/*

File: UserCalendarPreferences.js

Abstract: Defines JavaScript functionalities for the back of the 

          Reminders widget. Calls the Cocoa RemindersPlugIn plug-in 

          to fetch all iCal calendars. Updates or retrieves the 

          widget's custom preferredCalendars key.

Version: <1.0>

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*/

/* Indicate whether the back of the widget is showing some calendars */

var noCalendars = false;

/*

    Returns the value of the preferredCalendarKey key.

*/

function retrievePreferredCalendarKey()

{

    var retrievedKey = widget.preferenceForKey("preferredCalendars");

    var value = (retrievedKey && retrievedKey.length > 0) ? retrievedKey : "";

    return value;

}

/*

    Retrieves the user's calendar preferences. Returns an array that contains 

    the uids of calendars selected by users; the array will be empty if the 

    user never chooses any calendars.

*/

function userCalendarPreferences()

{

    /* Get the user's preferred calendars */ 

    preferredCalendars = retrievePreferredCalendarKey();    

    /* calendarUIDs is empty if the user did not previously select any calendars on the widget's back */

    /* All preferred calendars'uids are separated by a "&", break and place them into an array */

    var calendarUIDs = (preferredCalendars.length > 0) ? preferredCalendars.split(" & ") : new Array();

    return calendarUIDs;

}

/*

    Lists all available calendars on the back of the widget. By default all calendars are selected. 

    Calls the plug-in's calendars method to fetch these calendars. 

*/

function displayUserCalendarPreferences()

{   

    /* Clear the widget back's scroll area */

    clearResults("backContent","backScrollArea");

    /* Call the plug-in, check for available calendars if RemindersPlugIn exists and show an error message otherwise */

    if (RemindersPlugIn)

    {

        /* Get all available calendars */

        var calendars = RemindersPlugIn.calendars("");

        /* Get the user's preferred calendars */

        var calendarUIDs = userCalendarPreferences();

        /* Display all iCal calendars if calendars is not empty and an error message otherwise */

        if (calendars && calendars.length!=0) 

        {

            var scrollAreaDiv = document.getElementById("backContent");

            /* Iterate through calendars, which is an array of CalendarItems objects */

            for(var i=0; i<calendars.length; i++)

            {

                /* Create a checkbox */

                var color = createAnHTMLElement("input","input"+i,"","");

                color.setAttribute("type","checkbox");

                color.setAttribute("name","calendars");

                color.setAttribute("size","1");

                color.setAttribute("value",calendars[i].uid);

                /* Check all checkboxes on the widget's back if the user did not select any */

                if (calendarUIDs.length==0)

                {

                    color.checked = true;

                }

                else if ((calendarUIDs.length >0) & (contains(calendarUIDs,calendars[i].uid)))

                {

                    /* Check this box if its associated calendar was previuously selected */

                    color.checked = true;

                }

                else if ((calendarUIDs.length >0) & (!contains(calendarUIDs,calendars[i].uid)))

                {

                    /* Uncheck this box if its associated calendar was not previuously selected */

                    color.checked = false;

                }

                var container = createAnHTMLElement("div","","container","");

                container.appendChild(color);

                var title = document.createTextNode(calendars[i].title);

                container.appendChild(title);

                scrollAreaDiv.appendChild(container);

            }

            document.getElementById("backScrollArea").object.refresh();         

        }   

        else

        {

            /* Indicate iCal does not contain any calendars */  

            noCalendars = true;

            showErrorMessage(CALENDAR_ERR,"","backContent","backScrollArea");

        }

    }

    else

    {

        showErrorMessage(PLUGIN_ERR,"","backContent","backScrollArea");

    }

}

/*

    Fetches all calendars selected by the user. It returns false and shows a warning message and icon if

    the user left all calendar preferences unchecked. It updates the preferredCalendars key and returns 

    true if the user checked at least one calendar preference on the back of the widget.

*/

function retrieveSelectedCalendars()

{

    var preferences = new Array();

    /* Warning message and icon are shown whenever all calendar preferences are left unchecked on the widget's back */

    var warning = document.getElementById("warning");

    var indicator = document.getElementById("indicator");

    /* Reference to all checkboxes */

    var checkboxes = document.getElementsByName("calendars");

    var j = 0;

    /* Loop through all checkboxes */

    for(i=0; i<checkboxes.length; i++)

    {

        /* If this checkbox is selected, get its associated uid */

        if(checkboxes[i].checked==true)

        {

            preferences[j] = checkboxes[i].value;

            j++;

        }

    }

    /* Update the preferredCalendars key and return true if users selected some calendars.

       Show a warning message and icon and return false if users left all options unchecked. 

       Users must choose at least one of the calendar options before switching back to the front

       of the widget.

    */

    if (preferences.length>0)

    {

        /* Join all selected calendars'uids using a "&" */

        var preferredCalendarValues = preferences.join(" & ");

        if(window.widget)

        {

            /* Update the preferredCalendars key */

            widget.setPreferenceForKey(preferredCalendarValues,"preferredCalendars");

            /* Hide the warning message and icon if they are visible */

            warning.style.display = "none";

            indicator.style.display = "none";

            return true;

        }

    }

    else

    {

        /* Show the warning message and icon, users did not select any calendars (all checkboxes were left unchecked) */

        warning.style.display = "block";

        indicator.style.display = "block";

    }

    return false;

}

/*

    Determines whether an array structure contains a given parameter.

    Returns true if the array contains the specified element and false otherwise.

*/

function contains(array,element)

{

    /* Iterate through all objects in array */

    for (var index in array)

    {

        /* Compare each array's object with the specified element and return true if they are equal */

        if (array[index]==element)

        {

            return true;

        }

    }

    return false;

}

/*

    Called when the done button is clicked from the back of the widget.

    Calls the flipToFront function to take users to the front of the widget.

*/

function showFront(event)

{

    /* If noCalendars is true, then there are no calendars on the back of the widget.

       So, do not show the warning message and icon and let users go to the front of the widget. */

    if (noCalendars)

    {

        flipToFront();

    }

    else

    {

         /* noCalendars is set to false, so the back of the widget must be showing one or more calendars. 

            Let's make sure that users did not leave all options unchecked. */

        if (retrieveSelectedCalendars())

        {

            flipToFront();

        }

    }

}

/*

    Takes users from the back of the widget to its front.

    Calls the retrieveSelectedCalendars function to check whether users

    chose at least one option from the back of the widget. 

*/

function flipToFront()

{

    var front = document.getElementById("front");

    var back = document.getElementById("back");

    if (window.widget) 

    {

        widget.prepareForTransition("ToFront");

    }   

    /* Show the front of the widget and hide its back */    

    front.style.display = "block";

    back.style.display = "none";     

    if (window.widget) 

    {   

        /* Show events when the widget switches to its front */

        showEvents();

        setTimeout('widget.performTransition();', 0);

    }   

}