Blog/app/internal/logic/listpostslogic.go

package logic

import (
	"context"
	"database/sql"
	"time"

	"git.cialloo.com/CiallooWeb/Blog/app/internal/svc"
	"git.cialloo.com/CiallooWeb/Blog/app/internal/types"

	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/zeromicro/go-zero/core/logx"
)

type ListPostsLogic struct {
	logx.Logger
	ctx    context.Context
	svcCtx *svc.ServiceContext
}

// Get a list of blog posts
func NewListPostsLogic(ctx context.Context, svcCtx *svc.ServiceContext) *ListPostsLogic {
	return &ListPostsLogic{
		Logger: logx.WithContext(ctx),
		ctx:    ctx,
		svcCtx: svcCtx,
	}
}

func (l *ListPostsLogic) ListPosts(req *types.ListPostsReq) (resp *types.ListPostsResp, err error) {
	// Set default values
	page := req.Page
	if page < 1 {
		page = 1
	}
	pageSize := req.PageSize
	if pageSize < 1 || pageSize > 100 {
		pageSize = 10 // Default page size
	}
	offset := (page - 1) * pageSize

	// Build query with optional tag filter
	var countQuery string
	var postsQuery string
	var args []interface{}

	if len(req.TagIds) > 0 {
		// Filter by tags - posts that have ALL specified tags
		countQuery = `
			SELECT COUNT(DISTINCT p.id)
			FROM posts p
			INNER JOIN post_hashtags ph ON p.id = ph.post_id
			WHERE ph.hashtag_id = ANY($1)
			GROUP BY p.id
			HAVING COUNT(DISTINCT ph.hashtag_id) = $2
		`

		postsQuery = `
			SELECT DISTINCT p.id, p.title, p.created_at, p.updated_at, p.cover_id
			FROM posts p
			INNER JOIN post_hashtags ph ON p.id = ph.post_id
			WHERE ph.hashtag_id = ANY($1)
			GROUP BY p.id, p.title, p.created_at, p.updated_at, p.cover_id
			HAVING COUNT(DISTINCT ph.hashtag_id) = $2
			ORDER BY p.created_at DESC
			LIMIT $3 OFFSET $4
		`

		args = []interface{}{req.TagIds, len(req.TagIds), pageSize, offset}
	} else {
		// No tag filter - get all posts
		countQuery = `SELECT COUNT(*) FROM posts`
		postsQuery = `
			SELECT p.id, p.title, p.created_at, p.updated_at, p.cover_id
			FROM posts p
			ORDER BY p.created_at DESC
			LIMIT $1 OFFSET $2
		`
		args = []interface{}{pageSize, offset}
	}

	// Get total count
	var totalCount int
	if len(req.TagIds) > 0 {
		// Count posts matching tag filter
		rows, err := l.svcCtx.DB.QueryContext(l.ctx, countQuery, req.TagIds, len(req.TagIds))
		if err != nil {
			l.Errorf("Failed to get total count: %v", err)
			return nil, err
		}
		defer rows.Close()

		totalCount = 0
		for rows.Next() {
			totalCount++
		}
	} else {
		err = l.svcCtx.DB.QueryRowContext(l.ctx, countQuery).Scan(&totalCount)
		if err != nil {
			l.Errorf("Failed to get total count: %v", err)
			return nil, err
		}
	}

	// Get posts with pagination
	rows, err := l.svcCtx.DB.QueryContext(l.ctx, postsQuery, args...)
	if err != nil {
		l.Errorf("Failed to get posts: %v", err)
		return nil, err
	}
	defer rows.Close()

	posts := []types.ListPostsRespPosts{}
	for rows.Next() {
		var post types.ListPostsRespPosts
		var coverID sql.NullInt64
		var createdAt, updatedAt time.Time

		err := rows.Scan(&post.PostId, &post.Title, &createdAt, &updatedAt, &coverID)
		if err != nil {
			l.Errorf("Failed to scan post: %v", err)
			continue
		}

		// Convert timestamps to Unix milliseconds
		post.CreatedAt = createdAt.UnixMilli()
		post.UpdatedAt = updatedAt.UnixMilli()

		// If cover image exists, get its URL
		if coverID.Valid {
			coverQuery := `SELECT file_key FROM files WHERE id = $1`
			var fileKey string
			err = l.svcCtx.DB.QueryRowContext(l.ctx, coverQuery, coverID.Int64).Scan(&fileKey)
			if err == nil {
				// Generate presigned URL for cover image
				expiration := time.Duration(l.svcCtx.Config.S3.PresignedURLExpiration) * time.Second
				presignClient := s3.NewPresignClient(l.svcCtx.S3Client)
				getObjectInput := &s3.GetObjectInput{
					Bucket: &l.svcCtx.Config.S3.Bucket,
					Key:    &fileKey,
				}
				presignedReq, err := presignClient.PresignGetObject(l.ctx, getObjectInput, func(opts *s3.PresignOptions) {
					opts.Expires = expiration
				})
				if err == nil {
					post.CoverImageUrl = presignedReq.URL
				}
			}
		}

		posts = append(posts, post)
	}

	return &types.ListPostsResp{
		Posts:      posts,
		TotalCount: totalCount,
	}, nil
}