git ssb

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var Value = require('./value')
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module.exports = Set
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function Set (defaultValues) {
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  var object = []
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  var sources = []
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  var releases = []
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  if (defaultValues && defaultValues.length) {
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    defaultValues.forEach(function (valueOrObs) {
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      if (!~sources.indexOf(valueOrObs)) {
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        sources.push(valueOrObs)
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        releases[sources.length - 1] = typeof valueOrObs === 'function'
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          ? valueOrObs(refresh)
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          : null
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      }
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    })
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    update()
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  }
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  var observable = Value(object)
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  var broadcast = observable.set
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  observable.add = function (valueOrObs) {
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    if (!~sources.indexOf(valueOrObs)) {
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      sources.push(valueOrObs)
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      releases[sources.length - 1] = typeof valueOrObs === 'function'
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        ? valueOrObs(refresh)
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        : null
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      refresh()
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    }
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  }
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  observable.clear = function () {
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    releases.forEach(tryInvoke)
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    sources.length = 0
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    releases.length = 0
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    refresh()
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  }
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  observable.delete = function (valueOrObs) {
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    var index = sources.indexOf(valueOrObs)
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    if (~index) {
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      sources.splice(index, 1)
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      releases.splice(index, 1).forEach(tryInvoke)
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      refresh()
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    }
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  }
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  observable.has = function (valueOrObs) {
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    return !!~object.indexOf(valueOrObs)
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  }
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  observable.set = function (values) {
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    sources.length = 0
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    values.forEach(function (value) {
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      sources.push(value)
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    })
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    refresh()
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  }
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  observable.getLength = function () {
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    return sources.length
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  }
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  observable.destroy = observable.clear
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  return observable
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  function refresh () {
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    update()
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    broadcast(object)
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  }
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  function update () {
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    var currentValues = object.map(get)
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    var newValues = sources.map(resolve)
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    currentValues.filter(notIncluded, newValues).forEach(removeFrom, object)
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    newValues.filter(notIncluded, currentValues).forEach(addTo, object)
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  }
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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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