git ssb

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const binarySearchInsert = require('binary-search-insert')
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const comparator = function (a, b) {
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  return a.ticks - b.ticks
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}
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const instancesComparator = function (a, b) {
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  return a[1].ticks - b[1].ticks
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}
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module.exports = class Scheduler {
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  constructor () {
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    this._waits = []
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    this._running = new Set()
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    this._loadingInstances = new Map()
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    this.instances = new Map()
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    this.locks = new Set()
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  }
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  getLock (id) {
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    this.locks.add(id)
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    return id
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  }
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  releaseLock (id) {
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    this.locks.delete(id)
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  }
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  update (instance) {
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    this._update(instance)
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    this._checkWaits()
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  }
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  _update (instance) {
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    this._running.add(instance.id)
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    this.instances.delete(instance.id)
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    const instanceArray = [...this.instances]
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    binarySearchInsert(instanceArray, instancesComparator, [instance.id, instance])
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    this.instances = new Map(instanceArray)
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  }
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  getInstance (id) {
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    return this.instances.get(id) || this._loadingInstances.get(id)
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  }
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  done (instance) {
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    this._running.delete(instance.id)
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    this.instances.delete(instance.id)
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    this._checkWaits()
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  }
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  wait (ticks = Infinity, id) {
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    this._running.delete(id)
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    return new Promise((resolve, reject) => {
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      binarySearchInsert(this._waits, comparator, {
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        ticks: ticks,
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        resolve: resolve
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      })
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      this._checkWaits()
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    })
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  }
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  smallest () {
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    return this.instances.size ? [...this.instances][0][1].ticks : 0
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  }
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  _checkWaits () {
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    if (!this.locks.size) {
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      // if there are no running containers
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      if (!this.isRunning()) {
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        // clear any remanding waits
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        this._waits.forEach(wait => wait.resolve())
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        this._waits = []
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      } else if (!this._running.size) {
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        const smallest = this._waits[0].ticks
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        for (let instance of this.instances) {
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          instance = instance[1]
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          if (instance.ticks > smallest) {
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            break
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          } else {
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            instance.ticks = smallest
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            this._update(instance)
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          }
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        }
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        return this._checkWaits()
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      } else {
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        const smallest = this.smallest()
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        for (const index in this._waits) {
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          const wait = this._waits[index]
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          if (wait.ticks <= smallest) {
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            wait.resolve()
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          } else {
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            this._waits.splice(0, index)
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            break
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          }
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        }
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      }
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    }
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  }
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  isRunning () {
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    return this.instances.size
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  }
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}
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