utils.js

'use strict';

/**
 * Removes tokens that matches given criteria from start and end of given list
 * @param  {Token[]} tokens
 * @return {Token[]}
 */
export function trimTokens(tokens) {
	tokens = tokens.slice();
	let len;
	while (len !== tokens.length) {
		len = tokens.length;
		if (isFormattingToken(tokens[0])) {
			tokens.shift();
		}

		if (isFormattingToken(last(tokens))) {
			tokens.pop();
		}
	}

	return tokens;
}

/**
 * Trims formatting tokens (whitespace and comments) from the beginning and end
 * of given token list
 * @param  {Token[]} tokens
 * @return {Token[]}
 */
export function trimFormatting(tokens) {
	return trimTokens(tokens, isFormattingToken);
}

/**
 * Check if given token is a formatting one (whitespace or comment)
 * @param  {Token}  token
 * @return {Boolean}
 */
export function isFormattingToken(token) {
	const type = token && token.type;
	return type === 'whitespace' || type === 'comment';
}

/**
 * Consumes string char-by-char from given stream
 * @param  {StreamReader} stream
 * @param  {String} string
 * @return {Boolean} Returns `true` if string was completely consumed
 */
export function eatString(stream, string) {
	const start = stream.pos;

	for (let i = 0, il = string.length; i < il; i++) {
		if (!stream.eat(string.charCodeAt(i))) {
			stream.pos = start;
			return false;
		}
	}

	return true;
}

export function consume(stream, match) {
	const start = stream.pos;
	if (stream.eat(match)) {
		stream.start = start;
		return true;
	}

	return false;
}

export function consumeWhile(stream, match) {
	const start = stream.pos;
	if (stream.eatWhile(match)) {
		stream.start = start;
		return true;
	}

	return false;
}

export function last(arr) {
	return arr[arr.length - 1];
}

export function valueOf(token) {
	return token && token.valueOf();
}