janus/lib/collection/derived/taken-list.js

the two-faced application library-framework

// Generated by CoffeeScript 1.12.2
(function() {
  var DerivedList, TakenList, Varying, max, min,
    extend = function(child, parent) { for (var key in parent) { if (hasProp.call(parent, key)) child[key] = parent[key]; } function ctor() { this.constructor = child; } ctor.prototype = parent.prototype; child.prototype = new ctor(); child.__super__ = parent.prototype; return child; },
    hasProp = {}.hasOwnProperty;

  min = Math.min, max = Math.max;

  DerivedList = require('../list').DerivedList;

  Varying = require('../../core/varying').Varying;

  TakenList = (function(superClass) {
    extend(TakenList, superClass);

    function TakenList(parent, number1) {
      var elem, i, idx, len, ref, take;
      this.parent = parent;
      this.number = number1;
      TakenList.__super__.constructor.call(this);
      this.number = Varying.of(this.number);
      this.reactTo(this.number, false, (function(_this) {
        return function() {
          return _this._rebalance();
        };
      })(this));
      take = this._take();
      ref = this.parent.list;
      for (idx = i = 0, len = ref.length; i < len; idx = ++i) {
        elem = ref[idx];
        if (idx < take) {
          this._add(elem, idx);
        }
      }
      this.listenTo(this.parent, 'added', (function(_this) {
        return function(elem, idx) {
          return _this._add(elem, idx);
        };
      })(this));
      this.listenTo(this.parent, 'moved', (function(_this) {
        return function(elem, idx, oldIdx) {
          return _this._moveElem(elem, oldIdx, idx);
        };
      })(this));
      this.listenTo(this.parent, 'removed', (function(_this) {
        return function(_, idx) {
          return _this._removeAt(idx);
        };
      })(this));
    }

    TakenList.prototype._take = function() {
      var number;
      number = this.number.get();
      if (number < 0) {
        return max(0, this.parent.list.length + number);
      } else {
        return min(this.number.get(), this.parent.list.length);
      }
    };

    TakenList.prototype._add = function(elem, idx, take) {
      if (take == null) {
        take = this._take();
      }
      if (idx < take) {
        TakenList.__super__._add.call(this, [elem], idx);
      }
      if (this.list.length > take) {
        this._removeAt(take);
      }
    };

    TakenList.prototype._moveElem = function(elem, oldIdx, newIdx) {
      var take;
      take = this._take();
      if (oldIdx < take) {
        if (newIdx < take) {
          this._moveAt(oldIdx, newIdx);
        } else {
          this._removeAt(oldIdx);
        }
      } else if (newIdx < take) {
        this._add(elem, newIdx);
      }
    };

    TakenList.prototype._removeAt = function(idx) {
      TakenList.__super__._removeAt.call(this, idx);
      if (this.list.length < this._take()) {
        this._add(this.parent.list[this.list.length], this.list.length);
      }
    };

    TakenList.prototype._rebalance = function() {
      var take;
      take = this._take();
      if (this.list.length < take) {
        while (this.list.length !== take) {
          this._add(this.parent.at_(this.list.length), this.list.length);
        }
      } else if (this.list.length > take) {
        while (this.list.length !== take) {
          this._removeAt(take);
        }
      }
    };

    return TakenList;

  })(DerivedList);

  module.exports = {
    TakenList: TakenList
  };

}).call(this);