package service

import (
	"context"
	"encoding/json"
	"fmt"
	"strconv"
	"sync"
	"time"

	"with_you/internal/config"
	apperrors "with_you/internal/errors"
	"with_you/internal/model"
	"with_you/internal/pkg/ws"
	"with_you/internal/repository"

	"go.uber.org/zap"
	"gorm.io/gorm"
)

// 通话相关常量
const (
	CallLifetimeMs = 60000  // 通话邀请有效期 60秒 (参考 Matrix)
	CallTimeoutMs  = 120000 // 通话超时(无人接听) 120秒
)

// ActiveCall 内存中的活跃通话
type ActiveCall struct {
	ID             string
	ConversationID string
	CallerID       string
	CalleeID       string
	CallType       model.CallType
	Status         model.CallStatus
	MediaType      string // voice 或 video
	CreatedAt      time.Time
	StartedAt      *time.Time
	Duration       int64 // 通话时长（秒）
	// 参与者状态
	Participants map[string]*ActiveParticipant
	// ICE Servers
	ICEServers []config.ICEServerConfig
}

// ActiveParticipant 内存中的活跃参与者
type ActiveParticipant struct {
	UserID   string
	Status   model.ParticipantStatus
	JoinedAt *time.Time
}

// CallService 通话服务接口
type CallService interface {
	Invite(ctx context.Context, callerID, calleeID, conversationID, mediaType string) (*ActiveCall, bool, error)
	Accept(ctx context.Context, callID, userID string) (*ActiveCall, error)
	Reject(ctx context.Context, callID, userID string) error
	Busy(ctx context.Context, callID, userID string) error
	End(ctx context.Context, callID, userID string, reason string) (*ActiveCall, error)
	RelaySignal(ctx context.Context, callID, fromUserID string, signalType string, payload json.RawMessage) error
	SetMuted(ctx context.Context, callID, userID string, muted bool) error
	GetCallHistory(ctx context.Context, userID string, page, pageSize int) ([]model.CallSession, int64, error)
	GetICEServers() []config.ICEServerConfig
	StartCleanupTicker()
}

type callService struct {
	callRepo repository.CallRepository
	hub      *ws.Hub
	config   *config.Config
	db       *gorm.DB

	// 内存中的活跃通话状态
	activeCalls       map[string]*ActiveCall     // callID -> ActiveCall
	activeCallsByUser map[string]map[string]bool // userID -> set of callIDs
	activeCallsByConv map[string]string          // conversationID -> callID
	mu                sync.RWMutex
}

// NewCallService 创建通话服务
func NewCallService(
	callRepo repository.CallRepository,
	hub *ws.Hub,
	cfg *config.Config,
	db *gorm.DB,
) CallService {
	svc := &callService{
		callRepo:          callRepo,
		hub:               hub,
		config:            cfg,
		db:                db,
		activeCalls:       make(map[string]*ActiveCall),
		activeCallsByUser: make(map[string]map[string]bool),
		activeCallsByConv: make(map[string]string),
	}

	// 订阅 WebSocket 断开事件
	hub.OnDisconnect(svc.handleUserDisconnect)

	// 自动启动超时清理
	svc.StartCleanupTicker()

	return svc
}

// generateCallID 生成通话ID
func (s *callService) generateCallID() string {
	id := time.Now().UnixNano()
	return strconv.FormatInt(id, 10)
}

// getActiveCall 从内存获取活跃通话
func (s *callService) getActiveCall(callID string) *ActiveCall {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.activeCalls[callID]
}

// getActiveCallByConversation 从内存获取会话的活跃通话
func (s *callService) getActiveCallByConversation(conversationID string) *ActiveCall {
	s.mu.RLock()
	callID, exists := s.activeCallsByConv[conversationID]
	if !exists {
		s.mu.RUnlock()
		return nil
	}
	call := s.activeCalls[callID]
	s.mu.RUnlock()
	return call
}

// getActiveCallsByUser 获取用户的所有活跃通话
func (s *callService) getActiveCallsByUser(userID string) []*ActiveCall {
	s.mu.RLock()
	callIDs, exists := s.activeCallsByUser[userID]
	if !exists {
		s.mu.RUnlock()
		return nil
	}
	var calls []*ActiveCall
	for callID := range callIDs {
		if call, ok := s.activeCalls[callID]; ok {
			calls = append(calls, call)
		}
	}
	s.mu.RUnlock()
	return calls
}

// storeActiveCall 存储活跃通话到内存
func (s *callService) storeActiveCall(call *ActiveCall) {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.activeCalls[call.ID] = call

	// 按会话索引
	s.activeCallsByConv[call.ConversationID] = call.ID

	// 按用户索引
	for userID := range call.Participants {
		if s.activeCallsByUser[userID] == nil {
			s.activeCallsByUser[userID] = make(map[string]bool)
		}
		s.activeCallsByUser[userID][call.ID] = true
	}
}

// removeActiveCall 从内存移除活跃通话
func (s *callService) removeActiveCall(callID string) *ActiveCall {
	s.mu.Lock()
	defer s.mu.Unlock()

	call, exists := s.activeCalls[callID]
	if !exists {
		return nil
	}

	delete(s.activeCalls, callID)
	delete(s.activeCallsByConv, call.ConversationID)

	for userID := range call.Participants {
		if userCalls, ok := s.activeCallsByUser[userID]; ok {
			delete(userCalls, callID)
			if len(userCalls) == 0 {
				delete(s.activeCallsByUser, userID)
			}
		}
	}

	return call
}

// isParticipant 检查用户是否是通话参与者
func isParticipant(call *ActiveCall, userID string) bool {
	_, ok := call.Participants[userID]
	return ok
}

func (s *callService) Invite(ctx context.Context, callerID, calleeID, conversationID, mediaType string) (*ActiveCall, bool, error) {
	// 检查会话是否有活跃通话
	if active := s.getActiveCallByConversation(conversationID); active != nil {
		return nil, false, apperrors.Wrap(fmt.Errorf("call %s", active.ID), apperrors.ErrCallInProgress)
	}

	now := time.Now()
	callID := s.generateCallID()

	call := &ActiveCall{
		ID:             callID,
		ConversationID: conversationID,
		CallerID:       callerID,
		CalleeID:       calleeID,
		CallType:       model.CallTypePrivate,
		Status:         model.CallStatusCalling,
		MediaType:      mediaType,
		CreatedAt:      now,
		Participants: map[string]*ActiveParticipant{
			callerID: {UserID: callerID, Status: model.ParticipantStatusJoined, JoinedAt: &now},
			calleeID: {UserID: calleeID, Status: model.ParticipantStatusInvited},
		},
		ICEServers: s.config.WebRTC.ICEServers,
	}

	// 存储到内存
	s.storeActiveCall(call)

	// 检查被叫方是否在线
	calleeOnline := s.hub.HasClients(calleeID)

	// 发送来电通知
	payload := map[string]any{
		"call_id":         call.ID,
		"conversation_id": conversationID,
		"caller_id":       callerID,
		"call_type":       call.CallType,
		"media_type":      mediaType,
		"created_at":      now.UnixMilli(),
		"lifetime":        CallLifetimeMs,
		"ice_servers":     s.config.WebRTC.ICEServers,
	}

	online := s.hub.PublishToUserOnline(calleeID, "call_incoming", payload)

	if online {
		zap.L().Debug("Call invite sent to online callee",
			zap.String("call_id", call.ID),
			zap.String("callee_id", calleeID),
		)
	} else {
		zap.L().Debug("Call invite created for offline callee",
			zap.String("call_id", call.ID),
			zap.String("callee_id", calleeID),
		)
	}

	return call, calleeOnline, nil
}

func (s *callService) Accept(ctx context.Context, callID, userID string) (*ActiveCall, error) {
	call := s.getActiveCall(callID)
	if call == nil {
		return nil, apperrors.ErrCallNotFound
	}

	// 检查用户是否是参与者
	if !isParticipant(call, userID) {
		return nil, apperrors.ErrNotCallParticipant
	}

	// 检查通话状态
	if call.Status != model.CallStatusCalling {
		return nil, apperrors.ErrCallAlreadyAnswered
	}

	// 使用原子操作更新状态
	s.mu.Lock()
	if call.Status != model.CallStatusCalling {
		s.mu.Unlock()
		return nil, apperrors.ErrCallAlreadyAnswered
	}
	now := time.Now()
	call.Status = model.CallStatusConnected
	call.StartedAt = &now
	call.Participants[userID].Status = model.ParticipantStatusJoined
	call.Participants[userID].JoinedAt = &now
	s.mu.Unlock()

	// 通知拨打方
	s.hub.PublishToUserOnline(call.CallerID, "call_accepted", map[string]any{
		"call_id":     callID,
		"started_at":  now.UnixMilli(),
		"ice_servers": s.config.WebRTC.ICEServers,
	})

	// 通知被叫方其他设备
	s.hub.PublishToUserOnline(userID, "call_answered_elsewhere", map[string]any{
		"call_id": callID,
		"reason":  "answered_on_another_device",
	})

	return call, nil
}

func (s *callService) Reject(ctx context.Context, callID, userID string) error {
	call := s.getActiveCall(callID)
	if call == nil {
		return apperrors.ErrCallNotFound
	}

	s.mu.Lock()
	if call.Status != model.CallStatusCalling {
		s.mu.Unlock()
		return apperrors.ErrInvalidCallState
	}
	if !isParticipant(call, userID) {
		s.mu.Unlock()
		return apperrors.ErrNotCallParticipant
	}

	call.Status = model.CallStatusRejected
	call.Participants[userID].Status = model.ParticipantStatusRejected
	s.mu.Unlock()

	// 从内存移除
	s.removeActiveCall(callID)

	// 保存到数据库作为历史记录
	s.saveCallHistory(call, model.CallStatusRejected, 0)

	// 通知拨打方
	s.hub.PublishToUserOnline(call.CallerID, "call_rejected", map[string]any{
		"call_id": callID,
		"reason":  "rejected",
	})

	return nil
}

func (s *callService) Busy(ctx context.Context, callID, userID string) error {
	call := s.getActiveCall(callID)
	if call == nil {
		return apperrors.ErrCallNotFound
	}

	s.mu.Lock()
	if call.Status != model.CallStatusCalling {
		s.mu.Unlock()
		return apperrors.ErrInvalidCallState
	}
	if !isParticipant(call, userID) {
		s.mu.Unlock()
		return apperrors.ErrNotCallParticipant
	}

	call.Status = model.CallStatusMissed
	s.mu.Unlock()

	// 从内存移除
	s.removeActiveCall(callID)

	// 保存到数据库作为历史记录
	s.saveCallHistory(call, model.CallStatusMissed, 0)

	// 通知拨打方
	s.hub.PublishToUserOnline(call.CallerID, "call_busy", map[string]any{
		"call_id": callID,
	})

	return nil
}

func (s *callService) End(ctx context.Context, callID, userID string, reason string) (*ActiveCall, error) {
	call := s.getActiveCall(callID)
	if call == nil {
		return nil, apperrors.ErrCallNotFound
	}

	s.mu.Lock()
	if call.Status != model.CallStatusCalling && call.Status != model.CallStatusConnected {
		s.mu.Unlock()
		return nil, apperrors.ErrCallNotActive
	}
	// 允许系统结束通话时 userID 为空
	if userID != "" && !isParticipant(call, userID) {
		s.mu.Unlock()
		return nil, apperrors.ErrNotCallParticipant
	}

	now := time.Now()
	var duration int64
	if call.StartedAt != nil {
		duration = int64(now.Sub(*call.StartedAt).Seconds())
	}

	endStatus := model.CallStatusEnded
	if call.Status == model.CallStatusCalling {
		switch reason {
		case "timeout":
			endStatus = model.CallStatusMissed
		case "disconnect":
			endStatus = model.CallStatusMissed
		default:
			endStatus = model.CallStatusCancelled
		}
	}

	call.Status = endStatus
	call.Duration = duration
	if userID != "" {
		call.Participants[userID].Status = model.ParticipantStatusLeft
	}
	s.mu.Unlock()

	// 从内存移除
	s.removeActiveCall(callID)

	// 保存到数据库作为历史记录
	s.saveCallHistory(call, endStatus, duration)

	// 通知其他参与者
	for pUserID := range call.Participants {
		if pUserID != userID {
			s.hub.PublishToUserOnline(pUserID, "call_ended", map[string]any{
				"call_id":  callID,
				"ended_by": userID,
				"reason":   reason,
				"duration": duration,
				"ended_at": now.UnixMilli(),
			})
		}
	}

	return call, nil
}

func (s *callService) RelaySignal(ctx context.Context, callID, fromUserID string, signalType string, payload json.RawMessage) error {
	call := s.getActiveCall(callID)
	if call == nil {
		return apperrors.ErrCallNotFound
	}

	s.mu.RLock()
	if call.Status != model.CallStatusCalling && call.Status != model.CallStatusConnected {
		s.mu.RUnlock()
		return apperrors.ErrCallNotActive
	}
	if !isParticipant(call, fromUserID) {
		s.mu.RUnlock()
		return apperrors.ErrNotCallParticipant
	}
	s.mu.RUnlock()

	for pUserID := range call.Participants {
		if pUserID != fromUserID {
			s.hub.PublishToUserOnlineReliable(pUserID, signalType, map[string]any{
				"call_id": callID,
				"from_id": fromUserID,
				"payload": json.RawMessage(payload),
			})
		}
	}
	return nil
}

func (s *callService) SetMuted(ctx context.Context, callID, userID string, muted bool) error {
	call := s.getActiveCall(callID)
	if call == nil {
		return apperrors.ErrCallNotFound
	}

	s.mu.RLock()
	if call.Status != model.CallStatusCalling && call.Status != model.CallStatusConnected {
		s.mu.RUnlock()
		return apperrors.ErrCallNotActive
	}
	if !isParticipant(call, userID) {
		s.mu.RUnlock()
		return apperrors.ErrNotCallParticipant
	}
	s.mu.RUnlock()

	for pUserID := range call.Participants {
		if pUserID != userID {
			s.hub.PublishToUserOnline(pUserID, "call_peer_muted", map[string]any{
				"call_id": callID,
				"user_id": userID,
				"muted":   muted,
			})
		}
	}
	return nil
}

func (s *callService) GetCallHistory(ctx context.Context, userID string, page, pageSize int) ([]model.CallSession, int64, error) {
	return s.callRepo.GetCallHistory(userID, page, pageSize)
}

func (s *callService) GetICEServers() []config.ICEServerConfig {
	return s.config.WebRTC.ICEServers
}

// saveCallHistory 保存通话历史到数据库
func (s *callService) saveCallHistory(call *ActiveCall, status model.CallStatus, duration int64) {
	ctx := context.Background()
	now := time.Now()

	dbCall := &model.CallSession{
		ID:             call.ID,
		ConversationID: call.ConversationID,
		CallerID:       call.CallerID,
		CallType:       call.CallType,
		Status:         status,
		StartedAt:      call.StartedAt,
		EndedAt:        &now,
		Duration:       duration,
		CreatedAt:      call.CreatedAt,
		UpdatedAt:      now,
	}

	var participants []*model.CallParticipant
	for _, p := range call.Participants {
		participants = append(participants, &model.CallParticipant{
			CallID:    call.ID,
			UserID:    p.UserID,
			Status:    p.Status,
			JoinedAt:  p.JoinedAt,
			CreatedAt: call.CreatedAt,
			UpdatedAt: now,
		})
	}

	if err := s.callRepo.CreateCallWithParticipants(ctx, dbCall, participants); err != nil {
		zap.L().Error("Failed to save call history",
			zap.String("call_id", call.ID),
			zap.Error(err),
		)
	}
}

// StartCleanupTicker 启动超时清理定时器
func (s *callService) StartCleanupTicker() {
	go func() {
		ticker := time.NewTicker(30 * time.Second)
		defer ticker.Stop()

		for range ticker.C {
			s.cleanupExpiredCalls()
		}
	}()
}

// cleanupExpiredCalls 清理过期的通话
func (s *callService) cleanupExpiredCalls() {
	ctx := context.Background()

	s.mu.RLock()
	var expiredCalls []string
	now := time.Now()
	for _, call := range s.activeCalls {
		if call.Status == model.CallStatusCalling {
			elapsed := now.Sub(call.CreatedAt)
			if elapsed.Milliseconds() > CallTimeoutMs {
				expiredCalls = append(expiredCalls, call.ID)
			}
		}
	}
	s.mu.RUnlock()

	for _, callID := range expiredCalls {
		zap.L().Info("Cleaning up expired call",
			zap.String("call_id", callID),
		)
		_, _ = s.End(ctx, callID, "", "timeout")
	}
}

// handleUserDisconnect 处理用户 WebSocket 断开连接事件
func (s *callService) handleUserDisconnect(userID string, remainingCount int) {
	// 如果用户还有其他连接，不处理
	if remainingCount > 0 {
		return
	}

	ctx := context.Background()

	// 获取用户参与的所有活跃通话
	calls := s.getActiveCallsByUser(userID)
	if len(calls) == 0 {
		return
	}

	zap.L().Info("User disconnected, ending active calls",
		zap.String("user_id", userID),
		zap.Int("active_calls", len(calls)),
	)

	// 结束所有活跃通话
	for _, call := range calls {
		_, err := s.End(ctx, call.ID, userID, "disconnect")
		if err != nil {
			zap.L().Error("Failed to end call on user disconnect",
				zap.String("user_id", userID),
				zap.String("call_id", call.ID),
				zap.Error(err),
			)
		}
	}
}