dev/js/src/state/manager.js

/**
 * Create a state manager object, that can deserialize and
 * serialize states of associated states.
 * At the moment this requires an element for serialization,
 * but it may very well serialize in a cookie.
 *
 * @author Nils Diewald
 */

"use strict";

define(['state'], function(stateClass) {

  return {
    // Create new state amanger.
    // Expects an object with a value
    // to contain the serialization of all states.
    create : function (element) {
      return Object.create(this)._init(element);
    },


    // Initialize state manager
    _init : function (element) {
      this._e = element;
      this._states = {};
      this._defaults = {};
      this._parse(element.value);

      return this;
    },


    // Parse a value and populate states
    _parse : function (value) {
      if (value == null || value == undefined || value == '')
        return;

      this._states = JSON.parse('{' + value + '}');
    },

    // Return element
    element : function() {
      return this._e;
    },

    // Return the string representation of all states
    toString : function () {

      if (this._states.size === 0)
        return undefined;
      
      return JSON.stringify(this._states).slice(1,-1);
    },


    // Update the query component for states
    _update : function () {
      this._e.setAttribute("value", this.toString());
    },


    // Create new state that is automatically associated
    // with the state manager
    newState : function (name, values, defValue) {

      const t = this;
      let s = stateClass.create(values);

      if (this._states[name] != undefined) {
        if (values.includes(this._states[name]))
          s.setIfNotYet(this._states[name]);
      };

      // Set default value
      // TODO: It would be better to make this part
      // of the state and serialize correctly using TOJSON()
      if (defValue !== undefined) {
        s.setIfNotYet(defValue);
        t._defaults[name] = defValue;
      };
      
      // Associate with dummy object
      s.associate({
        setState : function (value) {
          if (t._defaults[name] !== undefined && t._defaults[name] == value) {
            delete t._states[name];
          } else {
            t._states[name] = value;
          };
          t._update();
        }
      });
      
      // Load state
      if (t._states[name] !== undefined) {
        s.set(t._states[name]);
      };

      return s;
    }
  };
});