add api/list/tag/tag_name_here

exchange/exchange.go

@@ -112,6 +112,32 @@ func (ex *Exchange) GetFeedItem(ID string) (string, error) {
 	return item.Content, nil
 }
 
+func (ex *Exchange) ListTag(tag string, n int) (string, error) {
+	feeds := []*rss.Feed{}
+	feedNames, err := ex.SClient.List(nsForFeeds, "", true, -1)
+	if err != nil {
+		return "", err
+	}
+	for _, feedName := range feedNames {
+		b, err := ex.SClient.Get(nsForFeeds, feedName)
+		if err != nil {
+			return "", err
+		}
+		feed, err := rss.Deserialize(b)
+		if err != nil {
+			return "", err
+		}
+
+		for i := range feed.Tags {
+			if feed.Tags[i] == tag {
+				feeds = append(feeds, feed)
+			}
+		}
+	}
+	b, err := json.Marshal(feeds)
+	return string(b), err
+}
+
 func (ex *Exchange) GetFeedTagRSS(tag string) (string, error) {
 	feedNames, err := ex.SClient.List(nsForFeeds, "", true, -1)
 	if err != nil {