export default function(markdownIt: any) {
	markdownIt.core.ruler.push('anchorHeader', (state: any): boolean => {
		const tokens = state.tokens;
		const Token = state.Token;
		const doneNames = [];

		const headingTextToAnchorName = (text: string, doneNames: string[]) => {
			const allowed = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
			let lastWasDash = true;
			let output = '';
			for (let i = 0; i < text.length; i++) {
				const c = text[i];
				if (allowed.indexOf(c) < 0) {
					if (lastWasDash) continue;
					lastWasDash = true;
					output += '-';
				} else {
					lastWasDash = false;
					output += c;
				}
			}

			output = output.toLowerCase();

			while (output.length && output[output.length - 1] === '-') {
				output = output.substr(0, output.length - 1);
			}

			let temp = output;
			let index = 1;
			while (doneNames.indexOf(temp) >= 0) {
				temp = `${output}-${index}`;
				index++;
			}
			output = temp;

			return output;
		};

		const createAnchorTokens = (anchorName: string) => {
			const output = [];

			{
				const token = new Token('heading_anchor_open', 'a', 1);
				token.attrs = [
					['name', anchorName],
					['href', `#${anchorName}`],
					['class', 'heading-anchor'],
				];
				output.push(token);
			}

			{
				const token = new Token('text', '', 0);
				token.content = '🔗';
				output.push(token);
			}

			{
				const token = new Token('heading_anchor_close', 'a', -1);
				output.push(token);
			}

			return output;
		};

		let insideHeading = false;
		for (let i = 0; i < tokens.length; i++) {
			const token = tokens[i];

			if (token.type === 'heading_open') {
				insideHeading = true;
				continue;
			}

			if (token.type === 'heading_close') {
				insideHeading = false;
				continue;
			}

			if (insideHeading && token.type === 'inline') {
				const anchorName = headingTextToAnchorName(token.content, doneNames);
				doneNames.push(anchorName);
				const anchorTokens = createAnchorTokens(anchorName);
				// token.children = anchorTokens.concat(token.children);
				token.children = token.children.concat(anchorTokens);
			}
		}

		return true;
	});
}