| 9 | import wrapAsync from './wrapAsync'; |
| 10 | |
| 11 | export default function queue(worker, concurrency, payload) { |
| 12 | if (concurrency == null) { |
| 13 | concurrency = 1; |
| 14 | } |
| 15 | else if(concurrency === 0) { |
| 16 | throw new Error('Concurrency must not be zero'); |
| 17 | } |
| 18 | |
| 19 | var _worker = wrapAsync(worker); |
| 20 | var numRunning = 0; |
| 21 | var workersList = []; |
| 22 | |
| 23 | function _insert(data, insertAtFront, callback) { |
| 24 | if (callback != null && typeof callback !== 'function') { |
| 25 | throw new Error('task callback must be a function'); |
| 26 | } |
| 27 | q.started = true; |
| 28 | if (!isArray(data)) { |
| 29 | data = [data]; |
| 30 | } |
| 31 | if (data.length === 0 && q.idle()) { |
| 32 | // call drain immediately if there are no tasks |
| 33 | return setImmediate(function() { |
| 34 | q.drain(); |
| 35 | }); |
| 36 | } |
| 37 | |
| 38 | for (var i = 0, l = data.length; i < l; i++) { |
| 39 | var item = { |
| 40 | data: data[i], |
| 41 | callback: callback || noop |
| 42 | }; |
| 43 | |
| 44 | if (insertAtFront) { |
| 45 | q._tasks.unshift(item); |
| 46 | } else { |
| 47 | q._tasks.push(item); |
| 48 | } |
| 49 | } |
| 50 | setImmediate(q.process); |
| 51 | } |
| 52 | |
| 53 | function _next(tasks) { |
| 54 | return rest(function(args){ |
| 55 | numRunning -= 1; |
| 56 | |
| 57 | for (var i = 0, l = tasks.length; i < l; i++) { |
| 58 | var task = tasks[i]; |
| 59 | var index = indexOf(workersList, task, 0); |
| 60 | if (index >= 0) { |
| 61 | workersList.splice(index) |
| 62 | } |
| 63 | |
| 64 | task.callback.apply(task, args); |
| 65 | |
| 66 | if (args[0] != null) { |
| 67 | q.error(args[0], task.data); |
| 68 | } |