQuotaReleasedWithoutSubscriber(t *testing.T) {
	b, w, done := startTCPClient(t, "ep-large-nosub")
	defer func() { _ = b.Close() }()
	defer func() {
		_ = w.Close()
		select {
		case <-done:
		case <-time.After(3 * time.Second):
		}
	}()

	writeConnect(t, w, "ep-large-nosub", 30, 0)
	readExactPacket(t, w, packets.Connack, 3*time.Second)
	waitSession(t, b, "ep-large-nosub")

	payload := bytes.Repeat([]byte("z"), 70*1024)
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	err := b.PublishDown(ctx, "ep-large-nosub", "", payload, port.PublishOpts{QoS: 1})
	cancel()
	if err != nil {
		t.Fatal(err)
	}
	if n := len(b.largeSem); n != 0 {
		t.Fatalf("held slots without subscriber: %d", n)
	}
}

func startTCPClient(t *testing.T, _ string) (*Broker, net.Conn, chan struct{}) {
	t.Helper()
	b, err := New(Options{Authenticator: AllowAuthenticator{}})
	if err != nil {
		t.Fatal(err)
	}
	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 b, w, done
}

func waitSession(t *testing.T, b *Broker, endpoint string) {
	t.Helper()
	deadline := time.Now().Add(3 * time.Second)
	for time.Now().Before(deadline) {
		if _, ok := b.ConnInfoOf(endpoint); ok {
			return
		}
		time.Sleep(5 * time.Millisecond)
	}
	t.Fatal("session not established")
}

func autoPuback(w net.Conn, stop <-chan struct{}, writeMu *sync.Mutex) {
	for {
		select {
		case <-stop:
			return
		default:
		}
		_ = w.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
		hdr := make([]byte, 1)
		if _, err := io.ReadFull(w, hdr); err != nil {
			continue
		}
		rem, err := readRemainingLengthConn(w)
		if err != nil {
			continue
		}
		body := make([]byte, rem)
		if _, err := io.ReadFull(w, body); err != nil {
			continue
		}
		if hdr[0]>>4 != packets.Publish {
			continue
		}
		qos := (hdr[0] >> 1) & 0x3
		if qos == 0 {
			continue
		}
		pk := new(packets.Packet)
		pk.ProtocolVersion = 5
		pk.FixedHeader = packets.FixedHeader{Type: packets.Publish, Remaining: rem, Qos: qos}
		if decErr := pk.PublishDecode(body); decErr != nil {
			continue
		}
		ack := packets.Packet{
			FixedHeader:     packets.FixedHeader{Type: packets.Puback},
			ProtocolVersion: 5,
			PacketID:        pk.PacketID,
		}
		var ab bytes.Buffer
		_ = ack.PubackEncode(&ab)
		writeMu.Lock()
		_, _ = w.Write(ab.Bytes())
		writeMu.Unlock()
	}
}