import { DateTime } from "luxon";

export default function(eleventyConfig) {
	eleventyConfig.addFilter("readableDate", (dateObj, format, zone) => {
		// Formatting tokens for Luxon: https://moment.github.io/luxon/#/formatting?id=table-of-tokens
		return DateTime.fromJSDate(dateObj, { zone: zone || "utc" }).toFormat(format || "dd LLLL yyyy");
	});

	eleventyConfig.addFilter("htmlDateString", (dateObj) => {
		// dateObj input: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#valid-date-string
		return DateTime.fromJSDate(dateObj, { zone: "utc" }).toFormat('yyyy-LL-dd');
	});

	// Get the first `n` elements of a collection.
	eleventyConfig.addFilter("head", (array, n) => {
		if(!Array.isArray(array) || array.length === 0) {
			return [];
		}
		if( n < 0 ) {
			return array.slice(n);
		}

		return array.slice(0, n);
	});

	eleventyConfig.addFilter('mentionsForUrl', (webmentions, url) => {
		const allowedTypes = ['in-reply-to', 'mention-of']

		const allowedHTML = {
			allowedTags: ['b', 'i', 'em', 'strong', 'a'],
			allowedAttributes: {
			a: ['href']
			}
		}

		const clean = (entry) => {
			const { html, text } = entry.content
			if (html) {
			entry.content.value = sanitizeHTML(text, allowedHTML)
			};
			return entry;
		}

		// sort webmentions by published timestamp chronologically.
		// swap a.published and b.published to reverse order.
		const orderByDate = (a, b) => new Date(b.published) - new Date(a.published)

		// only allow webmentions that have an author name and a timestamp
		const checkRequiredFields = (entry) => {
			const { author, published } = entry
			return !!author && !!author.name && !!published
		}

		return webmentions
			.filter((entry) => entry['wm-target'] === url)
			.filter((entry) => allowedTypes.includes(entry['wm-property']))
			.filter(checkRequiredFields)
			.sort(orderByDate)
			.map(clean)

	});

	eleventyConfig.addFilter('likesForUrl', (webmentions, url) => {
		const allowedTypes = ['like-of']
		return webmentions
			.filter((entry) => entry['wm-target'] === url)
			.filter((entry) => allowedTypes.includes(entry['wm-property']))
	});

	eleventyConfig.addFilter('repostsForUrl', (webmentions, url) => {
		const allowedTypes = ['repost-of']
		return webmentions
			.filter((entry) => entry['wm-target'] === url)
			.filter((entry) => allowedTypes.includes(entry['wm-property']))
	});

	eleventyConfig.addFilter('size', (mentions) => {
		return !mentions ? 0 : mentions.length
	});

	eleventyConfig.addFilter('webmentionsByType', (mentions, mentionType) => {
		return mentions.filter(entry => !!entry['mentionType'])
	});

	// Return the smallest number argument
	eleventyConfig.addFilter("min", (...numbers) => {
		return Math.min.apply(null, numbers);
	});

	// Return the keys used in an object
	eleventyConfig.addFilter("getKeys", target => {
		return Object.keys(target);
	});

	eleventyConfig.addFilter("filterTagList", function filterTagList(tags) {
		return (tags || []).filter(tag => ["all", "posts"].indexOf(tag) === -1);
	});

};