feat(deferreds/promises): Q-like deferred/promise implementation with a ton of specs

1 files changed, 206 insertions, 0 deletions

diff --git a/src/Deferred.js b/src/Deferred.js
new file mode 100644
index 00000000..bf20d413
--- /dev/null
+++ b/src/Deferred.js
@@ -0,0 +1,206 @@
+'use strict';
+
+/**
+ * inspired by Kris Kowal's Q (https://github.com/kriskowal/q)
+ */
+
+/**
+ * Constructs a promise manager.
+ *
+ * @param {function(function)=} nextTick Function for executing functions in the next turn. Falls
+ *    back to `setTimeout` if undefined.
+ * @param {function(...*)=} exceptionHandler Function into which unexpected exceptions are passed for
+ *     debugging purposes. Falls back to `console.error` if undefined,
+ * @returns {object} Promise manager.
+ */
+function qFactory(nextTick, exceptionHandler) {
+
+  nextTick = nextTick || function(callback) {
+    setTimeout(callback, 0); // very rare since most of queueing will be handled within $apply
+  };
+
+  exceptionHandler = exceptionHandler || function(e) {
+    // TODO(i): console.error is somehow reset to function(a) {}, it might be a JSTD bug
+    if (console && console.log) {
+      console.log(e);
+    }
+  }
+
+  var defer = function() {
+    var pending = [],
+        value, deferred;
+
+    deferred = {
+
+      resolve: function(val) {
+        if (pending) {
+          var callbacks = pending;
+          pending = undefined;
+          value = ref(val);
+
+          if (callbacks.length) {
+            nextTick(function() {
+              var callback;
+              for (var i = 0, ii = callbacks.length; i < ii; i++) {
+                callback = callbacks[i];
+                value.then(callback[0], callback[1]);
+              }
+            });
+          }
+        }
+      },
+
+
+      reject: function(reason) {
+        deferred.resolve(reject(reason));
+      },
+
+
+      promise: {
+        then: function(callback, errback) {
+          var result = defer();
+
+          var wrappedCallback = function(value) {
+            try {
+              result.resolve((callback || defaultCallback)(value));
+            } catch(e) {
+              exceptionHandler(e);
+              result.reject(e);
+            }
+          };
+
+          var wrappedErrback = function(reason) {
+            try {
+              result.resolve((errback || defaultErrback)(reason));
+            } catch(e) {
+              exceptionHandler(e);
+              result.reject(e);
+            }
+          };
+
+          if (pending) {
+            pending.push([wrappedCallback, wrappedErrback]);
+          } else {
+            value.then(wrappedCallback, wrappedErrback);
+          }
+
+          return result.promise;
+        }
+      }
+    };
+
+    return deferred;
+  };
+
+
+  var ref = function(value) {
+    if (value && value.then) return value;
+    return {
+      then: function(callback) {
+        var result = defer();
+        nextTick(function() {
+          result.resolve(callback(value));
+        });
+        return result.promise;
+      }
+    };
+  };
+
+
+  var reject = function(reason) {
+    return {
+      then: function(callback, errback) {
+        var result = defer();
+        nextTick(function() {
+          result.resolve(errback(reason));
+        });
+        return result.promise;
+      }
+    };
+  };
+
+
+  var when = function(value, callback, errback) {
+    var result = defer(),
+        done;
+
+    var wrappedCallback = function(value) {
+      try {
+        return (callback || defaultCallback)(value);
+      } catch (e) {
+        exceptionHandler(e);
+        return reject(e);
+      }
+    };
+
+    var wrappedErrback = function(reason) {
+      try {
+        return (errback || defaultErrback)(reason);
+      } catch (e) {
+        exceptionHandler(e);
+        return reject(e);
+      }
+    };
+
+    nextTick(function() {
+      ref(value).then(function(value) {
+        if (done) return;
+        done = true;
+        result.resolve(ref(value).then(wrappedCallback, wrappedErrback));
+      }, function(reason) {
+        if (done) return;
+        done = true;
+        result.resolve(wrappedErrback(reason));
+      });
+    });
+
+    return result.promise;
+  };
+
+
+  function defaultCallback(value) {
+    return value;
+  }
+
+
+  function defaultErrback(reason) {
+    return reject(reason);
+  }
+
+
+  function all(promises) {
+    var deferred = defer(),
+        counter = promises.length,
+        results = [];
+
+    forEach(promises, function(promise, index) {
+      promise.then(function(value) {
+        if (index in results) return;
+        results[index] = value;
+        if (!(--counter)) deferred.resolve(results);
+      }, function(reason) {
+        if (index in results) return;
+        deferred.reject(reason);
+      });
+    });
+
+    return deferred.promise;
+  }
+
+  return {
+    defer: defer,
+    reject: reject,
+    when: when,
+    all: all
+  };
+}
+
+// TODO(i): move elsewhere
+function $QProvider() {
+
+  this.$get = ['$rootScope', '$exceptionHandler', function($rootScope, $exceptionHandler) {
+    return qFactory(function(callback) {
+      $rootScope.$evalAsync(callback);
+    }, $exceptionHandler);
+  }];
+}