Adds .success() and .fail() to ChainFind (#316)

This is just an initial code, we should improve in the future and make
more parts of the code use the "Promise" (like Model.get)

lib/ChainFind.js

@@ -1,10 +1,12 @@
 var _               = require("lodash");
 var Singleton       = require("./Singleton");
 var ChainInstance   = require("./ChainInstance");
+var Promise         = require("./Promise").Promise;
 
 module.exports = ChainFind;
 
 function ChainFind(Model, opts) {
+	var promise = null;
 	var chain = {
 		find: function () {
 			var cb = null;
@@ -110,6 +112,20 @@ function ChainFind(Model, opts) {
 		run: function (cb) {
 			return this.all(cb);
 		},
+		success: function (cb) {
+			if (!promise) {
+				promise = new Promise();
+				promise.handle(this.all);
+			}
+			return promise.success(cb);
+		},
+		fail: function (cb) {
+			if (!promise) {
+				promise = new Promise();
+				promise.handle(this.all);
+			}
+			return promise.fail(cb);
+		},
 		all: function (cb) {
 			opts.driver.find(opts.only, opts.table, opts.conditions, {
 				limit  : opts.limit,

lib/Promise.js

@@ -0,0 +1,30 @@
+exports.Promise = Promise;
+
+function Promise(opts) {
+	opts = opts || {};
+
+	var success_cb = opts.success || null;
+	var fail_cb    = opts.fail    || null;
+
+	return {
+		handle: function (promise) {
+			promise(function (err) {
+				if (err) {
+					if (fail_cb) fail_cb(err);
+				} else {
+					var args = Array.prototype.slice.call(arguments, 1);
+
+					if (success_cb) success_cb.apply(null, args);
+				}
+			});
+		},
+		success: function (cb) {
+			success_cb = cb;
+			return this;
+		},
+		fail: function (cb) {
+			fail_cb = cb;
+			return this;
+		}
+	};
+}

test/integration/model-find-chain.js

@@ -461,4 +461,32 @@ describe("Model.find() chaining", function() {
 			});
 		});
 	});
+
+	describe(".success()", function () {
+		before(setup());
+
+		it("should return a Promise with .fail() method", function (done) {
+			Person.find().success(function (people) {
+				should(Array.isArray(people));
+
+				return done();
+			}).fail(function (err) {
+				// never called..
+			});
+		});
+	});
+
+	describe(".fail()", function () {
+		before(setup());
+
+		it("should return a Promise with .success() method", function (done) {
+			Person.find().fail(function (err) {
+				// never called..
+			}).success(function (people) {
+				should(Array.isArray(people));
+
+				return done();
+			});
+		});
+	});
 });