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'use strict'
module.exports = RunQueue
var validate = require('aproba')
function RunQueue (opts) {
validate('Z|O', [opts])
if (!opts) opts = {}
this.finished = false
this.inflight = 0
this.maxConcurrency = opts.maxConcurrency || 1
this.queued = 0
this.queue = []
this.currentPrio = null
this.currentQueue = null
this.Promise = opts.Promise || global.Promise
this.deferred = {}
}
RunQueue.prototype = {}
RunQueue.prototype.run = function () {
if (arguments.length !== 0) throw new Error('RunQueue.run takes no arguments')
var self = this
var deferred = this.deferred
if (!deferred.promise) {
deferred.promise = new this.Promise(function (resolve, reject) {
deferred.resolve = resolve
deferred.reject = reject
self._runQueue()
})
}
return deferred.promise
}
RunQueue.prototype._runQueue = function () {
var self = this
while ((this.inflight < this.maxConcurrency) && this.queued) {
if (!this.currentQueue || this.currentQueue.length === 0) {
// wait till the current priority is entirely processed before
// starting a new one
if (this.inflight) return
var prios = Object.keys(this.queue)
for (var ii = 0; ii < prios.length; ++ii) {
var prioQueue = this.queue[prios[ii]]
if (prioQueue.length) {
this.currentQueue = prioQueue
this.currentPrio = prios[ii]
break
}
}
}
--this.queued
++this.inflight
var next = this.currentQueue.shift()
var args = next.args || []
// we explicitly construct a promise here so that queue items can throw
// or immediately return to resolve
var queueEntry = new this.Promise(function (resolve) {
resolve(next.cmd.apply(null, args))
})
queueEntry.then(function () {
--self.inflight
if (self.finished) return
if (self.queued <= 0 && self.inflight <= 0) {
self.finished = true
self.deferred.resolve()
}
self._runQueue()
}, function (err) {
self.finished = true
self.deferred.reject(err)
})
}
}
RunQueue.prototype.add = function (prio, cmd, args) {
if (this.finished) throw new Error("Can't add to a finished queue. Create a new queue.")
if (Math.abs(Math.floor(prio)) !== prio) throw new Error('Priorities must be a positive integer value.')
validate('NFA|NFZ', [prio, cmd, args])
prio = Number(prio)
if (!this.queue[prio]) this.queue[prio] = []
++this.queued
this.queue[prio].push({cmd: cmd, args: args})
// if this priority is higher than the one we're currently processing,
// switch back to processing its queue.
if (this.currentPrio > prio) {
this.currentQueue = this.queue[prio]
this.currentPrio = prio
}
}
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