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'use strict';
import arrayEach from 'lodash-es/_arrayEach';
import arrayEvery from 'lodash-es/_arrayEvery';
import baseHas from 'lodash-es/_baseHas';
import forOwn from 'lodash-es/forOwn';
import indexOf from 'lodash-es/indexOf';
import isArray from 'lodash-es/isArray';
import okeys from 'lodash-es/keys';
import noop from 'lodash-es/noop';
import once from 'lodash-es/once';
import rest from 'lodash-es/rest';
import setImmediate from './internal/setImmediate';
export default function (tasks, concurrency, callback) {
if (typeof arguments[1] === 'function') {
// concurrency is optional, shift the args.
callback = concurrency;
concurrency = null;
}
callback = once(callback || noop);
var keys = okeys(tasks);
var remainingTasks = keys.length;
if (!remainingTasks) {
return callback(null);
}
if (!concurrency) {
concurrency = remainingTasks;
}
var results = {};
var runningTasks = 0;
var hasError = false;
var listeners = [];
function addListener(fn) {
listeners.unshift(fn);
}
function removeListener(fn) {
var idx = indexOf(listeners, fn);
if (idx >= 0) listeners.splice(idx, 1);
}
function taskComplete() {
remainingTasks--;
arrayEach(listeners.slice(), function (fn) {
fn();
});
}
addListener(function () {
if (!remainingTasks) {
callback(null, results);
}
});
arrayEach(keys, function (k) {
if (hasError) return;
var task = isArray(tasks[k]) ? tasks[k]: [tasks[k]];
var taskCallback = rest(function(err, args) {
runningTasks--;
if (args.length <= 1) {
args = args[0];
}
if (err) {
var safeResults = {};
forOwn(results, function(val, rkey) {
safeResults[rkey] = val;
});
safeResults[k] = args;
hasError = true;
callback(err, safeResults);
}
else {
results[k] = args;
setImmediate(taskComplete);
}
});
var requires = task.slice(0, task.length - 1);
// prevent dead-locks
var len = requires.length;
var dep;
while (len--) {
if (!(dep = tasks[requires[len]])) {
throw new Error('Has non-existent dependency in ' +
requires.join(', '));
}
if (isArray(dep) && indexOf(dep, k) >= 0) {
throw new Error('Has cyclic dependencies');
}
}
function ready() {
return runningTasks < concurrency && !baseHas(results, k) &&
arrayEvery(requires, function (x) {
return baseHas(results, x);
});
}
if (ready()) {
runningTasks++;
task[task.length - 1](taskCallback, results);
}
else {
addListener(listener);
}
function listener() {
if (ready()) {
runningTasks++;
removeListener(listener);
task[task.length - 1](taskCallback, results);
}
}
});
}
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