/**
 * Internal dependencies
 */
import type { Admin } from './';

/**
 * Regular expression matching a displayed PHP error within a markup string.
 *
 * @see https://github.com/php/php-src/blob/598175e/main/main.c#L1257-L1297
 *
 * @type {RegExp}
 */
const REGEXP_PHP_ERROR =
	/(<b>)?(Fatal error|Recoverable fatal error|Warning|Parse error|Notice|Strict Standards|Deprecated|Unknown error)(<\/b>)?: (.*?) in (.*?) on line (<b>)?\d+(<\/b>)?/;

/**
 * Returns a promise resolving to one of either a string or null. A string will
 * be resolved if an error message is present in the contents of the page. If no
 * error is present, a null value will be resolved instead. This requires the
 * environment be configured to display errors.
 *
 * @see http://php.net/manual/en/function.error-reporting.php
 *
 * @param {Admin} this
 *
 * @return {Promise<?string>} Promise resolving to a string or null, depending
 *                            whether a page error is present.
 */
export async function getPageError( this: Admin ) {
	const content = await this.page.content();
	const match = content.match( REGEXP_PHP_ERROR );
	return match ? match[ 0 ] : null;
}