/* Read More — FreshRSS extension.
 * Collapses long articles in reader view behind a "Read more" button.
 * Collapsing uses max-height (never display:none) so FreshRSS's
 * mark-as-read-on-scroll keeps measuring a non-zero article height. */
(function (root) {
	'use strict';

	const THRESHOLD_RATIO = 1.5;
	const STATE = { collapsed: 'collapsed', short: 'short', expanded: 'expanded' };
	const defaultMeasure = (el) => el.scrollHeight;

	function shouldCollapse(contentHeight, collapsedHeight) {
		return contentHeight >= collapsedHeight * THRESHOLD_RATIO;
	}

	function expand(flux, text, button) {
		text.classList.remove('read-more-collapsed');
		text.style.removeProperty('--read-more-height');
		button.remove();
		flux.dataset.readMore = STATE.expanded;
	}

	function collapse(flux, text, opts) {
		const doc = flux.ownerDocument;
		text.classList.add('read-more-collapsed');
		text.style.setProperty('--read-more-height', opts.collapsedHeight + 'px');
		const button = doc.createElement('button');
		button.type = 'button';
		button.className = 'btn read-more-btn';
		button.textContent = opts.label;
		button.addEventListener('click', function (ev) {
			ev.preventDefault();
			ev.stopPropagation();
			expand(flux, text, button);
		});
		text.after(button);
		flux.dataset.readMore = STATE.collapsed;
	}

	function processEntry(flux, opts) {
		const state = flux.dataset.readMore;
		if (state !== undefined && state !== STATE.short) {
			return;
		}
		const text = flux.querySelector('.text');
		if (!text) {
			return;
		}
		const measure = opts.measure || defaultMeasure;
		if (shouldCollapse(measure(text), opts.collapsedHeight)) {
			collapse(flux, text, opts);
		} else {
			flux.dataset.readMore = STATE.short;
		}
	}

	function processEntries(rootNode, opts) {
		rootNode.querySelectorAll('.flux').forEach((flux) => processEntry(flux, opts));
	}

	function init(win, measure) {
		const context = win.context;
		if (!context || context.current_view !== 'reader') {
			return;
		}
		const conf = (context.extensions && context.extensions.read_more) || {};
		const opts = {
			collapsedHeight: Number(conf.collapsed_height) || 250,
			label: conf.label || 'Read more',
			measure: measure,
		};
		const doc = win.document;
		processEntries(doc, opts);
		doc.body.addEventListener('freshrss:load-more', () => processEntries(doc, opts));
		// Late-loading images can make a "short" article long enough to collapse.
		doc.addEventListener('load', function (ev) {
			const target = ev.target;
			if (!target || target.tagName !== 'IMG' || !target.closest) {
				return;
			}
			const flux = target.closest('.flux[data-read-more="short"]');
			if (flux) {
				processEntry(flux, opts);
			}
		}, true);
	}

	const api = { THRESHOLD_RATIO, shouldCollapse, processEntries, init };
	root.ReadMore = api;
	if (typeof module !== 'undefined' && module.exports) {
		module.exports = api;
	}

	if (root.document && root.document.addEventListener) {
		if (typeof root.context !== 'undefined' && typeof root.context.extensions !== 'undefined') {
			init(root);
		} else {
			root.document.addEventListener('freshrss:globalContextLoaded', () => init(root), false);
		}
	}
}(typeof window !== 'undefined' ? window : globalThis));