Simplify checking of server capabilities

lib/imap.js

@@ -95,7 +95,7 @@ ImapConnection.prototype.connect = function(loginCb) {
               return;
             }
             // Next, get the list of available namespaces if supported (RFC2342)
-            if (!reentry && self.capabilities.indexOf('NAMESPACE') > -1) {
+            if (!reentry && self._supports('NAMESPACE')) {
               var fnMe = arguments.callee;
               // Re-enter this function after we've obtained the available
               // namespaces
@@ -513,8 +513,7 @@ ImapConnection.prototype.connect = function(loginCb) {
       self._state.requests.shift();
       if (self._state.requests.length === 0
           && recentCmd !== 'LOGOUT') {
-        if (self._state.status === STATES.BOXSELECTED &&
-            self.capabilities.indexOf('IDLE') > -1) {
+        if (self._state.status === STATES.BOXSELECTED && self._supports('IDLE')) {
           // According to RFC 2177, we should re-IDLE at least every 29
           // minutes to avoid disconnection by the server
           self._send('IDLE', undefined, true);
@@ -525,7 +524,7 @@ ImapConnection.prototype.connect = function(loginCb) {
               self._state.ext.idle.timeWaited += self._state.tmoKeepalive;
               if (self._state.ext.idle.timeWaited >= self._state.ext.idle.MAX_WAIT)
                 self._send('IDLE', undefined, true); // restart IDLE
-            } else if (self.capabilities.indexOf('IDLE') === -1)
+            } else if (!self._supports('IDLE'))
               self._noop();
           }
         }, self._state.tmoKeepalive);
@@ -602,7 +601,7 @@ ImapConnection.prototype.getBoxes = function(namespace, cb) {
   cb = arguments[arguments.length - 1];
   if (arguments.length !== 2)
     namespace = '';
-  this._send(((this.capabilities.indexOf('XLIST') == -1) ? 'LIST' : 'XLIST')
+  this._send((!this._supports('XLIST') ? 'LIST' : 'XLIST')
              + ' "' + utils.escape(namespace) + '" "*"', cb);
 };
 
@@ -765,7 +764,7 @@ ImapConnection.prototype._fetch = function(which, uids, options) {
 
   var extensions = '';
   // always fetch GMail-specific bits of information when on GMail
-  if (this.capabilities.indexOf('X-GM-EXT-1') > -1)
+  if (this._supports('X-GM-EXT-1'))
     extensions = 'X-GM-THRID X-GM-MSGID X-GM-LABELS ';
 
   this._send(which + 'FETCH ' + uids.join(',') + ' (' + extensions
@@ -922,7 +921,11 @@ ImapConnection.prototype.__defineGetter__('seq', function() {
 ImapConnection.prototype._fnTmrConn = function(loginCb) {
   loginCb(new Error('Connection timed out'));
   this._state.conn.destroy();
-}
+};
+
+ImapConnection.prototype._supports = function(capability) {
+  return (this.capabilities.indexOf(capability) > -1);
+};
 
 ImapConnection.prototype._store = function(which, uids, flags, isAdding, cb) {
   var isKeywords = (arguments.callee.caller === this.addKeywords
@@ -982,11 +985,10 @@ ImapConnection.prototype._login = function(cb) {
       };
 
   if (this._state.status === STATES.NOAUTH) {
-    if (this.capabilities.indexOf('LOGINDISABLED') !== -1)
+    if (this._supports('LOGINDISABLED'))
       return cb(new Error('Logging in is disabled on this server'));
 
-    if (this.capabilities.indexOf('AUTH=XOAUTH') !== -1
-        && 'xoauth' in this._options) {
+    if (this._supports('AUTH=XOAUTH') && 'xoauth' in this._options) {
       this._send('AUTHENTICATE XOAUTH ' + utils.escape(this._options.xoauth),
                  fnReturn);
     } else if (this._options.username !== undefined