window.onload = init;

function init() {
	if(document.getElementById('big_pic')) {
			
		//write gallery-nav
		galleryNav=document.createElement('p')
		galleryNav.id='gallery_nav'
		galleryNav.innerHTML='<a id="left">&lt;</a>&nbsp; <span id="picnr">1</span>&nbsp; <a id="right">&gt;</a>&nbsp; <a id="infolink">Information</a>'
		mainDiv=document.getElementById('main')
		mainDiv.insertBefore(galleryNav,mainDiv.firstChild)
		
		//get thumbnails
		thumbs=new Array()
		col=document.getElementsByTagName('img') //return HTMLCollection, not(!) Array
		for(i=0;i<col.length;i++) 
			thumbs.push(col[i]);
		thumbs.shift()
		
		//information-text
		var infolink=document.getElementById('infolink');
		infolink.onclick = toggleDisplay;
		
		//prev-link
		var left=document.getElementById('left')
		left.onclick=previous
	
		//next-link
		var right=document.getElementById('right')
		right.onclick=next
	
		//update picnr if you click on thumbnails, too
		for(i=0;i<thumbs.length;i++) {
			thumbs[i].onclick=updatePicnr
		}
	}	
}


//Information
function toggleDisplay() {
	var tags=document.getElementsByTagName('div');
	for (var i=0; i<tags.length; i++) {
		if(tags[i].className=='body') { //only 1 post per page!
			document.getElementById('big_pic').innerHTML = '<div class="schmale_Spalte">' + tags[i].innerHTML + '</div>';
			break;
		}
	}
}


function previous() { 
	pic_nr=document.getElementById('picnr')
	if(pic_nr.innerHTML>1) {
		pic_nr.innerHTML--
	} else {
		pic_nr.innerHTML=thumbs.length
	}
	changeImage(pic_nr.innerHTML)
}
function next() { 
	pic_nr = document.getElementById('picnr')
	if(pic_nr.innerHTML<thumbs.length) {
		pic_nr.innerHTML++
	} else {
		pic_nr.innerHTML=1
	}	
	changeImage(pic_nr.innerHTML)
}
function changeImage(nr) {
	pic_id=thumbs[--nr].alt.replace('_thumb', '');
	new Ajax.Updater('big_pic', '/galleries/update_big_pic/'+pic_id, {asynchronous:true, evalScripts:true});
}
function updatePicnr() {
	pic_nr=document.getElementById('picnr')
	for(i=0;i<thumbs.length;i++) {
		if(thumbs[i].alt==this.alt)
			pic_nr.innerHTML=i+1
	}	
}