Added unique index check in insert

lib/mock/monk.js

@@ -28,6 +28,16 @@ function Collection (name) {
     this._name = name;
     this._lastId = 0;
     this._data = {};
+    this._indexes = {
+        'unique': []
+    };
+}
+
+Collection.prototype.index = function (property, type) {
+    if (! 'unique' in type) {
+        throw new Error("Mock monk only supports unique indexes");
+    }
+    this._indexes['unique'].push(property);
 }
 
 Collection.prototype.insert = function (ob, callback) {
@@ -45,8 +55,28 @@ Collection.prototype.insert = function (ob, callback) {
         throw new Error("cannot insert object, _id already exists");
     }
 
-    this._data[id] = dataSet;
-    promise.fulfill.call(promise, false, copy(dataSet));
+    var canInsert = true;
+    if (this._indexes['unique'].length > 0) {
+        var index  = this._indexes['unique'],
+            unique = {};
+
+        for (var i = 0; i < index.length; i++) {
+            var property = index[i];
+            unique[property] = dataSet[property];
+        }
+
+        this.count(unique, function (err, results) {
+            if (results > 0) {
+                promise.emit('error', 'duplicate key error index: one of ' + index.join(','));
+                canInsert = false;
+            }
+        });
+    }
+
+    if (canInsert) {
+        this._data[id] = dataSet;
+        promise.fulfill.call(promise, false, copy(dataSet));
+    }
     return promise;
 }