package service

import (
	"context"
	"errors"
	"net/http"

	"fashionapi/internal/dto"
	"fashionapi/internal/model"
	"fashionapi/internal/pkg/hashid"
	"fashionapi/internal/repository"
)

// StreetSnapService 街拍业务接口。
type StreetSnapService interface {
	List(ctx context.Context, q dto.StreetSnapQuery) ([]dto.PublicStreetSnap, int64, error)
	Detail(ctx context.Context, id string) (*dto.PublicStreetSnapDetail, error)
	// Popular 返回热度前 N 个街拍（按图片数降序），供 SSG 首页热门街拍展示。
	Popular(ctx context.Context, limit int) ([]dto.PublicStreetSnap, error)
}

type streetSnapService struct {
	repo repository.StreetSnapRepository
}

// NewStreetSnapService 创建街拍服务。
func NewStreetSnapService(repo repository.StreetSnapRepository) StreetSnapService {
	return &streetSnapService{repo: repo}
}

// ErrStreetSnapNotFound 街拍不存在。
var ErrStreetSnapNotFound = NewError(http.StatusNotFound, "street snap not found")

// List 查询街拍列表，并按需附带每条的前 N 张图。
func (s *streetSnapService) List(ctx context.Context, q dto.StreetSnapQuery) ([]dto.PublicStreetSnap, int64, error) {
	q.Normalize()

	rows, total, err := s.repo.List(ctx, q)
	if err != nil {
		return nil, 0, internalErr(err.Error())
	}

	list := make([]dto.PublicStreetSnap, 0, len(rows))
	ids := make([]uint32, 0, len(rows))
	for _, r := range rows {
		ids = append(ids, r.ID)
		list = append(list, dto.PublicStreetSnap{
			UID:        hashid.Encode(r.ID),
			Title:      r.Title,
			Cover:      r.Cover,
			ImageCount: r.ImageCount,
		})
	}

	if q.Images > 0 && len(list) > 0 {
		if err := s.attachImages(ctx, list, ids, q.Images); err != nil {
			return nil, 0, internalErr(err.Error())
		}
	}
	return list, total, nil
}

// attachImages 用单次 IN 查询为列表批量补齐图片，避免前端逐条请求详情。
func (s *streetSnapService) attachImages(ctx context.Context, list []dto.PublicStreetSnap, ids []uint32, limit int) error {
	grouped, err := s.repo.ImagesBySnapIDs(ctx, ids)
	if err != nil {
		return err
	}
	for i := range list {
		imgs, ok := grouped[ids[i]]
		if !ok {
			continue
		}
		if len(imgs) > limit {
			imgs = imgs[:limit]
		}
		list[i].Images = toPublicSnapImages(imgs)
	}
	return nil
}

// Detail 查询街拍详情，含完整图片集。
func (s *streetSnapService) Detail(ctx context.Context, id string) (*dto.PublicStreetSnapDetail, error) {
	snap, err := s.repo.FindByID(ctx, id)
	if err != nil {
		if errors.Is(err, repository.ErrNotFound) {
			return nil, ErrStreetSnapNotFound
		}
		return nil, internalErr(err.Error())
	}

	imgs, err := s.repo.ListImages(ctx, id)
	if err != nil {
		return nil, internalErr(err.Error())
	}

	return &dto.PublicStreetSnapDetail{
		UID:    hashid.Encode(snap.ID),
		Title:  snap.Title,
		Cover:  snap.Cover,
		Images: toPublicSnapImages(imgs),
	}, nil
}

// IDs 返回全部街拍的编码 uid（供 SSG 枚举详情页路径使用，对外暴露的即编码串）。
// Popular 返回热度前 N 个街拍（按图片数降序），供 SSG 首页热门街拍展示。
func (s *streetSnapService) Popular(ctx context.Context, limit int) ([]dto.PublicStreetSnap, error) {
	rows, err := s.repo.Popular(ctx, limit)
	if err != nil {
		return nil, internalErr(err.Error())
	}
	list := make([]dto.PublicStreetSnap, 0, len(rows))
	for _, r := range rows {
		list = append(list, dto.PublicStreetSnap{
			UID:        hashid.Encode(r.ID),
			Title:      r.Title,
			Cover:      r.Cover,
			ImageCount: r.ImageCount,
		})
	}
	return list, nil
}

// toPublicSnapImages 把图片实体映射为对外结构（只保留 url 与名称）。
func toPublicSnapImages(imgs []model.StreetSnapImage) []dto.PublicArticleImage {
	if len(imgs) == 0 {
		return nil
	}
	out := make([]dto.PublicArticleImage, 0, len(imgs))
	for _, im := range imgs {
		out = append(out, dto.PublicArticleImage{Image: im.Image, Name: im.Name})
	}
	return out
}