package gameserver

import (
	"encoding/binary"
	"sync"
	"testing"
	"time"

	"google.golang.org/protobuf/proto"

	"gac-hkrpg-go/internal/common"
	kcplib "gac-hkrpg-go/pkg/kcp"
	goproto "gac-hkrpg-go/protocol/proto"
)

// TestGatewayHandshakeAndLogin simulates a game client: NetOperation
// handshake -> KCP session -> PlayerGetTokenCsReq -> expect ScRsp back.
func TestGatewayHandshakeAndLogin(t *testing.T) {
	gw, err := NewGateway("127.0.0.1", 0)
	if err != nil {
		t.Fatal(err)
	}
	go func() {
		_ = gw.Listen()
	}()

	client, err := newTestClient(t, gw.conn.LocalAddr().String())
	if err != nil {
		t.Fatal(err)
	}

	// 1. handshake
	conv, token, err := client.handshake()
	if err != nil {
		t.Fatalf("handshake failed: %v", err)
	}
	t.Logf("handshake ok: conv=%d token=%d", conv, token)

	// 2. configure the SERVER-side session held by the gateway
	player, _ := common.LoadFreesrData()
	if player == nil {
		player = &common.FreesrData{}
	}
	serverSession := gw.GetSession(conv)
	if serverSession == nil {
		t.Fatal("gateway did not register the session")
	}
	serverSession.SetJSON(player)

	// 3. send PlayerGetTokenCsReq (cmd 5)
	reqID := uint16(goproto.CmdIDByName["PlayerGetTokenCsReq"])
	rspID := uint16(goproto.CmdIDByName["PlayerGetTokenScRsp"])
	if err := client.sendCmd(reqID, nil); err != nil {
		t.Fatalf("send cmd: %v", err)
	}

	cmdID, body, err := client.recvCmd(3 * time.Second)
	if err != nil {
		t.Fatalf("no response: %v", err)
	}
	if cmdID != rspID {
		t.Fatalf("unexpected cmd id: got %d want %d", cmdID, rspID)
	}

	rsp := &goproto.PlayerGetTokenScRsp{}
	if err := proto.Unmarshal(body, rsp); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if rsp.Retcode != 0 || rsp.Uid != playerUID {
		t.Fatalf("bad token rsp: retcode=%d uid=%d", rsp.Retcode, rsp.Uid)
	}
	t.Logf("login token ok: retcode=%d uid=%d msg=%q", rsp.Retcode, rsp.Uid, rsp.Msg)

	// 4. exercise the SceneCastSkill fix: attack with no real monsters ->
	//    must NOT enter battle (no battle_info in the response)
	skillReqID := uint16(goproto.CmdIDByName["SceneCastSkillCsReq"])
	skillRspID := uint16(goproto.CmdIDByName["SceneCastSkillScRsp"])
	skillReq := &goproto.SceneCastSkillCsReq{
		CastEntityId:          1,
		CasterId:              1,
		SkillIndex:            0,
		HitTargetEntityIdList: []uint32{1005, 20010, 3}, // prop / npc / own avatar: none are monsters
	}
	reqBody, _ := proto.Marshal(skillReq)
	if err := client.sendCmd(skillReqID, reqBody); err != nil {
		t.Fatalf("send cast skill: %v", err)
	}
	cmdID, body, err = client.recvCmd(3 * time.Second)
	if err != nil {
		t.Fatalf("no cast skill response: %v", err)
	}
	if cmdID != skillRspID {
		t.Fatalf("unexpected cast skill cmd id: got %d want %d", cmdID, skillRspID)
	}
	skillRsp := &goproto.SceneCastSkillScRsp{}
	if err := proto.Unmarshal(body, skillRsp); err != nil {
		t.Fatalf("unmarshal cast skill rsp: %v", err)
	}
	if skillRsp.BattleInfo != nil || len(skillRsp.MonsterBattleInfo) != 0 {
		t.Fatalf("camera bug regression: server entered battle on non-monster targets")
	}
	if skillRsp.CastEntityId != 1 || skillRsp.Retcode != 0 {
		t.Fatalf("bad cast skill rsp: %+v", skillRsp)
	}
	t.Log("SceneCastSkill fix verified: no battle triggered for non-monster targets")

	// 5. attacking a real scene monster DOES start a battle
	serverSession.MonsterEntities[30001] = 30124011
	skillReq.HitTargetEntityIdList = []uint32{30001}
	reqBody, _ = proto.Marshal(skillReq)
	if err := client.sendCmd(skillReqID, reqBody); err != nil {
		t.Fatalf("send cast skill 2: %v", err)
	}
	cmdID, body, err = client.recvCmd(3 * time.Second)
	if err != nil {
		t.Fatalf("no response for monster attack: %v", err)
	}
	if cmdID != skillRspID {
		t.Fatalf("unexpected cmd: got %d want %d", cmdID, skillRspID)
	}
	skillRsp = &goproto.SceneCastSkillScRsp{}
	if err := proto.Unmarshal(body, skillRsp); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if skillRsp.BattleInfo == nil || len(skillRsp.MonsterBattleInfo) == 0 {
		t.Fatalf("expected battle to start for a real monster target")
	}
	t.Log("SceneCastSkill verified: battle starts for real monster target")

	// 6. GetUnreleasedBlockInfo (4190): Endgame entry gates on this reply
	if err := client.sendCmd(4190, nil); err != nil {
		t.Fatalf("send GetUnreleasedBlockInfo: %v", err)
	}
	cmdID, body, err = client.recvCmd(3 * time.Second)
	if err != nil {
		t.Fatalf("no GetUnreleasedBlockInfo response: %v", err)
	}
	if cmdID != 4112 {
		t.Fatalf("unexpected GetUnreleasedBlockInfoScRsp id: got %d want 4112", cmdID)
	}
	blockRsp := &goproto.GetUnreleasedBlockInfoScRsp{}
	if err := proto.Unmarshal(body, blockRsp); err != nil {
		t.Fatalf("unmarshal GetUnreleasedBlockInfo: %v", err)
	}
	if blockRsp.Retcode != 0 {
		t.Fatalf("unexpected UnreleasedBlockInfo retcode: %d", blockRsp.Retcode)
	}
	t.Log("GetUnreleasedBlockInfo verified: 4190 -> 4112 retcode 0")

	// 7. SetClientPaused must be acked (pause menu waits for it)
	pauseReq, _ := proto.Marshal(&goproto.SetClientPausedCsReq{Paused: true})
	if err := client.sendCmd(1466, pauseReq); err != nil {
		t.Fatalf("send SetClientPaused: %v", err)
	}
	cmdID, body, err = client.recvCmd(3 * time.Second)
	if err != nil {
		t.Fatalf("no SetClientPaused response: %v", err)
	}
	if cmdID != 1490 { // SetClientPausedScRsp
		t.Fatalf("unexpected SetClientPausedScRsp id: got %d want 1490", cmdID)
	}
	t.Log("SetClientPaused verified: acked")
}

// ---------------------------------------------------------------------------
// minimal KCP test client
// ---------------------------------------------------------------------------

type testClient struct {
	conn  *testUDPConn
	mu    sync.Mutex
	kcp   *kcplib.KCP
	now   uint32
	conv  uint32
	token uint32
}

func newTestClient(t *testing.T, serverAddr string) (*testClient, error) {
	conn, err := dialUDP(serverAddr)
	if err != nil {
		return nil, err
	}
	c := &testClient{conn: conn}
	return c, nil
}

func (c *testClient) handshake() (uint32, uint32, error) {
	// head=0xFF, tail=0xFFFFFFFF, data=client seed
	op := make([]byte, 20)
	binary.BigEndian.PutUint32(op[0:], 0xFF)
	binary.BigEndian.PutUint32(op[12:], 0xABCD1234)
	binary.BigEndian.PutUint32(op[16:], 0xFFFFFFFF)
	if _, err := c.conn.write(op); err != nil {
		return 0, 0, err
	}

	c.conn.setReadDeadline(time.Now().Add(3 * time.Second))
	reply, err := c.conn.read()
	if err != nil {
		return 0, 0, err
	}
	rsp, err := DecodeNetOperation(reply)
	if err != nil {
		return 0, 0, err
	}
	if rsp.Head != NetOpAcceptHead || rsp.Tail != NetOpAcceptTail || rsp.Data != 0xABCD1234 {
		return 0, 0, errBadHandshake
	}
	c.conv, c.token = rsp.Param1, rsp.Param2

	c.kcp = kcplib.New(c.conv, c.token, false, func(data []byte) error {
		_, err := c.conn.write(data)
		return err
	})
	return c.conv, c.token, nil
}

func (c *testClient) sendCmd(cmdID uint16, body []byte) error {
	pkt := (&NetPacket{CmdType: cmdID, Body: body}).Encode()
	c.mu.Lock()
	defer c.mu.Unlock()
	if _, err := c.kcp.Send(pkt); err != nil {
		return err
	}
	if err := c.kcp.Update(c.kcp.Now()); err != nil {
		return err
	}
	return c.kcp.Flush()
}

func (c *testClient) recvCmd(timeout time.Duration) (uint16, []byte, error) {
	deadline := time.Now().Add(timeout)
	buf := make([]byte, 65536)
	for time.Now().Before(deadline) {
		c.mu.Lock()
		now := c.now
		c.now += 50
		if err := c.kcp.Update(now); err != nil {
			c.mu.Unlock()
			return 0, nil, err
		}
		for {
			n, err := c.kcp.Recv(buf)
			if err != nil {
				break
			}
			pkt, err := DecodeNetPacket(buf[:n])
			if err != nil {
				continue
			}
			c.mu.Unlock()
			return pkt.CmdType, pkt.Body, nil
		}
		c.mu.Unlock()

		c.conn.setReadDeadline(time.Now().Add(10 * time.Millisecond))
		data, err := c.conn.read()
		if err == nil && len(data) >= 28 {
			c.mu.Lock()
			_ = c.kcp.Input(data)
			_ = c.kcp.Flush()
			c.mu.Unlock()
		}
	}
	return 0, nil, errTimeout
}

var (
	errBadHandshake = errString("bad handshake reply")
	errTimeout      = errString("timeout")
)

type errString string

func (e errString) Error() string { return string(e) }