<?php
if ( ! defined( 'ABSPATH' ) ) { exit; }

/**
 * WordPress.org free core.
 *
 * Free is intentionally simple: unlimited exact-match internal-link rules with
 * no placement, volume, styling, variation, analytics, external-link, affiliate,
 * CSV, or page-exclusion controls. Paid-plan code is not part of this build.
 */
class Dawnal_Free_Plugin {
    /** @var string */
    private $table_name;

    /** @var bool */
    private $dom_available = false;

    /** @var bool */
    private $fs_active = false;

    public function __construct() {
        global $wpdb;
        $this->table_name    = $wpdb->prefix . 'dawn_auto_links';
        $this->dom_available = class_exists( 'DOMDocument' );
        $this->fs_active     = ( function_exists( 'dawnal_fs' ) && dawnal_fs() );

        add_action( 'admin_menu', array( $this, 'add_menu' ) );
        add_action( 'admin_enqueue_scripts', array( $this, 'admin_assets' ) );
        add_action( 'admin_notices', array( $this, 'admin_notices' ) );

        // Free deliberately links exact matches everywhere in eligible rendered
        // content, including headings. The main singular post/page title is also
        // eligible. Existing links and technical markup remain protected.
        add_filter( 'the_content', array( $this, 'auto_link_content' ), 99 );
        add_filter( 'elementor/widget/render_content', array( $this, 'auto_link_content' ), 99 );
        add_filter( 'elementor/frontend/the_content', array( $this, 'auto_link_content' ), 99 );
        add_filter( 'the_title', array( $this, 'auto_link_title' ), 99, 2 );
    }

    public static function activate_static() {
        $self = new self();
        $self->activate();
    }

    public static function deactivate_static() {
        wp_cache_delete( DAWNAL_CACHE_KEY_RULES );
        delete_transient( 'dawnal_admin_notice' );
        dawnal_log( 'Free plugin deactivated: cleared cache/transients.' );
    }

    private function activate() {
        global $wpdb;

        delete_option( 'dawnal_last_activation_error' );
        delete_option( 'dawnal_last_activation_error_data' );
        delete_option( 'dawnal_last_activation_error_time' );

        $wp_ok  = version_compare( get_bloginfo( 'version' ), '5.0', '>=' );
        $php_ok = version_compare( PHP_VERSION, '7.4', '>=' );

        if ( ! $wp_ok || ! $php_ok ) {
            dawnal_set_activation_error(
                'Requirements not met',
                array(
                    'wp_version'  => get_bloginfo( 'version' ),
                    'php_version' => PHP_VERSION,
                    'wp_ok'       => $wp_ok,
                    'php_ok'      => $php_ok,
                )
            );
            return;
        }

        if ( ! function_exists( 'dbDelta' ) ) {
            require_once ABSPATH . 'wp-admin/includes/upgrade.php';
        }

        $charset_collate = $wpdb->get_charset_collate();
        $sql = "CREATE TABLE {$this->table_name} (
id mediumint(9) NOT NULL AUTO_INCREMENT,
keyword varchar(255) NOT NULL,
variations text DEFAULT NULL,
url text NOT NULL,
link_type varchar(20) NOT NULL DEFAULT 'internal',
enabled tinyint(1) NOT NULL DEFAULT 1,
clicks bigint(20) NOT NULL DEFAULT 0,
created_at datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY  (id),
UNIQUE KEY unique_keyword (keyword),
KEY keyword_idx (keyword),
KEY type_idx (link_type),
KEY clicks_idx (clicks)
) {$charset_collate};";

        try {
            dbDelta( $sql );
        } catch ( Throwable $e ) {
            dawnal_set_activation_error(
                'dbDelta threw exception',
                array(
                    'message' => $e->getMessage(),
                    'file'    => $e->getFile(),
                    'line'    => $e->getLine(),
                )
            );
            return;
        }

        $table_exists = $wpdb->get_var( $wpdb->prepare( 'SHOW TABLES LIKE %s', $this->table_name ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
        if ( ! $table_exists ) {
            dawnal_set_activation_error(
                'Database table missing after dbDelta',
                array(
                    'table'    => $this->table_name,
                    'db_error' => $wpdb->last_error,
                )
            );
            return;
        }

        // Do not create or overwrite premium behavior/settings options here.
        // Existing dawnal_* options are deliberately preserved for seamless upgrades.
        update_option( 'dawnal_activation_version', DAWNAL_VERSION, false );
        update_option( 'dawnal_activated_successfully', 1, false );
        wp_cache_delete( DAWNAL_CACHE_KEY_RULES );

        dawnal_log(
            'Free plugin activated OK',
            array(
                'version'  => DAWNAL_VERSION,
                'table'    => $this->table_name,
                'dom'      => $this->dom_available ? 'yes' : 'no',
                'freemius' => $this->fs_active ? 'yes' : 'no',
            )
        );
    }

    public function admin_notices() {
        $screen = function_exists( 'get_current_screen' ) ? get_current_screen() : null;
        $err    = get_option( 'dawnal_last_activation_error', '' );
        if ( $err && current_user_can( 'activate_plugins' ) ) {
            $show = false;
            if ( $screen && isset( $screen->id ) ) {
                $show = ( 'plugins' === $screen->id || false !== strpos( $screen->id, 'rootlinkd' ) );
            }
            if ( $show ) {
                echo '<div class="notice notice-error"><p><strong>rootlinkd:</strong> Activation issue: ' . esc_html( $err ) . '.</p></div>';
            }
        }
    }

    public function add_menu() {
        add_menu_page(
            'rootlinkd',
            'rootlinkd',
            'manage_options',
            'rootlinkd',
            array( $this, 'main_page' ),
            'dashicons-admin-links',
            58
        );
    }

    public function admin_assets( $hook ) {
        if ( false === strpos( (string) $hook, 'rootlinkd' ) ) { return; }

        $css = '
.dal-wrap{max-width:1180px}.dal-tabs{display:flex;gap:0;border-bottom:1px solid #c3c4c7;margin:18px 0 22px}.dal-tabs a{padding:10px 14px;text-decoration:none;border:1px solid transparent;border-bottom:0;color:#1d2327}.dal-tabs a.is-active{background:#fff;border-color:#c3c4c7;font-weight:600;margin-bottom:-1px}.dal-card{background:#fff;border:1px solid #dcdcde;border-radius:10px;padding:20px;margin:0 0 20px}.dal-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:16px}.dal-pill{display:inline-block;padding:2px 8px;border-radius:999px;font-size:11px;font-weight:600}.dal-upsell{background:#111827;color:#fff;border-radius:10px;padding:18px;margin-top:22px}.dal-upsell h3{color:#fff}.dal-upsell a.button{background:#fff;border-color:#fff;color:#111827}.dal-url{font-size:11px;word-break:break-all}
';
        wp_register_style( 'dawnal-admin-free', false, array(), DAWNAL_VERSION );
        wp_enqueue_style( 'dawnal-admin-free' );
        wp_add_inline_style( 'dawnal-admin-free', $css );
    }

    public function main_page() {
        if ( ! current_user_can( 'manage_options' ) ) { return; }

        $current_tab = isset( $_GET['tab'] ) ? sanitize_key( wp_unslash( $_GET['tab'] ) ) : 'rules'; // phpcs:ignore WordPress.Security.NonceVerification.Recommended
        if ( ! in_array( $current_tab, array( 'rules', 'upgrade' ), true ) ) {
            $current_tab = 'rules';
        }
        $tabs = array(
            'rules'   => 'Rules',
            'upgrade' => '⭐ Upgrade',
        );
        ?>
        <div class="wrap dal-wrap">
            <h1>rootlinkd</h1>
            <nav class="dal-tabs">
                <?php foreach ( $tabs as $tab_key => $tab_label ) : ?>
                    <a class="<?php echo $current_tab === $tab_key ? 'is-active' : ''; ?>" href="<?php echo esc_url( admin_url( 'admin.php?page=rootlinkd&tab=' . $tab_key ) ); ?>"><?php echo esc_html( $tab_label ); ?></a>
                <?php endforeach; ?>
            </nav>
            <?php
            if ( 'upgrade' === $current_tab ) {
                $this->upgrade_page_content();
            } else {
                $this->rules_page_content();
            }
            ?>
        </div>
        <?php
    }

    public function rules_page_content() {
        if ( ! current_user_can( 'manage_options' ) ) { return; }
        global $wpdb;

        $error_msg   = '';
        $success_msg = '';
        $edit_rule   = null;

        if ( isset( $_GET['action'], $_GET['id'] ) ) {
            $action = sanitize_key( wp_unslash( $_GET['action'] ) );
            $id     = absint( $_GET['id'] );
            if ( 'delete' === $action ) {
                check_admin_referer( 'dawnal_delete_' . $id );
                $wpdb->delete( $this->table_name, array( 'id' => $id ), array( '%d' ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
                wp_cache_delete( DAWNAL_CACHE_KEY_RULES );
                $success_msg = 'Rule deleted.';
            } elseif ( 'toggle' === $action ) {
                check_admin_referer( 'dawnal_toggle_' . $id );
                $row = $wpdb->get_row( $wpdb->prepare( "SELECT enabled FROM {$this->table_name} WHERE id = %d", $id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                if ( $row ) {
                    $new = ( 1 === (int) $row->enabled ) ? 0 : 1;
                    $wpdb->update( $this->table_name, array( 'enabled' => $new ), array( 'id' => $id ), array( '%d' ), array( '%d' ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
                    wp_cache_delete( DAWNAL_CACHE_KEY_RULES );
                    $success_msg = $new ? 'Rule enabled.' : 'Rule disabled.';
                }
            } elseif ( 'edit' === $action ) {
                check_admin_referer( 'dawnal_edit_' . $id );
                $edit_rule = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM {$this->table_name} WHERE id = %d", $id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                if ( ! $edit_rule ) { $error_msg = 'Rule not found.'; }
            }
        }

        if ( isset( $_POST['dawnal_save_rule'] ) ) {
            check_admin_referer( 'dawnal_save_rule' );
            $keyword = isset( $_POST['keyword'] ) ? sanitize_text_field( wp_unslash( $_POST['keyword'] ) ) : '';
            $url     = isset( $_POST['url'] ) ? esc_url_raw( wp_unslash( $_POST['url'] ) ) : '';
            $edit_id = isset( $_POST['edit_id'] ) ? absint( $_POST['edit_id'] ) : 0;

            if ( '' === $keyword || '' === $url ) {
                $error_msg = 'Both keyword and URL are required.';
            } elseif ( ! $this->is_internal_url( $url ) ) {
                $error_msg = '<strong>rootlinkd Free creates internal links only.</strong> External and affiliate link handling is available in a paid plan.';
            } else {
                $insert_data = array(
                    'keyword'    => $keyword,
                    'variations' => '',
                    'url'        => $url,
                    'link_type'  => 'internal',
                    'enabled'    => 1,
                );
                // Preserve premium-only data and click history when an existing rule
                // is edited from Free. Free must never erase stored upgrade data.
                $update_data = array(
                    'keyword'   => $keyword,
                    'url'       => $url,
                    'link_type' => 'internal',
                );

                if ( $edit_id > 0 ) {
                    $existing = $wpdb->get_var( $wpdb->prepare( "SELECT id FROM {$this->table_name} WHERE keyword = %s AND id <> %d", $keyword, $edit_id ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                    if ( $existing ) {
                        $error_msg = 'Another rule already uses that keyword.';
                    } else {
                        $wpdb->update( $this->table_name, $update_data, array( 'id' => $edit_id ), array( '%s', '%s', '%s' ), array( '%d' ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
                        $success_msg = 'Rule updated.';
                        $edit_rule   = null;
                    }
                } else {
                    $existing = $wpdb->get_var( $wpdb->prepare( "SELECT id FROM {$this->table_name} WHERE keyword = %s", $keyword ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                    if ( $existing ) {
                        $error_msg = 'A rule already uses that keyword.';
                    } else {
                        $wpdb->insert( $this->table_name, $insert_data, array( '%s', '%s', '%s', '%s', '%d' ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
                        $success_msg = 'Rule added.';
                    }
                }
                wp_cache_delete( DAWNAL_CACHE_KEY_RULES );
            }
        }

        $rules = $wpdb->get_results( "SELECT * FROM {$this->table_name} ORDER BY LENGTH(keyword) DESC, keyword ASC" ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
        $rule_count = is_array( $rules ) ? count( $rules ) : 0;
        ?>
        <div>
            <?php if ( $error_msg ) : ?><div class="notice notice-error"><p><?php echo wp_kses_post( $error_msg ); ?></p></div><?php endif; ?>
            <?php if ( $success_msg ) : ?><div class="notice notice-success is-dismissible"><p><?php echo esc_html( $success_msg ); ?></p></div><?php endif; ?>

            <div class="dal-card">
                <h2 style="margin-top:0;"><?php echo $edit_rule ? 'Edit Rule' : 'Add Internal Link Rule'; ?></h2>
                <p>Free includes unlimited exact-match internal-link rules. Set one keyword or phrase and one internal destination URL per rule.</p>
                <?php // Post to the clean Rules URL: the current URL may still carry an edit/delete/toggle link nonce. ?>
                <form method="post" action="<?php echo esc_url( admin_url( 'admin.php?page=rootlinkd&tab=rules' ) ); ?>">
                    <?php wp_nonce_field( 'dawnal_save_rule' ); ?>
                    <input type="hidden" name="edit_id" value="<?php echo $edit_rule ? esc_attr( (string) $edit_rule->id ) : '0'; ?>">
                    <table class="form-table">
                        <tr>
                            <th><label for="dawnal_keyword">Keyword or phrase</label></th>
                            <td><input class="regular-text" id="dawnal_keyword" name="keyword" required value="<?php echo $edit_rule ? esc_attr( $edit_rule->keyword ) : ''; ?>"></td>
                        </tr>
                        <tr>
                            <th><label for="dawnal_url">Internal destination URL</label></th>
                            <td><input class="regular-text" id="dawnal_url" name="url" type="url" required placeholder="<?php echo esc_attr( home_url( '/example/' ) ); ?>" value="<?php echo $edit_rule ? esc_attr( $edit_rule->url ) : ''; ?>"><p class="description">Free accepts URLs on this WordPress site's domain only.</p></td>
                        </tr>
                    </table>
                    <?php submit_button( $edit_rule ? 'Update Rule' : 'Save Link Rule', 'primary', 'dawnal_save_rule' ); ?>
                </form>
            </div>

            <h2>Rules (<?php echo esc_html( number_format_i18n( $rule_count ) ); ?>)</h2>
            <table class="wp-list-table widefat fixed striped">
                <thead><tr><th style="width:24%;">Keyword</th><th>Destination URL</th><th style="width:10%;">Enabled</th><th style="width:22%;">Actions</th></tr></thead>
                <tbody>
                <?php if ( $rules ) : foreach ( $rules as $rule ) : ?>
                    <tr>
                        <td><strong><?php echo esc_html( $rule->keyword ); ?></strong></td>
                        <td><code class="dal-url"><?php echo esc_html( $rule->url ); ?></code><?php if ( ! $this->is_internal_url( $rule->url ) ) : ?> <span class="dal-pill" style="background:#fef3c7;color:#92400e;">Paid rule inactive in Free</span><?php endif; ?></td>
                        <td><?php echo (int) $rule->enabled === 1 ? '<span class="dal-pill" style="background:#dcfce7;color:#166534;">ON</span>' : '<span class="dal-pill" style="background:#fee2e2;color:#991b1b;">OFF</span>'; ?></td>
                        <td>
                            <a class="button button-small" href="<?php echo esc_url( wp_nonce_url( add_query_arg( array( 'page' => 'rootlinkd', 'tab' => 'rules', 'action' => 'edit', 'id' => (int) $rule->id ), admin_url( 'admin.php' ) ), 'dawnal_edit_' . (int) $rule->id ) ); ?>">Edit</a>
                            <a class="button button-small" href="<?php echo esc_url( wp_nonce_url( add_query_arg( array( 'page' => 'rootlinkd', 'tab' => 'rules', 'action' => 'toggle', 'id' => (int) $rule->id ), admin_url( 'admin.php' ) ), 'dawnal_toggle_' . (int) $rule->id ) ); ?>"><?php echo (int) $rule->enabled === 1 ? 'Disable' : 'Enable'; ?></a>
                            <a class="button button-small" href="<?php echo esc_url( wp_nonce_url( add_query_arg( array( 'page' => 'rootlinkd', 'tab' => 'rules', 'action' => 'delete', 'id' => (int) $rule->id ), admin_url( 'admin.php' ) ), 'dawnal_delete_' . (int) $rule->id ) ); ?>" onclick="return confirm('Delete this rule?');">Delete</a>
                        </td>
                    </tr>
                <?php endforeach; else : ?>
                    <tr><td colspan="4" style="text-align:center;padding:30px;">No rules yet. Add your first internal link rule above.</td></tr>
                <?php endif; ?>
                </tbody>
            </table>

            <div class="dal-upsell">
                <h3>Want control over where all those links appear?</h3>
                <p>Paid plans add placement controls, heading/title protection, first-paragraph exclusion, per-page limits, keyword variations, external and affiliate links, analytics, CSV tools, styles, randomization, and more.</p>
                <a class="button" href="<?php echo esc_url( admin_url( 'admin.php?page=rootlinkd&tab=upgrade' ) ); ?>">See what paid unlocks</a>
            </div>
        </div>
        <?php
    }

    public function upgrade_page_content() {
        $upgrade_url = ( $this->fs_active && function_exists( 'dawnal_fs' ) && method_exists( dawnal_fs(), 'get_upgrade_url' ) ) ? dawnal_fs()->get_upgrade_url() : 'https://rootlinkd.com/pricing/';
        ?>
        <div class="dal-card">
            <h2 style="margin-top:0;">Upgrade rootlinkd</h2>
            <p>Free automates exact-match internal links with no placement or volume controls. Paid plans add control, intelligence, monetization, and workflow tools.</p>
            <div class="dal-grid">
                <div><h3>FREE</h3><ul><li>Unlimited internal-link rules</li><li>Exact keyword/phrase only</li><li>Every eligible match can link</li><li>Theme-default link appearance</li></ul></div>
                <div><h3>PRO</h3><ul><li>1 site</li><li>Placement and volume controls</li><li>Heading/title-safe behavior</li><li>Skip first paragraphs</li><li>External links, variations, styles and per-page disable</li></ul></div>
                <div><h3>BUSINESS</h3><ul><li>5 sites</li><li>Affiliate links</li><li>More keyword variations</li><li>Analytics and randomizer</li><li>CSV import/export</li></ul></div>
                <div><h3>DEVELOPER</h3><ul><li>Everything in Business</li><li>Unlimited sites</li><li>Unlimited keyword variations</li><li>Destination URL autocomplete</li></ul></div>
            </div>
            <p><a class="button button-primary button-hero" href="<?php echo esc_url( $upgrade_url ); ?>">View Premium Plans</a></p>
        </div>
        <?php
    }

    private function is_internal_url( $url ) {
        $url_host  = wp_parse_url( $url, PHP_URL_HOST );
        $home_host = wp_parse_url( home_url( '/' ), PHP_URL_HOST );
        if ( empty( $url_host ) || empty( $home_host ) ) { return false; }
        $url_host  = strtolower( preg_replace( '/^www\./i', '', $url_host ) );
        $home_host = strtolower( preg_replace( '/^www\./i', '', $home_host ) );
        return hash_equals( $home_host, $url_host );
    }

    /**
     * Fetch every enabled internal rule. Free deliberately has no rule-count cap.
     * Premium rows are preserved in the shared table but ignored here.
     *
     * @return array<int,object>
     */
    private function get_internal_rules() {
        global $wpdb;

        $rules = wp_cache_get( DAWNAL_CACHE_KEY_RULES );
        if ( false === $rules ) {
            $rules = $wpdb->get_results( "SELECT * FROM {$this->table_name} WHERE enabled = 1 ORDER BY LENGTH(keyword) DESC, keyword ASC" ); // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
            wp_cache_set( DAWNAL_CACHE_KEY_RULES, $rules, '', DAWNAL_CACHE_TTL );
        }

        if ( empty( $rules ) || ! is_array( $rules ) ) { return array(); }

        $internal_rules = array();
        foreach ( $rules as $rule ) {
            if ( empty( $rule->keyword ) || empty( $rule->url ) ) { continue; }
            if ( ! $this->is_internal_url( (string) $rule->url ) ) { continue; }
            $internal_rules[] = (object) array(
                'id'      => (int) $rule->id,
                'keyword' => (string) $rule->keyword,
                'url'     => (string) $rule->url,
            );
        }

        return $internal_rules;
    }

    /**
     * Exact keyword/phrase matcher. Case-insensitive and Unicode aware, while
     * avoiding matches embedded inside a larger letter/number/underscore token.
     */
    private function keyword_pattern( $keyword ) {
        return '/(?<![\p{L}\p{N}_])(' . preg_quote( $keyword, '/' ) . ')(?![\p{L}\p{N}_])/iu';
    }

    public function auto_link_content( $content ) {
        if ( empty( $content ) || is_feed() ) { return $content; }
        if ( is_admin() && ! wp_doing_ajax() ) { return $content; }
        if ( false !== strpos( $content, 'dal-auto-link' ) ) { return $content; }

        $rules = $this->get_internal_rules();
        if ( empty( $rules ) ) { return $content; }

        if ( $this->dom_available ) {
            return $this->auto_link_with_dom( $content, $rules );
        }
        return $this->auto_link_with_regex( $content, $rules );
    }

    /**
     * Link the main singular post/page title. We intentionally avoid archive,
     * navigation, admin and secondary-loop titles because themes commonly wrap
     * those in an existing permalink; inserting another <a> would create invalid
     * nested anchors. On a singular main title, Free has no title-exclusion control.
     */
    public function auto_link_title( $title, $post_id = 0 ) {
        if ( empty( $title ) || is_admin() || is_feed() ) { return $title; }
        if ( false !== strpos( $title, 'dal-auto-link' ) || false !== stripos( $title, '<a ' ) ) { return $title; }
        if ( ! function_exists( 'is_singular' ) || ! is_singular() ) { return $title; }
        if ( function_exists( 'in_the_loop' ) && ! in_the_loop() ) { return $title; }
        if ( function_exists( 'is_main_query' ) && ! is_main_query() ) { return $title; }
        if ( function_exists( 'get_queried_object_id' ) ) {
            $queried_id = (int) get_queried_object_id();
            if ( $queried_id > 0 && (int) $post_id > 0 && $queried_id !== (int) $post_id ) { return $title; }
        }

        $rules = $this->get_internal_rules();
        if ( empty( $rules ) ) { return $title; }

        return $this->link_plain_text( $title, $rules, true );
    }

    /**
     * DOM mode links every match of every internal rule. Headings are NOT skipped
     * in Free. Existing anchors and technical markup are always protected so the
     * plugin cannot create nested links or corrupt scripts/styles/code.
     */
    private function auto_link_with_dom( $content, $rules ) {
        try {
            $dom      = new DOMDocument( '1.0', 'UTF-8' );
            $previous = libxml_use_internal_errors( true );
            $html     = '<?xml encoding="utf-8" ?><body>' . $content . '</body>';
            $loaded   = $dom->loadHTML( $html, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD );
            libxml_clear_errors();
            libxml_use_internal_errors( $previous );

            if ( ! $loaded ) { return $this->auto_link_with_regex( $content, $rules ); }

            $xpath = new DOMXPath( $dom );

            foreach ( $rules as $rule ) {
                $keyword = trim( (string) $rule->keyword );
                if ( '' === $keyword ) { continue; }
                $pattern = $this->keyword_pattern( $keyword );

                // Re-query after every rule so links inserted by earlier rules are
                // excluded from subsequent matching. H1-H6 remain eligible.
                $text_nodes = $xpath->query( '//text()[not(ancestor::a) and not(ancestor::script) and not(ancestor::style) and not(ancestor::code) and not(ancestor::pre) and not(ancestor::textarea)]' );
                if ( ! $text_nodes ) { continue; }

                // Snapshot because the live DOM is modified while iterating.
                $nodes = array();
                foreach ( $text_nodes as $text_node ) { $nodes[] = $text_node; }

                foreach ( $nodes as $text_node ) {
                    if ( ! $text_node->parentNode ) { continue; }
                    $text = $text_node->nodeValue;
                    if ( ! is_string( $text ) || '' === trim( $text ) ) { continue; }

                    $matched = preg_match_all( $pattern, $text, $matches, PREG_OFFSET_CAPTURE );
                    if ( ! $matched || empty( $matches[1] ) ) { continue; }

                    $parent = $text_node->parentNode;
                    $cursor = 0;
                    foreach ( $matches[1] as $match ) {
                        $match_text   = $match[0];
                        $match_offset = (int) $match[1];
                        if ( $match_offset > $cursor ) {
                            $parent->insertBefore( $dom->createTextNode( substr( $text, $cursor, $match_offset - $cursor ) ), $text_node );
                        }

                        $link = $dom->createElement( 'a' );
                        // esc_url_raw(): DOMDocument encodes attribute values itself on
                        // saveHTML(). esc_url() here would double-encode "&" in query strings.
                        $link->setAttribute( 'href', esc_url_raw( (string) $rule->url ) );
                        $link->setAttribute( 'class', 'dal-auto-link' );
                        $link->appendChild( $dom->createTextNode( $match_text ) );
                        $parent->insertBefore( $link, $text_node );

                        $cursor = $match_offset + strlen( $match_text );
                    }

                    if ( $cursor < strlen( $text ) ) {
                        $parent->insertBefore( $dom->createTextNode( substr( $text, $cursor ) ), $text_node );
                    }
                    $parent->removeChild( $text_node );
                }
            }

            $body = $dom->getElementsByTagName( 'body' )->item( 0 );
            if ( ! $body ) { return $content; }

            $final = '';
            foreach ( $body->childNodes as $child ) { $final .= $dom->saveHTML( $child ); }
            return $final ?: $content;
        } catch ( Throwable $e ) {
            dawnal_log( 'Free DOM linking error, falling back to regex.', array( 'msg' => $e->getMessage() ) );
            return $this->auto_link_with_regex( $content, $rules );
        }
    }

    /**
     * Regex fallback tokenizes HTML tags so replacements happen only in text,
     * never attributes. Existing anchors and technical elements are skipped.
     * Headings and paragraphs are deliberately NOT skipped in Free.
     */
    private function auto_link_with_regex( $content, $rules ) {
        $parts = preg_split(
            '/(<!--.*?-->|<!\[CDATA\[.*?\]\]>|<[^>]+>)/s',
            $content,
            -1,
            PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY
        );
        if ( false === $parts ) { return $content; }

        $protected = array( 'a', 'script', 'style', 'code', 'pre', 'textarea' );
        $stack     = array();
        $output    = '';

        foreach ( $parts as $part ) {
            if ( isset( $part[0] ) && '<' === $part[0] ) {
                if ( preg_match( '/^<\s*\/\s*([a-z0-9:-]+)/i', $part, $m ) ) {
                    $tag = strtolower( $m[1] );
                    if ( in_array( $tag, $protected, true ) ) {
                        for ( $i = count( $stack ) - 1; $i >= 0; $i-- ) {
                            if ( $stack[ $i ] === $tag ) {
                                array_splice( $stack, $i, 1 );
                                break;
                            }
                        }
                    }
                } elseif ( preg_match( '/^<\s*([a-z0-9:-]+)/i', $part, $m ) ) {
                    $tag = strtolower( $m[1] );
                    if ( in_array( $tag, $protected, true ) && ! preg_match( '/\/\s*>$/', $part ) ) {
                        $stack[] = $tag;
                    }
                }
                $output .= $part;
                continue;
            }

            $output .= empty( $stack ) ? $this->link_plain_text( $part, $rules, false ) : $part;
        }

        return $output;
    }

    /**
     * Link all exact matches in a plain-text fragment. Longer keywords are already
     * ordered first. Temporary control-character placeholders prevent later rules
     * from re-linking text already claimed by an earlier rule.
     */
    private function link_plain_text( $text, $rules, $escape_match_text = false ) {
        if ( '' === $text ) { return $text; }

        $original_text = $text;
        $placeholders  = array();
        $token_seed    = 0;

        foreach ( $rules as $rule ) {
            $keyword = trim( (string) $rule->keyword );
            if ( '' === $keyword ) { continue; }
            $pattern = $this->keyword_pattern( $keyword );

            $text = preg_replace_callback(
                $pattern,
                function ( $match ) use ( $rule, $escape_match_text, &$placeholders, &$token_seed ) {
                    $token_seed++;
                    $token = "\x1A" . str_repeat( "\x1B", $token_seed ) . "\x1A";
                    $label = $escape_match_text ? esc_html( $match[1] ) : $match[1];
                    $placeholders[ $token ] = '<a href="' . esc_url( (string) $rule->url ) . '" class="dal-auto-link">' . $label . '</a>';
                    return $token;
                },
                $text
            );
            if ( null === $text ) { return $original_text; }
        }

        if ( empty( $placeholders ) ) { return $original_text; }

        // Title context: escape the unmatched portions too, so the whole returned
        // string is escaped. Placeholder tokens are control characters that
        // esc_html() leaves intact; the links swapped in afterwards are built from
        // esc_url() and esc_html() above.
        if ( $escape_match_text ) {
            $text = esc_html( $text );
        }

        return strtr( $text, $placeholders );
    }
}