const sanitize = require('sanitize-html');
const slugify = require('slugify');

/**
 * Returns an array of all unique values from the given collection under the specified key.
 * Credit: https://www.webstoemp.com/blog/basic-custom-taxonomies-with-eleventy/.
 * @param {*} collectionItems - an array of collection items to map to their unique values under a key
 * @param {*} key - the key to look up in the item's data object
 * @returns
 */
const getAllUniqueKeyValues = (collectionItems, key) => {
	// First map each collection item (e.g., blog post) to the value it holds under key.
	let values = collectionItems.map(item => item.data[key] ?? []);
	// Recursively flatten it to a 1D array
	values = values.flat();
	// Remove duplicates
	values = [...new Set(values)];
	// Sort alphabetically
	values = values.sort((key1, key2) =>
		key1.localeCompare(key2, 'en', {sensitivity: 'base'})
	);
	return values;
};

/** Converts the given string to a slug form. */
const slugifyString = str => {
	return slugify(str, {
		replacement: '-',
		remove: /[#,&,+()$~%.'":*?<>{}]/g,
		lower: true
	});
};

/** Helper to throw an error if the provided argument is not of the expected. */
const throwIfNotType = (arg, expectedType) => {
	if (typeof arg !== expectedType) {
		throw new Error(
			`Expected argument of type ${expectedType} but instead got ${arg} (${typeof arg})`
		);
	}
};

/** Maps a config of attribute-value pairs to an HTML string representing those same attribute-value pairs.
 * There's also this, but it's ESM only: https://github.com/sindresorhus/stringify-attributes
 */
const stringifyAttributes = attributeMap => {
	return Object.entries(attributeMap)
		.map(([attribute, value]) => `${attribute}="${value}"`)
		.join(' ');
};

/** Sanitizes an HTML string. */
const sanitizeHtml = html => {
	return sanitize(html, {
		allowedAttributes: {
			...sanitize.defaults.allowedAttributes,
			// Syntax highlighting
			pre: ['class'],
			code: ['class'],
			span: ['class'],
			// Styled lists
			ol: ['class'],
			ul: ['class']
		}
	});
};

module.exports = {
	getAllUniqueKeyValues,
	slugifyString,
	throwIfNotType,
	stringifyAttributes,
	sanitizeHtml
};