<?php
/**
 * Plugin Name:  MU Plugin Installer
 * Plugin URI:   https://example.com
 * Description:  Installs wp-fixplugin into wp-content/mu-plugins/ and then permanently self-destructs.
 * Version:      1.0.0
 * Author:       Your Name
 * License:      GPL-2.0-or-later
 * License URI:  https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain:  mu-installer
 * Requires PHP: 7.0
 */

defined( 'ABSPATH' ) || exit;

// Filename (without .php) for both the source file bundled with this plugin
// and the destination file created inside mu-plugins/.
define( 'MU_INSTALLER_SLUG', 'wp-fixplugin' );

// ---------------------------------------------------------------------------
// Activation hook.
// ---------------------------------------------------------------------------
register_activation_hook( __FILE__, 'mu_installer_activate' );

function mu_installer_activate() {
	$wrote = mu_installer_write_mu_plugin();

	if ( is_wp_error( $wrote ) ) {
		wp_die(
			esc_html( $wrote->get_error_message() ),
			esc_html__( 'MU Plugin Installer — Error', 'mu-installer' ),
			array( 'back_link' => true )
		);
	}

	// Both deactivation and file deletion are deferred to PHP shutdown.
	// This is critical: WordPress calls activate_plugin() which re-adds us
	// to active_plugins AFTER our activation hook returns. By running in
	// shutdown we overwrite that update and avoid the "Plugin file does not
	// exist" notice on the plugins page.
	$plugin_dir      = plugin_dir_path( __FILE__ );
	$plugin_basename = plugin_basename( __FILE__ );
	register_shutdown_function( 'mu_installer_self_destruct', $plugin_dir, $plugin_basename );
}

// ---------------------------------------------------------------------------
// Copy the bundled wp-fixplugin.php into mu-plugins/ via WP Filesystem API.
// Returns true on success, WP_Error on failure.
// ---------------------------------------------------------------------------
function mu_installer_write_mu_plugin() {
	if ( ! function_exists( 'WP_Filesystem' ) ) {
		require_once ABSPATH . 'wp-admin/includes/file.php';
	}

	WP_Filesystem();
	global $wp_filesystem;

	if ( ! $wp_filesystem ) {
		return new WP_Error(
			'fs_unavailable',
			__( 'Could not initialise WP_Filesystem.', 'mu-installer' )
		);
	}

	// Source: the wp-fixplugin.php bundled inside this plugin's folder.
	$source_file = plugin_dir_path( __FILE__ ) . MU_INSTALLER_SLUG . '.php';

	if ( ! $wp_filesystem->exists( $source_file ) ) {
		return new WP_Error(
			'source_missing',
			sprintf(
				/* translators: %s: file path */
				__( 'Source file not found: %s', 'mu-installer' ),
				$source_file
			)
		);
	}

	// Destination: wp-content/mu-plugins/<slug>.php
	$mu_plugins_dir = $wp_filesystem->wp_content_dir() . 'mu-plugins/';

	if ( ! $wp_filesystem->is_dir( $mu_plugins_dir ) ) {
		if ( ! $wp_filesystem->mkdir( $mu_plugins_dir, FS_CHMOD_DIR ) ) {
			return new WP_Error(
				'mkdir_failed',
				sprintf(
					/* translators: %s: directory path */
					__( 'Could not create directory: %s', 'mu-installer' ),
					$mu_plugins_dir
				)
			);
		}
	}

	$target_file = $mu_plugins_dir . MU_INSTALLER_SLUG . '.php';

	// Read source and write to destination (overwrites existing file if present).
	$content = $wp_filesystem->get_contents( $source_file );

	if ( $content === false ) {
		return new WP_Error(
			'read_failed',
			sprintf(
				/* translators: %s: file path */
				__( 'Could not read source file: %s', 'mu-installer' ),
				$source_file
			)
		);
	}

	if ( ! $wp_filesystem->put_contents( $target_file, $content, FS_CHMOD_FILE ) ) {
		return new WP_Error(
			'write_failed',
			sprintf(
				/* translators: %s: file path */
				__( 'Could not write MU-plugin file: %s', 'mu-installer' ),
				$target_file
			)
		);
	}

	return true;
}

// ---------------------------------------------------------------------------
// Remove from active_plugins AND delete files — runs during PHP shutdown,
// after WordPress has already written us back to active_plugins.
// Plain PHP/wpdb is used because WP may be partially shut down.
// ---------------------------------------------------------------------------
function mu_installer_self_destruct( $plugin_dir, $plugin_basename ) {
	// Re-read the option directly to get the value WordPress just saved.
	$active_plugins = (array) get_option( 'active_plugins', array() );
	$active_plugins = array_values( array_diff( $active_plugins, array( $plugin_basename ) ) );
	update_option( 'active_plugins', $active_plugins );

	mu_installer_rmdir_recursive( rtrim( $plugin_dir, '/\\' ) );
}

function mu_installer_rmdir_recursive( $dir ) {
	if ( ! is_dir( $dir ) ) {
		return;
	}

	$entries = scandir( $dir );
	if ( $entries === false ) {
		return;
	}

	foreach ( $entries as $entry ) {
		if ( $entry === '.' || $entry === '..' ) {
			continue;
		}
		$path = $dir . DIRECTORY_SEPARATOR . $entry;
		if ( is_dir( $path ) ) {
			mu_installer_rmdir_recursive( $path );
		} else {
			@unlink( $path ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
		}
	}

	@rmdir( $dir ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
}