/*Singleton object*/
var tag_suggestion_list = {
	input_el: null,
	list_element: document.createElement('ol'),
	suggestion_elements: [],
	hover_last: -1,
}
tag_suggestion_list.list_element.setAttribute("class","tag-suggestion-list");
tag_suggestion_list.list_element.setAttribute("style","position:absolute;");

function appendTag(name){
	return function(event){
		var ie = tag_suggestion_list.input_el;
		var prev = ie.value.split(";");
		prev.pop();
		prev.push(name);
		ie.value = prev.join(";");
		ie.value += ";";
		ie.focus();
		tag_suggestion_list.list_element.style = "display:none;"; 
	}
}

function hoverTag(name, root){
	return function(event){
		var ie = tag_suggestion_list.input_el;
		if(ie.value.slice(-1) == ";"){//comming from another tab completion
			var prev = ie.value.slice(hover_last);

		}else{
			var prev = ie.value.split(";");
			prev.pop()
			prev.push(name)
			ie.value = prev.join(";");
		}
	}
}

/**
 * Stolen from medium.com/@jh3y
 * returns x, y coordinates for absolute positioning of a span within a given text input
 * at a given selection point
 * @param {object} input - the input element to obtain coordinates for
 * @param {number} selectionPoint - the selection point for the input
 */
function getCursorXY(input, selectionPoint){
	const {
		offsetLeft: inputX,
		offsetTop: inputY,
	} = input
	const div = document.createElement('div')
	const copyStyle = getComputedStyle(input)
	for (const prop of copyStyle) {
		div.style[prop] = copyStyle[prop]
	}
	const swap = '.'
	const inputValue = input.tagName === 'INPUT' ? input.value.replace(/ /g, swap) : input.value
	const textContent = inputValue.substr(0, selectionPoint)
	div.textContent = textContent
	if (input.tagName === 'TEXTAREA') div.style.height = 'auto'
	if (input.tagName === 'INPUT') div.style.width = 'auto'
	const span = document.createElement('span')
	span.textContent = inputValue.substr(selectionPoint) || '.'
	div.appendChild(span)
	document.body.appendChild(div)
	const { offsetLeft: spanX, offsetTop: spanY } = span
	document.body.removeChild(div)
	return {
		x: inputX + spanX,
		y: inputY + spanY,
	}
}

function display_suggestions(elem, sugg, event){
	//Check that the value hasn't change since we fired
	//off the request
	var tags_so_far = elem.value.split(";");
	recent = elem.value.split(";").pop().trim();
	if(recent == sugg[0]){
		var v = getCursorXY(elem,elem.value.length);
		var sugx = v.x;
		var sugy = v.y;
		var sty = `position:absolute; margin-left:${sugx}px;`;
		tag_suggestion_list.list_element.style = sty; 
		for(var i in tag_suggestion_list.suggestion_elements){
			tag_suggestion_list.list_element.removeChild(tag_suggestion_list.suggestion_elements[i]);

		}
		tag_suggestion_list.suggestion_elements = [];
		var hover_last = 0;
		for(var i in tags_so_far){
			hover_last += tags_so_far[i].length + 1;
		}
		tag_suggestion_list.hover_last = hover_last;
		for(var i in sugg){
			if(i == 0){
				continue;
			}
			var suggestion_el = document.createElement("li");
			var suggestion_but = document.createElement("input")
			suggestion_el.appendChild(suggestion_but);
			suggestion_but.setAttribute("type","button");
			suggestion_but.setAttribute("value",sugg[i]);
			suggestion_el.setAttribute("class"," button-clear tag-suggestion");
			tag_suggestion_list.list_element.appendChild(suggestion_el);
			tag_suggestion_list.suggestion_elements.push(suggestion_el);
			suggestion_but.onkeyup = function(event){
				if(event.key == "Tab"){
					hoverTag(event.target.value)(event);
				}else if(event.key == ";"){
					appendTag(event.target.value)(event);
				}

			}
			suggestion_but.onclick = function(event){
				appendTag(event.target.value)(event);
			}
			suggestion_but.onblur = function(event){
				var other_input = false;
				for(var i in tag_suggestion_list.suggestion_elements){
					if(tag_suggestion_list.suggestion_elements[i].firstChild == event.relatedTarget){
						other_input = true;
						break;
					}

				}
				if(!other_input){
					tag_suggestion_list.list_element.style = "display:none;"; 
				}
			}

		}
		if(tag_suggestion_list.suggestion_elements.length > 0){

			var last_element = tag_suggestion_list.suggestion_elements[tag_suggestion_list.suggestion_elements.length - 1];
			//last_element.firstChild.last_element = true;
			last_element.firstChild.onblur = function(event){
				tag_suggestion_list.suggestion_elements[0].firstChild.focus();

			}
		}
	}
}

function hint_tags(elem, event){
	//Get the most recent tag
	var recent = elem.value.split(";").pop().trim();
	if(recent.length > 0){
		//Ask the server for tags that look like this
		var xhr = new XMLHttpRequest();
		xhr.open("GET", "/_api?call=suggest&data=" + recent);
		xhr.onreadystatechange = function(e){
			if(xhr.readyState === 4){
				suggestions = xhr.response.split(";");
				display_suggestions(elem,suggestions, event);

			}
		}
		xhr.send()
	}
}

function init(){
	var head_el = document.head;
	var extra_css_el = document.createElement("link");
	document.head.appendChild(extra_css_el);
	extra_css_el.setAttribute("rel","stylesheet");
	extra_css_el.setAttribute("href","/_css/suggest_tags.css");
	var tag_el_list = document.getElementsByName("tags");
	console.assert(tag_el_list.length == 1);
	var tag_el = tag_el_list[0];
	tag_suggestion_list.input_el = tag_el;
	tag_el.onkeyup = function(event){
		hint_tags(tag_el, event);
	}
	tag_el.onblur = function(event){
		var not_suggestion = true;
		var ies = tag_suggestion_list.suggestion_elements;
		for(var i in ies){
			if(event.relatedTarget == ies[i].firstChild){
				not_suggestion = false;
				break;
			}
		}
		if(not_suggestion){
			tag_suggestion_list.list_element.style = "display:none;"; 
		}
	}

	var fieldset = tag_el.parentNode;
	fieldset.appendChild(tag_suggestion_list.list_element);
	var paste_el = document.getElementsByName("tags");
}
document.addEventListener("DOMContentLoaded",init,false);