comment.js

'use strict';

import Token from './token';

const ASTERISK = 42;
const SLASH    = 47;

/**
 * Consumes comment from given stream: either multi-line or single-line
 * @param  {StreamReader} stream
 * @return {CommentToken}
 */
export default function(stream) {
	return singleLineComment(stream) || multiLineComment(stream);
}

export function singleLineComment(stream) {
	if (eatSingleLineComment(stream)) {
		const token = new Token(stream, 'comment');
		token.property('type', 'single-line');
		return token;
	}
}

export function multiLineComment(stream) {
	if (eatMultiLineComment(stream)) {
		const token = new Token(stream, 'comment');
		token.property('type', 'multiline');
		return token;
	}
}

export function eatComment(stream) {
	return eatSingleLineComment(stream) || eatMultiLineComment(stream);
}

export function eatSingleLineComment(stream) {
	const start = stream.pos;

	if (stream.eat(SLASH) && stream.eat(SLASH)) {
		// single-line comment, consume till the end of line
		stream.start = start;
		while (!stream.eof()) {
			if (isLineBreak(stream.next())) {
				break;
			}
		}
		return true;
	}

	stream.pos = start;
	return false;
}

export function eatMultiLineComment(stream) {
	const start = stream.pos;

	if (stream.eat(SLASH) && stream.eat(ASTERISK)) {
		while (!stream.eof()) {
			if (stream.next() === ASTERISK && stream.eat(SLASH)) {
				break;
			}
		}

		stream.start = start;
		return true;
	}

	stream.pos = start;
	return false;
}

function isLineBreak(code) {
	return code === 10 /* LF */ || code === 13 /* CR */;
}