expanded-computed.filterBy

import Ember from "ember";

let STEP_GUID = 0;
const {
  A,
  computed,
  defineProperty,
  get
  } = Ember;

const Descriptor = computed(function() {}).constructor;

function ExpandedFilterByProperty(array, path, value) {
  this.isDescriptor = true;

  if (path.indexOf('@each') !== -1) {
    throw new Error('Using @each in an expanded-filter-by is not allowed');
  }

  let stepPath;
  let subPath;
  let stepName;
  let leafValue;
  let watchPath;

  if (path.indexOf('.') !== -1) {
    subPath = path.split('.');

    if (subPath.length > 2) {
      throw new Error('Expanding @each more than two leafs in an expanded-filter-by is not allowed');
    }

    // this is the new step we need to create for this computed to function
    stepName = `-computed-filter-by-step-${STEP_GUID++}`;
    leafValue = subPath.shift();
    stepPath = `${array}.@each.${leafValue}`;

    // this is the new path that uses the step
    watchPath = `${stepName}.@each.${subPath[0]}`;
  }

  this.setup = function(context /*, key*/) {
    // creates the step
    defineProperty(context, stepName, computed(stepPath, function() {
      let v = this.get(array);

      if (v) {
        return v.map(function(i) {
          return get(i, leafValue);
        });
      }
      return null;
    }));
  };

  this._dependentKeys = [watchPath];

  this._getter = function() {
    let arr = new A(this.get(array));
    return arr.filterBy(path, value);
  };

  this._meta = undefined;
  this._readOnly = true;
  this._suspended = undefined;
  this._volatile = false;
}

ExpandedFilterByProperty.prototype = new Descriptor();

export default function expandedFilterByProperty(array, path, value) {
  return new ExpandedFilterByProperty(array, path, value);
}