// ---------- SETUP THE ADVERTISING FOR OAH.ORG ---------- 

//-----------create articles object--------------
function setAdAttribute(year, month, day, image, link, advertiser) {
	this.year = year; 
	this.month = month; // Months are a 0 indexed array, so Jan = 0, Feb = 1, and so forth
	this.day = day;
	this.image = image;
	this.link = link;
	this.advertiser = advertiser;
}

//-----------create articles array--------------
var ads300x100 = new Array();

ads300x100[0] = new setAdAttribute('2010', '0', '14', 'iupress.jpg', 'http://www.iupress.indiana.edu/catalog/', 'IU Press');
ads300x100[1] = new setAdAttribute('2010', '11', '1', 'oxford.jpg', 'http://www.oxfordjournals.org/our_journals/', 'Oxford Press');
ads300x100[2] = new setAdAttribute('2010', '1', '01', 'uofillinois.jpg', 'http://www.press.uillinois.edu/', 'Illinois Press');
ads300x100[3] = new setAdAttribute('2010', '11', '25', 'yalepress.jpg', 'http://yalepress.yale.edu/yupbooks/home.asp', 'Yale Press');

var ads300x250 = new Array();
ads300x250[0] = new setAdAttribute('2010', '0', '14', 'thechronicle.jpg', 'http://www.thechronicle.com/', 'The Chronicle of Higher Education');

var ads468x60 = new Array();
ads468x60[0] = new setAdAttribute('2010', '0', '14', 'newyorktimes.jpg', 'http://www.newyorktimes.com/', 'New York Times');

var ads728x90 = new Array();
ads728x90[0] = new setAdAttribute('2010', '0', '14', 'npr.jpg', 'http://www.npr.com/', 'NPR');

function getAds(array, num_sold) {
	// empty array to hold the indexes of the selected ads
	var ads_for_page = [];
	
	var counter=0;
	while (counter<num_sold)
	  {
		var selected_ad = selectAd(array);
		var key = ads_for_page.exist(selected_ad);

		if (key == false) {
			ads_for_page.push(selected_ad);

			counter++;
		} 
	  }
	
	// build img string
	var img_string = "";
	
	for (i = 0; i < ads_for_page.length; i++) {
				img_string = img_string + '<a href="'+array[ads_for_page[i]].link+'" target="_blank"><img src="img/ads/'+array[ads_for_page[i]].image+'"/></a>';
			}
	
	//determine div type
	var ad_div;
		
	switch (array) {
		case (ads300x100): 
			ad_div = 'advertising';
			break;
			
		case (ads300x250): 
			ad_div = 'advertising';
			break;
			
		default:
			ad_div = 'advertising_banner';
			break;
	}
	
	// print to page
	document.write('<div id="'+ad_div+'"><h1><a href="#">Support our advertisers</a></h1>');
	document.write(img_string);
	document.write('</div>');
	
}

function selectAd(array) {
	
	// randomly select an index between 0 and the length of the supplied array.
	var max = array.length;
	var random_index = Math.floor(Math.random()*max);

	// get today's date and the expiration date for the ad at the random index.
	var today = new Date();
	var expiration = new Date();
	var year = array[random_index].year;
	var month = array[random_index].month;
	var day = array[random_index].day;
	expiration.setFullYear(year,month,day);
	
	// determine div type
	if (expiration<today)
		{
		getAd(array);
		}
			else
			{
			return random_index;
			}
}



// determines if an item exists in an array.
Array.prototype.exist=function(item) {
	for (i=0;i<this.length;i++) {
		if (this[i]==item) return true;
		}
	return false;
}