establish a limit on look back time for a valid rate

lib/common/defaults.js

@@ -42,6 +42,6 @@ Defaults.TWO_STEP_BALANCE_THRESHOLD = 100;
 
 Defaults.FIAT_RATE_PROVIDER = 'BitPay';
 Defaults.FIAT_RATE_FETCH_INTERVAL = 10; // In minutes
-
+Defaults.FIAT_RATE_MAX_LOOK_BACK_TIME = 120; // In minutes
 
 module.exports = Defaults;

lib/fiatrateservice.js

@@ -112,12 +112,15 @@ FiatRateService.prototype.getRate = function(opts, cb) {
 
   opts = opts || {};
 
+  var now = Date.now();
   var provider = opts.provider || self.defaultProvider;
-  var ts = (_.isNumber(opts.ts) || _.isArray(opts.ts)) ? opts.ts : Date.now();
+  var ts = (_.isNumber(opts.ts) || _.isArray(opts.ts)) ? opts.ts : now;
 
   async.map([].concat(ts), function(ts, cb) {
     self.storage.fetchFiatRate(provider, opts.code, ts, function(err, rate) {
       if (err) return cb(err);
+      if (rate && (now - rate.ts) > Defaults.FIAT_RATE_MAX_LOOK_BACK_TIME * 60 * 1000) rate = null;
+
       return cb(null, {
         ts: +ts,
         rate: rate ? rate.value : undefined,

test/integration/fiatrateservice.js

@@ -174,6 +174,35 @@ describe('Fiat rate service', function() {
         });
       });
     });
+
+    it('should not get rate older than 2hs', function(done) {
+      var clock = sinon.useFakeTimers(0, 'Date');
+      service.storage.storeFiatRate('BitPay', [{
+        code: 'USD',
+        value: 123.45,
+      }], function(err) {
+        should.not.exist(err);
+        clock.tick((120 * 60 - 1) * 1000); // Almost 2 hours
+        service.getRate({
+          code: 'USD',
+        }, function(err, res) {
+          should.not.exist(err);
+          res.rate.should.equal(123.45);
+          res.fetchedOn.should.equal(0);
+          clock.restore();
+          clock.tick(2 * 1000); // 2 seconds later...
+          service.getRate({
+            code: 'USD',
+          }, function(err, res) {
+            should.not.exist(err);
+            should.not.exist(res.rate);
+            clock.restore();
+            done();
+          });
+        });
+      });
+    });
+
   });
 
   describe('#fetch', function() {