<?php
defined( 'ABSPATH' ) || exit;

/**
 * AWBSEO Robots.txt Editor
 *
 * Allows admins to edit the virtual robots.txt served by WordPress.
 * Uses WordPress's built-in robots_txt filter - no file writes needed.
 *
 * NOTE: If a physical robots.txt file exists in the site root, WordPress
 * serves that file directly and the filter has no effect. The admin UI
 * warns the user in that case.
 */
class AWBSEO_Robots_Txt {

    const OPTION_KEY = 'awbseo_robots_txt'; 

    public static function init() {
        add_filter( 'robots_txt', [ __CLASS__, 'filter_output' ], 99, 2 );
        add_action( 'wp_ajax_awbseo_save_robots_txt',  [ __CLASS__, 'ajax_save' ] );
        add_action( 'wp_ajax_awbseo_reset_robots_txt', [ __CLASS__, 'ajax_reset' ] );
    }

    // ── Filter ────────────────────────────────────────────────────────────────

    /**
     * Replace WordPress's default robots.txt output with our custom content.
     * Only fires when no physical robots.txt file exists on disk.
     */
    public static function filter_output( $output, $public ) {
        $custom = get_option( self::OPTION_KEY, '' );
        if ( trim( $custom ) === '' ) {
            return $output; // Nothing saved - use WP default.
        }
        return $custom;
    }

    // ── Helpers ───────────────────────────────────────────────────────────────

    /**
     * True if a physical robots.txt file sits in the site root.
     * WordPress does NOT apply the robots_txt filter in that case.
     */
    public static function physical_file_exists() {
        return file_exists( ABSPATH . 'robots.txt' );
    }

    /**
     * The content currently stored in our option (empty string = not set).
     */
    public static function get_custom() {
        return get_option( self::OPTION_KEY, '' );
    }

    /**
     * What WordPress would output by default (before our filter).
     */
    public static function get_wp_default() {
        $site_url = parse_url( site_url() );
        $path     = ! empty( $site_url['path'] ) ? $site_url['path'] : '';
        $public   = get_option( 'blog_public' );

        $out  = "User-agent: *\n";
        if ( '0' === $public ) {
            $out .= "Disallow: /\n";
        } else {
            $out .= "Disallow: {$path}/wp-admin/\n";
            $out .= "Allow: " . wp_parse_url( admin_url( 'admin-ajax.php' ), PHP_URL_PATH ) . "\n";
        }

        $sitemap = home_url( '/sitemap.xml' );
        $out    .= "\nSitemap: {$sitemap}\n";

        return $out;
    }

    /**
     * Returns the effective robots.txt that visitors see right now.
     * Fetches via HTTP so it reflects physical files and other filters.
     */
    public static function get_live() {
        $response = wp_remote_get(
            home_url( '/robots.txt' ),
            [ 'timeout' => 8, 'redirection' => 0, 'sslverify' => false ]
        );
        if ( is_wp_error( $response ) || wp_remote_retrieve_response_code( $response ) !== 200 ) {
            return '';
        }
        return wp_remote_retrieve_body( $response );
    }

    /**
     * Preset directives for common AI training bots.
     * Returns an array keyed by preset slug.
     */
    public static function get_presets() {
        return [
            'block_ai_training' => [
                'label'       => 'Block AI training bots',
                'description' => 'Blocks GPTBot, CCBot, Google-Extended, anthropic-ai, Claude-Web, PerplexityBot, Amazonbot, and Meta-ExternalAgent from crawling your site for training data.',
                'rules'       => implode( "\n", [
                    '# Block AI training crawlers',
                    'User-agent: GPTBot',
                    'Disallow: /',
                    '',
                    'User-agent: CCBot',
                    'Disallow: /',
                    '',
                    'User-agent: Google-Extended',
                    'Disallow: /',
                    '',
                    'User-agent: anthropic-ai',
                    'Disallow: /',
                    '',
                    'User-agent: Claude-Web',
                    'Disallow: /',
                    '',
                    'User-agent: PerplexityBot',
                    'Disallow: /',
                    '',
                    'User-agent: Amazonbot',
                    'Disallow: /',
                    '',
                    'User-agent: Meta-ExternalAgent',
                    'Disallow: /',
                ] ),
            ],
            'block_wp_admin' => [
                'label'       => 'Block /wp-admin/ (recommended)',
                'description' => 'Standard rule to disallow bots from crawling the admin area.',
                'rules'       => implode( "\n", [
                    'User-agent: *',
                    'Disallow: /wp-admin/',
                    'Allow: /wp-admin/admin-ajax.php',
                ] ),
            ],
            'add_sitemap' => [
                'label'       => 'Add sitemap reference',
                'description' => 'Tells crawlers where your XML sitemap lives.',
                'rules'       => 'Sitemap: ' . home_url( '/sitemap.xml' ),
            ],
            'block_search' => [
                'label'       => 'Block internal search pages',
                'description' => 'Prevents crawlers from indexing paginated search result pages.',
                'rules'       => implode( "\n", [
                    'User-agent: *',
                    'Disallow: /?s=',
                    'Disallow: /search/',
                ] ),
            ],
        ];
    }

    // ── AJAX ─────────────────────────────────────────────────────────────────

    public static function ajax_save() {
        check_ajax_referer( 'awbseo_admin', 'nonce' );
        if ( ! current_user_can( 'manage_options' ) ) wp_send_json_error( 'Forbidden' );

        // wp_unslash + allow newlines; strip any HTML.
        $content = wp_strip_all_tags( wp_unslash( $_POST['content'] ?? '' ) );
        update_option( self::OPTION_KEY, $content, false );

        wp_send_json_success( [ 'message' => 'robots.txt saved.' ] );
    }

    public static function ajax_reset() {
        check_ajax_referer( 'awbseo_admin', 'nonce' );
        if ( ! current_user_can( 'manage_options' ) ) wp_send_json_error( 'Forbidden' );

        delete_option( self::OPTION_KEY );

        wp_send_json_success( [
            'message' => 'Reset to WordPress default.',
            'content' => self::get_wp_default(),
        ] );
    }
}