git ssb

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var keys = exports.keys =
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function (object) {
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  return values(Object.keys(object))
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}
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function abortCb(cb, abort, onAbort) {
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  cb(abort)
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  onAbort && onAbort(abort === true ? null: abort)
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  return
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}
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var once = exports.once =
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function (value, onAbort) {
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  return function (abort, cb) {
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    if(abort)
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      return abortCb(cb, abort, onAbort)
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    if(value != null) {
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      var _value = value; value = null
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      cb(null, _value)
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    } else
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      cb(true)
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  }
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}
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var values = exports.values = exports.readArray =
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function (array, onAbort) {
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  if(!array)
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    return function (abort, cb) {
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      if(abort) return abortCb(cb, abort, onAbort)
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      return cb(true)
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    }
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  if(!Array.isArray(array))
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    array = Object.keys(array).map(function (k) {
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      return array[k]
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    })
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  var i = 0
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  return function (abort, cb) {
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    if(abort)
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      return abortCb(cb, abort, onAbort)
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    cb(i >= array.length || null, array[i++])
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  }
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}
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var count = exports.count =
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function (max) {
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  var i = 0; max = max || Infinity
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  return function (end, cb) {
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    if(end) return cb && cb(end)
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    if(i > max)
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      return cb(true)
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    cb(null, i++)
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  }
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}
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var infinite = exports.infinite =
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function (generate) {
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  generate = generate || Math.random
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  return function (end, cb) {
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    if(end) return cb && cb(end)
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    return cb(null, generate())
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  }
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}
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var defer = exports.defer = function () {
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  var _read, cbs = [], _end
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  var read = function (end, cb) {
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    if(!_read) {
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      _end = end
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      cbs.push(cb)
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    } 
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    else _read(end, cb)
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  }
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  read.resolve = function (read) {
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    if(_read) throw new Error('already resolved')
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    _read = read
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    if(!_read) throw new Error('no read cannot resolve!' + _read)
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    while(cbs.length)
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      _read(_end, cbs.shift())
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  }
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  read.abort = function(err) {
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    read.resolve(function (_, cb) {
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      cb(err || true)
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    })
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  }
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  return read
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}
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var empty = exports.empty = function () {
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  return function (abort, cb) {
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    cb(true)
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  }
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}
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var error = exports.error = function (err) {
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  return function (abort, cb) {
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    cb(err)
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  }
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}
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var depthFirst = exports.depthFirst =
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function (start, createStream) {
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  var reads = []
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  reads.unshift(once(start))
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  return function next (end, cb) {
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    if(!reads.length)
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      return cb(true)
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    reads[0](end, function (end, data) {
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      if(end) {
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        //if this stream has ended, go to the next queue
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        reads.shift()
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        return next(null, cb)
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      }
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      reads.unshift(createStream(data))
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      cb(end, data)
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    })
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  }
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}
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//width first is just like depth first,
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//but push each new stream onto the end of the queue
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var widthFirst = exports.widthFirst =
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function (start, createStream) {
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  var reads = []
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  reads.push(once(start))
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  return function next (end, cb) {
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    if(!reads.length)
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      return cb(true)
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    reads[0](end, function (end, data) {
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      if(end) {
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        reads.shift()
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        return next(null, cb)
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      }
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      reads.push(createStream(data))
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      cb(end, data)
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    })
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  }
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}
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//this came out different to the first (strm)
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//attempt at leafFirst, but it's still a valid
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//topological sort.
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var leafFirst = exports.leafFirst =
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function (start, createStream) {
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  var reads = []
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  var output = []
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  reads.push(once(start))
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  return function next (end, cb) {
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    reads[0](end, function (end, data) {
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      if(end) {
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        reads.shift()
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        if(!output.length)
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          return cb(true)
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        return cb(null, output.shift())
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      }
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      reads.unshift(createStream(data))
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      output.unshift(data)
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      next(null, cb)
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    })
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  }
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}
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