Add tag filtering to ListPosts and enhance ListTags with post count

app/internal/logic/listpostslogic.go

@@ -39,23 +39,71 @@ func (l *ListPostsLogic) ListPosts(req *types.ListPostsReq) (resp *types.ListPos
 	}
 	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
-	countQuery := `SELECT COUNT(*) FROM posts`
-	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
+	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
-	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
-	`
-	rows, err := l.svcCtx.DB.QueryContext(l.ctx, postsQuery, pageSize, offset)
+	rows, err := l.svcCtx.DB.QueryContext(l.ctx, postsQuery, args...)
 	if err != nil {
 		l.Errorf("Failed to get posts: %v", err)
 		return nil, err