const _ = require('lodash');
const Markdown = require('markedLegacy');
const renderer = new Markdown.Renderer();

//Processes the markdown within an HTML block if it's just a class-wrapper
renderer.html = function (html) {
	if(_.startsWith(_.trim(html), '<div') && _.endsWith(_.trim(html), '</div>')){
		const openTag = html.substring(0, html.indexOf('>')+1);
		html = html.substring(html.indexOf('>')+1);
		html = html.substring(0, html.lastIndexOf('</div>'));
		return `${openTag} ${Markdown(html)} </div>`;
	}
	// if(_.startsWith(_.trim(html), '<style') && _.endsWith(_.trim(html), '</style>')){
	// 	const openTag = html.substring(0, html.indexOf('>')+1);
	// 	html = html.substring(html.indexOf('>')+1);
	// 	html = html.substring(0, html.lastIndexOf('</style>'));
	// 	html = html.replaceAll(/\s(\.[^{]*)/gm, '.legacy $1');
	// 	return `${openTag} ${html} </style>`;
	// }
	return html;
};

renderer.link = function (href, title, text) {
	let self = false;
	if(href[0] == '#') {
		self = true;
	}
	href = cleanUrl(this.options.sanitize, this.options.baseUrl, href);

	if(href === null) {
		return text;
	}
	let out = `<a href="${escape(href)}"`;
	if(title) {
		out += ` title="${title}"`;
	}
	if(self) {
		out += ' target="_self"';
	}
	out += `>${text}</a>`;
	return out;
};

const nonWordAndColonTest = /[^\w:]/g;
const cleanUrl = function (sanitize, base, href) {
	if(sanitize) {
		let prot;
		try {
			prot = decodeURIComponent(unescape(href))
        .replace(nonWordAndColonTest, '')
        .toLowerCase();
		} catch {
			return null;
		}
		if(prot.indexOf('javascript:') === 0 || prot.indexOf('vbscript:') === 0 || prot.indexOf('data:') === 0) {
			return null;
		}
	}
	try {
		href = encodeURI(href).replace(/%25/g, '%');
	} catch {
		return null;
	}
	return href;
};

const escapeTest = /[&<>"']/;
const escapeReplace = /[&<>"']/g;
const escapeTestNoEncode = /[<>"']|&(?!#?\w+;)/;
const escapeReplaceNoEncode = /[<>"']|&(?!#?\w+;)/g;
const escapeReplacements = {
	'&'  : '&amp;',
	'<'  : '&lt;',
	'>'  : '&gt;',
	'"'  : '&quot;',
	'\'' : '&#39;'
};
const getEscapeReplacement = (ch)=>escapeReplacements[ch];
const escape = function (html, encode) {
	if(encode) {
		if(escapeTest.test(html)) {
			return html.replace(escapeReplace, getEscapeReplacement);
		}
	} else {
		if(escapeTestNoEncode.test(html)) {
			return html.replace(escapeReplaceNoEncode, getEscapeReplacement);
		}
	}

	return html;
};

const tagTypes = ['div', 'span', 'a'];
const tagRegex = new RegExp(`(${
	_.map(tagTypes, (type)=>{
		return `\\<${type}\\b|\\</${type}>`;
	}).join('|')})`, 'g');

// Special "void" tags that can be self-closed but don't need to be.
const voidTags = new Set([
	'area', 'base', 'br', 'col', 'command', 'hr', 'img',
	'input', 'keygen', 'link', 'meta', 'param', 'source'
]);


module.exports = {
	marked : Markdown,
	render : (rawBrewText)=>{
		return Markdown(
			rawBrewText,
			{ renderer: renderer }
		);
	},

	validate : (rawBrewText)=>{
		const errors = [];
		const leftovers = _.reduce(rawBrewText.split('\n'), (acc, line, _lineNumber)=>{
			const lineNumber = _lineNumber + 1;
			const matches = line.match(tagRegex);
			if(!matches || !matches.length) return acc;

			_.each(matches, (match)=>{
				_.each(tagTypes, (type)=>{
					if(match == `<${type}`){
						acc.push({
							type : type,
							line : lineNumber
						});
					}
					if(match === `</${type}>`){
						// Closing tag: Check we expect it to be closed.
						// The accumulator may contain a sequence of voidable opening tags,
						// over which we skip before checking validity of the close.
						while (acc.length && voidTags.has(_.last(acc).type) && _.last(acc).type != type) {
							acc.pop();
						}
						// Now check that what remains in the accumulator is valid.
						if(!acc.length){
							errors.push({
								line : lineNumber,
								type : type,
								text : 'Unmatched closing tag',
								id   : 'CLOSE'
							});
						} else if(_.last(acc).type == type){
							acc.pop();
						} else {
							errors.push({
								line : `${_.last(acc).line} to ${lineNumber}`,
								type : type,
								text : 'Type mismatch on closing tag',
								id   : 'MISMATCH'
							});
							acc.pop();
						}
					}
				});
			});
			return acc;
		}, []);

		_.each(leftovers, (unmatched)=>{
			errors.push({
				line : unmatched.line,
				type : unmatched.type,
				text : 'Unmatched opening tag',
				id   : 'OPEN'
			});
		});

		return errors;
	},
};