File manager

"use strict";
module.exports = function (Promise, apiRejection, tryConvertToPromise,
    createContext, INTERNAL, debug) {
    var util = require("./util");
    var TypeError = require("./errors").TypeError;
    var inherits = require("./util").inherits;
    var errorObj = util.errorObj;
    var tryCatch = util.tryCatch;
    var NULL = {};

    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 = new Promise(INTERNAL);
        function iterator() {
            if (i >= len) return ret._fulfill();
            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;
    }

    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;
    }

    function ResourceList(length) {
        this.length = length;
        this.promise = null;
        this[length-1] = null;
    }

    ResourceList.prototype._resultCancelled = function() {
        var len = this.length;
        for (var i = 0; i < len; ++i) {
            var item = this[i];
            if (item instanceof Promise) {
                item.cancel();
            }
        }
    };

    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("expecting a function but got " + util.classString(fn));
        }
        var input;
        var spreadArgs = true;
        if (len === 2 && Array.isArray(arguments[0])) {
            input = arguments[0];
            len = input.length;
            spreadArgs = false;
        } else {
            input = arguments;
            len--;
        }
        var resources = new ResourceList(len);
        for (var i = 0; i < len; ++i) {
            var resource = input[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 reflectedResources = new Array(resources.length);
        for (var i = 0; i < reflectedResources.length; ++i) {
            reflectedResources[i] = Promise.resolve(resources[i]).reflect();
        }

        var resultPromise = Promise.all(reflectedResources)
            .then(function(inspections) {
                for (var i = 0; i < inspections.length; ++i) {
                    var inspection = inspections[i];
                    if (inspection.isRejected()) {
                        errorObj.e = inspection.error();
                        return errorObj;
                    } else if (!inspection.isFulfilled()) {
                        resultPromise.cancel();
                        return;
                    }
                    inspections[i] = inspection.value();
                }
                promise._pushContext();

                fn = tryCatch(fn);
                var ret = spreadArgs
                    ? fn.apply(undefined, inspections) : fn(inspections);
                var promiseCreated = promise._popContext();
                debug.checkForgottenReturns(
                    ret, promiseCreated, "Promise.using", promise);
                return ret;
            });

        var promise = resultPromise.lastly(function() {
            var inspection = new Promise.PromiseInspection(resultPromise);
            return dispose(resources, inspection);
        });
        resources.promise = promise;
        promise._setOnCancel(resources);
        return promise;
    };

    Promise.prototype._setDisposable = function (disposer) {
        this._bitField = this._bitField | 131072;
        this._disposer = disposer;
    };

    Promise.prototype._isDisposable = function () {
        return (this._bitField & 131072) > 0;
    };

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

    Promise.prototype._unsetDisposable = function () {
        this._bitField = this._bitField & (~131072);
        this._disposer = undefined;
    };

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

};