Add ability to provide origin to NodeHttpImpl

* src/dapi/http/NodeHttpImpl.js (_parseUrl): Add method.
  (__construct): Add argument.
  (requestData): Use it.

* test/dapi/http/NodeHttpImplTest.js: Add tests.

src/dapi/http/NodeHttpImpl.js

@@ -45,6 +45,12 @@ module.exports = Class( 'NodeHttpImpl' )
      */
     'private _urlParser': '',
 
+    /**
+     * Request origin
+     * @type {string}
+     */
+    'private _origin': '',
+
 
     /**
      * Initialize with protocol handlers and URL parser
@@ -53,13 +59,17 @@ module.exports = Class( 'NodeHttpImpl' )
      * to a handler object conforming to Node's http(s) APIs---that is, it
      * should provide a `#request` method.
      *
+     * `origin` is prepended to all request URLs.
+     *
      * @param {Object} proto_handlers protocol handler key-value map
      * @param {Object} url_parser     URL parser
+     * @param {string} origin         request origin
      */
-    constructor( proto_handlers, url_parser )
+    constructor( proto_handlers, url_parser, origin )
     {
         this._protoHandlers = proto_handlers;
         this._urlParser     = url_parser;
+        this._origin        = ( origin !== undefined ) ? ''+origin : '';
     },
 
 
@@ -79,7 +89,7 @@ module.exports = Class( 'NodeHttpImpl' )
      */
     'public requestData'( url, method, data, callback )
     {
-        const options  = this._urlParser.parse( url );
+        const options  = this._parseUrl( url );
         const protocol = options.protocol.replace( /:$/, '' );
         const handler  = this._protoHandlers[ protocol ];
 
@@ -120,6 +130,25 @@ module.exports = Class( 'NodeHttpImpl' )
     },
 
 
+    /**
+     * Parse given URL
+     *
+     * If the URL begins with a slash, the origin is prepended.
+     *
+     * @param {string} url URL
+     *
+     * @return {Object} parsed URL
+     */
+    'private _parseUrl'( url )
+    {
+        const origin = ( url[ 0 ] === '/' )
+              ? this._origin
+              : '';
+
+        return this._urlParser.parse( origin + url );
+    },
+
+
     /**
      * Set request options
      *

test/dapi/http/NodeHttpImplTest.js

@@ -90,6 +90,53 @@ describe( "NodeHttpImpl", () =>
     } );
 
 
+    describe( "given an origin", () =>
+    {
+        it( "prepends to URL if URL begins with a slash", done =>
+        {
+            const origin = 'https://foo.com';
+            const path   = '/quux/quuux';
+
+            const url = _createMockUrl( given_url =>
+            {
+                expect( given_url ).to.equal( origin + path );
+                done();
+            } );
+
+            const http = _createMockHttp( ( _, callback ) =>
+            {
+                callback( res );
+                res.trigger( 'end' );
+            } );
+
+            Sut( { http: http }, url, origin )
+                .requestData( path, 'GET', {}, () => {} );
+        } );
+
+
+        it( "does not prepend to URL that does not begin with a slash", done =>
+        {
+            const origin = 'https://bar.com';
+            const path   = 'http://foo.com/quux/quuux';
+
+            const url = _createMockUrl( given_url =>
+            {
+                expect( given_url ).to.equal( path );
+                done();
+            } );
+
+            const http = _createMockHttp( ( _, callback ) =>
+            {
+                callback( res );
+                res.trigger( 'end' );
+            } );
+
+            Sut( { http: http }, url, origin )
+                .requestData( path, 'GET', {}, () => {} );
+        } );
+    } );
+
+
     it( "returns response when no error", done =>
     {
         const res    = _createMockResp();