/*
 * Returns either true or false, depending if the regexp matches the passed
 * string.
 */
function
is_email (str)
{
    str = new String(str);

    res = (str.search('@') >= 1 &&
           str.lastIndexOf('.') >  str.search('@') &&
           str.lastIndexOf('.') >= str.length-5)

    return res;
}



/*
 * Checks if all needed fields have been filled before submitting the form.
 */
function
check_fields ()
{
    var cust_name   = document.getElementById ("Best_Name").value;
    var cust_street = document.getElementById ("Best_Strasse").value;
    var cust_city   = document.getElementById ("Best_Ort").value;
    var cust_tel    = document.getElementById ("Best_Telefon").value;
    var cust_mail   = document.getElementById ("Best_Email").value;
    var dec_fname   = document.getElementById ("Verst_Vorname").value;
    var dec_lname   = document.getElementById ("Verst_Nachname").value;

    if (cust_name   &&
        cust_street &&
        cust_city   &&
        cust_tel    &&
        dec_fname   &&
        dec_lname   &&
        cust_mail)
    {
        if (is_email (cust_mail)) {
            return check_date ();
        }
        else {
            window.alert ("Die von Ihnen angegebene Email-Adresse scheint " +
                "ungültig zu sein.");
        }
    }
    else {
        window.alert ("Bitte erfassen Sie alle erforderlichen Daten " +
            "(mit einem * gekennzeichnete Felder)");
    }

    return false;
}



/*
 * It is not allowed to order less than two days before the date of the
 * ceremony. This function checks the date fields and if necessary informs the
 * user of this.
 */
function
check_date ()
{
    var rc = false; /* init */

    /* Get the values of the date elements: */
    var selday   = document.getElementsByName ("Tag")[0].value;
    var selmonth = document.getElementsByName ("Monat")[0].value;
    var selyear  = document.getElementsByName ("Jahr")[0].value;
    var selhour  = document.getElementsByName ("Stunde")[0].value;
    var selmin   = document.getElementsByName ("Minute")[0].value;

    /* Check time input: */
    if (isNaN(selhour)      ||
        isNaN(selmin)       ||
        selhour > 24        ||
        selhour < 0         ||
        selmin  > 60        ||
        selmin  < 0)
    {
        /* If the selected time is invalid, manipulate the selected day so it
         * holds an invalid data. This will force the next comparison to throw
         * an alert box: */
        selday = "asdf";
    }

    /* Has a valid date been chosen? */
    if (is_valid_date (selday, selmonth, selyear)) {
        /* To get the days in between the current date and the one of the
         * ceremony, the selected date is converted into milliseconds before
         * subtracting it from the current timestamp: */
        var selms  = Date.parse(selmonth + "/" + selday + "/" + selyear + " " +
                                selhour  + ":" + selmin + ":00");

        /* Convert current datetime into milliseconds: */
        var curdat   = new Date();
        var curday   = curdat.getDate();
        var curmonth = curdat.getMonth() + 1;   /* starts with 0! */
        var curyear  = get_current_year();
        var curhour  = curdat.getHours();
        var curmin   = curdat.getMinutes();
        var curms    = Date.parse(curmonth +"/"+ curday + "/" + curyear + " " +
                                  curhour  + ":" + curmin + ":00");
        /* Add two days to the current datetime - the resulting datetime tells
         * the earliest possible ceremony: */
        var earliest = curms + 259200000;
        /* 72 hours * 60 minutes * 60 seconds * 1000 milliseconds */

        /* Date of ceremony in the past? */
        if (selms < curms) {
            window.alert ("Bitte wählen Sie einen zukünftigen Tag.");
        }
        else {
            /* Two days at least in between? */
            if (selms < earliest) {
                window.alert ("Die Bestellung muss mind. 3 Tage vor der " +
                    "Trauerfeier erfolgen.");
            }
            else {
                rc = true;
            }
        }
    }
    else {
        window.alert ("Bitte wählen Sie ein gültiges Datum der " + 
            "Trauerfeier aus.");
    }

    return rc;
}



/*
 * Checks if the passed date is valid. This check is done so no one does select
 * the 30th of february and so forth.
 */
function
is_valid_date (day, month, year)
{
    var rc = false; /* init return code */

    if (!isNaN(day)   ||        /* Are day and   */
        !isNaN(month) ||        /* month and     */
        !isNaN(year))           /* year numbers? */
    {
        var curyear = get_current_year ();

        /* Validate year: */
        if (year < curyear   ||
            year > curyear + 50)
        {
            return rc;
        }

        /* Validate month: */
        if (month < 0   ||
            month > 12)
        {
            return rc;
        }

        /* Table that assigns the number of days for each month:        */
        var month_table = new Array(31,     /* January                  */
                                    65535,  /* February, temp-value     */
                                    31,     /* March                    */
                                    30,     /* April                    */
                                    31,     /* May                      */
                                    30,     /* June                     */
                                    31,     /* July                     */
                                    31,     /* August                   */
                                    30,     /* September                */
                                    31,     /* October                  */
                                    30,     /* November                 */
                                    31      /* December                 */
                                    );

        /* For February a temp-value was assigned, because the number of days
         * for this month switch every year, but can be calculated: */
        if (((year % 4)   == 0)   &&
           ((year % 100) != 0)    ||
           ((year % 400) == 0))
        {
            month_table[1] = 29;
        }
        else {
            month_table[1] = 28;
        }

        /* Validate day: */
        if (day > 0 &&
            day <= month_table[month-1])
        {
            rc = true;  /* finally: valid date */
        }
    }

    return rc;
}



/*
 * Returns the current year, 4 bytes.
 */
function
get_current_year ()
{
    var dato = new Date (); /* create new dateobject */
    var year = dato.getYear();

    /* Some browser use only two bytes for saving the current year; so the
     * following check will add 1900 years if neccessary: */
    if (year < 999) {
        year += 1900;
    }

    return year;
}



/*
 * If an input field with the passed id can be found, a popup opens and lists
 * all possible sayings. The user is able to click onto once which auto-closes
 * the popup and writes the saying into the matching field.
 */
function
choose_saying (input_name)
{
    /* Does input field exist? */
    if (document.getElementById (input_name)) {
        // Calculate the screen coordinates where the window should open:
        var width  = 550;
        var height = 400;
        var x      = screen.availWidth/2  - width/2;
        var y      = screen.availHeight/2 - height/2;

        var newwin = window.open("sprueche.php?for=" + input_name, "", 
            "width=" + width + ",height=" + height + ",left=" + x + 
            ",top=" + y + ",screenX=" + x + ",screenY=" + y + 
            ",scrollbars=yes");

    }
    else {
        window.alert ("Ungültiges Eingabefeld: " + input_name);
    }
}