using.js

"use strict";
module.exports = function (Promise, apiRejection, tryConvertToPromise,
    createContext) {
    var TypeError = require("./errors.js").TypeError;
    var inherits = require("./util.js").inherits;
    var PromiseInspection = Promise.PromiseInspection;

    function inspectionMapper(inspections) {
        var len = inspections.length;
        for (var i = 0; i < len; ++i) {
            var inspection = inspections[i];
            if (inspection.isRejected()) {
                return Promise.reject(inspection.error());
            }
            inspections[i] = inspection._settledValue;
        }
        return inspections;
    }

    function thrower(e) {
        setTimeout(function(){throw e;}, 0);
    }

    function castPreservingDisposable(thenable) {
        var maybePromise = tryConvertToPromise(thenable);
        if (maybePromise !== thenable &&
            typeof thenable._isDisposable === "function" &&
            typeof thenable._getDisposer === "function" &&
            thenable._isDisposable()) {
            maybePromise._setDisposable(thenable._getDisposer());
        }
        return maybePromise;
    }
    function dispose(resources, inspection) {
        var i = 0;
        var len = resources.length;
        var ret = Promise.defer();
        function iterator() {
            if (i >= len) return ret.resolve();
            var maybePromise = castPreservingDisposable(resources[i++]);
            if (maybePromise instanceof Promise &&
                maybePromise._isDisposable()) {
                try {
                    maybePromise = tryConvertToPromise(
                        maybePromise._getDisposer().tryDispose(inspection),
                        resources.promise);
                } catch (e) {
                    return thrower(e);
                }
                if (maybePromise instanceof Promise) {
                    return maybePromise._then(iterator, thrower,
                                              null, null, null);
                }
            }
            iterator();
        }
        iterator();
        return ret.promise;
    }

    function disposerSuccess(value) {
        var inspection = new PromiseInspection();
        inspection._settledValue = value;
        inspection._bitField = 268435456;
        return dispose(this, inspection).thenReturn(value);
    }

    function disposerFail(reason) {
        var inspection = new PromiseInspection();
        inspection._settledValue = reason;
        inspection._bitField = 134217728;
        return dispose(this, inspection).thenThrow(reason);
    }

    function Disposer(data, promise, context) {
        this._data = data;
        this._promise = promise;
        this._context = context;
    }

    Disposer.prototype.data = function () {
        return this._data;
    };

    Disposer.prototype.promise = function () {
        return this._promise;
    };

    Disposer.prototype.resource = function () {
        if (this.promise().isFulfilled()) {
            return this.promise().value();
        }
        return null;
    };

    Disposer.prototype.tryDispose = function(inspection) {
        var resource = this.resource();
        var context = this._context;
        if (context !== undefined) context._pushContext();
        var ret = resource !== null
            ? this.doDispose(resource, inspection) : null;
        if (context !== undefined) context._popContext();
        this._promise._unsetDisposable();
        this._data = null;
        return ret;
    };

    Disposer.isDisposer = function (d) {
        return (d != null &&
                typeof d.resource === "function" &&
                typeof d.tryDispose === "function");
    };

    function FunctionDisposer(fn, promise, context) {
        this.constructor$(fn, promise, context);
    }
    inherits(FunctionDisposer, Disposer);

    FunctionDisposer.prototype.doDispose = function (resource, inspection) {
        var fn = this.data();
        return fn.call(resource, resource, inspection);
    };

    function maybeUnwrapDisposer(value) {
        if (Disposer.isDisposer(value)) {
            this.resources[this.index]._setDisposable(value);
            return value.promise();
        }
        return value;
    }

    Promise.using = function () {
        var len = arguments.length;
        if (len < 2) return apiRejection(
                        "you must pass at least 2 arguments to Promise.using");
        var fn = arguments[len - 1];
        if (typeof fn !== "function") return apiRejection("fn must be a function\u000a\u000a    See http://goo.gl/916lJJ\u000a");
        len--;
        var resources = new Array(len);
        for (var i = 0; i < len; ++i) {
            var resource = arguments[i];
            if (Disposer.isDisposer(resource)) {
                var disposer = resource;
                resource = resource.promise();
                resource._setDisposable(disposer);
            } else {
                var maybePromise = tryConvertToPromise(resource);
                if (maybePromise instanceof Promise) {
                    resource =
                        maybePromise._then(maybeUnwrapDisposer, null, null, {
                            resources: resources,
                            index: i
                    }, undefined);
                }
            }
            resources[i] = resource;
        }

        var promise = Promise.settle(resources)
            .then(inspectionMapper)
            .then(function(vals) {
                promise._pushContext();
                var ret;
                try {
                    ret = fn.apply(undefined, vals);
                } finally {
                    promise._popContext();
                }
                return ret;
            })
            ._then(
                disposerSuccess, disposerFail, undefined, resources, undefined);
        resources.promise = promise;
        return promise;
    };

    Promise.prototype._setDisposable = function (disposer) {
        this._bitField = this._bitField | 262144;
        this._disposer = disposer;
    };

    Promise.prototype._isDisposable = function () {
        return (this._bitField & 262144) > 0;
    };

    Promise.prototype._getDisposer = function () {
        return this._disposer;
    };

    Promise.prototype._unsetDisposable = function () {
        this._bitField = this._bitField & (~262144);
        this._disposer = undefined;
    };

    Promise.prototype.disposer = function (fn) {
        if (typeof fn === "function") {
            return new FunctionDisposer(fn, this, createContext());
        }
        throw new TypeError();
    };

};