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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module.exports = class Scheduler {
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  constructor () {
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    this._waits = []
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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 () {
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    const id = Symbol('lock')
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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.instances.delete(instance.id)
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    const instanceArray = [...this.instances]
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    binarySearchInsert(instanceArray, comparator, [instance.id, {
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      ticks: instance.ticks,
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      instance: instance
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    }])
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    this.instances = new Map(instanceArray)
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    this._checkWaits()
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  }
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  getInstance (id) {
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    const item = this.instances.get(id)
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    if (item) {
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      return item.instance
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    }
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  }
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  done (instance) {
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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) {
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    if (!this.locks.size && ticks <= this.smallest()) {
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      return
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    } else {
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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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      })
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    }
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  }
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  smallest () {
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    return [...this.instances][0][1].ticks
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  }
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  _checkWaits () {
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    if (!this.locks.size) {
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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 {
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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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