package repository

import (
	"context"
	"errors"

	"fashionapi/internal/dto"
	"fashionapi/internal/model"

	"gorm.io/gorm"
)

// ArticleRepository 走秀档案（文章）数据访问接口。
type ArticleRepository interface {
	// List 按筛选条件分页查询文章，同时返回符合条件的总数。
	List(ctx context.Context, q dto.ArticleQuery) ([]model.RunwayRow, int64, error)
	// FindByID 查询单篇文章（含 JOIN 出的品牌名）。不存在时返回 ErrNotFound。
	FindByID(ctx context.Context, id string) (*model.RunwayRow, error)
	// ListImages 查询某篇文章的全部图片，按排序值升序。
	ListImages(ctx context.Context, runwayID string) ([]model.BrandRunwayImage, error)
	// ImagesByRunwayIDs 批量查询多篇文章的图片，单次 IN 查询避免 N+1。
	ImagesByRunwayIDs(ctx context.Context, ids []uint32) (map[uint32][]model.BrandRunwayImage, error)
	// IDs 返回全部未删除文章的 id（升序），供 SSG 的 getStaticPaths 枚举路径使用。
	// 只回主键，不带回封面/描述等大字段，比拉 size=500 再 .map(id) 省得多。
	IDs(ctx context.Context) ([]uint32, error)
}

type articleRepository struct {
	db *gorm.DB
}

// NewArticleRepository 创建文章仓储。
func NewArticleRepository(db *gorm.DB) ArticleRepository {
	return &articleRepository{db: db}
}

// selectColumns 列表查询的投影列：只取对外需要的字段，不做 SELECT *。
const articleListColumns = `brand_runway.id, brand_runway.brand_id, brand_runway.title,
	brand_runway.title_en, brand_runway.title_cn,
	brand_runway.description, brand_runway.description_en, brand_runway.description_cn,
	brand_runway.cover, brand_runway.year, brand_runway.image_count,
	brand_runway.created_at, brand_runway.collection_type, brand_runway.season,
	brand_runway.season_code, b.name AS brand_name, b.name_en AS brand_name_en, b.name_cn AS brand_name_cn`

const articleDetailColumns = `brand_runway.id, brand_runway.title, brand_runway.title_en, brand_runway.title_cn,
	brand_runway.description, brand_runway.description_en, brand_runway.description_cn,
	brand_runway.cover, brand_runway.year, brand_runway.image_count, brand_runway.created_at,
	brand_runway.source_url, b.name AS brand_name, b.name_en AS brand_name_en, b.name_cn AS brand_name_cn`

// brandJoin 关联品牌表取品牌名；LEFT JOIN 保证品牌被软删时文章依然可见。
const brandJoin = "LEFT JOIN brand b ON b.id = brand_runway.brand_id AND b.is_deleted = 0"

// filterScope 把查询条件编译为 GORM Scope。
//
// 用 Scope 而非复用同一个 *gorm.DB：GORM v2 中在 Count 等终结方法之后复用同一实例
// 会带上残留的 Statement 状态，Scope 每次作用于全新查询，杜绝这类隐患。
func filterScope(q dto.ArticleQuery) func(*gorm.DB) *gorm.DB {
	return func(db *gorm.DB) *gorm.DB {
		db = db.Where("brand_runway.is_deleted = 0")

		if q.Keyword != "" {
			kw := "%" + q.Keyword + "%"
			db = db.Where("brand_runway.title_en LIKE ? OR brand_runway.title_cn LIKE ?", kw, kw)
		}
		if q.BrandID != "" && q.BrandID != "0" {
			db = db.Where("brand_runway.brand_id = ?", q.BrandID)
		}
		// 多值筛选统一策略：单值用 = （命中索引更精准），多值用 IN，空集合不加条件。
		db = whereMulti(db, "brand_runway.brand_id", toAnySlice(q.BrandIDs))
		db = whereMulti(db, "brand_runway.collection_type", toAnySlice(q.CollectionTypes))
		db = whereMulti(db, "brand_runway.season", toAnySlice(q.Seasons))
		db = whereMulti(db, "brand_runway.year", toAnySlice(q.Years))

		if q.SeasonCode != "" {
			db = db.Where("brand_runway.season_code = ?", q.SeasonCode)
		}
		return db
	}
}

// whereMulti 按值数量选择 = 或 IN。
func whereMulti(db *gorm.DB, column string, values []any) *gorm.DB {
	switch len(values) {
	case 0:
		return db
	case 1:
		return db.Where(column+" = ?", values[0])
	default:
		return db.Where(column+" IN ?", values)
	}
}

func toAnySlice[T any](in []T) []any {
	if len(in) == 0 {
		return nil
	}
	out := make([]any, 0, len(in))
	for _, v := range in {
		out = append(out, v)
	}
	return out
}

// orderBy 把 sort 参数映射为 ORDER BY 子句。
//
// 白名单映射而非直接拼接用户输入，从根上排除 SQL 注入；
// 每个分支都以 created_at + id 兜底，保证分页结果稳定不跳行。
func orderBy(sort string) string {
	switch sort {
	case "year_desc":
		return "brand_runway.year DESC, brand_runway.created_at DESC, brand_runway.id DESC"
	case "year_asc":
		return "brand_runway.year ASC, brand_runway.created_at DESC, brand_runway.id DESC"
	case "image_count":
		return "brand_runway.image_count DESC, brand_runway.created_at DESC, brand_runway.id DESC"
	default: // newest
		return "brand_runway.created_at DESC, brand_runway.id DESC"
	}
}

func (r *articleRepository) List(ctx context.Context, q dto.ArticleQuery) ([]model.RunwayRow, int64, error) {
	scope := filterScope(q)

	var total int64
	if err := r.db.WithContext(ctx).
		Model(&model.BrandRunway{}).
		Scopes(scope).
		Count(&total).Error; err != nil {
		return nil, 0, err
	}
	if total == 0 {
		return []model.RunwayRow{}, 0, nil
	}

	var rows []model.RunwayRow
	if err := r.db.WithContext(ctx).
		Model(&model.BrandRunway{}).
		Scopes(scope).
		Select(articleListColumns).
		Joins(brandJoin).
		Order(orderBy(q.Sort)).
		Offset(q.Offset()).
		Limit(q.Size).
		Scan(&rows).Error; err != nil {
		return nil, 0, err
	}
	return rows, total, nil
}

func (r *articleRepository) FindByID(ctx context.Context, id string) (*model.RunwayRow, error) {
	var row model.RunwayRow
	err := r.db.WithContext(ctx).
		Model(&model.BrandRunway{}).
		Select(articleDetailColumns).
		Joins(brandJoin).
		Where("brand_runway.id = ? AND brand_runway.is_deleted = 0", id).
		First(&row).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrNotFound
		}
		return nil, err
	}
	return &row, nil
}

func (r *articleRepository) ListImages(ctx context.Context, runwayID string) ([]model.BrandRunwayImage, error) {
	var imgs []model.BrandRunwayImage
	err := r.db.WithContext(ctx).
		Where("runway_id = ? AND is_deleted = 0", runwayID).
		Order("sort_order ASC, id ASC").
		Find(&imgs).Error
	return imgs, err
}

func (r *articleRepository) ImagesByRunwayIDs(ctx context.Context, ids []uint32) (map[uint32][]model.BrandRunwayImage, error) {
	result := make(map[uint32][]model.BrandRunwayImage, len(ids))
	if len(ids) == 0 {
		return result, nil
	}

	var imgs []model.BrandRunwayImage
	err := r.db.WithContext(ctx).
		Select("runway_id, image, name, sort_order").
		Where("runway_id IN ? AND is_deleted = 0", ids).
		Order("sort_order ASC, id ASC").
		Find(&imgs).Error
	if err != nil {
		return nil, err
	}
	for _, im := range imgs {
		result[im.RunwayID] = append(result[im.RunwayID], im)
	}
	return result, nil
}

// IDs 返回全部未删除文章的 id（升序），供 SSG 构建期枚举详情页路径。
func (r *articleRepository) IDs(ctx context.Context) ([]uint32, error) {
	var ids []uint32
	if err := r.db.WithContext(ctx).
		Model(&model.BrandRunway{}).
		Where("is_deleted = 0").
		Order("id ASC").
		Pluck("id", &ids).Error; err != nil {
		return nil, err
	}
	return ids, nil
}