/*******************************/
/* EVENT LISTENER MANIPULATION */
/*******************************/

/*	Adds an event listener to a button (or other clickable element), attaching 
	it to both "click" and "keyup" events (for use with keyboard navigation).
	Optionally also attaches the listener to the 'mousedown' event, making the 
	element activate on mouse down instead of mouse up. */
Element.prototype.addActivateEvent = function(func, includeMouseDown) {
	let ael = this.activateEventListener = (event) => { if (event.button === 0 || event.key === ' ') func(event) };
	if (includeMouseDown) this.addEventListener("mousedown", ael);
	this.addEventListener("click", ael);
	this.addEventListener("keyup", ael);
}

/*	Removes event listener from a clickable element, automatically detaching it
	from all relevant event types. */
Element.prototype.removeActivateEvent = function() {
	let ael = this.activateEventListener;
	this.removeEventListener("mousedown", ael);
	this.removeEventListener("click", ael);
	this.removeEventListener("keyup", ael);
}

/***********/
/* UTILITY */
/***********/

String.prototype.hasPrefix = function (prefix) {
	return (this.lastIndexOf(prefix, 0) === 0);
}

/***********/
/* HELPERS */
/***********/

/*	This function sends a message to the background script (background.js), 
	which then updates the page action icon (i.e., the browser toolbar icon)
	to reflect whether killing stickies is enabled on the current page.
	*/
function updateIcon(shouldKillSticky, tabID) {
	chrome.runtime.sendMessage({ "killingStickies" : shouldKillSticky, "tabID": tabID });
}

/*	This is the code that actually does the sticky killing! It simply selects
	all elements whose 'position' CSS property has a computed value of either
	'sticky' or 'fixed', and removes those elements.
	*/
function killSticky() {
	console.log("Killing all stickies!");
	document.querySelectorAll('body *').forEach(element => {
		if (getComputedStyle(element).position === 'fixed' || 
			getComputedStyle(element).position === 'sticky') {
			element.remove();
		}
	});
	// Compensate for full-screen paywalls.
	restoreScrollability();
}

/*	Full-screen paywalls not only bring up sticky elements, they also make
	the page un-scrollable. This ensures that the page remains scrollable.
	*/
function restoreScrollability() {
	document.querySelectorAll("html, body").forEach(container => {
		container.style.setProperty("overflow-y", "auto", "important");
	});
}