git ssb

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var resolve = require('./resolve')
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var LazyWatcher = require('./lib/lazy-watcher')
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module.exports = Map
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function Map (obs, lambda, opts) {
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  var releases = []
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  var binder = LazyWatcher(update, listen, unlisten)
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  var lastValues = new global.Map()
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  var items = []
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  var raw = []
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  var values = []
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  var watches = []
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  binder.value = values
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  // incremental update
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  var queue = []
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  var maxTime = null
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  if (opts && opts.maxTime) {
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    maxTime = opts.maxTime
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  }
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  var result = function MutantMap (listener) {
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    if (!listener) {
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      return binder.getValue()
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    }
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    return binder.addListener(listener)
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  }
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  result.get = function (index) {
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    return raw[index]
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  }
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  result.getLength = function (index) {
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    return raw.length
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  }
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  result.includes = function (valueOrObs) {
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    return !!~raw.indexOf(valueOrObs)
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  }
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  result.indexOf = function (valueOrObs) {
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    return raw.indexOf(valueOrObs)
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  }
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  return result
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  // scoped
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  function listen () {
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    if (typeof obs === 'function') {
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      releases.push(obs(binder.onUpdate))
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    }
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    rebindAll()
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  }
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  function unlisten () {
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    while (releases.length) {
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      releases.pop()()
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    }
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    rebindAll()
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  }
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  function update () {
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    var changed = false
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    if (items.length !== getLength(obs)) {
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      changed = true
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    }
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    var startedAt = Date.now()
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    for (var i = 0, len = getLength(obs); i < len; i++) {
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      var item = get(obs, i)
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      var currentItem = items[i]
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      items[i] = item
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      if (typeof item === 'object' || item !== currentItem) {
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        if (maxTime && Date.now() - startedAt > maxTime) {
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          queueUpdateItem(i)
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        } else {
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          updateItem(i)
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        }
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        changed = true
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      }
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    }
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    if (changed) {
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      // clean up cache
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      Array.from(lastValues.keys()).filter(notIncluded, obs).forEach(deleteEntry, lastValues)
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      items.length = getLength(obs)
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      values.length = items.length
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      for (var index = items.length; index < raw.length; index++) {
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        rebind(index)
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      }
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    }
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    return changed
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  }
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  function queueUpdateItem (i) {
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    if (!queue.length) {
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      setImmediate(flushQueue)
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    }
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    if (!~queue.indexOf(i)) {
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      queue.push(i)
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    }
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  }
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  function flushQueue () {
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    var startedAt = Date.now()
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    while (queue.length && (!maxTime || Date.now() - startedAt < maxTime)) {
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      updateItem(queue.pop())
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    }
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    binder.broadcast()
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    if (queue.length) {
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      setImmediate(flushQueue)
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    }
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  }
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  function updateItem (i) {
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    var item = get(obs, i)
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    if (typeof item === 'object') {
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      raw[i] = lambda(item)
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    } else {
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      if (!lastValues.has(item)) {
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        lastValues.set(item, lambda(item))
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      }
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      raw[i] = lastValues.get(item)
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    }
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    values[i] = resolve(raw[i])
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    rebind(i)
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  }
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  function rebind (index) {
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    if (watches[index]) {
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      watches[index]()
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      watches[index] = null
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    }
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    if (binder.live) {
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      if (typeof raw[index] === 'function') {
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        watches[index] = updateValue(raw[index], index)
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      }
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    }
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  }
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  function rebindAll () {
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    for (var i = 0; i < raw.length; i++) {
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      rebind(i)
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    }
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  }
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  function updateValue (obs, index) {
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    return obs(function (value) {
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      if (values[index] !== value || typeof value === 'object') {
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        values[index] = value
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        binder.broadcast()
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      }
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    })
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  }
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}
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function get (target, index) {
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  if (typeof target === 'function' && !target.get) {
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    target = target()
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  }
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  if (Array.isArray(target)) {
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    return target[index]
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  } else if (target && target.get) {
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    return target.get(index)
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  }
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}
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function getLength (target) {
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  if (typeof target === 'function' && !target.getLength) {
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    target = target()
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  }
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  if (Array.isArray(target)) {
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    return target.length
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  } else if (target && target.get) {
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    return target.getLength()
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  }
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  return 0
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}
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function notIncluded (value) {
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  if (this.includes) {
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    return !this.includes(value)
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  } else if (this.indexOf) {
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    return !~this.indexOf(value)
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  } else if (typeof this === 'function') {
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    var array = this()
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    if (array && array.includes) {
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      return !array.includes(value)
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    }
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  }
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  return true
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}
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function deleteEntry (entry) {
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  this.delete(entry)
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}
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