add endpoint to query blog article tags

Signed-off-by: Tobias Erbshäußer <tobias@tesoft.dev>

backend/db.go

@@ -322,6 +322,54 @@ func (db *Database) SetBlogArticleStatus(id int64, status ArticleStatus) error {
 	return nil
 }
 
+func (db *Database) GetBlogTags(showAll bool, offset int, limit int) ([]string, int64, error) {
+	filter := ""
+	filterArgs := make([]interface{}, 0)
+
+	if !showAll {
+		filter = " WHERE blog_article.status = ?"
+		filterArgs = append(filterArgs, ArticleStatusPublished)
+	}
+
+	args := make([]interface{}, 0, len(filterArgs)*2+2)
+	args = append(args, filterArgs...)
+	args = append(args, filterArgs...)
+	args = append(args, limit)
+	args = append(args, offset)
+
+	joins := " INNER JOIN blog_article_to_tag ON blog_article_to_tag.tag_id = blog_tag.id" +
+		" INNER JOIN blog_article ON blog_article.id = blog_article_to_tag.article_id"
+
+	rows, err := db.db.Query(
+		"SELECT blog_tag.name, (SELECT COUNT(*) FROM blog_tag"+joins+filter+") FROM blog_tag"+joins+filter+" LIMIT ? OFFSET ?",
+		args...,
+	)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	tags := make([]string, 0)
+	total := int64(0)
+
+	for rows.Next() {
+		var name string
+		err := rows.Scan(&name, &total)
+		if err != nil {
+			_ = rows.Close()
+			return nil, 0, err
+		}
+
+		tags = append(tags, name)
+	}
+
+	err = rows.Close()
+	if err != nil {
+		return nil, 0, err
+	}
+
+	return tags, total, nil
+}
+
 func migrate(db *sql.DB, rootPassword string) error {
 	tx, err := db.Begin()
 	if err != nil {