package chat

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"hfb_sys/backend/internal/model"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

func (r *Repository) resolveSite(ctx context.Context, siteCode string) (*model.DistributionSite, error) {
	siteCode = strings.TrimSpace(siteCode)
	if siteCode == "" {
		return nil, nil
	}
	var site model.DistributionSite
	if err := r.db.WithContext(ctx).Where("site_code = ? AND status = 'active'", siteCode).First(&site).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("distribution site unavailable")
		}
		return nil, err
	}
	return &site, nil
}

// userSiteConversationFilter 限制用户在当前站点能看到的会话。
// 账号群只有一个：本站发布的群按站点归属显示；跨站成交时，租客在下单的站点也能看到这个群。
func userSiteConversationFilter(siteID uint64, userID uint64) (string, []any) {
	if siteID > 0 {
		filter := `(
			c.distribution_site_id = ?
			OR (
				c.order_id IS NOT NULL
				AND c.order_id IN (
					SELECT ro.id FROM rental_orders ro
					WHERE ro.distribution_site_id = ?
						AND ro.distribution_mode != 'two_party_distributor_receive'
				)
			)
			OR (
				c.type = ?
				AND c.listing_id IN (
					SELECT ro.listing_id FROM rental_orders ro
					WHERE ro.distribution_site_id = ?
						AND ro.renter_id = ?
						AND ro.distribution_mode != 'two_party_distributor_receive'
				)
			)
		)`
		return filter, []any{siteID, siteID, ConversationTypeListingGroup, siteID, userID}
	}
	filter := `(
		(
			(c.distribution_site_id IS NULL OR c.distribution_site_id = 0)
			AND (
				c.order_id IS NULL
				OR c.order_id NOT IN (
					SELECT ro.id FROM rental_orders ro
					WHERE ro.distribution_site_id IS NOT NULL
						AND ro.distribution_site_id > 0
						AND ro.distribution_mode != 'two_party_distributor_receive'
				)
			)
		)
		OR (
			c.type = ?
			AND c.listing_id IN (
				SELECT ro.listing_id FROM rental_orders ro
				WHERE ro.renter_id = ?
					AND ro.distribution_mode = 'two_party_distributor_receive'
			)
		)
	)`
	return filter, []any{ConversationTypeListingGroup, userID}
}

func (r *Repository) ListConversations(ctx context.Context, principal Principal, page, pageSize int, siteCode ...string) (*PaginatedResult, error) {
	page, pageSize = normalizePagination(page, pageSize)
	db := r.db.WithContext(ctx)

	var code string
	if len(siteCode) > 0 {
		code = siteCode[0]
	}
	site, err := r.resolveSite(ctx, code)
	if err != nil {
		return nil, err
	}

	countDB := db.Table("chat_conversations AS c").
		Joins("JOIN chat_participants AS cp ON cp.conversation_id = c.id").
		Where("cp.participant_type = ? AND cp.participant_id = ?", principal.Type, principal.ID).
		Where("c.status = ?", "active")

	dataQuery := r.conversationQuery(ctx, principal).
		Where("c.status = ?", "active")

	if principal.Type == "user" {
		siteID := uint64(0)
		if site != nil {
			siteID = site.ID
		}
		filter, args := userSiteConversationFilter(siteID, principal.ID)
		countDB = countDB.Where(filter, args...)
		dataQuery = dataQuery.Where(filter, args...)
	}

	var total int64
	if err := countDB.Count(&total).Error; err != nil {
		return nil, err
	}

	var rows []conversationRow
	offset := (page - 1) * pageSize
	err = dataQuery.
		Order("COALESCE(c.last_message_at, c.created_at) DESC, c.id DESC").
		Offset(offset).
		Limit(pageSize).
		Scan(&rows).Error
	if err != nil {
		return nil, err
	}
	items := make([]ConversationDTO, 0, len(rows))
	for _, row := range rows {
		items = append(items, row.toDTO(nil))
	}
	return &PaginatedResult{Items: items, Total: total, Page: page, PageSize: pageSize}, nil
}

func (r *Repository) FindConversation(ctx context.Context, principal Principal, id uint64) (*ConversationDTO, error) {
	db := r.db.WithContext(ctx)
	// 管理员可以查看任意会话，无需是 participant
	if principal.Type == "admin" {
		var conversation model.ChatConversation
		if err := db.First(&conversation, id).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return nil, ErrConversationNotFound
			}
			return nil, err
		}
		participants, err := r.participants(ctx, conversation.ID)
		if err != nil {
			return nil, err
		}
		var state model.ChatAdminConversationState
		if err := db.Where("conversation_id = ? AND admin_user_id = ?", conversation.ID, principal.ID).First(&state).Error; err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
		var unreadCount int64
		if err := db.Table("chat_messages AS cm").
			Where("cm.conversation_id = ?", conversation.ID).
			Where("(cm.admin_attention_type <> ? OR cm.sender_type = ?)", "", "user").
			Where("cm.id > ?", state.LastReadMessageID).
			Count(&unreadCount).Error; err != nil {
			return nil, err
		}
		dto := ConversationDTO{
			ID:                 conversation.ID,
			OrderID:            conversation.OrderID,
			ListingID:          conversation.ListingID,
			DistributionSiteID: conversation.DistributionSiteID,
			Type:               conversation.Type,
			SupportScene:       conversation.SupportScene,
			Title:              conversation.Title,
			Status:             conversation.Status,
			Role:               "admin", // 管理员角色
			AdminRemark:        state.Remark,
			Participants:       participants,
			LastMessageID:      conversation.LastMessageID,
			LastMessagePreview: conversation.LastMessagePreview,
			LastMessageAt:      conversation.LastMessageAt,
			UnreadCount:        unreadCount,
			CreatedAt:          conversation.CreatedAt,
			UpdatedAt:          conversation.UpdatedAt,
		}
		return &dto, nil
	}

	// 普通用户需要是 participant
	var row conversationRow
	err := r.conversationQuery(ctx, principal).Where("c.id = ?", id).First(&row).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrConversationNotFound
		}
		return nil, err
	}
	participants, err := r.participants(ctx, row.ID)
	if err != nil {
		return nil, err
	}
	dto := row.toDTO(participants)
	return &dto, nil
}

func (r *Repository) FindOrderConversation(ctx context.Context, userID uint64, orderID uint64) (*ConversationDTO, error) {
	principal := Principal{Type: "user", ID: userID}
	var order model.RentalOrder
	if err := r.db.WithContext(ctx).First(&order, orderID).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrConversationNotFound
		}
		return nil, err
	}

	if order.ListingID > 0 {
		var row conversationRow
		err := r.conversationQuery(ctx, principal).
			Where("c.listing_id = ? AND c.type = ?", order.ListingID, ConversationTypeListingGroup).
			First(&row).Error
		if err == nil {
			participants, err := r.participants(ctx, row.ID)
			if err != nil {
				return nil, err
			}
			dto := row.toDTO(participants)
			return &dto, nil
		}
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
	}

	var row conversationRow
	err := r.conversationQuery(ctx, principal).Where("c.order_id = ?", orderID).First(&row).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrConversationNotFound
		}
		return nil, err
	}
	participants, err := r.participants(ctx, row.ID)
	if err != nil {
		return nil, err
	}
	dto := row.toDTO(participants)
	return &dto, nil
}

func (r *Repository) EnsureSupportConversation(ctx context.Context, userID uint64, scene string, siteCode ...string) (*ConversationDTO, error) {
	var code string
	if len(siteCode) > 0 {
		code = siteCode[0]
	}
	site, err := r.resolveSite(ctx, code)
	if err != nil {
		return nil, err
	}

	scene, title, groupCode, welcome := resolveSupportScene(scene)
	if site != nil {
		title = fmt.Sprintf("【%s】%s", site.SiteName, title)
		welcome = fmt.Sprintf("您好，欢迎咨询【%s】在线客服！请直接描述您遇到的问题，客服会尽快回复。", site.SiteName)
	}

	var conversationID uint64
	err = r.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var existing model.ChatConversation
		existingQuery := tx.Table("chat_conversations AS c").
			Select("c.*").
			Joins("JOIN chat_participants AS cp ON cp.conversation_id = c.id").
			Where(
				"c.type = ? AND c.support_scene = ? AND cp.participant_type = ? AND cp.participant_id = ?",
				ConversationTypeGeneralSupport, scene, "user", userID,
			)

		if site != nil {
			existingQuery = existingQuery.Where("c.distribution_site_id = ?", site.ID)
		} else {
			existingQuery = existingQuery.Where("c.distribution_site_id IS NULL OR c.distribution_site_id = 0")
		}

		err := existingQuery.Order("c.id ASC").Limit(1).Find(&existing).Error
		if err != nil {
			return err
		}

		// 兼容旧数据：主站 scene=general 时也匹配未回填 support_scene 的历史会话
		if site == nil && existing.ID == 0 && scene == SupportSceneGeneral {
			err = tx.Table("chat_conversations AS c").
				Select("c.*").
				Joins("JOIN chat_participants AS cp ON cp.conversation_id = c.id").
				Where(
					"c.type = ? AND (c.support_scene = '' OR c.support_scene IS NULL) AND cp.participant_type = ? AND cp.participant_id = ? AND (c.distribution_site_id IS NULL OR c.distribution_site_id = 0)",
					ConversationTypeGeneralSupport, "user", userID,
				).
				Order("c.id ASC").
				Limit(1).
				Find(&existing).Error
			if err != nil {
				return err
			}
			if existing.ID > 0 && existing.SupportScene == "" {
				_ = tx.Model(&existing).Update("support_scene", SupportSceneGeneral).Error
			}
		}
		// 兼容旧摸大红场景码 mohong → crash
		if site == nil && existing.ID == 0 && scene == SupportSceneCrash {
			err = tx.Table("chat_conversations AS c").
				Select("c.*").
				Joins("JOIN chat_participants AS cp ON cp.conversation_id = c.id").
				Where(
					"c.type = ? AND c.support_scene = ? AND cp.participant_type = ? AND cp.participant_id = ? AND (c.distribution_site_id IS NULL OR c.distribution_site_id = 0)",
					ConversationTypeGeneralSupport, SupportSceneMohong, "user", userID,
				).
				Order("c.id ASC").
				Limit(1).
				Find(&existing).Error
			if err != nil {
				return err
			}
		}
		if existing.ID > 0 {
			conversationID = existing.ID
			return nil
		}

		now := time.Now()
		conversation := model.ChatConversation{
			Type:         ConversationTypeGeneralSupport,
			SupportScene: scene,
			Title:        title,
			Status:       "active",
		}
		if site != nil {
			conversation.DistributionSiteID = &site.ID
		}
		if err := tx.Create(&conversation).Error; err != nil {
			return err
		}

		participants := []model.ChatParticipant{
			{
				ConversationID:  conversation.ID,
				ParticipantType: "user",
				ParticipantID:   userID,
				Role:            "customer",
				JoinedAt:        now,
			},
		}

		var supportID uint64
		if site != nil && site.DefaultSupportGroupID != nil && *site.DefaultSupportGroupID > 0 {
			var member model.ChatSupportGroupMember
			if err := tx.Where("group_id = ?", *site.DefaultSupportGroupID).Order("id ASC").First(&member).Error; err == nil && member.AdminID > 0 {
				supportID = member.AdminID
			}
		}
		if supportID == 0 {
			supportID = pickSupportAdminForScene(tx, groupCode)
		}

		if supportID > 0 {
			participants = append(participants, model.ChatParticipant{
				ConversationID:  conversation.ID,
				ParticipantType: "admin",
				ParticipantID:   supportID,
				Role:            "support",
				JoinedAt:        now,
			})
		}
		for _, participant := range participants {
			if err := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&participant).Error; err != nil {
				return err
			}
		}

		message := model.ChatMessage{
			ConversationID: conversation.ID,
			SenderType:     "system",
			SenderRole:     "system",
			ContentType:    "system",
			Content:        welcome,
			AttachmentURLS: emptyJSONList(),
		}
		if err := tx.Create(&message).Error; err != nil {
			return err
		}
		conversation.LastMessageID = &message.ID
		conversation.LastMessagePreview = truncatePreview(message.Content)
		conversation.LastMessageAt = &message.CreatedAt
		if err := tx.Save(&conversation).Error; err != nil {
			return err
		}
		conversationID = conversation.ID
		return nil
	})
	if err != nil {
		return nil, err
	}
	item, err := r.FindConversation(ctx, Principal{Type: "user", ID: userID}, conversationID)
	if err != nil {
		return nil, err
	}
	r.NotifyNewConversation(conversationID)
	return item, nil
}