<?php
/**
 * Virtual file server — registers rewrite rules and serves generated files.
 *
 * @package AIDF
 * @since   1.0.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Serves AI Discovery Files at their root URLs via WordPress rewrite rules.
 */
class AIDF_Server {

	/**
	 * Initialise hooks.
	 *
	 * @return void
	 */
	public static function init() {
		add_action( 'init', array( __CLASS__, 'register_rewrite_rules' ) );
		add_filter( 'query_vars', array( __CLASS__, 'register_query_vars' ) );
		add_action( 'template_redirect', array( __CLASS__, 'serve_file' ) );
		add_filter( 'redirect_canonical', array( __CLASS__, 'prevent_trailing_slash' ) );
	}

	/**
	 * Prevent WordPress from adding a trailing slash to AI Discovery File URLs.
	 *
	 * @param  string $redirect_url The URL WordPress wants to redirect to.
	 * @return string|false The URL to redirect to, or false to cancel.
	 */
	public static function prevent_trailing_slash( $redirect_url ) {
		if ( get_query_var( 'aidf_file' ) ) {
			return false;
		}
		return $redirect_url;
	}

	/**
	 * Register rewrite rules for every AI Discovery File.
	 *
	 * @return void
	 */
	public static function register_rewrite_rules() {
		$file_types = AIDF_Plugin::get_file_types();

		foreach ( $file_types as $slug => $meta ) {
			$filename = preg_quote( $meta['filename'], '/' );
			add_rewrite_rule(
				'^' . $filename . '$',
				'index.php?aidf_file=' . $slug,
				'top'
			);
		}

		// Domain verification file for AI Visibility Directory.
		add_rewrite_rule(
			'^ai-visibility-verify\.txt$',
			'index.php?aidf_file=verify',
			'top'
		);
	}

	/**
	 * Register the aidf_file query variable.
	 *
	 * @param  array<int, string> $vars Existing query vars.
	 * @return array<int, string>
	 */
	public static function register_query_vars( $vars ) {
		$vars[] = 'aidf_file';
		return $vars;
	}

	/**
	 * Intercept requests for AI Discovery Files and serve generated content.
	 *
	 * @return void
	 */
	public static function serve_file() {
		$file_slug = get_query_var( 'aidf_file' );

		if ( empty( $file_slug ) ) {
			return;
		}

		// Handle verification file separately (not an AI Discovery File).
		if ( 'verify' === $file_slug ) {
			$settings    = AIDF_Plugin::get_settings();
			$verify_code = isset( $settings['verify_code'] ) ? $settings['verify_code'] : '';

			if ( empty( $verify_code ) ) {
				status_header( 404 );
				nocache_headers();
				echo esc_html__( '404 — Verification file not configured.', 'ai-discovery-files' );
				exit;
			}

			status_header( 200 );
			header( 'Content-Type: text/plain; charset=utf-8' );
			header( 'Cache-Control: no-store' );
			header( 'X-Robots-Tag: noindex' );
			// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Plain text output, validated on save (hex only).
			echo $verify_code;
			exit;
		}

		$file_types = AIDF_Plugin::get_file_types();

		if ( ! isset( $file_types[ $file_slug ] ) ) {
			return;
		}

		$settings     = AIDF_Plugin::get_settings();
		$active_files = isset( $settings['active_files'] ) ? (array) $settings['active_files'] : array();

		if ( ! in_array( $file_slug, $active_files, true ) ) {
			// File type exists but is not enabled — return 404.
			status_header( 404 );
			nocache_headers();
			echo esc_html__( '404 — This AI Discovery File is not enabled.', 'ai-discovery-files' );
			exit;
		}

		// Handle llm.txt as a redirect to llms.txt.
		if ( 'llm-txt' === $file_slug ) {
			wp_safe_redirect( home_url( '/llms.txt' ), 301 );
			exit;
		}

		$meta    = $file_types[ $file_slug ];
		$content = AIDF_Generator::generate( $file_slug );

		if ( false === $content ) {
			status_header( 500 );
			nocache_headers();
			echo esc_html__( '500 — Could not generate AI Discovery File.', 'ai-discovery-files' );
			exit;
		}

		// Log AI crawler access when logging is enabled.
		if ( class_exists( 'AIDF_Crawler_Logger' ) ) {
			AIDF_Crawler_Logger::maybe_log_hit( $file_slug );
		}

		// Send appropriate headers.
		status_header( 200 );
		header( 'Content-Type: ' . $meta['content_type'] );
		header( 'Cache-Control: public, max-age=3600, s-maxage=0' );
		header( 'X-Robots-Tag: noindex' );
		header( 'X-AIDF-Generator: AI Discovery Files for WordPress/' . AIDF_VERSION );

		// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Content is pre-built plain text / JSON.
		echo $content;
		exit;
	}

	/**
	 * Check whether a physical file already exists for a given file type.
	 *
	 * @param  string $file_slug The file type slug.
	 * @return bool
	 */
	public static function physical_file_exists( $file_slug ) {
		$file_types = AIDF_Plugin::get_file_types();

		if ( ! isset( $file_types[ $file_slug ] ) ) {
			return false;
		}

		$abspath  = untrailingslashit( ABSPATH );
		$filepath = $abspath . '/' . $file_types[ $file_slug ]['filename'];

		return file_exists( $filepath );
	}

	/**
	 * Get the public URL for a given file type.
	 *
	 * @param  string $file_slug The file type slug.
	 * @return string
	 */
	public static function get_file_url( $file_slug ) {
		$file_types = AIDF_Plugin::get_file_types();

		if ( ! isset( $file_types[ $file_slug ] ) ) {
			return '';
		}

		return home_url( '/' . $file_types[ $file_slug ]['filename'] );
	}
}