package handler

import (
	"net/http"
	"strings"
	"time"
	"unicode/utf8"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
	"kefu-sys/server/internal/middleware"
	"kefu-sys/server/internal/model"
	"kefu-sys/server/internal/ws"
)

type SessionHandler struct{}

func NewSessionHandler() *SessionHandler { return &SessionHandler{} }

type SendMessageReq struct {
	Content string `json:"content" binding:"required"`
	Type    string `json:"type"`
}

type SessionListItem struct {
	model.Session
	UnreadCount int `json:"unread_count"`
}

type CreateNoteReq struct {
	Content string `json:"content" binding:"required"`
}

func (h *SessionHandler) SendMessage(c *gin.Context) {
	userID := middleware.GetUserID(c)
	id := c.Param("id")

	var req SendMessageReq
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "参数错误"})
		return
	}
	if req.Type == "" {
		req.Type = "text"
	}
	content, err := validateMessageContent(req.Type, req.Content)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
		return
	}

	session, ok := loadTenantSession(c, id)
	if !ok {
		return
	}
	if !canOperateSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权向该会话发送消息"})
		return
	}
	if session.Status == "ended" || session.Status == "archived" {
		c.JSON(http.StatusConflict, gin.H{"code": 409, "message": "会话已结束"})
		return
	}

	msg := model.Message{
		SessionID:  session.ID,
		SenderType: "agent",
		SenderID:   &userID,
		Content:    content,
		Type:       req.Type,
		SentAt:     time.Now(),
	}

	if err := model.CreateMessage(&msg); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "发送失败"})
		return
	}
	if middleware.GetRole(c) == "agent" {
		model.DB.Model(&model.Session{}).Where("id = ?", session.ID).Update("last_read_seq", msg.Seq)
		session.LastReadSeq = msg.Seq
	}
	broadcastSessionMessage(session, msg)

	middleware.JSON(c, msg)
}

type CreateSessionReq struct {
	ChannelID  uint   `json:"channel_id"`
	CustomerID uint   `json:"customer_id"`
	Priority   string `json:"priority"`
}

type AssignSessionReq struct {
	AgentID uint `json:"agent_id"`
}

func isTenantManager(c *gin.Context) bool {
	return middleware.HasAnyRole(c, "admin", "supervisor")
}

func loadTenantSession(c *gin.Context, id string) (*model.Session, bool) {
	var session model.Session
	if err := model.DB.First(&session, id).Error; err != nil {
		c.JSON(http.StatusNotFound, gin.H{"code": 404, "message": "会话不存在"})
		return nil, false
	}
	if session.TenantID != middleware.GetTenantID(c) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权访问其他租户会话"})
		return nil, false
	}
	return &session, true
}

func canReadSession(c *gin.Context, session *model.Session) bool {
	if isTenantManager(c) {
		return true
	}
	if middleware.GetRole(c) == "agent" {
		userID := middleware.GetUserID(c)
		return session.Status == "waiting" || (session.AgentID != nil && *session.AgentID == userID)
	}
	return false
}

func canOperateSession(c *gin.Context, session *model.Session) bool {
	if isTenantManager(c) {
		return true
	}
	return middleware.GetRole(c) == "agent" && session.AgentID != nil && *session.AgentID == middleware.GetUserID(c)
}

func broadcastSessionMessage(session *model.Session, message model.Message) {
	payload, err := ws.NewEvent("message", session.ID, message)
	if err == nil {
		ws.DefaultHub.BroadcastToSession(session.TenantID, session.ID, session.AgentID, payload)
	}
}

func broadcastSessionUpdate(session *model.Session) {
	payload, err := ws.NewEvent("session_updated", session.ID, gin.H{"status": session.Status})
	if err == nil {
		ws.DefaultHub.BroadcastToTenantStaff(session.TenantID, payload)
	}
}

func loadAssignableAgent(tenantID, agentID uint) error {
	var agent model.User
	if err := model.DB.First(&agent, agentID).Error; err != nil {
		return err
	}
	if agent.TenantID != tenantID || agent.Role != "agent" || agent.Status == "disabled" {
		return gorm.ErrRecordNotFound
	}
	return nil
}

func unreadCount(session model.Session) int {
	var count int64
	model.DB.Model(&model.Message{}).
		Where("session_id = ? AND sender_type = ? AND seq > ?", session.ID, "visitor", session.LastReadSeq).
		Count(&count)
	return int(count)
}

func (h *SessionHandler) List(c *gin.Context) {
	tenantID := middleware.GetTenantID(c)
	page, pageSize := middleware.GetPageParams(c)
	status := c.Query("status")
	priority := c.Query("priority")

	var sessions []model.Session
	var total int64

	query := model.DB.Where("tenant_id = ?", tenantID)
	if middleware.GetRole(c) == "agent" {
		query = query.Where("agent_id = ? OR status = ?", middleware.GetUserID(c), "waiting")
	}
	if status != "" {
		query = query.Where("status = ?", status)
	}
	if priority != "" {
		query = query.Where("priority = ?", priority)
	}

	query.Model(&model.Session{}).Count(&total)
	if err := query.Order("created_at desc").Offset((page - 1) * pageSize).Limit(pageSize).Find(&sessions).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "查询会话失败"})
		return
	}

	items := make([]SessionListItem, 0, len(sessions))
	for _, session := range sessions {
		item := SessionListItem{Session: session}
		if middleware.GetRole(c) == "agent" && session.AgentID != nil && *session.AgentID == middleware.GetUserID(c) {
			item.UnreadCount = unreadCount(session)
		}
		items = append(items, item)
	}

	middleware.JSONList(c, items, total, page, pageSize)
}

func (h *SessionHandler) Get(c *gin.Context) {
	id := c.Param("id")

	session, ok := loadTenantSession(c, id)
	if !ok {
		return
	}
	if !canReadSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权查看该会话"})
		return
	}

	var messages []model.Message
	if err := model.DB.Where("session_id = ?", session.ID).Order("seq asc").Find(&messages).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "查询消息失败"})
		return
	}
	var events []model.SessionEvent
	model.DB.Where("session_id = ?", session.ID).Order("created_at asc").Find(&events)
	var pendingCount int64
	model.DB.Model(&model.Session{}).Where("customer_id = ? AND tenant_id = ? AND status = ?", session.CustomerID, session.TenantID, "waiting").Count(&pendingCount)

	middleware.JSON(c, gin.H{"session": session, "messages": messages, "events": events, "pending_count": pendingCount})
}

func (h *SessionHandler) MarkRead(c *gin.Context) {
	session, ok := loadTenantSession(c, c.Param("id"))
	if !ok {
		return
	}
	if !canReadSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权标记该会话已读"})
		return
	}
	if session.AgentID == nil || middleware.GetRole(c) != "agent" || *session.AgentID != middleware.GetUserID(c) {
		middleware.JSON(c, gin.H{"last_read_seq": session.LastReadSeq})
		return
	}
	var maxSeq int
	if err := model.DB.Model(&model.Message{}).Where("session_id = ?", session.ID).Select("COALESCE(MAX(seq), 0)").Scan(&maxSeq).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "标记已读失败"})
		return
	}
	if err := model.DB.Model(&model.Session{}).Where("id = ?", session.ID).Update("last_read_seq", maxSeq).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "标记已读失败"})
		return
	}
	middleware.JSON(c, gin.H{"last_read_seq": maxSeq})
}

func (h *SessionHandler) AddNote(c *gin.Context) {
	session, ok := loadTenantSession(c, c.Param("id"))
	if !ok {
		return
	}
	if !canOperateSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权添加内部备注"})
		return
	}
	var req CreateNoteReq
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "参数错误"})
		return
	}
	content := strings.TrimSpace(req.Content)
	if content == "" || utf8.RuneCountInString(content) > 500 {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "内部备注需为 1 至 500 字"})
		return
	}
	event := model.SessionEvent{SessionID: session.ID, OperatorID: middleware.GetUserID(c), Action: "note", Detail: content}
	if err := model.DB.Create(&event).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "保存内部备注失败"})
		return
	}
	middleware.JSON(c, event)
}

func (h *SessionHandler) ListAvailableAgents(c *gin.Context) {
	type agentItem struct {
		ID       uint   `json:"id"`
		Nickname string `json:"nickname"`
		Status   string `json:"status"`
	}
	var users []model.User
	if err := model.DB.Where("tenant_id = ? AND role = ? AND status = ?", middleware.GetTenantID(c), "agent", "online").
		Order("nickname asc").Find(&users).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "查询在线客服失败"})
		return
	}
	items := make([]agentItem, 0, len(users))
	for _, user := range users {
		items = append(items, agentItem{ID: user.ID, Nickname: user.Nickname, Status: user.Status})
	}
	middleware.JSON(c, items)
}

func (h *SessionHandler) Create(c *gin.Context) {
	if !isTenantManager(c) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "仅主管或管理员可创建会话"})
		return
	}
	var req CreateSessionReq
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "参数错误"})
		return
	}

	tenantID := middleware.GetTenantID(c)
	var channel model.Channel
	if err := model.DB.Where("id = ? AND tenant_id = ? AND status = ?", req.ChannelID, tenantID, "enabled").First(&channel).Error; err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "渠道不存在或未启用"})
		return
	}
	var customer model.Customer
	if err := model.DB.Where("id = ? AND tenant_id = ?", req.CustomerID, tenantID).First(&customer).Error; err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "客户不存在"})
		return
	}

	session := model.Session{
		TenantID:   tenantID,
		ChannelID:  req.ChannelID,
		CustomerID: req.CustomerID,
		Priority:   req.Priority,
		Status:     "waiting",
	}

	if session.Priority == "" {
		session.Priority = "normal"
	}

	if err := model.DB.Create(&session).Error; err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "创建会话失败"})
		return
	}
	model.DB.Model(&model.Customer{}).Where("id = ? AND tenant_id = ?", customer.ID, tenantID).
		Updates(map[string]interface{}{"conversation_count": gorm.Expr("conversation_count + 1"), "last_contact_at": time.Now()})

	middleware.JSON(c, session)
}

func (h *SessionHandler) Assign(c *gin.Context) {
	id := c.Param("id")
	session, ok := loadTenantSession(c, id)
	if !ok {
		return
	}
	var req AssignSessionReq
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "参数错误"})
		return
	}

	if session.Status != "waiting" {
		c.JSON(http.StatusConflict, gin.H{"code": 409, "message": "会话已被分配"})
		return
	}
	if middleware.GetRole(c) == "agent" {
		req.AgentID = middleware.GetUserID(c)
	} else if !isTenantManager(c) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权分配会话"})
		return
	}
	if req.AgentID == 0 {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "请选择目标客服"})
		return
	}
	if err := loadAssignableAgent(session.TenantID, req.AgentID); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "目标客服不存在或不可用"})
		return
	}

	result := model.DB.Model(&model.Session{}).
		Where("id = ? AND tenant_id = ? AND status = ?", session.ID, session.TenantID, "waiting").
		Updates(map[string]interface{}{"agent_id": req.AgentID, "status": "active", "last_read_seq": 0})

	if result.Error != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "分配失败"})
		return
	}
	if result.RowsAffected == 0 {
		c.JSON(http.StatusConflict, gin.H{"code": 409, "message": "会话已被分配"})
		return
	}

	model.DB.Create(&model.SessionEvent{SessionID: session.ID, OperatorID: middleware.GetUserID(c), Action: "assign", Detail: "会话分配"})
	session.AgentID = &req.AgentID
	session.Status = "active"
	broadcastSessionUpdate(session)
	middleware.JSON(c, gin.H{"message": "分配成功"})
}

func (h *SessionHandler) Transfer(c *gin.Context) {
	id := c.Param("id")
	session, ok := loadTenantSession(c, id)
	if !ok {
		return
	}
	if !canOperateSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权转接该会话"})
		return
	}
	var req AssignSessionReq
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "参数错误"})
		return
	}

	if err := loadAssignableAgent(session.TenantID, req.AgentID); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "目标客服不存在或不可用"})
		return
	}
	result := model.DB.Model(&model.Session{}).
		Where("id = ? AND tenant_id = ? AND status = ?", session.ID, session.TenantID, "active").
		Updates(map[string]interface{}{"agent_id": req.AgentID, "last_read_seq": 0})
	if result.Error != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "转接失败"})
		return
	}
	if result.RowsAffected == 0 {
		c.JSON(http.StatusConflict, gin.H{"code": 409, "message": "会话不可转接"})
		return
	}

	model.DB.Create(&model.SessionEvent{
		SessionID:  session.ID,
		OperatorID: middleware.GetUserID(c),
		Action:     "transfer",
		Detail:     "会话转接",
	})
	session.AgentID = &req.AgentID
	broadcastSessionUpdate(session)

	middleware.JSON(c, gin.H{"message": "转接成功"})
}

func (h *SessionHandler) End(c *gin.Context) {
	id := c.Param("id")
	reason := c.Query("reason")
	session, ok := loadTenantSession(c, id)
	if !ok {
		return
	}
	if !canOperateSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权结束该会话"})
		return
	}
	if reason == "" {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "请填写结束原因"})
		return
	}
	if reason != "resolved" && reason != "no_response" && reason != "visitor_left" && reason != "transferred" && reason != "other" {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "结束原因无效"})
		return
	}
	now := time.Now()

	result := model.DB.Model(&model.Session{}).
		Where("id = ? AND tenant_id = ? AND status <> ?", session.ID, session.TenantID, "ended").
		Updates(map[string]interface{}{"status": "ended", "end_reason": reason, "ended_at": now})

	if result.RowsAffected == 0 {
		c.JSON(http.StatusNotFound, gin.H{"code": 404, "message": "会话不存在"})
		return
	}

	model.DB.Create(&model.SessionEvent{
		SessionID:  session.ID,
		OperatorID: middleware.GetUserID(c),
		Action:     "end",
		Detail:     "结束会话: " + reason,
	})
	session.Status = "ended"
	session.EndedAt = &now
	broadcastSessionUpdate(session)

	middleware.JSON(c, gin.H{"message": "已结束"})
}

func (h *SessionHandler) UpdatePriority(c *gin.Context) {
	id := c.Param("id")
	priority := c.Query("priority")
	session, ok := loadTenantSession(c, id)
	if !ok {
		return
	}
	if !canOperateSession(c, session) {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "无权更新该会话"})
		return
	}
	if priority != "urgent" && priority != "normal" {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "优先级无效"})
		return
	}

	result := model.DB.Model(&model.Session{}).
		Where("id = ? AND tenant_id = ?", session.ID, session.TenantID).
		Update("priority", priority)
	if result.Error != nil || result.RowsAffected == 0 {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "更新失败"})
		return
	}
	session.Priority = priority
	broadcastSessionUpdate(session)

	middleware.JSON(c, gin.H{"message": "已更新"})
}