'use strict';

let bililiteRange; // create one global variable

(function(){
	
const datakey = Symbol(); // use as the key to modify elements.

bililiteRange = function(el){
	var ret;
	if (el.setSelectionRange){
		// Element is an input or textarea 
		// note that some input elements do not allow selections
		try{
			el.selectionStart = el.selectionStart;
			ret = new InputRange();
		}catch(e){
			ret = new NothingRange();
		}
	}else{
		// Standards, with any other kind of element
		ret = new W3CRange();
	}
	ret._el = el;
	// determine parent document, as implemented by John McLear <john@mclear.co.uk>
	ret._doc = el.ownerDocument;
	ret._win = ret._doc.defaultView;
	ret._bounds = [0, ret.length];
	
	// selection tracking. We want clicks to set the selection to the clicked location but tabbing in or element.focus() should restore
	// the selection to what it was.
	// There's no good way to do this. I just assume that a mousedown (or a drag and drop
	// into the element) within 100 ms of the focus event must have caused the focus, and
	// therefore we should not restore the selection.
	if (!(el[datakey])){ // we haven't processed this element yet	
		const data = createDataObject (el);
		startupHooks.forEach ( hook => hook (el, ret, data) );
	}	
	return ret;
}

bililiteRange.version = 3.2;

const startupHooks = new Set();
bililiteRange.addStartupHook = fn => startupHooks.add(fn);
startupHooks.add (trackSelection);
startupHooks.add (fixInputEvents);
startupHooks.add (correctNewlines);

function trackSelection (element, range, data){
	data.selection = [0,0];
	range.listen('focusout', evt => data.selection = range._nativeSelection() );	
	range.listen('mousedown', evt => data.mousetime = evt.timeStamp );
	range.listen('drop', evt => data.mousetime = evt.timeStamp );
	range.listen('focus', evt => {
		if ('mousetime' in data && evt.timeStamp - data.mousetime < 100) return;
		range._nativeSelect(range._nativeRange(data.selection))
	})
}

function fixInputEvents (element, range, data){
	// DOM 3 input events, https://www.w3.org/TR/input-events-1/
	// have a data field with the text inserted, but thatisn't enough to fully describe the change;
	// we need to know the old text (or at least its length)
	// and *where* the new text was inserted.
	// So we enhance input events with that information. 
	// the "newText" should always be the same as the 'data' field, if it is defined
	data.oldText = range.all();
	data.liveRanges = new Set();
	range.listen('input', evt => {
		const newText = range.all();
		if (!evt.bililiteRange){
			evt.bililiteRange = diff (data.oldText, newText);
			if (evt.bililiteRange.unchanged){
				// no change. Assume that whatever happened, happened at the selection point (and use whatever data the browser gives us).
				evt.bililiteRange.start = range.clone().bounds('selection')[1] - (evt.data || '').length;
			}
		}
		data.oldText = newText;
		
		// Also update live ranges on this element
		data.liveRanges.forEach( rng => {
			const start = evt.bililiteRange.start;
			const oldend = start + evt.bililiteRange.oldText.length;
			const newend = start + evt.bililiteRange.newText.length;
			// adjust bounds; this tries to emulate the algorithm that Microsoft Word uses for bookmarks
			let [b0, b1] = rng.bounds();
			if (b0 <= start){
				// no change
			}else if (b0 > oldend){
				b0  += newend - oldend;
			}else{
				b0  = newend;
			}
			if (b1 < start){
				// no change
			}else if (b1 >= oldend){
				b1 += newend - oldend;
			}else{
				b1 = start;
			}
			rng.bounds([b0, b1]);				
		})
	});
}

function diff (oldText, newText){
	// Try to find the changed text, assuming it was a continuous change
	if (oldText == newText){
		return {
			unchanged: true,
			start: 0,
			oldText,
			newText
		}
	}

	const oldlen = oldText.length;
	const	newlen = newText.length;
	for (var i = 0; i < newlen && i < oldlen; ++i){
		if (newText.charAt(i) != oldText.charAt(i)) break;
	}
	const start = i;
	for (i = 0; i < newlen && i < oldlen; ++i){
		let newpos = newlen-i-1, oldpos = oldlen-i-1;
		if (newpos < start || oldpos < start) break;
		if (newText.charAt(newpos) != oldText.charAt(oldpos)) break;
	}
	const oldend = oldlen-i;
	const newend = newlen-i;
	return {
		start,
		oldText: oldText.slice(start, oldend),
		newText: newText.slice(start, newend)
	}
};
bililiteRange.diff = diff; // expose

function correctNewlines (element, range, data){
	// we need to insert newlines rather than create new elements, so character-based calculations work
	range.listen('paste', evt => {
		if (evt.defaultPrevented) return;
		// windows adds \r's to clipboard!
		range.clone().bounds('selection').
			text(evt.clipboardData.getData("text/plain").replace(/\r/g,''), {inputType: 'insertFromPaste'}).
			bounds('endbounds').
			select().
			scrollIntoView();
		evt.preventDefault();
	});
	range.listen('keydown', function(evt){
		if (evt.ctrlKey || evt.altKey || evt.shiftKey || evt.metaKey) return;
		if (evt.defaultPrevented) return;
		if (evt.key == 'Enter'){
			range.clone().bounds('selection').
				text('\n', {inputType: 'insertLineBreak'}).
				bounds('endbounds').
				select().
				scrollIntoView();
			evt.preventDefault();
		}
	});
}

// convenience function for defining input events
function inputEventInit(type, oldText, newText, start, inputType){
	return {
		type,
		inputType,
		data: newText,
		bubbles: true,
		bililiteRange: {
			unchanged: (oldText == newText),
			start,
			oldText,
			newText
		}
	};
}

// base class
function Range(){}
Range.prototype = {
	 // allow use of range[0] and range[1] for start and end of bounds 
	get 0(){
		return this.bounds()[0];
	},
	set 0(x){
		this.bounds([x, this[1]]);
		return x;
	},
	get 1(){
		return this.bounds()[1];
	},
	set 1(x){
		this.bounds([this[0], x]);
		return x;
	},
	all: function(text){
		if (arguments.length){
			return this.bounds('all').text(text, {inputType: 'insertReplacementText'});
		}else{
			return this._el[this._textProp];
		}
	},
	bounds: function(s){
		if (typeof s === 'number'){
			this._bounds = [s,s];
		}else if (bililiteRange.bounds[s]){
			this.bounds(bililiteRange.bounds[s].apply(this, arguments));
		}else if (s && s.bounds){
			this._bounds = s.bounds(); // copy bounds from an existing range
		}else if (s){
			this._bounds = s; // don't do error checking now; things may change at a moment's notice
		}else{
			// constrain bounds now
			var b = [
				Math.max(0, Math.min (this.length, this._bounds[0])),
				Math.max(0, Math.min (this.length, this._bounds[1]))
			];
			b[1] = Math.max(b[0], b[1]);
			return b;
		}
		return this; // allow for chaining
	},
	clone: function(){
		return bililiteRange(this._el).bounds(this.bounds());
	},
	get data(){
		return this._el[datakey];
	},
	dispatch: function(opts = {}){
		var event = new Event (opts.type, opts);
		event.view = this._win;
		for (let prop in opts) try { event[prop] = opts[prop] } catch(e){}; // ignore read-only errors for properties that were copied in the previous line
		this._el.dispatchEvent(event); // note that the event handlers will be called synchronously, before the "return this;"
		return this;
	},
	get document() {
		return this._doc;
	},
	dontlisten: function (type, func = console.log){
		this._el.removeEventListener(type, func);
		return this;
	},
	get element() {
		return this._el
	},
	get length() {
		return this._el[this._textProp].length;
	},
	live (on = true){
		this.data.liveRanges[on ? 'add' : 'delete'](this);
		return this;
	},
	listen: function (type, func = console.log){
		this._el.addEventListener(type, func);
		return this;
	},
	scrollIntoView: function(scroller = (top => this._el.scrollTop = top) ){
		var top = this.top();
		// scroll into position if necessary
		if (this._el.scrollTop > top || this._el.scrollTop+this._el.clientHeight < top){
			scroller.call(this._el, top);
		}
		return this;
	},
	select: function(){
		var b = this.data.selection = this.bounds();
		if (this._el === this._doc.activeElement){
			// only actually select if this element is active!
			this._nativeSelect(this._nativeRange(b));
		}
		this.dispatch({type: 'select', bubbles: true});
		return this; // allow for chaining
	},
	selection: function(text){
		if (arguments.length){
			return this.bounds('selection').text(text).bounds('endbounds').select();
		}else{
			return this.bounds('selection').text();
		}
	},
	sendkeys: function (text){
		this.data.sendkeysOriginalText = this.text();
		this.data.sendkeysBounds = undefined;
		function simplechar (rng, c){
			if (/^{[^}]*}$/.test(c)) c = c.slice(1,-1);	// deal with unknown {key}s
			rng.text(c).bounds('endbounds');
		}
		text.replace(/{[^}]*}|[^{]+|{/g, part => (bililiteRange.sendkeys[part] || simplechar)(this, part, simplechar) );
		this.bounds(this.data.sendkeysBounds);
		this.dispatch({type: 'sendkeys', detail: text});
		return this;
	},
	text: function(text, {inputType = 'insertText'} = {}){
		if ( text !== undefined ){
			let eventparams = [this.text(), text, this[0], inputType];
			this.dispatch (inputEventInit('beforeinput',...eventparams));
			this._nativeSetText(text, this._nativeRange(this.bounds()));
			this[1] = this[0]+text.length;
			this.dispatch (inputEventInit('input',...eventparams));
			return this; // allow for chaining
		}else{
			return this._nativeGetText(this._nativeRange(this.bounds()));
		}
	},
	top: function(){
		return this._nativeTop(this._nativeRange(this.bounds()));
	},
	get window() {
		return this._win;
	},
	wrap: function (n){
		this._nativeWrap(n, this._nativeRange(this.bounds()));
		return this;
	},
};

// allow extensions ala jQuery
bililiteRange.prototype = Range.prototype;
bililiteRange.extend = function(fns){
	Object.assign(bililiteRange.prototype, fns);
};

bililiteRange.override = (name, fn) => {
	const oldfn = bililiteRange.prototype[name];
	bililiteRange.prototype[name] = function(){
		const oldsuper = this.super;
		this.super = oldfn;
		const ret = fn.apply(this, arguments);
		this.super = oldsuper;
		return ret;
	};
}

//bounds functions
bililiteRange.bounds = {
	all: function() { return [0, this.length] },
	start: function() { return 0 },
	end: function() { return this.length },
	selection: function() {
		if (this._el === this._doc.activeElement){
			this.bounds ('all'); // first select the whole thing for constraining
			return this._nativeSelection();
		}else{
			return this.data.selection;
		}
	},
	startbounds: function() { return  this[0] },
	endbounds: function() { return  this[1] },
	union: function (name,...rest) {
		const b = this.clone().bounds(...rest);
		return [ Math.min(this[0], b[0]), Math.max(this[1], b[1]) ];
	},
	intersection: function (name,...rest) {
		const b = this.clone().bounds(...rest);
		return [ Math.max(this[0], b[0]), Math.min(this[1], b[1]) ];
	}
};

// sendkeys functions
bililiteRange.sendkeys = {
	'{tab}': function (rng, c, simplechar){
		simplechar(rng, '\t'); // useful for inserting what would be whitespace
	},
	'{newline}': function (rng){
		rng.text('\n', {inputType: 'insertLineBreak'}).bounds('endbounds');
	},
	'{backspace}': function (rng){
		var b = rng.bounds();
		if (b[0] == b[1]) rng.bounds([b[0]-1, b[0]]); // no characters selected; it's just an insertion point. Remove the previous character
		rng.text('', {inputType: 'deleteContentBackward'}); // delete the characters and update the selection
	},
	'{del}': function (rng){
		var b = rng.bounds();
		if (b[0] == b[1]) rng.bounds([b[0], b[0]+1]); // no characters selected; it's just an insertion point. Remove the next character
		rng.text('', {inputType: 'deleteContentForward'}).bounds('endbounds'); // delete the characters and update the selection
	},
	'{rightarrow}':  function (rng){
		var b = rng.bounds();
		if (b[0] == b[1]) ++b[1]; // no characters selected; it's just an insertion point. Move to the right
		rng.bounds([b[1], b[1]]);
	},
	'{leftarrow}': function (rng){
		var b = rng.bounds();
		if (b[0] == b[1]) --b[0]; // no characters selected; it's just an insertion point. Move to the left
		rng.bounds([b[0], b[0]]);
	},
	'{selectall}': function (rng){
		rng.bounds('all');
	},
	'{selection}': function (rng){
		// insert the characters without the sendkeys processing
		rng.text(rng.data.sendkeysOriginalText).bounds('endbounds');
	},
	'{mark}': function (rng){
		rng.data.sendkeysBounds = rng.bounds();
	}
};
// Synonyms from the DOM standard (http://www.w3.org/TR/DOM-Level-3-Events-key/)
bililiteRange.sendkeys['{Enter}'] = bililiteRange.sendkeys['{enter}'] = bililiteRange.sendkeys['{newline}'];
bililiteRange.sendkeys['{Backspace}'] = bililiteRange.sendkeys['{backspace}'];
bililiteRange.sendkeys['{Delete}'] = bililiteRange.sendkeys['{del}'];
bililiteRange.sendkeys['{ArrowRight}'] = bililiteRange.sendkeys['{rightarrow}'];
bililiteRange.sendkeys['{ArrowLeft}'] = bililiteRange.sendkeys['{leftarrow}'];

// an input element in a standards document. "Native Range" is just the bounds array
function InputRange(){}
InputRange.prototype = new Range();
InputRange.prototype._textProp = 'value';
InputRange.prototype._nativeRange = function(bounds) {
	return bounds || [0, this.length];
};
InputRange.prototype._nativeSelect = function (rng){
	this._el.setSelectionRange(rng[0], rng[1]);
};
InputRange.prototype._nativeSelection = function(){
	return [this._el.selectionStart, this._el.selectionEnd];
};
InputRange.prototype._nativeGetText = function(rng){
	return this._el.value.substring(rng[0], rng[1]);
};
InputRange.prototype._nativeSetText = function(text, rng){
	var val = this._el.value;
	this._el.value = val.substring(0, rng[0]) + text + val.substring(rng[1]);
};
InputRange.prototype._nativeEOL = function(){
	this.text('\n');
};
InputRange.prototype._nativeTop = function(rng){
	if (rng[0] == 0) return 0; // the range starts at the top
	// I can't remember where I found this clever hack to find the location of text in a text area
	var clone = this._el.cloneNode(true);
	clone.style.visibility = 'hidden';
	clone.style.position = 'absolute';
	this._el.parentNode.insertBefore(clone, this._el);
	clone.style.height = '1px';
	clone.value = this._el.value.slice(0, rng[0]);
	var top = clone.scrollHeight;
	// this gives the bottom of the text, so we have to subtract the height of a single line
	clone.value = 'X';
	top -= clone.scrollHeight;
	clone.parentNode.removeChild(clone);
	return top;
}
InputRange.prototype._nativeWrap = function() {throw new Error("Cannot wrap in a text element")};

function W3CRange(){}
W3CRange.prototype = new Range();
W3CRange.prototype._textProp = 'textContent';
W3CRange.prototype._nativeRange = function (bounds){
	var rng = this._doc.createRange();
	rng.selectNodeContents(this._el);
	if (bounds){
		w3cmoveBoundary (rng, bounds[0], true, this._el);
		rng.collapse (true);
		w3cmoveBoundary (rng, bounds[1]-bounds[0], false, this._el);
	}
	return rng;					
};
W3CRange.prototype._nativeSelect = function (rng){
	this._win.getSelection().removeAllRanges();
	this._win.getSelection().addRange (rng);
};
W3CRange.prototype._nativeSelection = function (){
	// returns [start, end] for the selection constrained to be in element
	var rng = this._nativeRange(); // range of the element to constrain to
	if (this._win.getSelection().rangeCount == 0) return [this.length, this.length]; // append to the end
	var sel = this._win.getSelection().getRangeAt(0);
	return [
		w3cstart(sel, rng),
		w3cend (sel, rng)
	];
};
W3CRange.prototype._nativeGetText = function (rng){
	return rng.toString();
};
W3CRange.prototype._nativeSetText = function (text, rng){
	rng.deleteContents();
	rng.insertNode (this._doc.createTextNode(text));
	this._el.normalize(); // merge the text with the surrounding text
};
W3CRange.prototype._nativeEOL = function(){
	var rng = this._nativeRange(this.bounds());
	rng.deleteContents();
	var br = this._doc.createElement('br');
	br.setAttribute ('_moz_dirty', ''); // for Firefox
	rng.insertNode (br);
	rng.insertNode (this._doc.createTextNode('\n'));
	rng.collapse (false);
};
W3CRange.prototype._nativeTop = function(rng){
	if (this.length == 0) return 0; // no text, no scrolling
	if (rng.toString() == ''){
		var textnode = this._doc.createTextNode('X');
		rng.insertNode (textnode);
	}
	var startrng = this._nativeRange([0,1]);
	var top = rng.getBoundingClientRect().top - startrng.getBoundingClientRect().top;
	if (textnode) textnode.parentNode.removeChild(textnode);
	return top;
}
W3CRange.prototype._nativeWrap = function(n, rng) {
	rng.surroundContents(n);
};

// W3C internals
function nextnode (node, root){
	//  in-order traversal
	// we've already visited node, so get kids then siblings
	if (node.firstChild) return node.firstChild;
	if (node.nextSibling) return node.nextSibling;
	if (node===root) return null;
	while (node.parentNode){
		// get uncles
		node = node.parentNode;
		if (node == root) return null;
		if (node.nextSibling) return node.nextSibling;
	}
	return null;
}
function w3cmoveBoundary (rng, n, bStart, el){
	// move the boundary (bStart == true ? start : end) n characters forward, up to the end of element el. Forward only!
	// if the start is moved after the end, then an exception is raised
	if (n <= 0) return;
	var node = rng[bStart ? 'startContainer' : 'endContainer'];
	if (node.nodeType == 3){
	  // we may be starting somewhere into the text
	  n += rng[bStart ? 'startOffset' : 'endOffset'];
	}
	while (node){
		if (node.nodeType == 3){
			var length = node.nodeValue.length;
			if (n <= length){
				rng[bStart ? 'setStart' : 'setEnd'](node, n);
				// special case: if we end next to a <br>, include that node.
				if (n == length){
					// skip past zero-length text nodes
					for (var next = nextnode (node, el); next && next.nodeType==3 && next.nodeValue.length == 0; next = nextnode(next, el)){
						rng[bStart ? 'setStartAfter' : 'setEndAfter'](next);
					}
					if (next && next.nodeType == 1 && next.nodeName == "BR") rng[bStart ? 'setStartAfter' : 'setEndAfter'](next);
				}
				return;
			}else{
				rng[bStart ? 'setStartAfter' : 'setEndAfter'](node); // skip past this one
				n -= length; // and eat these characters
			}
		}
		node = nextnode (node, el);
	}
}
var     START_TO_START                 = 0; // from the w3c definitions
var     START_TO_END                   = 1;
var     END_TO_END                     = 2;
var     END_TO_START                   = 3;
// from the Mozilla documentation, for range.compareBoundaryPoints(how, sourceRange)
// -1, 0, or 1, indicating whether the corresponding boundary-point of range is respectively before, equal to, or after the corresponding boundary-point of sourceRange. 
    // * Range.END_TO_END compares the end boundary-point of sourceRange to the end boundary-point of range.
    // * Range.END_TO_START compares the end boundary-point of sourceRange to the start boundary-point of range.
    // * Range.START_TO_END compares the start boundary-point of sourceRange to the end boundary-point of range.
    // * Range.START_TO_START compares the start boundary-point of sourceRange to the start boundary-point of range. 
function w3cstart(rng, constraint){
	if (rng.compareBoundaryPoints (START_TO_START, constraint) <= 0) return 0; // at or before the beginning
	if (rng.compareBoundaryPoints (END_TO_START, constraint) >= 0) return constraint.toString().length;
	rng = rng.cloneRange(); // don't change the original
	rng.setEnd (constraint.endContainer, constraint.endOffset); // they now end at the same place
	return constraint.toString().length - rng.toString().length;
}
function w3cend (rng, constraint){
	if (rng.compareBoundaryPoints (END_TO_END, constraint) >= 0) return constraint.toString().length; // at or after the end
	if (rng.compareBoundaryPoints (START_TO_END, constraint) <= 0) return 0;
	rng = rng.cloneRange(); // don't change the original
	rng.setStart (constraint.startContainer, constraint.startOffset); // they now start at the same place
	return rng.toString().length;
}

function NothingRange(){}
NothingRange.prototype = new Range();
NothingRange.prototype._textProp = 'value';
NothingRange.prototype._nativeRange = function(bounds) {
	return bounds || [0,this.length];
};
NothingRange.prototype._nativeSelect = function (rng){ // do nothing
};
NothingRange.prototype._nativeSelection = function(){
	return [0,0];
};
NothingRange.prototype._nativeGetText = function (rng){
	return this._el[this._textProp].substring(rng[0], rng[1]);
};
NothingRange.prototype._nativeSetText = function (text, rng){
	var val = this._el[this._textProp];
	this._el[this._textProp] = val.substring(0, rng[0]) + text + val.substring(rng[1]);
};
NothingRange.prototype._nativeEOL = function(){
	this.text('\n');
};
NothingRange.prototype._nativeTop = function(){
	return 0;
};
NothingRange.prototype._nativeWrap = function() {throw new Error("Wrapping not implemented")};


// data for elements, similar to jQuery data, but allows for monitoring with custom events
const monitored = new Set();

function signalMonitor(prop, value, element){
	const attr = `data-${prop}`;
	element.dispatchEvent(new CustomEvent(attr, {bubbles: true, detail: value}));
	try{
		element.setAttribute (attr, value); // illegal attribute names will throw. Ignore it			
	} finally { /* ignore */ }
}

function createDataObject (el){
	return el[datakey] = new Proxy(new Data(el), {
		set(obj, prop, value) {
			obj[prop] = value;
			if (monitored.has(prop)) signalMonitor(prop, value, obj.sourceElement);
			return true; // in strict mode, 'set' returns a success flag 
		}
	});
}

var Data = function(el) {
	Object.defineProperty(this, 'sourceElement', {
		value: el
	});
}

Data.prototype = {};
// for use with ex options. JSON.stringify(range.data) should return only the options that were
// both defined with bililiteRange.option() *and* actually had a value set on this particular data object.
// JSON.stringify (range.data.all) should return all the options that were defined.
Object.defineProperty(Data.prototype, 'toJSON', {
	value: function(){
		let ret = {};
		for (let key in Data.prototype) if (this.hasOwnProperty(key)) ret[key] = this[key];
		return ret;
	}
});
Object.defineProperty(Data.prototype, 'all', {
	get: function(){
		let ret = {};
		for (let key in Data.prototype) ret[key] = this[key];
		return ret;
	}
});
Object.defineProperty(Data.prototype, 'trigger', {
	value: function(){
		monitored.forEach(prop => signalMonitor (prop, this[prop], this.sourceElement));
	}
});

bililiteRange.createOption = function (name, desc = {}){
	desc = Object.assign({
		enumerable: true, // use these as the defaults
		writable: true,
		configurable: true
	}, Object.getOwnPropertyDescriptor(Data.prototype, name), desc);
	if ('monitored' in desc) monitored[desc.monitored ? 'add' : 'delete'](name);
	Object.defineProperty(Data.prototype, name, desc);
	return Data.prototype[name]; // return the default value
}

})();