package expiry

import (
	"errors"
	"fmt"
	"time"

	"gorm.io/gorm"
)

// Repository 封装保质期模块的数据访问能力。
type Repository struct {
	db *gorm.DB
}

var (
	ErrExpiryItemNotFound = errors.New("expiry item not found")
)

func NewRepository(db *gorm.DB) *Repository {
	return &Repository{db: db}
}

// Create 创建物品。
func (r *Repository) Create(item *ExpiryItem) error {
	if err := r.db.Create(item).Error; err != nil {
		return fmt.Errorf("create expiry item: %w", err)
	}
	return nil
}

// Update 更新物品。
func (r *Repository) Update(item *ExpiryItem) error {
	updates := map[string]interface{}{
		"mini_program_id": item.MiniProgramID,
		"name":            item.Name,
		"category":        item.Category,
		"production_date": item.ProductionDate,
		"expiry_date":     item.ExpiryDate,
		"shelf_life_days": item.ShelfLifeDays,
		"quantity":        item.Quantity,
		"location":        item.Location,
		"remark":          item.Remark,
		"status":          item.Status,
	}

	tx := r.db.Model(&ExpiryItem{}).
		Where("id = ? AND user_id = ?", item.ID, item.UserID).
		Updates(updates)
	if tx.Error != nil {
		return fmt.Errorf("update expiry item: %w", tx.Error)
	}
	if tx.RowsAffected == 0 {
		return ErrExpiryItemNotFound
	}
	return nil
}

// Delete 软删除物品。
func (r *Repository) Delete(id, userID uint) error {
	tx := r.db.Where("id = ? AND user_id = ?", id, userID).Delete(&ExpiryItem{})
	if tx.Error != nil {
		return fmt.Errorf("delete expiry item: %w", tx.Error)
	}
	if tx.RowsAffected == 0 {
		return ErrExpiryItemNotFound
	}
	return nil
}

// FindByID 根据 ID 查询单个物品。
func (r *Repository) FindByID(id, userID uint) (*ExpiryItem, error) {
	var item ExpiryItem
	err := r.db.Where("id = ? AND user_id = ?", id, userID).First(&item).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrExpiryItemNotFound
		}
		return nil, fmt.Errorf("find expiry item by id: %w", err)
	}
	return &item, nil
}

// FindByUser 按用户 + 筛选条件分页查询物品列表。
func (r *Repository) FindByUser(
	userID uint,
	filters map[string]interface{},
	page, pageSize int,
) ([]ExpiryItem, int64, error) {
	if page <= 0 {
		page = 1
	}
	if pageSize <= 0 {
		pageSize = 20
	}
	if pageSize > 100 {
		pageSize = 100
	}

	query := r.db.Model(&ExpiryItem{}).Where("user_id = ?", userID)
	now := dateOnly(time.Now())
	sevenDaysLater := now.AddDate(0, 0, 7)

	if status, ok := filters["status"].(string); ok && status != "" && status != "all" {
		switch status {
		case StatusExpiring:
			query = query.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}).
				Where("expiry_date BETWEEN ? AND ?", now, sevenDaysLater)
		case StatusExpired:
			query = query.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}).
				Where("expiry_date < ?", now)
		case StatusNormal:
			query = query.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}).
				Where("expiry_date > ?", sevenDaysLater)
		case StatusUsed, StatusDiscarded:
			query = query.Where("status = ?", status)
		}
	}

	if category, ok := filters["category"].(string); ok && category != "" && category != "all" {
		query = query.Where("category = ?", category)
	}

	orderBy := "expiry_date ASC"
	if sort, ok := filters["sort"].(string); ok && sort != "" {
		switch sort {
		case "created_at":
			orderBy = "created_at DESC"
		case "expiry_date":
			orderBy = "expiry_date ASC"
		}
	}
	query = query.Order(orderBy).Order("id DESC")

	var total int64
	if err := query.Count(&total).Error; err != nil {
		return nil, 0, fmt.Errorf("count expiry items: %w", err)
	}

	var items []ExpiryItem
	offset := (page - 1) * pageSize
	if err := query.Offset(offset).Limit(pageSize).Find(&items).Error; err != nil {
		return nil, 0, fmt.Errorf("list expiry items: %w", err)
	}

	return items, total, nil
}

// GetSummary 获取首页汇总统计数据。
func (r *Repository) GetSummary(userID uint) (map[string]int, error) {
	now := dateOnly(time.Now())
	sevenDaysLater := now.AddDate(0, 0, 7)

	base := r.db.Model(&ExpiryItem{}).Where("user_id = ?", userID)

	count := func(tx *gorm.DB) (int64, error) {
		var v int64
		if err := tx.Count(&v).Error; err != nil {
			return 0, err
		}
		return v, nil
	}

	totalItems, err := count(base.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}))
	if err != nil {
		return nil, fmt.Errorf("count total items: %w", err)
	}

	expiringSoon, err := count(base.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}).
		Where("expiry_date BETWEEN ? AND ?", now, sevenDaysLater))
	if err != nil {
		return nil, fmt.Errorf("count expiring items: %w", err)
	}

	expired, err := count(base.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}).
		Where("expiry_date < ?", now))
	if err != nil {
		return nil, fmt.Errorf("count expired items: %w", err)
	}

	normal, err := count(base.Where("status NOT IN ?", []string{StatusUsed, StatusDiscarded}).
		Where("expiry_date > ?", sevenDaysLater))
	if err != nil {
		return nil, fmt.Errorf("count normal items: %w", err)
	}

	used, err := count(base.Where("status = ?", StatusUsed))
	if err != nil {
		return nil, fmt.Errorf("count used items: %w", err)
	}

	discarded, err := count(base.Where("status = ?", StatusDiscarded))
	if err != nil {
		return nil, fmt.Errorf("count discarded items: %w", err)
	}

	return map[string]int{
		"total_items":   int(totalItems),
		"expiring_soon": int(expiringSoon),
		"expired":       int(expired),
		"normal":        int(normal),
		"used":          int(used),
		"discarded":     int(discarded),
	}, nil
}

// UpdateStatus 更新物品状态（used/discarded）。
func (r *Repository) UpdateStatus(id, userID uint, status string) error {
	tx := r.db.Model(&ExpiryItem{}).
		Where("id = ? AND user_id = ?", id, userID).
		Update("status", status)
	if tx.Error != nil {
		return fmt.Errorf("update expiry item status: %w", tx.Error)
	}
	if tx.RowsAffected == 0 {
		return ErrExpiryItemNotFound
	}
	return nil
}

// GetSettings 查询用户提醒设置。
func (r *Repository) GetSettings(userID uint) (*ExpiryUserSettings, error) {
	var settings ExpiryUserSettings
	err := r.db.Where("user_id = ?", userID).First(&settings).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, nil
		}
		return nil, fmt.Errorf("find expiry settings: %w", err)
	}
	return &settings, nil
}

// UpdateSettings 更新用户提醒设置（不存在则创建）。
func (r *Repository) UpdateSettings(userID uint, remindDays []int) (*ExpiryUserSettings, error) {
	settings, err := r.GetSettings(userID)
	if err != nil {
		return nil, err
	}

	if settings == nil {
		settings = &ExpiryUserSettings{
			UserID:     userID,
			RemindDays: copyIntSlice(remindDays),
		}
		if err := r.db.Create(settings).Error; err != nil {
			return nil, fmt.Errorf("create expiry settings: %w", err)
		}
		return settings, nil
	}

	settings.RemindDays = copyIntSlice(remindDays)
	if err := r.db.Model(&ExpiryUserSettings{}).
		Where("user_id = ?", userID).
		Update("remind_days", settings.RemindDays).Error; err != nil {
		return nil, fmt.Errorf("update expiry settings: %w", err)
	}
	return settings, nil
}

func copyIntSlice(values []int) []int {
	if len(values) == 0 {
		return nil
	}
	copied := make([]int, len(values))
	copy(copied, values)
	return copied
}