//
// Rotator.js - Rotate content based on date and/or time
//
// Version 1.1 by David Methvin, Windows Magazine
//
// Tested with JavaScript on Netscape 3.0+ and IE 3.0+
//
// For info/examples see http://www.winmag.com/web/howto/rotator/


// Array to map unit names into actual time increments
function makeUnits() {
  this["h"] = 60*60*1000;       // hours
  this["d"] = 24*60*60*1000;    // days
  this["w"] = 7*24*60*60*1000;  // weeks
}
units = new makeUnits();

// Define a new Rotator event
//
//   whenstr    Date and time the event occurs. Note that time
//              is expressed in 24-hour format. Examples:
//                      12 Aug 1998 15:30
//                      17 Oct 1999     (assumes 00:00 for time)
//                      13 Dec          (assumes this year)
//                      07:30           (assumes today)
//              
//   runtime    How long the event runs. A number followed by
//              either h for hours, d for days, or w for weeks.
//
//   whatstr    Text that will be returned by the object if this
//              event is currently active.
//
function RotatorEvent(whenstr, runtime, whatstr) {

  // Create variable with current date and time
  var now = new Date();

  // Fix up short date and time formats
  if ( whenstr.length < 10 ) {
    if ( whenstr.substring(2,3) == ":" ) {
      // Prepend current date to time-only format
      whenstr = now.getDate() + now.toString().substring(3,8) + (now.getYear()) + " " + whenstr;
    } else {
      // Append current year to day-and-date format
      whenstr = whenstr + " " + (now.getYear());
    }
  }

  // Create and check variable from event date/time format
  var when = new Date(whenstr);
  if ( when == 0 || isNaN(when) ) alert("Bad date: "+whenstr);

  // Calcuate event duration based on units (hours, days, weeks)
  var unit = units[runtime.substring(runtime.length-1)];
  if ( typeof(unit) == "undefined" ) alert("Bad duration: "+runtime);
  var len = runtime.substring(0,runtime.length-1) * unit;

  // See if this event is currently active
  if ( now.getTime() < when.getTime() ) return;     // hasn't started yet
  if ( when.getTime()+len < now.getTime() ) return; // already finished

  // Event is active, assign its text string to the object
  this.content = whatstr;
}

function GetEvent() {
  return this.content;
}

// Create the content rotation object
function Rotator(str) { 
  this.content = str;           // default text for the event
  this.event   = RotatorEvent;  // function to define new events
  this.getEvent = GetEvent;     // function to get winning event
}