git ssb

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var LazyWatcher = require('./lib/lazy-watcher')
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module.exports = Set
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function Set (defaultValues, opts) {
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  var instance = new ProtoSet(defaultValues, opts)
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  var observable = instance.MutantSet.bind(instance)
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  observable.add = instance.add.bind(instance)
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  observable.clear = instance.clear.bind(instance)
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  observable.delete = instance.delete.bind(instance)
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  observable.has = instance.has.bind(instance)
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  observable.set = instance.set.bind(instance)
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  observable.get = instance.get.bind(instance)
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  observable.getLength = instance.getLength.bind(instance)
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  return observable
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}
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// optimise memory usage
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function ProtoSet (defaultValues, opts) {
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  var self = this
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  self.object = []
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  self.sources = []
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  self.releases = []
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  self.binder = LazyWatcher.call(self, self._update, self._listen, self._unlisten)
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  self.binder.value = this.object
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  if (opts && opts.nextTick) {
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    self.binder.nextTick = true
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  }
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  if (defaultValues && defaultValues.length) {
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    defaultValues.forEach(function (valueOrObs) {
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      if (!~self.sources.indexOf(valueOrObs)) {
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        self.sources.push(valueOrObs)
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      }
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    })
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    this._update()
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  }
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}
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ProtoSet.prototype.MutantSet = function (listener) {
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  if (!listener) {
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    return this.binder.getValue()
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  }
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  return this.binder.addListener(listener)
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}
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ProtoSet.prototype.add = function (valueOrObs) {
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  if (!~this.sources.indexOf(valueOrObs)) {
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    this.sources.push(valueOrObs)
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    if (this.binder.live) {
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      this.releases[this.sources.length - 1] = this._bind(valueOrObs)
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    }
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    this.binder.onUpdate()
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  }
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}
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ProtoSet.prototype.clear = function () {
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  this.releases.forEach(tryInvoke)
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  this.sources.length = 0
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  this.releases.length = 0
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  this.binder.onUpdate()
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}
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ProtoSet.prototype.delete = function (valueOrObs) {
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  var index = this.sources.indexOf(valueOrObs)
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  if (~index) {
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    this.sources.splice(index, 1)
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    this.releases.splice(index, 1).forEach(tryInvoke)
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    this.binder.onUpdate()
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  }
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}
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ProtoSet.prototype.has = function (valueOrObs) {
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  return !!~this.object.indexOf(valueOrObs)
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}
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ProtoSet.prototype.set = function (values) {
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  var self = this
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  var changed = false
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  if (Array.isArray(values)) {
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    for (var i = this.sources.length - 1; i >= 0; i -= 1) {
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      if (!~values.indexOf(this.sources[i])) {
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        changed = true
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        self.sources.splice(i, 1)
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      }
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    }
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    values.forEach(function (value) {
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      if (!~self.sources.indexOf(value)) {
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        changed = true
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        self.sources.push(value)
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      }
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    })
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  } else {
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    if (self.sources.length > 0) {
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      self.sources.length = 0
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      changed = true
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    }
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  }
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  if (changed) {
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    self.binder.onUpdate()
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  }
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}
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ProtoSet.prototype.get = function (index) {
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  return this.sources[index]
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}
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ProtoSet.prototype.getLength = function () {
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  return this.sources.length
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}
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ProtoSet.prototype._bind = function (valueOrObs) {
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  return typeof valueOrObs === 'function' ? valueOrObs(this.binder.onUpdate) : null
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}
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ProtoSet.prototype._listen = function () {
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  var self = this
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  self.sources.forEach(function (obs, i) {
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    self.releases[i] = self._bind(obs)
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  })
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}
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ProtoSet.prototype._unlisten = function () {
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  this.releases.forEach(tryInvoke)
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  this.releases.length = 0
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}
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ProtoSet.prototype._update = function () {
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  var currentValues = this.object.map(get)
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  var newValues = this.sources.map(resolve)
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  currentValues.filter(notIncluded, newValues).forEach(removeFrom, this.object)
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  newValues.filter(notIncluded, currentValues).forEach(addTo, this.object)
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  return true
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}
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function get (value) {
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  return value
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}
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function resolve (source) {
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  return typeof source === 'function' ? source() : source
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}
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function notIncluded (value) {
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  return !~this.indexOf(value)
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}
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function removeFrom (item) {
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  var index = this.indexOf(item)
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  if (~index) {
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    this.splice(index, 1)
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  }
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}
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function addTo (item) {
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  this.push(item)
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}
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function tryInvoke (func) {
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  if (typeof func === 'function') {
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    func()
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  }
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}
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