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'use strict';
import arrayEach from 'lodash-es/_arrayEach';
import isArray from 'lodash-es/isArray';
import noop from 'lodash-es/noop';
import setImmediate from './setImmediate';
import queue from './queue';
export default function(worker, concurrency) {
function _compareTasks(a, b) {
return a.priority - b.priority;
}
function _binarySearch(sequence, item, compare) {
var beg = -1,
end = sequence.length - 1;
while (beg < end) {
var mid = beg + ((end - beg + 1) >>> 1);
if (compare(item, sequence[mid]) >= 0) {
beg = mid;
} else {
end = mid - 1;
}
}
return beg;
}
function _insert(q, data, priority, callback) {
if (callback != null && typeof callback !== 'function') {
throw new Error('task callback must be a function');
}
q.started = true;
if (!isArray(data)) {
data = [data];
}
if (data.length === 0) {
// call drain immediately if there are no tasks
return setImmediate(function() {
q.drain();
});
}
arrayEach(data, function(task) {
var item = {
data: task,
priority: priority,
callback: typeof callback === 'function' ? callback : noop
};
q.tasks.splice(_binarySearch(q.tasks, item, _compareTasks) + 1, 0, item);
if (q.tasks.length === q.concurrency) {
q.saturated();
}
setImmediate(q.process);
});
}
// Start with a normal queue
var q = queue(worker, concurrency);
// Override push to accept second parameter representing priority
q.push = function(data, priority, callback) {
_insert(q, data, priority, callback);
};
// Remove unshift function
delete q.unshift;
return q;
}
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