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,
+	})
+}