add endpoint to query blog article tags

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

backend/blog.go

@@ -322,3 +322,44 @@ func (h *ApiHandler) ServeBlogPostUnpublish(writer http.ResponseWriter, request
 
 	WriteResponse(writer, http.StatusOK, map[string]interface{}{})
 }
+
+func (h *ApiHandler) ServeBlogTagsGet(writer http.ResponseWriter, request *http.Request) {
+	query := request.URL.Query()
+
+	var err error
+	var offset int
+	var limit int
+
+	offsetStr := query.Get("offset")
+	if offsetStr == "" {
+		offset = 0
+	} else {
+		offset, err = strconv.Atoi(offsetStr)
+		if err != nil || offset < 0 {
+			WriteError(writer, http.StatusBadRequest, "invalid offset", nil)
+			return
+		}
+	}
+
+	limitStr := query.Get("limit")
+	if limitStr == "" {
+		limit = 50
+	} else {
+		limit, err = strconv.Atoi(limitStr)
+		if err != nil || limit <= 0 || limit > 100 {
+			WriteError(writer, http.StatusBadRequest, "invalid limit", nil)
+			return
+		}
+	}
+
+	tags, total, err := h.db.GetBlogTags(IsAuthorized(request), offset, limit)
+	if err != nil {
+		WriteError(writer, http.StatusInternalServerError, "failed to query database", err)
+		return
+	}
+
+	WriteResponse(writer, http.StatusOK, map[string]interface{}{
+		"tags":  tags,
+		"total": total,
+	})
+}

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 {

backend/main.go

@@ -50,6 +50,9 @@ func main() {
 	mux.Handle("POST /api/blog/{id}/unpublish", apiHandler.ProcessAuth(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
 		apiHandler.ServeBlogPostUnpublish(writer, request)
 	}), true))
+	mux.Handle("GET /api/blog/tags", apiHandler.ProcessAuth(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		apiHandler.ServeBlogTagsGet(writer, request)
+	}), false))
 	mux.HandleFunc("POST /api/login", func(writer http.ResponseWriter, request *http.Request) {
 		apiHandler.ServeLoginPost(writer, request)
 	})