<?php
/**
 * Fatal error and database recovery alerts from inside the plugin.
 *
 * The fatal-error-handler.php drop-in is the main way fatal errors are caught. These hooks cover
 * sites where the drop-in could not be installed, or where WP_DISABLE_FATAL_ERROR_HANDLER is set.
 */

defined( 'ABSPATH' ) || exit;

class IDownAlert_Errors {

	const FATAL_TYPES = array( E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR, E_USER_ERROR, E_RECOVERABLE_ERROR );

	public static function init() {
		// Core's handler ends the request with wp_die() before later shutdown functions run,
		// so also report from the filter it applies while building its error page.
		add_filter( 'wp_php_error_message', array( __CLASS__, 'from_core_handler' ), 10, 2 );
		register_shutdown_function( array( __CLASS__, 'shutdown' ) );

		self::check_database_recovery();
	}

	/**
	 * @param string $message Error page message.
	 * @param array  $error   Error from error_get_last().
	 * @return string
	 */
	public static function from_core_handler( $message, $error ) {
		if ( is_array( $error ) ) {
			self::report( $error );
		}
		return $message;
	}

	public static function shutdown() {
		$error = error_get_last();
		if ( $error && in_array( $error['type'], self::FATAL_TYPES, true ) ) {
			self::report( $error );
		}
	}

	/**
	 * @param array $error Error from error_get_last().
	 */
	private static function report( array $error ) {
		try {
			IDownAlert_Emergency::fatal_error( $error, IDownAlert_Settings::emergency_config() );
		} catch ( Throwable $e ) {
			IDownAlert_Emergency::fatal_error( $error );
		}
	}

	/**
	 * The db-error.php drop-in leaves a flag file while the database is down. The first request
	 * that loads normally afterwards removes it and reports the recovery.
	 */
	private static function check_database_recovery() {
		$flag = IDownAlert_Emergency::db_flag_file();
		if ( '' === $flag || ! file_exists( $flag ) ) {
			return;
		}

		// phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents -- local file.
		$since = (int) @file_get_contents( $flag );
		// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- only the request that deletes the flag reports, so concurrent requests don't send duplicates.
		if ( ! @unlink( $flag ) ) {
			return;
		}

		$details = array();
		if ( $since > 0 ) {
			$details['Down since'] = gmdate( 'Y-m-d H:i:s', $since ) . ' UTC';
			$details['Downtime']   = human_time_diff( $since );
		}
		IDownAlert_Notifier::alert( 'errors', 'warning', 'Database connection restored (site is back up)', $details, 'db:up' );
	}
}