q.js

// vim:ts=4:sts=4:sw=4:
/*jshint browser: true, node: true,
  curly: true, eqeqeq: true, noarg: true, nonew: true, trailing: true,
  undef: true */
/*global define: false, Q: true, msSetImmediate: true, setImmediate: true,
  MessageChannel: true, ReturnValue: true, cajaVM: true, ses: true */
/*!
 *
 * Copyright 2009-2012 Kris Kowal under the terms of the MIT
 * license found at http://github.com/kriskowal/q/raw/master/LICENSE
 *
 * With parts by Tyler Close
 * Copyright 2007-2009 Tyler Close under the terms of the MIT X license found
 * at http://www.opensource.org/licenses/mit-license.html
 * Forked at ref_send.js version: 2009-05-11
 *
 * With parts by Mark Miller
 * Copyright (C) 2011 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * With formatStackTrace and formatSourcePosition functions
 * Copyright 2006-2008 the V8 project authors. All rights reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *     * Neither the name of Google Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

(function (definition) {

    // This file will function properly as a <script> tag, or a module
    // using CommonJS and NodeJS or RequireJS module formats.  In
    // Common/Node/RequireJS, the module exports the Q API and when
    // executed as a simple <script>, it creates a Q global instead.

    // RequireJS
    if (typeof define === "function") {
        define(definition);

    // CommonJS
    } else if (typeof exports === "object") {
        definition(void 0, exports);

    // SES (Secure EcmaScript)
    } else if (typeof ses !== "undefined") {
        if (!ses.ok()) {
            return;
        } else {
            ses.makeQ = function () {
                var Q = {};
                return definition(void 0, Q);
            };
        }

    // <script>
    } else {
        definition(void 0, Q = {});
    }

})(function (require, exports) {
"use strict";

// shims

// used for fallback "defend" and in "allResolved"
var noop = function () {};

// for the security conscious, defend may be a deep freeze as provided
// by cajaVM.  Otherwise we try to provide a shallow freeze just to
// discourage promise changes that are not compatible with secure
// usage.  If Object.freeze does not exist, fall back to doing nothing
// (no op).
var defend = Object.freeze || noop;
if (typeof cajaVM !== "undefined") {
    defend = cajaVM.def;
}

// use the fastest possible means to execute a task in a future turn
// of the event loop.
var nextTick;
if (typeof process !== "undefined") {
    // node
    nextTick = process.nextTick;
} else if (typeof msSetImmediate === "function") {
    // IE 10 only, at the moment
    nextTick = msSetImmediate;
} else if (typeof setImmediate === "function") {
    // https://github.com/NobleJS/setImmediate
    nextTick = setImmediate;
} else if (typeof MessageChannel !== "undefined") {
    // modern browsers
    // http://www.nonblocking.io/2011/06/windownexttick.html
    var channel = new MessageChannel();
    // linked list of tasks (single, with head node)
    var head = {}, tail = head;
    channel.port1.onmessage = function () {
        head = head.next;
        var task = head.task;
        delete head.task;
        task();
    };
    nextTick = function (task) {
        tail = tail.next = {task: task};
        channel.port2.postMessage(0);
    };
} else {
    // old browsers
    nextTick = function (task) {
        setTimeout(task, 0);
    };
}

// Attempt to make generics safe in the face of downstream
// modifications.
// There is no situation where this is necessary.
// If you need a security guarantee, these primordials need to be
// deeply frozen anyway, and if you don’t need a security guarantee,
// this is just plain paranoid.
// However, this does have the nice side-effect of reducing the size
// of the code by reducing x.call() to merely x(), eliminating many
// hard-to-minify characters.
// See Mark Miller’s explanation of what this does.
// http://wiki.ecmascript.org/doku.php?id=conventions:safe_meta_programming
var uncurryThis;
// I have kept both variations because the first is theoretically
// faster, if bind is available.
if (Function.prototype.bind) {
    var Function_bind = Function.prototype.bind;
    uncurryThis = Function_bind.bind(Function_bind.call);
} else {
    uncurryThis = function (f) {
        return function (thisp) {
            return f.call.apply(f, arguments);
        };
    };
}

var array_slice = uncurryThis(Array.prototype.slice);

var array_reduce = uncurryThis(
    Array.prototype.reduce || function (callback, basis) {
        var index = 0,
            length = this.length;
        // concerning the initial value, if one is not provided
        if (arguments.length === 1) {
            // seek to the first value in the array, accounting
            // for the possibility that is is a sparse array
            do {
                if (index in this) {
                    basis = this[index++];
                    break;
                }
                if (++index >= length) {
                    throw new TypeError();
                }
            } while (1);
        }
        // reduce
        for (; index < length; index++) {
            // account for the possibility that the array is sparse
            if (index in this) {
                basis = callback(basis, this[index], index);
            }
        }
        return basis;
    }
);

var object_create = Object.create || function (prototype) {
    function Type() { }
    Type.prototype = prototype;
    return new Type();
};

var object_keys = Object.keys || function (object) {
    var keys = [];
    for (var key in object) {
        keys.push(key);
    }
    return keys;
};

var object_toString = Object.prototype.toString;

// generator related shims

function isStopIteration(exception) {
    return (
        object_toString(exception) === "[object StopIteration]" ||
        exception instanceof QReturnValue
    );
}

var QReturnValue;
if (typeof ReturnValue !== "undefined") {
    QReturnValue = ReturnValue;
} else {
    QReturnValue = function (value) {
        this.value = value;
    };
}

// long stack traces

function formatStackTrace(error, frames) {
    var lines = [];
    try {
        lines.push(error.toString());
    } catch (e) {
        try {
            lines.push("<error: " + e + ">");
        } catch (ee) {
            lines.push("<error>");
        }
    }
    for (var i = 0; i < frames.length; i++) {
        var frame = frames[i];
        var line;

        // <Inserted by @domenic>
        if (typeof frame === "string") {
            lines.push(frame);
        // </Inserted by @domenic>
        } else {
            try {
                line = formatSourcePosition(frame);
            } catch (e) {
                try {
                    line = "<error: " + e + ">";
                } catch (ee) {
                    // Any code that reaches this point is seriously nasty!
                    line = "<error>";
                }
            }
            lines.push("    at " + line);
        }
    }
    return lines.join("\n");
}

function formatSourcePosition(frame) {
    var fileLocation = "";
    if (frame.isNative()) {
        fileLocation = "native";
    } else if (frame.isEval()) {
        fileLocation = "eval at " + frame.getEvalOrigin();
    } else {
        var fileName = frame.getFileName();
        if (fileName) {
            fileLocation += fileName;
            var lineNumber = frame.getLineNumber();
            if (lineNumber !== null) {
                fileLocation += ":" + lineNumber;
                var columnNumber = frame.getColumnNumber();
                if (columnNumber) {
                    fileLocation += ":" + columnNumber;
                }
            }
        }
    }
    if (!fileLocation) {
        fileLocation = "unknown source";
    }
    var line = "";
    var functionName = frame.getFunction().name;
    var addPrefix = true;
    var isConstructor = frame.isConstructor();
    var isMethodCall = !(frame.isToplevel() || isConstructor);
    if (isMethodCall) {
        var methodName = frame.getMethodName();
        line += frame.getTypeName() + ".";
        if (functionName) {
            line += functionName;
            if (methodName && (methodName !== functionName)) {
                line += " [as " + methodName + "]";
            }
        } else {
            line += methodName || "<anonymous>";
        }
    } else if (isConstructor) {
        line += "new " + (functionName || "<anonymous>");
    } else if (functionName) {
        line += functionName;
    } else {
        line += fileLocation;
        addPrefix = false;
    }
    if (addPrefix) {
        line += " (" + fileLocation + ")";
    }
    return line;
}

/**
 * Retrieves an array of structured stack frames parsed from the ``stack``
 * property of a given object.
 *
 * @param objectWithStack {Object} an object with a ``stack`` property: usually
 * an error or promise.
 *
 * @returns an array of stack frame objects. For more information, see
 * [V8's JavaScript stack trace API documentation](http://code.google.com/p/v8/wiki/JavaScriptStackTraceApi).
 */
function getStackFrames(objectWithStack) {
    var oldPrepareStackTrace = Error.prepareStackTrace;

    Error.prepareStackTrace = function (error, frames) {
        // Filter out frames from the innards of Node and Q.
        return frames.filter(function (frame) {
            var fileName = frame.getFileName();
            return (
                fileName !== "module.js" &&
                fileName !== "node.js" &&
                fileName !== qFileName
            );
        });
    };

    var stack = objectWithStack.stack;

    Error.prepareStackTrace = oldPrepareStackTrace;

    return stack;
}

// discover own file name for filtering stack traces
var qFileName;
if (Error.captureStackTrace) {
    qFileName = (function () {
        var fileName;

        var oldPrepareStackTrace = Error.prepareStackTrace;

        Error.prepareStackTrace = function (error, frames) {
            fileName = frames[0].getFileName();
        };

        // teases call of temporary prepareStackTrace
        // JSHint and Closure Compiler generate known warnings here
        new Error().stack;

        Error.prepareStackTrace = oldPrepareStackTrace;

        return fileName;
    })();
}


// end of shims
// beginning of real work

/**
 * Performs a task in a future turn of the event loop.
 * @param {Function} task
 */
exports.nextTick = nextTick;

/**
 * Constructs a {promise, resolve} object.
 *
 * The resolver is a callback to invoke with a more resolved value for the
 * promise. To fulfill the promise, invoke the resolver with any value that is
 * not a function. To reject the promise, invoke the resolver with a rejection
 * object. To put the promise in the same state as another promise, invoke the
 * resolver with that other promise.
 */
exports.defer = defer;
function defer() {
    // if "pending" is an "Array", that indicates that the promise has not yet
    // been resolved.  If it is "undefined", it has been resolved.  Each
    // element of the pending array is itself an array of complete arguments to
    // forward to the resolved promise.  We coerce the resolution value to a
    // promise using the ref promise because it handles both fully
    // resolved values and other promises gracefully.
    var pending = [], value;

    var deferred = object_create(defer.prototype);
    var promise = object_create(makePromise.prototype);

    promise.promiseSend = function () {
        var args = array_slice(arguments);
        if (pending) {
            pending.push(args);
        } else {
            nextTick(function () {
                value.promiseSend.apply(value, args);
            });
        }
    };

    promise.valueOf = function () {
        if (pending) {
            return promise;
        }
        return value.valueOf();
    };

    if (Error.captureStackTrace) {
        Error.captureStackTrace(promise, defer);
    }

    function become(resolvedValue) {
        if (!pending) {
            return;
        }
        value = resolve(resolvedValue);
        array_reduce(pending, function (undefined, pending) {
            nextTick(function () {
                value.promiseSend.apply(value, pending);
            });
        }, void 0);
        pending = void 0;
        return value;
    }

    defend(promise);

    deferred.promise = promise;
    deferred.resolve = become;
    deferred.reject = function (exception) {
        return become(reject(exception));
    };

    return deferred;
}

/**
 * Creates a Node-style callback that will resolve or reject the deferred
 * promise.
 * @returns a nodeback
 */
defer.prototype.node = // XXX deprecated
defer.prototype.makeNodeResolver = function () {
    var self = this;
    return function (error, value) {
        if (error) {
            self.reject(error);
        } else if (arguments.length > 2) {
            self.resolve(array_slice(arguments, 1));
        } else {
            self.resolve(value);
        }
    };
};

/**
 * @param makePromise {Function} a function that returns nothing and accepts
 * the resolve and reject functions for a deferred.
 * @returns a promise that may be resolved with the given resolve and reject
 * functions, or rejected by a thrown exception in makePromise
 */
exports.promise = promise;
function promise(makePromise) {
    var deferred = defer();
    call(
        makePromise,
        void 0,
        deferred.resolve,
        deferred.reject
    ).fail(deferred.reject);
    return deferred.promise;
}

/**
 * Constructs a Promise with a promise descriptor object and optional fallback
 * function.  The descriptor contains methods like when(rejected), get(name),
 * put(name, value), post(name, args), and delete(name), which all
 * return either a value, a promise for a value, or a rejection.  The fallback
 * accepts the operation name, a resolver, and any further arguments that would
 * have been forwarded to the appropriate method above had a method been
 * provided with the proper name.  The API makes no guarantees about the nature
 * of the returned object, apart from that it is usable whereever promises are
 * bought and sold.
 */
exports.makePromise = makePromise;
function makePromise(descriptor, fallback, valueOf, rejected) {
    if (fallback === void 0) {
        fallback = function (op) {
            return reject(new Error("Promise does not support operation: " + op));
        };
    }

    var promise = object_create(makePromise.prototype);

    promise.promiseSend = function (op, resolved /* ...args */) {
        var args = array_slice(arguments, 2);
        var result;
        try {
            if (descriptor[op]) {
                result = descriptor[op].apply(promise, args);
            } else {
                result = fallback.apply(promise, [op].concat(args));
            }
        } catch (exception) {
            result = reject(exception);
        }
        resolved(result);
    };

    if (valueOf) {
        promise.valueOf = valueOf;
    }

    if (rejected) {
        promise.promiseRejected = true;
    }

    defend(promise);

    return promise;
}

// provide thenables, CommonJS/Promises/A
makePromise.prototype.then = function (fulfilled, rejected) {
    return when(this, fulfilled, rejected);
};

// Chainable methods
array_reduce(
    [
        "isResolved", "isFulfilled", "isRejected",
        "when", "spread", "send",
        "get", "put", "del",
        "post", "invoke",
        "keys",
        "apply", "call", "bind",
        "fapply", "fcall", "fbind",
        "all", "allResolved",
        "view", "viewInfo",
        "timeout", "delay",
        "catch", "finally", "fail", "fin", "end"
    ],
    function (prev, name) {
        makePromise.prototype[name] = function () {
            return exports[name].apply(
                exports,
                [this].concat(array_slice(arguments))
            );
        };
    },
    void 0
);

makePromise.prototype.toSource = function () {
    return this.toString();
};

makePromise.prototype.toString = function () {
    return "[object Promise]";
};

defend(makePromise.prototype);

/**
 * If an object is not a promise, it is as "near" as possible.
 * If a promise is rejected, it is as "near" as possible too.
 * If it’s a fulfilled promise, the fulfillment value is nearer.
 * If it’s a deferred promise and the deferred has been resolved, the
 * resolution is "nearer".
 * @param object
 * @returns most resolved (nearest) form of the object
 */
exports.nearer = valueOf;
function valueOf(value) {
    // if !Object.isObject(value)
    // generates a known JSHint "constructor invocation without new" warning
    if (Object(value) !== value) {
        return value;
    } else {
        return value.valueOf();
    }
}

/**
 * @returns whether the given object is a promise.
 * Otherwise it is a fulfilled value.
 */
exports.isPromise = isPromise;
function isPromise(object) {
    return object && typeof object.promiseSend === "function";
}

/**
 * @returns whether the given object is a resolved promise.
 */
exports.isResolved = isResolved;
function isResolved(object) {
    return isFulfilled(object) || isRejected(object);
}

/**
 * @returns whether the given object is a value or fulfilled
 * promise.
 */
exports.isFulfilled = isFulfilled;
function isFulfilled(object) {
    return !isPromise(valueOf(object));
}

/**
 * @returns whether the given object is a rejected promise.
 */
exports.isRejected = isRejected;
function isRejected(object) {
    object = valueOf(object);
    return object && !!object.promiseRejected;
}

var rejections = [];
var errors = [];
if (typeof window !== "undefined" && window.console) {
    // This promise library consumes exceptions thrown in handlers so
    // they can be handled by a subsequent promise.  The rejected
    // promises get added to this array when they are created, and
    // removed when they are handled.
    console.log("Should be empty:", errors);
}

/**
 * Constructs a rejected promise.
 * @param exception value describing the failure
 */
exports.reject = reject;
function reject(exception) {
    var rejection = makePromise({
        "when": function (rejected) {
            // note that the error has been handled
            if (rejected) {
                var at = rejections.indexOf(this);
                if (at !== -1) {
                    errors.splice(at, 1);
                    rejections.splice(at, 1);
                }
            }
            return rejected ? rejected(exception) : reject(exception);
        }
    }, function fallback(op) {
        return reject(exception);
    }, function valueOf() {
        return this;
    }, true);
    // note that the error has not been handled
    rejections.push(rejection);
    errors.push(exception);
    return rejection;
}

/**
 * Constructs a promise for an immediate reference.
 * @param value immediate reference
 */
exports.begin = resolve; // XXX experimental
exports.resolve = resolve;
exports.ref = resolve; // XXX deprecated, use resolve
function resolve(object) {
    // If the object is already a Promise, return it directly.  This enables
    // the resolve function to both be used to created references from objects,
    // but to tolerably coerce non-promises to promises.
    if (isPromise(object)) {
        return object;
    }
    // assimilate thenables, CommonJS/Promises/A
    if (object && typeof object.then === "function") {
        var result = defer();
        object.then(result.resolve, result.reject);
        return result.promise;
    }
    return makePromise({
        "when": function (rejected) {
            return object;
        },
        "get": function (name) {
            return object[name];
        },
        "put": function (name, value) {
            return object[name] = value;
        },
        "del": function (name) {
            return delete object[name];
        },
        "post": function (name, value) {
            return object[name].apply(object, value);
        },
        "apply": function (self, args) {
            return object.apply(self, args);
        },
        "fapply": function (args) {
            return object.apply(void 0, args);
        },
        "viewInfo": function () {
            var on = object;
            var properties = {};

            function fixFalsyProperty(name) {
                if (!properties[name]) {
                    properties[name] = typeof on[name];
                }
            }

            while (on) {
                Object.getOwnPropertyNames(on).forEach(fixFalsyProperty);
                on = Object.getPrototypeOf(on);
            }
            return {
                "type": typeof object,
                "properties": properties
            };
        },
        "keys": function () {
            return object_keys(object);
        }
    }, void 0, function valueOf() {
        return object;
    });
}

/**
 * Annotates an object such that it will never be
 * transferred away from this process over any promise
 * communication channel.
 * @param object
 * @returns promise a wrapping of that object that
 * additionally responds to the "isDef" message
 * without a rejection.
 */
exports.master = master;
function master(object) {
    return makePromise({
        "isDef": function () {}
    }, function fallback(op) {
        var args = array_slice(arguments);
        return send.apply(void 0, [object].concat(args));
    }, function () {
        return valueOf(object);
    });
}

exports.viewInfo = viewInfo;
function viewInfo(object, info) {
    object = resolve(object);
    if (info) {
        return makePromise({
            "viewInfo": function () {
                return info;
            }
        }, function fallback(op) {
            var args = array_slice(arguments);
            return send.apply(void 0, [object].concat(args));
        }, function () {
            return valueOf(object);
        });
    } else {
        return send(object, "viewInfo");
    }
}

exports.view = view;
function view(object) {
    return viewInfo(object).when(function (info) {
        var view;
        if (info.type === "function") {
            view = function () {
                return apply(object, void 0, arguments);
            };
        } else {
            view = {};
        }
        var properties = info.properties || {};
        object_keys(properties).forEach(function (name) {
            if (properties[name] === "function") {
                view[name] = function () {
                    return post(object, name, arguments);
                };
            }
        });
        return resolve(view);
    });
}

/**
 * Registers an observer on a promise.
 *
 * Guarantees:
 *
 * 1. that fulfilled and rejected will be called only once.
 * 2. that either the fulfilled callback or the rejected callback will be
 *    called, but not both.
 * 3. that fulfilled and rejected will not be called in this turn.
 *
 * @param value     promise or immediate reference to observe
 * @param fulfilled function to be called with the fulfilled value
 * @param rejected  function to be called with the rejection exception
 * @return promise for the return value from the invoked callback
 */
exports.when = when;
function when(value, fulfilled, rejected) {
    var deferred = defer();
    var done = false;   // ensure the untrusted promise makes at most a
                        // single call to one of the callbacks

    function _fulfilled(value) {
        try {
            return fulfilled ? fulfilled(value) : value;
        } catch (exception) {
            return reject(exception);
        }
    }

    function _rejected(exception) {
        try {
            return rejected ? rejected(exception) : reject(exception);
        } catch (newException) {
            return reject(newException);
        }
    }

    nextTick(function () {
        resolve(value).promiseSend("when", function (value) {
            if (done) {
                return;
            }
            done = true;
            resolve(value).promiseSend("when", function (value) {
                deferred.resolve(_fulfilled(value));
            }, function (exception) {
                deferred.resolve(_rejected(exception));
            });
        }, function (exception) {
            if (done) {
                return;
            }
            done = true;
            deferred.resolve(_rejected(exception));
        });
    });

    return deferred.promise;
}

/**
 * Spreads the values of a promised array of arguments into the
 * fulfillment callback.
 * @param fulfilled callback that receives variadic arguments from the
 * promised array
 * @param rejected callback that receives the exception if the promise
 * is rejected.
 * @returns a promise for the return value or thrown exception of
 * either callback.
 */
exports.spread = spread;
function spread(promise, fulfilled, rejected) {
    return when(promise, function (values) {
        return fulfilled.apply(void 0, values);
    }, rejected);
}

/**
 * The async function is a decorator for generator functions, turning
 * them into asynchronous generators.  This presently only works in
 * Firefox/Spidermonkey, however, this code does not cause syntax
 * errors in older engines.  This code should continue to work and
 * will in fact improve over time as the language improves.
 *
 * Decorates a generator function such that:
 *  - it may yield promises
 *  - execution will continue when that promise is fulfilled
 *  - the value of the yield expression will be the fulfilled value
 *  - it returns a promise for the return value (when the generator
 *    stops iterating)
 *  - the decorated function returns a promise for the return value
 *    of the generator or the first rejected promise among those
 *    yielded.
 *  - if an error is thrown in the generator, it propagates through
 *    every following yield until it is caught, or until it escapes
 *    the generator function altogether, and is translated into a
 *    rejection for the promise returned by the decorated generator.
 *  - in present implementations of generators, when a generator
 *    function is complete, it throws ``StopIteration``, ``return`` is
 *    a syntax error in the presence of ``yield``, so there is no
 *    observable return value. There is a proposal[1] to add support
 *    for ``return``, which would permit the value to be carried by a
 *    ``StopIteration`` instance, in which case it would fulfill the
 *    promise returned by the asynchronous generator.  This can be
 *    emulated today by throwing StopIteration explicitly with a value
 *    property.
 *
 *  [1]: http://wiki.ecmascript.org/doku.php?id=strawman:async_functions#reference_implementation
 *
 */
exports.async = async;
function async(makeGenerator) {
    return function () {
        // when verb is "send", arg is a value
        // when verb is "throw", arg is an exception
        function continuer(verb, arg) {
            var result;
            try {
                result = generator[verb](arg);
            } catch (exception) {
                if (isStopIteration(exception)) {
                    return exception.value;
                } else {
                    return reject(exception);
                }
            }
            return when(result, callback, errback);
        }
        var generator = makeGenerator.apply(this, arguments);
        var callback = continuer.bind(continuer, "send");
        var errback = continuer.bind(continuer, "throw");
        return callback();
    };
}

/**
 * Throws a ReturnValue exception to stop an asynchronous generator.
 * Only useful presently in Firefox/SpiderMonkey since generators are
 * implemented.
 * @param value the return value for the surrounding generator
 * @throws ReturnValue exception with the value.
 * @example
 * Q.async(function () {
 *      var foo = yield getFooPromise();
 *      var bar = yield getBarPromise();
 *      Q.return(foo + bar);
 * })
 */
exports['return'] = _return;
function _return(value) {
    throw new QReturnValue(value);
}

/**
 * Constructs a promise method that can be used to safely observe resolution of
 * a promise for an arbitrarily named method like "propfind" in a future turn.
 */
exports.sender = sender; // XXX deprecated, use dispatcher
exports.Method = sender; // XXX deprecated, use dispatcher
function sender(op) {
    return function (object) {
        var args = array_slice(arguments, 1);
        return send.apply(void 0, [object, op].concat(args));
    };
}

/**
 * sends a message to a value in a future turn
 * @param object* the recipient
 * @param op the name of the message operation, e.g., "when",
 * @param ...args further arguments to be forwarded to the operation
 * @returns result {Promise} a promise for the result of the operation
 */
exports.send = send; // XXX deprecated, use dispatch
function send(object, op) {
    var deferred = defer();
    var args = array_slice(arguments, 2);
    object = resolve(object);
    nextTick(function () {
        object.promiseSend.apply(
            object,
            [op, deferred.resolve].concat(args)
        );
    });
    return deferred.promise;
}

/**
 * sends a message to a value in a future turn
 * @param object* the recipient
 * @param op the name of the message operation, e.g., "when",
 * @param args further arguments to be forwarded to the operation
 * @returns result {Promise} a promise for the result of the operation
 */
exports.dispatch = dispatch;
function dispatch(object, op, args) {
    var deferred = defer();
    object = resolve(object);
    nextTick(function () {
        object.promiseSend.apply(
            object,
            [op, deferred.resolve].concat(args)
        );
    });
    return deferred.promise;
}

/**
 * Constructs a promise method that can be used to safely observe resolution of
 * a promise for an arbitrarily named method like "propfind" in a future turn.
 *
 * "dispatcher" constructs methods like "get(promise, name)" and "put(promise)".
 */
exports.dispatcher = dispatcher;
function dispatcher(op) {
    return function (object) {
        var args = array_slice(arguments, 1);
        return dispatch(object, op, args);
    };
}

/**
 * Gets the value of a property in a future turn.
 * @param object    promise or immediate reference for target object
 * @param name      name of property to get
 * @return promise for the property value
 */
exports.get = dispatcher("get");

/**
 * Sets the value of a property in a future turn.
 * @param object    promise or immediate reference for object object
 * @param name      name of property to set
 * @param value     new value of property
 * @return promise for the return value
 */
exports.put = dispatcher("put");

/**
 * Deletes a property in a future turn.
 * @param object    promise or immediate reference for target object
 * @param name      name of property to delete
 * @return promise for the return value
 */
exports["delete"] = // XXX experimental
exports.del = dispatcher("del");

/**
 * Invokes a method in a future turn.
 * @param object    promise or immediate reference for target object
 * @param name      name of method to invoke
 * @param value     a value to post, typically an array of
 *                  invocation arguments for promises that
 *                  are ultimately backed with `resolve` values,
 *                  as opposed to those backed with URLs
 *                  wherein the posted value can be any
 *                  JSON serializable object.
 * @return promise for the return value
 */
// bound locally because it is used by other methods
var post = exports.post = dispatcher("post");

/**
 * Invokes a method in a future turn.
 * @param object    promise or immediate reference for target object
 * @param name      name of method to invoke
 * @param ...args   array of invocation arguments
 * @return promise for the return value
 */
exports.invoke = function (value, name) {
    var args = array_slice(arguments, 2);
    return post(value, name, args);
};

/**
 * Applies the promised function in a future turn.
 * @param object    promise or immediate reference for target function
 * @param thisp     the `this` object for the call
 * @param args      array of application arguments
 */
var apply = exports.apply = dispatcher("apply"); // XXX deprecated, use fapply

/**
 * Applies the promised function in a future turn.
 * @param object    promise or immediate reference for target function
 * @param args      array of application arguments
 */
var fapply = exports.fapply = dispatcher("fapply");

/**
 * Calls the promised function in a future turn.
 * @param object    promise or immediate reference for target function
 * @param thisp     the `this` object for the call
 * @param ...args   array of application arguments
 */
exports.call = call; // XXX deprecated, use fcall
function call(value, thisp) {
    var args = array_slice(arguments, 2);
    return apply(value, thisp, args);
}

/**
 * Calls the promised function in a future turn.
 * @param object    promise or immediate reference for target function
 * @param ...args   array of application arguments
 */
exports["try"] = fcall; // XXX experimental
exports.fcall = fcall;
function fcall(value) {
    var args = array_slice(arguments, 1);
    return fapply(value, args);
}

/**
 * Binds the promised function, transforming return values into a fulfilled
 * promise and thrown errors into a rejected one.
 * @param object    promise or immediate reference for target function
 * @param thisp   the `this` object for the call
 * @param ...args   array of application arguments
 */
exports.bind = bind; // XXX deprecated, use fbind
function bind(value, thisp) {
    var args = array_slice(arguments, 2);
    return function bound() {
        var allArgs = args.concat(array_slice(arguments));
        return apply(value, thisp, allArgs);
    };
}

/**
 * Binds the promised function, transforming return values into a fulfilled
 * promise and thrown errors into a rejected one.
 * @param object    promise or immediate reference for target function
 * @param ...args   array of application arguments
 */
exports.fbind = fbind;
function fbind(value) {
    var args = array_slice(arguments, 1);
    return function fbound() {
        var allArgs = args.concat(array_slice(arguments));
        return fapply(value, allArgs);
    };
}

/**
 * Requests the names of the owned properties of a promised
 * object in a future turn.
 * @param object    promise or immediate reference for target object
 * @return promise for the keys of the eventually resolved object
 */
exports.keys = dispatcher("keys");

/**
 * Turns an array of promises into a promise for an array.  If any of
 * the promises gets rejected, the whole array is rejected immediately.
 * @param {Array*} an array (or promise for an array) of values (or
 * promises for values)
 * @returns a promise for an array of the corresponding values
 */
// By Mark Miller
// http://wiki.ecmascript.org/doku.php?id=strawman:concurrency&rev=1308776521#allfulfilled
exports.all = all;
function all(promises) {
    return when(promises, function (promises) {
        var countDown = promises.length;
        if (countDown === 0) {
            return resolve(promises);
        }
        var deferred = defer();
        array_reduce(promises, function (undefined, promise, index) {
            when(promise, function (value) {
                promises[index] = value;
                if (--countDown === 0) {
                    deferred.resolve(promises);
                }
            })
            .fail(deferred.reject);
        }, void 0);
        return deferred.promise;
    });
}

/**
 * Waits for all promises to be resolved, either fulfilled or
 * rejected.  This is distinct from `all` since that would stop
 * waiting at the first rejection.  The promise returned by
 * `allResolved` will never be rejected.
 * @param promises a promise for an array (or an array) of promises
 * (or values)
 * @return a promise for an array of promises
 */
exports.allResolved = allResolved;
function allResolved(promises) {
    return when(promises, function (promises) {
        return when(all(promises.map(function (promise) {
            return when(promise, noop, noop);
        })), function () {
            return promises.map(resolve);
        });
    });
}

/**
 * Captures the failure of a promise, giving an oportunity to recover
 * with a callback.  If the given promise is fulfilled, the returned
 * promise is fulfilled.
 * @param {Any*} promise for something
 * @param {Function} callback to fulfill the returned promise if the
 * given promise is rejected
 * @returns a promise for the return value of the callback
 */
exports["catch"] = // XXX experimental
exports.fail = fail;
function fail(promise, rejected) {
    return when(promise, void 0, rejected);
}

/**
 * Provides an opportunity to observe the rejection of a promise,
 * regardless of whether the promise is fulfilled or rejected.  Forwards
 * the resolution to the returned promise when the callback is done.
 * The callback can return a promise to defer completion.
 * @param {Any*} promise
 * @param {Function} callback to observe the resolution of the given
 * promise, takes no arguments.
 * @returns a promise for the resolution of the given promise when
 * ``fin`` is done.
 */
exports["finally"] = // XXX experimental
exports.fin = fin;
function fin(promise, callback) {
    return when(promise, function (value) {
        return when(callback(), function () {
            return value;
        });
    }, function (exception) {
        return when(callback(), function () {
            return reject(exception);
        });
    });
}

/**
 * Terminates a chain of promises, forcing rejections to be
 * thrown as exceptions.
 * @param {Any*} promise at the end of a chain of promises
 * @returns nothing
 */
exports.end = end; // XXX stopgap
function end(promise) {
    when(promise, void 0, function (error) {
        // forward to a future turn so that ``when``
        // does not catch it and turn it into a rejection.
        nextTick(function () {
            // If possible (that is, if in V8), transform the error stack
            // trace by removing Node and Q cruft, then concatenating with
            // the stack trace of the promise we are ``end``ing. See #57.
            if (Error.captureStackTrace) {
                var errorStackFrames = getStackFrames(error);
                var promiseStackFrames = getStackFrames(promise);

                var combinedStackFrames = errorStackFrames.concat(
                    "From previous event:",
                    promiseStackFrames
                );
                error.stack = formatStackTrace(error, combinedStackFrames);
            }

            throw error;
        });
    });
}

/**
 * Causes a promise to be rejected if it does not get fulfilled before
 * some milliseconds time out.
 * @param {Any*} promise
 * @param {Number} milliseconds timeout
 * @returns a promise for the resolution of the given promise if it is
 * fulfilled before the timeout, otherwise rejected.
 */
exports.timeout = timeout;
function timeout(promise, ms) {
    var deferred = defer();
    when(promise, deferred.resolve, deferred.reject);
    setTimeout(function () {
        deferred.reject(new Error("Timed out after " + ms + "ms"));
    }, ms);
    return deferred.promise;
}

/**
 * Returns a promise for the given value (or promised value) after some
 * milliseconds.
 * @param {Any*} promise
 * @param {Number} milliseconds
 * @returns a promise for the resolution of the given promise after some
 * time has elapsed.
 */
exports.delay = delay;
function delay(promise, timeout) {
    if (timeout === void 0) {
        timeout = promise;
        promise = void 0;
    }
    var deferred = defer();
    setTimeout(function () {
        deferred.resolve(promise);
    }, timeout);
    return deferred.promise;
}

/**
 * Passes a continuation to a Node function, which is called with a given
 * `this` value and arguments provided as an array, and returns a promise.
 *
 *      var FS = require("fs");
 *      Q.napply(FS.readFile, FS, [__filename])
 *      .then(function (content) {
 *      })
 *
 */
exports.napply = napply;
function napply(callback, thisp, args) {
    return nbind(callback, thisp).apply(void 0, args);
}

/**
 * Passes a continuation to a Node function, which is called with a given
 * `this` value and arguments provided individually, and returns a promise.
 *
 *      var FS = require("fs");
 *      Q.ncall(FS.readFile, FS, __filename)
 *      .then(function (content) {
 *      })
 *
 */
exports.ncall = ncall;
function ncall(callback, thisp /*, ...args*/) {
    var args = array_slice(arguments, 2);
    return napply(callback, thisp, args);
}

/**
 * Wraps a NodeJS continuation passing function and returns an equivalent
 * version that returns a promise.
 *
 *      Q.nbind(FS.readFile, FS)(__filename)
 *      .then(console.log)
 *      .end()
 *
 */
exports.nbind = nbind;
function nbind(callback /* thisp, ...args*/) {
    if (arguments.length > 1) {
        var args = array_slice(arguments, 1);
        callback = callback.bind.apply(callback, args);
    }
    return function () {
        var deferred = defer();
        var args = array_slice(arguments);
        // add a continuation that resolves the promise
        args.push(deferred.makeNodeResolver());
        // trap exceptions thrown by the callback
        fapply(callback, args)
        .fail(deferred.reject);
        return deferred.promise;
    };
}

/**
 * Calls a method of a Node-style object that accepts a Node-style
 * callback with a given array of arguments, plus a provided callback.
 * @param object an object that has the named method
 * @param {String} name name of the method of object
 * @param {Array} args arguments to pass to the method; the callback
 * will be provided by Q and appended to these arguments.
 * @returns a promise for the value or error
 */
exports.npost = npost;
function npost(object, name, args) {
    return napply(object[name], name, args);
}

/**
 * Calls a method of a Node-style object that accepts a Node-style
 * callback, forwarding the given variadic arguments, plus a provided
 * callback argument.
 * @param object an object that has the named method
 * @param {String} name name of the method of object
 * @param ...args arguments to pass to the method; the callback will
 * be provided by Q and appended to these arguments.
 * @returns a promise for the value or error
 */
exports.ninvoke = ninvoke;
function ninvoke(object, name /*, ...args*/) {
    var args = array_slice(arguments, 2);
    return napply(object[name], name, args);
}

defend(exports);

});