// JavaScript Document

function link_init() {
	var img_div = document.getElementById("imgNav");
	var img_anchors = img_div.getElementsByTagName("a");
	var arr_length = img_src_arr.length;
	var first_ix = find_first_ix(cur_ix, arr_length);
	set_img_nav(first_ix, img_anchors, arr_length);	
	
	for (var i=0; i<img_anchors.length; i++) {	
		img_anchors[i].onclick = function() {
			var img_ix = this.getAttribute("title");
			change_main(img_ix, arr_length, img_anchors); 
			cur_ix = img_ix;
		}
	}
	
	var next_image = document.getElementById("next");
	next_image.onclick = function() {
	cur_ix++
	if(cur_ix  == arr_length) cur_ix = 0;
	change_main(cur_ix, arr_length, img_anchors);		
	}
	var prev_image = document.getElementById("previous");
	prev_image.onclick = function() {
	cur_ix--
	if(cur_ix  == -1) cur_ix = arr_length-1;
	change_main(cur_ix, arr_length, img_anchors);		
	}
	var next_5 = document.getElementById("next_five");
	next_5.onclick = function() {

	cur_ix = find_next5(parseInt(cur_ix), arr_length, "next") ;
		
	change_main(cur_ix, arr_length, img_anchors);		
	}
	var prev_5 = document.getElementById("prev_five");
	prev_5.onclick = function() {	
	cur_ix = find_next5(parseInt(cur_ix), arr_length, "prev") ;	
	change_main(cur_ix, arr_length, img_anchors);		
	}
}
function change_main(img_ix, arr_length, img_anchors) {
	var main_img = document.getElementById("main_img");
	main_img.setAttribute("src" , "i/large/" +img_src_arr[img_ix]);
	main_img.setAttribute("width" , img_w_arr[img_ix]);		
	main_img.setAttribute("height" , img_h_arr[img_ix]);		
	main_img.setAttribute("title" , img_name_arr[img_ix]);
	var the_name = document.getElementById("name_h2");
	the_name.innerHTML = img_name_arr[img_ix];
	var the_text = document.getElementById("text_p");
	the_text.innerHTML = img_text_arr[img_ix];
	set_img_nav(find_first_ix(img_ix, arr_length), img_anchors, arr_length);
}



function set_img_nav(first_ix, img_anchors, arr_length) {
	for (var i=0; i<img_anchors.length; i++) {		
		img_anchors[i].style.backgroundImage = "url(i/small/" +img_src_arr[first_ix]+ ")";
		img_anchors[i].setAttribute("title" , first_ix);
		first_ix++;
		if(first_ix  == arr_length) first_ix = 0;
	}
}

function find_first_ix(mid_ix, num_imgs) {
	if(num_imgs == 1) {
		 var first = 0;
		 return first;
	 }
	else if(num_imgs == 2) {
		var first = (mid_ix == 0) ? 0 : 1;
		return first;
	}
	else if(num_imgs > 2) {
		if(mid_ix > 1) {
			var first =  mid_ix - 2;
			return first;
			}
		else {
			var first = (mid_ix == 0) ? num_imgs - 2 : num_imgs - 1;
			return first;
			}
	}
}
function find_next5(cur_ix, num_imgs, next) {

	if(num_imgs == 1) return 0;
	if(num_imgs == 2) {
		return (cur_ix == 1) ? 0 : 1;
	}
	
	if(num_imgs == 3) {
		if(cur_ix == 0) return 2;
		if(cur_ix == 1) return 0;
		else return 1;
	}
	if(num_imgs == 4) {
	if(cur_ix == 0) return 2;
	if(cur_ix == 1) return 3;
	if(cur_ix == 2) return 1;	
	else return 0;
	}

	if(next == "next") {
	cur_ix += 5;			
		if(cur_ix  == num_imgs) return 0;
		else if (cur_ix  == num_imgs +1) return 1;
		else if (cur_ix  == num_imgs +2) return 2;
		else if (cur_ix  == num_imgs +3) return 3;	
		else if (cur_ix  == num_imgs +4) return 4;
		else return cur_ix;
	}
	else {
	cur_ix -= 5;	
		if(cur_ix  == -1) return num_imgs - 1;
		else if (cur_ix  == -2)  return num_imgs - 2;
		else if (cur_ix  ==  -3) return num_imgs - 3;
		else if (cur_ix  ==  -4)  return num_imgs - 4;	
		else if (cur_ix  ==  -5)  return num_imgs - 5;
		else return  cur_ix;
	}
}