Extract our permission policy into a separate class so that a system can more

easily make use of different permission policies in different circumstances
(one can imagine a hypothetical partner who has different access control
requirements, perhaps).


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5118 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/data/PermissionPolicy.java

@@ -0,0 +1,44 @@
+//
+// $Id$
+//
+// Narya library - tools for developing networked games
+// Copyright (C) 2002-2008 Three Rings Design, Inc., All Rights Reserved
+// http://www.threerings.net/code/narya/
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.threerings.presents.data;
+
+import com.threerings.io.Streamable;
+
+/**
+ * Encapsulates a fine-grained permissions policy. The default policy is to deny access to
+ * everything, systems using fine-grained permissions should create a custom policy and provide it
+ * at client resolution time via the ClientResolver.
+ */
+public class PermissionPolicy
+    implements Streamable, InvocationCodes
+{
+    /**
+     * Returns null if the specified client has the specified permission, an error code explaining
+     * the lack of access if they do not. {@link InvocationCodes#ACCESS_DENIED} should be returned
+     * if no more specific explanation is available.
+     */
+    public String checkAccess (ClientObject clobj, Permission perm, Object context)
+    {
+        // by default, you can't do it!
+        return ACCESS_DENIED;
+    }
+}