WIP url previewing

lib/client.js

@@ -1448,6 +1448,23 @@ MatrixClient.prototype.getCurrentUploads = function() {
     return this._http.getCurrentUploads();
 };
 
+/**
+ * Get a preview of the given URL as OpenGraph metadata
+ * @param {module:client.callback} callback Optional.
+ * @return {module:client.Promise} Resolves: Object of OG metadata.
+ * @return {module:http-api.MatrixError} Rejects: with an error response.
+ * May return synthesized attributes if the URL lacked OG meta.
+ */
+MatrixClient.prototype.getUrlPreview = function(url, callback) {
+    // FIXME: maintain a clientside cache to stop hammering synapse
+    // especially as synapse doesn't cache yet
+    return this._http.authedRequestWithPrefix(
+        callback, "GET", "/preview_url", {
+            url: url
+        }, undefined, httpApi.PREFIX_MEDIA_R0
+    );
+};
+
 /**
  * @param {string} roomId
  * @param {boolean} isTyping

lib/http-api.js

@@ -47,6 +47,11 @@ module.exports.PREFIX_UNSTABLE = "/_matrix/client/unstable";
  */
 module.exports.PREFIX_IDENTITY_V1 = "/_matrix/identity/api/v1";
 
+/**
+ * URI path for the media repo API
+ */
+module.exports.PREFIX_MEDIA_R0 = "/_matrix/media/r0";
+
 /**
  * Construct a MatrixHttpApi.
  * @constructor