[FEATURE] use Currency object and hex format in orderbook

instead of checking the value of the currency string, create a Currency object and work with that
the json format going to rippled will contain the hex value of the currency

src/js/ripple/orderbook.js

@@ -21,9 +21,9 @@ function OrderBook(remote, currency_gets, issuer_gets, currency_pays, issuer_pay
   var self = this;
 
   this._remote        = remote;
-  this._currency_gets = currency_gets;
+  this._currency_gets = Currency.from_json(currency_gets);
   this._issuer_gets   = issuer_gets;
-  this._currency_pays = currency_pays;
+  this._currency_pays = Currency.from_json(currency_pays);
   this._issuer_pays   = issuer_pays;
   this._subs          = 0;
   this._key           = key;
@@ -132,18 +132,18 @@ OrderBook.prototype._prepareSubscribe = function (request) {
 OrderBook.prototype.to_json = function () {
   var json = {
     taker_gets: {
-      currency: this._currency_gets
+      currency: this._currency_gets.to_hex()
     },
     taker_pays: {
-      currency: this._currency_pays
+      currency: this._currency_pays.to_hex()
     }
   };
 
-  if (this._currency_gets !== 'XRP') {
+  if (!this._currency_gets.is_native()) {
     json.taker_gets.issuer = this._issuer_gets;
   }
 
-  if (this._currency_pays !== 'XRP') {
+  if (!this._currency_pays.is_native()) {
     json.taker_pays.issuer = this._issuer_pays;
   }
 
@@ -159,17 +159,19 @@ OrderBook.prototype.to_json = function () {
 OrderBook.prototype.is_valid = function () {
   // XXX Should check for same currency (non-native) && same issuer
   return (
-    Currency.is_valid(this._currency_pays) &&
-    (this._currency_pays === 'XRP' || UInt160.is_valid(this._issuer_pays)) &&
-    Currency.is_valid(this._currency_gets) &&
-    (this._currency_gets === 'XRP' || UInt160.is_valid(this._issuer_gets)) &&
-    !(this._currency_pays === 'XRP' && this._currency_gets === 'XRP')
+    this._currency_pays && this._currency_pays.is_valid() &&
+    (this._currency_pays.is_native() || UInt160.is_valid(this._issuer_pays)) &&
+
+    this._currency_gets && this._currency_gets.is_valid() &&
+    (this._currency_gets.is_native() || UInt160.is_valid(this._issuer_gets)) &&
+
+    !(this._currency_pays.is_native() && this._currency_gets.is_native())
   );
 };
 
 OrderBook.prototype.trade = function(type) {
   var tradeStr = '0'
-  + ((this['_currency_' + type] === 'XRP') ? '' : '/'
+  + ((Currency.from_json(this['_currency_' + type]).is_native()) ? '' : '/'
      + this['_currency_' + type ] + '/'
      + this['_issuer_' + type]);
   return Amount.from_json(tradeStr);

src/js/ripple/remote.js

@@ -1439,7 +1439,7 @@ Remote.prototype.requestBookOffers = function(gets, pays, taker, callback) {
     currency: Currency.json_rewrite(gets.currency, {force_hex:true})
   };
 
-  if (request.message.taker_gets.currency !== 'XRP') {
+  if (!Currency.from_json(request.message.taker_gets.currency).is_native()) {
     request.message.taker_gets.issuer = UInt160.json_rewrite(gets.issuer);
   }
 
@@ -1447,7 +1447,7 @@ Remote.prototype.requestBookOffers = function(gets, pays, taker, callback) {
     currency: Currency.json_rewrite(pays.currency, {force_hex:true})
   };
 
-  if (request.message.taker_pays.currency !== 'XRP') {
+  if (!Currency.from_json(request.message.taker_pays.currency).is_native()) {
     request.message.taker_pays.issuer = UInt160.json_rewrite(pays.issuer);
   }
 
@@ -1757,7 +1757,7 @@ Remote.prototype.createPathFind = function(src_account, dst_account, dst_amount,
 };
 
 Remote.prepareTrade = function(currency, issuer) {
-  return currency + (currency === 'XRP' ? '' : ('/' + issuer));
+  return currency + (Currency.from_json(currency).is_native() ? '' : ('/' + issuer));
 };
 
 /**

src/js/ripple/request.js

@@ -343,7 +343,7 @@ Request.prototype.addBook = function(book, snapshot) {
       currency: Currency.json_rewrite(book[side].currency, {force_hex: true})
     };
 
-    if (obj.currency !== 'XRP') {
+    if (!Currency.from_json(obj.currency).is_native()) {
       obj.issuer = UInt160.json_rewrite(book[side].issuer);
     }
   }