/**
 * This file lists all the methods needed for invoking web help.
 * @requires jquery
 * @requires knockout
 */
define([
  "knockout",
  "jquery"
], function(ko, $) {
  /**
   * This file lists all the methods needed for invoking web help.
   * @class
   * @param {Object} parentContext The instance of [baseModel]{@linkcode BaseKOModel} for framework utility functions.
   * @alias Help
   * @memberof module:baseModel
   */
  "use strict";
  var HelpModel = function(parentContext) {
    /**
     * Assign <code>this</code> to <code>self</code>.
     * @member {Object}
     */
    var self = this;

    /**
     * Object to store the data of the web help configuration JSON.
     * @member {Object}
     */
    var jsonData = {};
    ko.utils.extend(self, parentContext);

    /**
     * The variable to hold the id for which web help needs to be opened.
     * @instance
     * @memberof Help
     * @alias webhelpID
     * @type {Observable.<String>}
     */
    self.webhelpID = ko.observable("");

    /**
     * In order to show webhelp on pressing the <code>F1</code> key, we have to modify (override) the default behavior of the <code>F1</code>
     * key. This function does that and calls a custom function [openWebHelpWindow]{@linkcode Help#openWebHelpWindow} which can be used to display custom
     * web help. Call to this function is implicit which follows the function definition.
     * @function showWebHelp
     * @memberof Help
     * @inner
     * @returns {void}
     */
    self.showWebHelp = function() {
      if ("onhelp" in window)
        window.onhelp = function() {
          self.openWebHelpWindow();
          return false;
        };
      else {
        var cancelKeyPress;
        document.onkeydown = function(evt) {
          cancelKeyPress = (evt.keyCode === 112);
          if (cancelKeyPress) {
            self.openWebHelpWindow();
            return false;
          }
        };
        document.onkeypress = function() {
          if (cancelKeyPress)
            return false;
        };
      }
    };

    /**
    * This function is used to parse the [webhelpID]{@linkcode Help#webhelpID} and thus determine and open the location of webhelp page using that.
    * @function parseLocationById
    * @memberof Help
    * @inner
    * @param {String} location  - This string contains the location of page the user is on and requesting the webhelp for.
    * @param {String} currentModule - This string contains the module for which the component exists.
    * @param {String} webhelpID  - This string contains the webhelpID of page the user is on and requesting the webhelp for.
    * @returns {void}
    */
    var parseLocationById = function(location, currentModule, webhelpID) {
      location += jsonData[currentModule][webhelpID];
      window.open(location, "_blank");
    };

    /**
     * This function handles the custom logic to display the user-defined webhelp on pressing <code>F1</code> key.
     * @function openWebHelpWindow
     * @memberof Help
     * @instance
     * @returns {void}
     */
    self.openWebHelpWindow = function() {
      var location = "/webhelp/Content/obdx/";
      var win = window.open("");
      window.oldOpen = window.open;
      // reassignment function
      window.open = function(url) {
        win.location = url;
        window.open = window.oldOpen;
        win.focus();
      };
      var currentModule = self.QueryParams.get("module");
      if (currentModule && !jsonData[currentModule]) {
        $.getJSON("../json/webhelpMappings/" + currentModule + ".json", function(data) {
          jsonData[currentModule] = data;
          parseLocationById(location, currentModule, self.webhelpID());
        }).fail(function() {
          window.open(location + "obdxintroduction.htm", "_blank");
        });
      } else {
        parseLocationById(location, currentModule, self.webhelpID());
      }
    };

    /**
     * This function sets the [webhelpID]{@linkcode Help#webhelpID} variable of the base-model from the components' [webhelpID]{@linkcode Help#webhelpID} defined inside the component
     * @function setwebhelpID
     * @memberof Help
     * @instance
     * @param {String} webhelpID  - This string contains the webhelpID of page the user is on and requesting the webhelp for.
     * @returns {void}
     */
    self.setwebhelpID = function(webhelpID) {
      this.webhelpID(webhelpID);
    };

    /**
     * Call to the showWebHelp function.
     */
    self.showWebHelp();
  };
  return HelpModel;
});