implement open graph metadata for apiV4 (#6343)

api4/openGraph.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package api4
+
+import (
+	"net/http"
+
+	l4g "github.com/alecthomas/log4go"
+	"github.com/mattermost/platform/app"
+	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/utils"
+)
+
+const OPEN_GRAPH_METADATA_CACHE_SIZE = 10000
+
+var openGraphDataCache = utils.NewLru(OPEN_GRAPH_METADATA_CACHE_SIZE)
+
+func InitOpenGraph() {
+	l4g.Debug(utils.T("api.opengraph.init.debug"))
+
+	BaseRoutes.OpenGraph.Handle("", ApiSessionRequired(getOpenGraphMetadata)).Methods("POST")
+}
+
+func getOpenGraphMetadata(c *Context, w http.ResponseWriter, r *http.Request) {
+	if !*utils.Cfg.ServiceSettings.EnableLinkPreviews {
+		c.Err = model.NewAppError("getOpenGraphMetadata", "api.post.link_preview_disabled.app_error", nil, "", http.StatusNotImplemented)
+		return
+	}
+
+	props := model.StringInterfaceFromJson(r.Body)
+
+	url := ""
+	ok := false
+	if url, ok = props["url"].(string); len(url) == 0 || !ok {
+		c.SetInvalidParam("url")
+		return
+	}
+
+	ogJSONGeneric, ok := openGraphDataCache.Get(url)
+	if ok {
+		w.Write(ogJSONGeneric.([]byte))
+		return
+	}
+
+	og := app.GetOpenGraphMetadata(url)
+
+	ogJSON, err := og.ToJSON()
+	openGraphDataCache.AddWithExpiresInSecs(props["url"], ogJSON, 3600) // Cache would expire after 1 hour
+	if err != nil {
+		w.Write([]byte(`{"url": ""}`))
+		return
+	}
+
+	w.Write(ogJSON)
+}