<?php

namespace WPPilot;

defined( 'ABSPATH' ) || exit;

/**
 * How this site sends email — the fact an owner needs before trusting a form
 * that emails its enquiries.
 *
 * Live, alaskaholiday.co, 2026-10-12: a booking form emailed every enquiry
 * through WordPress's built-in mailer on a host with no mail plugin. WordPress
 * hands such mail to PHP's mail(), which many hosts drop or spam-folder
 * without an error, and nothing told the owner.
 *
 * The answer is read from the code that would send the mail, not from a list
 * of plugin names: a plugin that replaces `wp_mail()` (a pluggable function),
 * short-circuits it (`pre_wp_mail`) or configures PHPMailer (`phpmailer_init`)
 * — every SMTP and mail-service plugin does one of these — is named by its
 * folder. Nothing is sent; this is no proof that any email arrives.
 */
class Mail_Status {

	/** The mail hooks a sending plugin attaches to. */
	private const HOOKS = array( 'pre_wp_mail', 'phpmailer_init' );

	/**
	 * `route` is `plugin` when a plugin sends or configures mail, else
	 * `wordpress_default`; `via` is that plugin's folder.
	 *
	 * @return array{route: string, via: ?string}
	 */
	public static function describe(): array {
		$via = self::plugin_folder_of_function( 'wp_mail' );
		if ( null === $via ) {
			foreach ( self::HOOKS as $hook ) {
				$via = self::plugin_folder_hooked_on( $hook );
				if ( null !== $via ) {
					break;
				}
			}
		}
		return null === $via
			? array( 'route' => 'wordpress_default', 'via' => null )
			: array( 'route' => 'plugin', 'via' => $via );
	}

	/**
	 * The plugin folder that defines a function, when a plugin does (a
	 * pluggable `wp_mail()` replaced before WordPress defined its own).
	 */
	private static function plugin_folder_of_function( string $name ): ?string {
		if ( ! function_exists( $name ) ) {
			return null;
		}
		try {
			$file = ( new \ReflectionFunction( $name ) )->getFileName();
		} catch ( \ReflectionException $e ) {
			return null;
		}
		return is_string( $file ) ? self::plugin_folder( $file ) : null;
	}

	/** The first plugin (not WPPilot) with a callback on a hook. */
	private static function plugin_folder_hooked_on( string $hook ): ?string {
		global $wp_filter;
		if ( ! isset( $wp_filter[ $hook ] ) || ! is_object( $wp_filter[ $hook ] ) || ! isset( $wp_filter[ $hook ]->callbacks ) ) {
			return null;
		}
		foreach ( (array) $wp_filter[ $hook ]->callbacks as $callbacks ) {
			foreach ( (array) $callbacks as $entry ) {
				$file = self::callback_file( $entry['function'] ?? null );
				if ( null === $file ) {
					continue;
				}
				$folder = self::plugin_folder( $file );
				if ( null !== $folder ) {
					return $folder;
				}
			}
		}
		return null;
	}

	/** The file a callback is defined in, when reflection can say. */
	private static function callback_file( mixed $callback ): ?string {
		try {
			if ( $callback instanceof \Closure || ( is_string( $callback ) && ! str_contains( $callback, '::' ) && function_exists( $callback ) ) ) {
				$file = ( new \ReflectionFunction( $callback ) )->getFileName();
			} elseif ( is_array( $callback ) && 2 === count( $callback ) && is_string( $callback[1] ) ) {
				$file = ( new \ReflectionMethod( $callback[0], $callback[1] ) )->getFileName();
			} elseif ( is_string( $callback ) && str_contains( $callback, '::' ) ) {
				$file = ( new \ReflectionMethod( $callback ) )->getFileName();
			} elseif ( is_object( $callback ) && method_exists( $callback, '__invoke' ) ) {
				$file = ( new \ReflectionMethod( $callback, '__invoke' ) )->getFileName();
			} else {
				return null;
			}
		} catch ( \ReflectionException $e ) {
			return null;
		}
		return is_string( $file ) ? $file : null;
	}

	/**
	 * The plugin folder (or must-use plugin file) a path is in, or null for
	 * WordPress itself, a theme, and WPPilot.
	 */
	public static function plugin_folder( string $file ): ?string {
		$file = wp_normalize_path( $file );
		$roots = array();
		if ( defined( 'WP_PLUGIN_DIR' ) ) {
			$roots[] = wp_normalize_path( WP_PLUGIN_DIR );
		}
		if ( defined( 'WPMU_PLUGIN_DIR' ) ) {
			$roots[] = wp_normalize_path( WPMU_PLUGIN_DIR );
		}
		foreach ( $roots as $root ) {
			$root = rtrim( $root, '/' ) . '/';
			if ( ! str_starts_with( $file, $root ) ) {
				continue;
			}
			$folder = strtok( substr( $file, strlen( $root ) ), '/' );
			if ( ! is_string( $folder ) || '' === $folder ) {
				return null;
			}
			$own = defined( 'WPPILOT_DIR' ) ? basename( rtrim( wp_normalize_path( WPPILOT_DIR ), '/' ) ) : 'wingpilot';
			return $folder === $own ? null : sanitize_key( preg_replace( '/\.php$/', '', $folder ) );
		}
		return null;
	}
}