<?php

declare(strict_types=1);

namespace App\Engine\Cfnpp\Expression;

/**
 * Token representing a comparison operator.
 *
 * @author Adam Pippin <hello@adampippin.ca>
 */
class TokenOperator extends Token
{
	/**
	 * List of valid operators this can parse.
	 * @var string[]
	 */
	public const OPERATORS = [
		'eq',
		'neq',
		'gt',
		'gte',
		'lt',
		'lte',
		'and',
		'or'
	];

	/**
	 * Operator this token represents.
	 * @var string
	 */
	protected $operator;

	/**
	 * Create a new operator token.
	 *
	 * @param string $operator
	 */
	public function __construct($operator)
	{
		$this->operator = $operator;
	}

	/**
	 * Get the operator this token represents.
	 *
	 * @return string
	 */
	public function getOperator(): string
	{
		return $this->operator;
	}

	/**
	 * Determine whether a operator token can be parsed from a stream.
	 *
	 * @param  string $stream
	 * @return bool
	 */
	public static function isToken(string $stream): bool
	{
		foreach (static::OPERATORS as $operator)
		{
			if (strlen($stream) > strlen($operator) &&
				substr($stream, 0, strlen($operator)) == $operator)
			{
				return true;
			}
		}
		return false;
	}

	/**
	 * Parse an operator token from a stream.
	 *
	 * Returns token, and modifies stream to remove all consumed characters
	 *
	 * @param  string $stream
	 * @return Token
	 */
	public static function getToken(string &$stream): Token
	{
		foreach (static::OPERATORS as $operator)
		{
			if (strlen($stream) > strlen($operator) &&
				substr($stream, 0, strlen($operator)) == $operator)
			{
				$operator = substr($stream, 0, strlen($operator));
				$stream = substr($stream, strlen($operator));
				return new TokenOperator($operator);
			}
		}
		throw new \Exception('Could not parse operator token!');
	}
}