Bake in support for promises.

This means we can specify the SDK's dependency on Q to make setting things up
significantly easier.

lib/http-api.js

@@ -3,7 +3,7 @@
  * This is an internal module. See {@link MatrixHttpApi} for the public class.
  * @module http-api
  */
-
+var q = require("q");
 var utils = require("./utils");
 
 /*
@@ -162,36 +162,39 @@ module.exports.MatrixHttpApi.prototype = {
                 "Expected callback to be a function but got " + typeof callback
             );
         }
-
-        return this.opts.request(
-        {
-            uri: uri,
-            method: method,
-            withCredentials: false,
-            qs: queryParams,
-            body: data,
-            json: true,
-            headers: HEADERS,
-            _matrix_opts: this.opts
-        },
-        requestCallback(callback)
+        var defer = q.defer();
+        this.opts.request(
+            {
+                uri: uri,
+                method: method,
+                withCredentials: false,
+                qs: queryParams,
+                body: data,
+                json: true,
+                headers: HEADERS,
+                _matrix_opts: this.opts
+            },
+            requestCallback(defer, callback)
         );
+        return defer.promise;
     }
 };
 
 
-var requestCallback = function(userDefinedCallback) {
-    if (!userDefinedCallback) {
-        return undefined;
-    }
+var requestCallback = function(defer, userDefinedCallback) {
+    userDefinedCallback = userDefinedCallback || function(){};
+    
     return function(err, response, body) {
-        if (err) {
-            return userDefinedCallback(err);
+        if (!err && response.statusCode >= 400) {
+            err = new module.exports.MatrixError(body);
         }
-        if (response.statusCode >= 400) {
-            return userDefinedCallback(new Error(body));
+
+        if (err) {
+            defer.reject(err);
+            userDefinedCallback(err);
         }
         else {
+            defer.resolve(body);
             userDefinedCallback(null, body);
         }
     };
@@ -212,4 +215,4 @@ module.exports.MatrixError = function MatrixError(errorJson) {
     this.data = errorJson;
 }
 module.exports.MatrixError.prototype = Object.create(Error.prototype);
-module.exports.MatrixError.prototype.constructor = MatrixError;
+module.exports.MatrixError.prototype.constructor = module.exports.MatrixError;