package service

import (
	"strings"
	"time"

	"github.com/freefire/jiang13-bbs/model"
	"gorm.io/gorm"
)

// OverviewService 首页聚合服务：一次请求返回统计、热门榜、活跃用户、板块计数
type OverviewService struct {
	db *gorm.DB
}

func NewOverviewService(db *gorm.DB) *OverviewService {
	return &OverviewService{db: db}
}

// OverviewStats 社区整体统计
type OverviewStats struct {
	Posts      int64 `json:"posts"`
	Users      int64 `json:"users"`
	Comments   int64 `json:"comments"`
	TodayPosts int64 `json:"today_posts"`
}

// ActiveUser 近 14 天活跃用户
type ActiveUser struct {
	ID            uint   `json:"id"`
	Username      string `json:"username"`
	Nickname      string `json:"nickname"`
	Avatar        string `json:"avatar"`
	ActivityCount int64  `json:"activity_count"`
}

// BoardCount 板块及其已发布帖子计数（Board 字段被 encoding/json 展平）
type BoardCount struct {
	model.Board
	PostCount int64 `json:"post_count"`
}

// LatestCommentItem 首页"最新评论"条目（纯文本摘要 + 所属帖子）
type LatestCommentItem struct {
	ID        uint      `json:"id"`
	Content   string    `json:"content"`
	CreatedAt time.Time `json:"created_at"`
	User      struct {
		ID       uint   `json:"id"`
		Username string `json:"username"`
		Nickname string `json:"nickname"`
		Avatar   string `json:"avatar"`
	} `json:"user"`
	Post struct {
		ID    uint   `json:"id"`
		Title string `json:"title"`
	} `json:"post"`
}

// NewUserItem 最新注册成员
type NewUserItem struct {
	ID        uint      `json:"id"`
	Username  string    `json:"username"`
	Nickname  string    `json:"nickname"`
	Avatar    string    `json:"avatar"`
	CreatedAt time.Time `json:"created_at"`
}

// OverviewData 首页聚合数据
type OverviewData struct {
	Stats          OverviewStats       `json:"stats"`
	Hot            []PostListItem      `json:"hot"`
	ActiveUsers    []ActiveUser        `json:"active_users"`
	Boards         []BoardCount        `json:"boards"`
	LatestComments []LatestCommentItem `json:"latest_comments"`
	NewUsers       []NewUserItem       `json:"new_users"`
	Checkin        *CheckinStatus      `json:"checkin,omitempty"`
}

// truncateText 折叠空白并按 rune 截断（评论为纯文本，无 HTML 注入面）
func truncateText(s string, n int) string {
	s = strings.Join(strings.Fields(s), " ")
	r := []rune(s)
	if len(r) > n {
		return string(r[:n]) + "…"
	}
	return s
}

const activeUserWindow = 14 * 24 * time.Hour

// Get 聚合首页数据。hot 的 liked 态由 handler 层按当前用户填充。
func (s *OverviewService) Get() (*OverviewData, error) {
	data := &OverviewData{
		Hot:            []PostListItem{},
		ActiveUsers:    []ActiveUser{},
		Boards:         []BoardCount{},
		LatestComments: []LatestCommentItem{},
		NewUsers:       []NewUserItem{},
	}

	now := time.Now()
	dayStart := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	since := now.Add(-activeUserWindow)

	// 统计
	postQ := s.db.Model(&model.Post{}).Where("status = ?", model.ContentStatusPublished)
	if err := postQ.Count(&data.Stats.Posts).Error; err != nil {
		return nil, err
	}
	if err := s.db.Model(&model.User{}).Count(&data.Stats.Users).Error; err != nil {
		return nil, err
	}
	if err := s.db.Model(&model.Comment{}).Where("status = ?", model.ContentStatusPublished).Count(&data.Stats.Comments).Error; err != nil {
		return nil, err
	}
	if err := s.db.Model(&model.Post{}).
		Where("status = ? AND created_at >= ?", model.ContentStatusPublished, dayStart).
		Count(&data.Stats.TodayPosts).Error; err != nil {
		return nil, err
	}

	// 热门榜：非置顶，按 赞 + 评论×2
	var hotPosts []model.Post
	if err := s.db.Where("status = ? AND pinned = 0", model.ContentStatusPublished).
		Order("(like_count + comment_count * 2) DESC, created_at DESC").
		Limit(5).Preload("Board").Preload("User").Find(&hotPosts).Error; err != nil {
		return nil, err
	}
	data.Hot = toPostListItems(hotPosts)

	// 活跃用户：近 14 天发帖+评论合并计数，JOIN 用户过滤封禁/软删
	type activityRow struct {
		UserID        uint
		ActivityCount int64
	}
	var rows []activityRow
	activitySQL := `
SELECT a.user_id AS user_id, COUNT(*) AS activity_count
FROM (
	SELECT user_id FROM posts WHERE status = ? AND created_at >= ? AND deleted_at IS NULL
	UNION ALL
	SELECT user_id FROM comments WHERE status = ? AND created_at >= ? AND deleted_at IS NULL
) AS a
JOIN users AS u ON u.id = a.user_id
WHERE u.banned = ? AND u.deleted_at IS NULL
GROUP BY a.user_id
ORDER BY activity_count DESC, a.user_id ASC
LIMIT 5`
	if err := s.db.Raw(activitySQL,
		model.ContentStatusPublished, since,
		model.ContentStatusPublished, since,
		false).Scan(&rows).Error; err != nil {
		return nil, err
	}
	if len(rows) > 0 {
		ids := make([]uint, 0, len(rows))
		for _, r := range rows {
			ids = append(ids, r.UserID)
		}
		var users []model.User
		if err := s.db.Where("id IN ?", ids).Find(&users).Error; err != nil {
			return nil, err
		}
		userMap := make(map[uint]model.User, len(users))
		for _, u := range users {
			userMap[u.ID] = u
		}
		for _, r := range rows {
			u, ok := userMap[r.UserID]
			if !ok {
				continue
			}
			data.ActiveUsers = append(data.ActiveUsers, ActiveUser{
				ID:            u.ID,
				Username:      u.Username,
				Nickname:      u.Nickname,
				Avatar:        u.Avatar,
				ActivityCount: r.ActivityCount,
			})
		}
	}

	// 板块 + 各自帖子计数（一条 GROUP BY）
	var boards []model.Board
	if err := s.db.Order("sort_order ASC, id ASC").Find(&boards).Error; err != nil {
		return nil, err
	}
	type countRow struct {
		BoardID uint
		Cnt     int64
	}
	var counts []countRow
	if err := s.db.Model(&model.Post{}).
		Select("board_id, COUNT(*) AS cnt").
		Where("status = ?", model.ContentStatusPublished).
		Group("board_id").Scan(&counts).Error; err != nil {
		return nil, err
	}
	countMap := make(map[uint]int64, len(counts))
	for _, c := range counts {
		countMap[c.BoardID] = c.Cnt
	}
	for _, b := range boards {
		data.Boards = append(data.Boards, BoardCount{Board: b, PostCount: countMap[b.ID]})
	}

	// 最新评论：JOIN 未封禁用户与已发布帖，一条 SQL 取齐
	type latestCommentRow struct {
		ID        uint
		Content   string
		CreatedAt time.Time
		UID       uint
		Username  string
		Nickname  string
		Avatar    string
		PID       uint
		Title     string
	}
	var commentRows []latestCommentRow
	commentSQL := `
SELECT c.id, c.content, c.created_at,
       u.id AS uid, u.username AS username, u.nickname AS nickname, u.avatar AS avatar,
       p.id AS pid, p.title AS title
FROM comments c
JOIN users u ON u.id = c.user_id AND u.banned = ? AND u.deleted_at IS NULL
JOIN posts p ON p.id = c.post_id AND p.status = ? AND p.deleted_at IS NULL
WHERE c.status = ? AND c.deleted_at IS NULL
ORDER BY c.created_at DESC
LIMIT 6`
	if err := s.db.Raw(commentSQL,
		false, model.ContentStatusPublished, model.ContentStatusPublished).
		Scan(&commentRows).Error; err != nil {
		return nil, err
	}
	for _, r := range commentRows {
		item := LatestCommentItem{
			ID:        r.ID,
			Content:   truncateText(r.Content, 60),
			CreatedAt: r.CreatedAt,
		}
		item.User.ID = r.UID
		item.User.Username = r.Username
		item.User.Nickname = r.Nickname
		item.User.Avatar = r.Avatar
		item.Post.ID = r.PID
		item.Post.Title = r.Title
		data.LatestComments = append(data.LatestComments, item)
	}

	// 最新注册成员
	var newUsers []model.User
	if err := s.db.Select("id, username, nickname, avatar, created_at").
		Where("banned = ?", false).
		Order("created_at DESC").Limit(8).Find(&newUsers).Error; err != nil {
		return nil, err
	}
	for _, u := range newUsers {
		data.NewUsers = append(data.NewUsers, NewUserItem{
			ID:        u.ID,
			Username:  u.Username,
			Nickname:  u.Nickname,
			Avatar:    u.Avatar,
			CreatedAt: u.CreatedAt,
		})
	}

	return data, nil
}