package service

import (
	"errors"
	"time"

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

// DailyCheckinPoints 每日签到固定积分
const DailyCheckinPoints = 5

// maxStreakScan 连续天数最多向前回溯的天数
const maxStreakScan = 400

// ErrAlreadyCheckedIn 今日已签到
var ErrAlreadyCheckedIn = errors.New("今日已签到")

// CheckinStatus 签到状态（首页右栏与签到接口共用）
type CheckinStatus struct {
	CheckedToday bool `json:"checked_today"`
	Streak       int  `json:"streak"`       // 连续签到天数
	TotalPoints  int  `json:"total_points"` // 累计积分（可用余额）
	TodayPoints  int  `json:"today_points"` // 今日签到可得积分
}

// CheckinService 每日签到
type CheckinService struct {
	db *gorm.DB
}

func NewCheckinService(db *gorm.DB) *CheckinService {
	return &CheckinService{db: db}
}

// localDay 取本地时区零点日期
func localDay(t time.Time) time.Time {
	y, m, d := t.Date()
	return time.Date(y, m, d, 0, 0, 0, 0, t.Location())
}

// streakFrom 从 anchor（含）起按日倒推连续签到天数
func streakFrom(dates map[string]bool, anchor time.Time) int {
	streak := 0
	for i := 0; i < maxStreakScan; i++ {
		day := anchor.AddDate(0, 0, -i)
		if !dates[day.Format("2006-01-02")] {
			break
		}
		streak++
	}
	return streak
}

// Status 查询用户签到状态
func (s *CheckinService) Status(userID uint) (*CheckinStatus, error) {
	today := localDay(time.Now())

	var todayRow model.Checkin
	err := s.db.Where("user_id = ? AND checkin_date::date = ?::date", userID, today).
		First(&todayRow).Error
	checkedToday := true
	if err != nil {
		if !errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, err
		}
		checkedToday = false
	}

	// 连续天数：今日已签从今天起算，未签从昨天起算（今日尚未签不打断连续）
	anchor := today
	if !checkedToday {
		anchor = today.AddDate(0, 0, -1)
	}
	var dates []time.Time
	if err := s.db.Model(&model.Checkin{}).
		Where("user_id = ? AND checkin_date >= ?", userID, anchor.AddDate(0, 0, -maxStreakScan)).
		Pluck("checkin_date", &dates).Error; err != nil {
		return nil, err
	}
	dateSet := make(map[string]bool, len(dates))
	for _, d := range dates {
		dateSet[localDay(d).Format("2006-01-02")] = true
	}

	var total int64
	if err := s.db.Model(&model.User{}).
		Where("id = ?", userID).
		Select("points").Scan(&total).Error; err != nil {
		return nil, err
	}

	return &CheckinStatus{
		CheckedToday: checkedToday,
		Streak:       streakFrom(dateSet, anchor),
		TotalPoints:  int(total),
		TodayPoints:  DailyCheckinPoints,
	}, nil
}

// CheckIn 执行今日签到（每日一条，唯一索引兜底并发）
func (s *CheckinService) CheckIn(userID uint) (*CheckinStatus, error) {
	today := localDay(time.Now())

	var status *CheckinStatus
	err := s.db.Transaction(func(tx *gorm.DB) error {
		var count int64
		if err := tx.Model(&model.Checkin{}).
			Where("user_id = ? AND checkin_date::date = ?::date", userID, today).
			Count(&count).Error; err != nil {
			return err
		}
		if count > 0 {
			return ErrAlreadyCheckedIn
		}
		row := model.Checkin{
			UserID:      userID,
			CheckinDate: today,
			Points:      DailyCheckinPoints,
		}
		if err := tx.Create(&row).Error; err != nil {
			return err
		}
		// 同步入账到用户积分余额
		if _, err := CreditTx(tx, userID, DailyCheckinPoints, model.PointReasonCheckin, "checkin", row.ID, "每日签到"); err != nil {
			return err
		}
		return nil
	})
	if err != nil {
		return nil, err
	}

	status, err = s.Status(userID)
	if err != nil {
		return nil, err
	}
	return status, nil
}