// @ts-check
/** @param {Node | null} el */
const remove = (el) => { if (el) el.parentElement.removeChild(el) };

const stripPx = (s) => +s.slice(0, -2);

/** @param {string} tag
 * @param {string} cls
 * @returns HTMLElement
 */
function newEl(tag, cls) {
	const el = document.createElement(tag);
	el.classList.add(cls);
	return el;
}

/** @type {<T extends any[]>(fn: (...args: T) => void, t: number) => ((...args: T) => void)} */
function debounce(f, ms) {
	let t = Date.now();
	return (...args) => {
		const now = Date.now();
		if (now - t < ms) return;
		t = now;
		f(...args);
	};
}

const clsPrefix = "newsfoot-footnote-";
const CONTAINER_CLS = `${clsPrefix}container`;
const POPOVER_CLS = `${clsPrefix}popover`;

/**
 * @param {Node} content
 * @returns {HTMLElement}
 */
function footnoteMarkup(content) {
	const popover = newEl("div", POPOVER_CLS);
	popover.appendChild(content);
	return popover;
}

class Footnote {
	/**
	 * @param {Node} content
	 * @param {Element} fnref
	 */
	constructor(content, fnref) {
		this.popover = footnoteMarkup(content);
		this.style = window.getComputedStyle(this.popover);
		this.fnref = fnref;
		this.fnref.closest(`.${CONTAINER_CLS}`).appendChild(this.popover);
		this.reposition();
		
		/** @type {(ev:MouseEvent) => void} */
		this.clickoutHandler = (ev) => {
			if (!(ev.target instanceof Element)) return;
			if (ev.target.closest(`.${POPOVER_CLS}`) === this.popover) return;
			this.cleanup();
		}
		document.addEventListener("click", this.clickoutHandler, {capture: true});
		
		this.resizeHandler = debounce(() => this.reposition(), 20);
		window.addEventListener("resize", this.resizeHandler);
	}
	
	cleanup() {
		remove(this.popover);
		document.removeEventListener("click", this.clickoutHandler, {capture: true});
		window.removeEventListener("resize", this.resizeHandler);
		delete this.popover;
		delete this.clickoutHandler;
		delete this.resizeHandler;
	}
	
	reposition() {
		const refRect = this.fnref.getBoundingClientRect();
		const center = refRect.left + (refRect.width / 2);
		const popoverHalfWidth = this.popover.clientWidth / 2;
		const marginLeft = stripPx(this.style.marginLeft);
		const marginRight = stripPx(this.style.marginRight);
		
		let offset = 0;
		if (center + popoverHalfWidth + marginRight > window.innerWidth) {
			offset = -((center + popoverHalfWidth + marginRight) - window.innerWidth);
		}
		else if (center - (popoverHalfWidth + marginLeft) < 0) {
			offset = (popoverHalfWidth + marginLeft) - center;
		}
		this.popover.style.transform = `translate(${offset}px)`;
	}
}

/** @param {Node} n */
function fragFromContents(n) {
	const frag = document.createDocumentFragment();
	n.childNodes.forEach((ch) => frag.appendChild(ch));
	return frag;
}

/** @param {HTMLAnchorElement} a */
function installContainer(a) {
	if (!a.parentElement.matches(`.${CONTAINER_CLS}`)) {
		const container = newEl("div", CONTAINER_CLS);
		a.parentElement.insertBefore(container, a);
		container.appendChild(a);
	}
}

document.addEventListener("click", (ev) => {
						  if (!(ev.target && ev.target instanceof HTMLAnchorElement)) return;
						  if (!ev.target.matches(".footnote")) return;
						  ev.preventDefault();
						  
						  const content = document.querySelector(`[id='${ev.target.hash.substring(1)}']`).cloneNode(true);
						  if (content instanceof HTMLElement) remove(content.querySelector(".reversefootnote"));
						  installContainer(ev.target);
						  void new Footnote(fragFromContents(content), ev.target);
						  });