63 lines
1.5 KiB
JavaScript
63 lines
1.5 KiB
JavaScript
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"use strict";
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var ensureNaturalNumber = require("type/natural-number/ensure")
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, ensurePlainFunction = require("type/plain-function/ensure")
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, ensure = require("type/ensure")
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, defineFunctionLength = require("../lib/private/define-function-length");
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module.exports = function (limit, callback) {
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limit = ensure(
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["limit", limit, ensureNaturalNumber, { min: 1 }],
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["callback", callback, ensurePlainFunction]
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)[0];
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var Promise = this, ongoingCount = 0, pending = [];
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var onSuccess, onFailure;
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var release = function () {
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--ongoingCount;
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if (ongoingCount >= limit) return;
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var next = pending.shift();
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if (!next) return;
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++ongoingCount;
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try {
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next.resolve(
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Promise.resolve(callback.apply(next.context, next.arguments)).then(
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onSuccess, onFailure
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)
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);
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} catch (exception) {
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release();
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next.reject(exception);
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}
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};
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onSuccess = function (value) {
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release();
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return value;
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};
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onFailure = function (exception) {
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release();
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throw exception;
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};
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return defineFunctionLength(callback.length, function () {
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if (ongoingCount >= limit) {
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var context = this, args = arguments;
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return new Promise(function (resolve, reject) {
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pending.push({
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context: context,
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arguments: args,
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resolve: resolve,
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reject: reject
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});
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});
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}
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++ongoingCount;
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try {
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return Promise.resolve(callback.apply(this, arguments)).then(onSuccess, onFailure);
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} catch (exception) { return onFailure(exception); }
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});
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};
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