package gameserver

import (
	"context"
	"fmt"
	"io"
	"log"
	"net"
	"path/filepath"
	"sync"

	"ananta-ps/internal/config"
	"ananta-ps/pkg/crypto/chacha8"
	"ananta-ps/pkg/protocol"
)

type Server struct {
	cfg          *config.Config
	templatePath string
	ln           net.Listener
	cancelFunc   context.CancelFunc
	wg           sync.WaitGroup
	sessions     map[string]*Session
	mu           sync.RWMutex
}

type Session struct {
	id          string
	conn        net.Conn
	readCipher  *chacha8.UxChaCha8
	sendCipher  *chacha8.UxChaCha8
	sendMu      sync.Mutex
	pid         uint64
	unitId      uint64
	templateId  uint32
	posX        float32
	posY        float32
	posZ        float32
	facing      float32
	activeScene uint64
	activeRaid  uint32
	universeId  uint32
}

func New(cfg *config.Config, templatePath string) *Server {
	if templatePath == "" {
		candidates := []string{
			"data/player_info_template.bin",
			"../data/player_info_template.bin",
		}
		for _, c := range candidates {
			abs, _ := filepath.Abs(c)
			templatePath = abs
			break
		}
	}

	return &Server{
		cfg:          cfg,
		templatePath: templatePath,
		sessions:     make(map[string]*Session),
	}
}

func (s *Server) Start() error {
	ctx, cancel := context.WithCancel(context.Background())
	s.cancelFunc = cancel

	addr := fmt.Sprintf("%s:%d", s.cfg.Network.BindHost, s.cfg.Network.GamePort)
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return fmt.Errorf("failed to listen on game server %s: %w", addr, err)
	}
	s.ln = ln
	log.Printf("[GAME-SERVER] Listening on %s:%d", s.cfg.Network.AdvertisedHost, s.cfg.Network.GamePort)

	s.wg.Add(1)
	go s.acceptLoop(ctx)

	return nil
}

func (s *Server) Stop() error {
	if s.cancelFunc != nil {
		s.cancelFunc()
	}
	if s.ln != nil {
		_ = s.ln.Close()
	}
	s.wg.Wait()
	return nil
}

func (s *Server) GetActiveSessions() []*Session {
	s.mu.RLock()
	defer s.mu.RUnlock()
	list := make([]*Session, 0, len(s.sessions))
	for _, sess := range s.sessions {
		list = append(list, sess)
	}
	return list
}

func (s *Server) acceptLoop(ctx context.Context) {
	defer s.wg.Done()
	for {
		conn, err := s.ln.Accept()
		if err != nil {
			select {
			case <-ctx.Done():
				return
			default:
				log.Printf("[GAME-SERVER] Accept error: %v", err)
				return
			}
		}

		go s.handleConnection(ctx, conn)
	}
}

func (sess *Session) SendPacket(packet *protocol.RpcPacket) error {
	sess.sendMu.Lock()
	defer sess.sendMu.Unlock()

	var payload []byte
	switch packet.Kind {
	case protocol.PacketKindInvoke:
		payload = protocol.BuildInvoke(packet.MethodID, packet.InvokeID, packet.Body)
	case protocol.PacketKindReturn:
		payload = protocol.BuildReturn(packet.MethodID, packet.InvokeID, packet.Error, packet.Body)
	case protocol.PacketKindNotify:
		payload = protocol.BuildNotify(packet.MethodID, packet.Body)
	}

	return protocol.WriteFrame(sess.conn, 0x09, payload, sess.sendCipher)
}

func (sess *Session) ReturnEmptyOk(invokeID int32, methodID uint32) error {
	return sess.SendPacket(&protocol.RpcPacket{
		Kind:     protocol.PacketKindReturn,
		InvokeID: invokeID,
		MethodID: methodID,
		Error:    0,
		Body:     nil,
	})
}

func (sess *Session) ReturnData(invokeID int32, methodID uint32, body []byte) error {
	return sess.SendPacket(&protocol.RpcPacket{
		Kind:     protocol.PacketKindReturn,
		InvokeID: invokeID,
		MethodID: methodID,
		Error:    0,
		Body:     body,
	})
}

func (sess *Session) NotifyData(methodID uint32, body []byte) error {
	return sess.SendPacket(&protocol.RpcPacket{
		Kind:     protocol.PacketKindNotify,
		MethodID: methodID,
		Body:     body,
	})
}

func (s *Server) handleConnection(ctx context.Context, conn net.Conn) {
	defer conn.Close()

	log.Printf("[GAME-SERVER] Client connected from %s", conn.RemoteAddr())

	readCipher, writeCipher, err := protocol.HandleHandshake(conn)
	if err != nil {
		log.Printf("[GAME-SERVER] Handshake error from %s: %v", conn.RemoteAddr(), err)
		return
	}

	sess := &Session{
		id:          conn.RemoteAddr().String(),
		conn:        conn,
		readCipher:  readCipher,
		sendCipher:  writeCipher,
		pid:         s.cfg.Player.Pid,
		unitId:      s.cfg.Player.InitialUnitId,
		templateId:  s.cfg.Player.InitialSpiritTemplateId,
		posX:        float32(s.cfg.World.Spawn.X),
		posY:        float32(s.cfg.World.Spawn.Y),
		posZ:        float32(s.cfg.World.Spawn.Z),
		facing:      s.cfg.World.Facing,
		activeRaid:  s.cfg.World.RaidId,
		activeScene: s.cfg.World.SceneInstanceId,
		universeId:  s.cfg.World.UniverseId,
	}

	s.mu.Lock()
	s.sessions[sess.id] = sess
	s.mu.Unlock()

	defer func() {
		s.mu.Lock()
		delete(s.sessions, sess.id)
		s.mu.Unlock()
	}()

	for {
		select {
		case <-ctx.Done():
			return
		default:
		}

		frame, err := protocol.ReadFrame(conn, sess.readCipher)
		if err != nil {
			if err != io.EOF {
				log.Printf("[GAME-SERVER] Connection %s read error: %v", conn.RemoteAddr(), err)
			}
			return
		}

		// Frame mode 0x03 is heartbeat
		if frame.Mode == 0x03 {
			_ = protocol.WriteFrame(conn, 0x03, frame.Payload, sess.sendCipher)
			continue
		}

		packet := protocol.ParseRpcPacket(frame.Payload)
		if err := s.dispatch(sess, &packet); err != nil {
			log.Printf("[GAME-SERVER] Dispatch error for method %d: %v", packet.MethodID, err)
		}
	}
}

func (s *Server) dispatch(sess *Session, pkt *protocol.RpcPacket) error {
	switch pkt.MethodID {
	case protocol.MethodLoginGame:
		log.Printf("[WORLD] LoginGame received, preparing world state for player %d", sess.pid)
		if err := sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID); err != nil {
			return err
		}

		// 1. SendServerTimeGame
		_ = sess.NotifyData(protocol.MethodSendServerTimeGame, protocol.EncodeServerTime(0))

		// 2. SyncPlayerInfo (from template binary)
		playerInfoBytes, err := protocol.EncodePlayerInfo(s.templatePath, s.cfg.Client.Aid, sess.pid, s.cfg.Player.AccountId, s.cfg.Player.DisplayName)
		if err == nil {
			_ = sess.NotifyData(protocol.MethodSyncPlayerInfo, playerInfoBytes)
		} else {
			log.Printf("[WORLD] Warning: player_info_template.bin load error: %v", err)
		}

		// 3. SyncEnterScene
		enterScenePayload := protocol.EncodeEnterScene(
			sess.pid,
			sess.activeRaid,
			sess.activeScene,
			sess.universeId,
			sess.unitId,
			sess.templateId,
			sess.posX,
			sess.posY,
			sess.posZ,
			sess.facing,
		)
		log.Printf("[WORLD-V7] Sending SyncEnterScene raid=%d instance=%d universe=%d unit=%d template=%d pos=(%.2f,%.2f,%.2f)",
			sess.activeRaid, sess.activeScene, sess.universeId, sess.unitId, sess.templateId, sess.posX, sess.posY, sess.posZ)
		return sess.NotifyData(protocol.MethodSyncEnterScene, enterScenePayload)

	case protocol.MethodAskLoadSceneCompleted:
		log.Printf("[WORLD-V7] AskLoadSceneCompleted ack received, committing V7 4-step handoff")
		if err := sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID); err != nil {
			return err
		}

		// V7 4-step Handoff:
		// Step 1: SyncLogicAgentEnter
		_ = sess.NotifyData(protocol.MethodSyncLogicAgentEnter, protocol.EncodeLogicAgentEnter(sess.unitId))

		// Step 2: SyncManagedLogicAgent
		_ = sess.NotifyData(protocol.MethodSyncManagedLogicAgent, protocol.EncodeManagedLogicAgent(sess.unitId, sess.pid, 0))

		// Step 3: SyncRaidBattleUnitSpirit
		unitProjection := protocol.EncodeRaidBattleUnitSpirit(sess.unitId, sess.templateId, sess.posX, sess.posY, sess.posZ, sess.facing, sess.pid)
		_ = sess.NotifyData(protocol.MethodSyncRaidBattleUnitSpirit, unitProjection)

		// Step 4: SyncPlayerCurrentSpirit
		return sess.NotifyData(protocol.MethodSyncPlayerCurrentSpirit, protocol.EncodePlayerCurrentSpirit(sess.pid, sess.templateId, sess.unitId, false))

	case protocol.MethodAskLoadingFinished:
		log.Printf("[WORLD-V7] AskLoadingFinished received, scene ready")
		if err := sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID); err != nil {
			return err
		}

		// 1. SyncSceneLoadCompleted
		_ = sess.NotifyData(protocol.MethodSyncSceneLoadCompleted, protocol.EncodeSceneLoadCompleted(sess.activeScene))

		// 2. SyncGamePause (false)
		wPause := protocol.NewUxWriter()
		wPause.Bool(false)
		_ = sess.NotifyData(protocol.MethodSyncGamePause, wPause.Bytes())

		// 3. Unlock Map Fog
		wFog := protocol.NewUxWriter()
		wFog.U32(uint32(sess.activeScene)).Bool(true)
		_ = sess.NotifyData(protocol.MethodSyncSceneFogMapAllUnlock, wFog.Bytes())

		// 4. Combat power
		wPower := protocol.NewUxWriter()
		wPower.U8(0xFF).Int7(1).U32(sess.templateId).F32(1000.0)
		_ = sess.NotifyData(protocol.MethodSyncAllSpiritCombatPower, wPower.Bytes())

		// 5. Unlock Diving
		wDive := protocol.NewUxWriter()
		wDive.UxString("EnableDive").U8(0xFF).Int7(1).UxString("true")
		return sess.NotifyData(protocol.MethodSyncRunGmUtils, wDive.Bytes())

	case protocol.MethodAskLoadedInSameScene:
		w := protocol.NewUxWriter()
		w.U64(sess.pid).F64(1.0)
		return sess.NotifyData(protocol.MethodSyncPlayerLoadRate, w.Bytes())

	case protocol.MethodAskMoveStart, protocol.MethodAskMoveStop:
		return sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID)

	case protocol.MethodAskUpdatePlayerPosition:
		r := protocol.NewUxReader(pkt.Body)
		if x, err := r.F32(); err == nil {
			sess.posX = x
		}
		if y, err := r.F32(); err == nil {
			sess.posY = y
		}
		if z, err := r.F32(); err == nil {
			sess.posZ = z
		}
		return sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID)

	case protocol.MethodAskPreSwitchSpirit:
		return sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID)

	case protocol.MethodAskSwitchSpirit:
		// Clean DRMK character swap
		r := protocol.NewUxReader(pkt.Body)
		newTemplateId := sess.templateId
		if tid, err := r.U32(); err == nil {
			newTemplateId = tid
		}
		newUnitId := sess.unitId + 1

		log.Printf("[SWITCH] Switching character %d -> %d", sess.templateId, newTemplateId)
		if err := sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID); err != nil {
			return err
		}

		_ = sess.NotifyData(protocol.MethodSyncLogicAgentLeave, protocol.EncodeLogicAgentLeave(sess.unitId))
		_ = sess.NotifyData(protocol.MethodSyncLogicAgentEnter, protocol.EncodeLogicAgentEnter(newUnitId))
		_ = sess.NotifyData(protocol.MethodSyncManagedLogicAgent, protocol.EncodeManagedLogicAgent(newUnitId, sess.pid, 0))

		newProj := protocol.EncodeRaidBattleUnitSpirit(newUnitId, newTemplateId, sess.posX, sess.posY, sess.posZ, sess.facing, sess.pid)
		_ = sess.NotifyData(protocol.MethodSyncRaidBattleUnitSpirit, newProj)
		_ = sess.NotifyData(protocol.MethodSyncPlayerCurrentSpirit, protocol.EncodePlayerCurrentSpirit(sess.pid, newTemplateId, newUnitId, true))

		wInSitu := protocol.NewUxWriter()
		wInSitu.U32(newTemplateId).U64(newUnitId)
		_ = sess.NotifyData(protocol.MethodSyncSwitchSpiritInSitu, wInSitu.Bytes())

		sess.templateId = newTemplateId
		sess.unitId = newUnitId
		return nil

	case protocol.MethodAskSummonVehicle, protocol.MethodAskDriveVehicle, protocol.MethodAskExitVehicle:
		return sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID)

	case protocol.MethodAskPlayerAttack, protocol.MethodAskPlayerCastSkill, protocol.MethodAskUnlockFightStyle:
		return sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID)

	default:
		if pkt.Kind == protocol.PacketKindInvoke {
			return sess.ReturnEmptyOk(pkt.InvokeID, pkt.MethodID)
		}
	}

	return nil
}

// Teleport moves an active session to the specified coordinates.
func (sess *Session) Teleport(x, y, z, facing float32) error {
	sess.posX = x
	sess.posY = y
	sess.posZ = z
	sess.facing = facing

	w := protocol.NewUxWriter()
	w.U64(sess.unitId).F32(x).F32(y).F32(z).F32(facing).U8(0).Bool(false).U8(6) // SetPositionType.Teleport = 6
	return sess.NotifyData(protocol.MethodSyncUnitPositionAndFacing, w.Bytes())
}