<?php
/**
 * Plugin Name: Add Smart Wayback Machine links to URLs
 * Plugin URI: https://vertikal.dk/wordpress-wayback-filter
 * Description: Custom filter to add Wayback Machine links to links in posts above a certain age
 * Version: 1.0.2
 * Author: Steven Snedker
 * License: GPL v2 or later
 * License URI: https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain: add-smart-wayback-machine-links-to-urls
 * Domain Path: /
 */

// Prevent direct access
if (!defined('ABSPATH')) {
    exit;
}

// Define plugin constants
define('WAYBACK_FILTER_VERSION', '1.2.1');
define('WAYBACK_FILTER_PLUGIN_DIR', plugin_dir_path(__FILE__));
define('WAYBACK_FILTER_PLUGIN_URL', plugin_dir_url(__FILE__));

/**
 * Main Wayback Filter class
 */
class WaybackFilter {

    /**
     * Constructor
     */
    public function __construct() {
        add_action('init', array($this, 'init'));
        add_action('wp_enqueue_scripts', array($this, 'enqueue_scripts'));
        add_action('admin_enqueue_scripts', array($this, 'admin_enqueue_scripts'));

        // Admin hooks
        add_action('admin_menu', array($this, 'add_admin_menu'));
        add_action('admin_init', array($this, 'register_settings'));

        // Content filtering hooks
        add_filter('the_content', array($this, 'filter_content'), 999);

        // Activation/Deactivation hooks
        register_activation_hook(__FILE__, array($this, 'activate'));
        register_deactivation_hook(__FILE__, array($this, 'deactivate'));
    }

    /**
     * Initialize the plugin
     */
    public function init() {
        // Nothing needed here for text domain loading
    }

    /**
     * Enqueue frontend scripts and styles
     */
    public function enqueue_scripts() {
        // Only enqueue on posts/pages where the filter might apply
        if (is_single() || is_page()) {
            wp_enqueue_script(
                'add-smart-wayback-machine-links-to-urls-js',
                WAYBACK_FILTER_PLUGIN_URL . 'js/add-smart-wayback-machine-links-to-urls.js',
                array('jquery'),
                WAYBACK_FILTER_VERSION,
                array('in_footer' => true, 'strategy' => 'defer')
            );
            wp_enqueue_style(
                'add-smart-wayback-machine-links-to-urls-css',
                WAYBACK_FILTER_PLUGIN_URL . 'css/add-smart-wayback-machine-links-to-urls.css',
                array(),
                WAYBACK_FILTER_VERSION
            );
        }
    }

    /**
     * Enqueue admin scripts
     */
    public function admin_enqueue_scripts($hook) {
        if ($hook === 'settings_page_add-smart-wayback-machine-links-to-urls') {
            wp_enqueue_script(
                'add-smart-wayback-machine-links-to-urls-admin-js',
                WAYBACK_FILTER_PLUGIN_URL . 'js/add-smart-wayback-machine-links-to-urls-admin.js',
                array('jquery'),
                WAYBACK_FILTER_VERSION,
                array('in_footer' => true)
            );
        }
    }

    /**
     * Add admin menu
     */
    public function add_admin_menu() {
        add_options_page(
            __('Add Smart Wayback Machine links to URLs Settings', 'add-smart-wayback-machine-links-to-urls'),
            __('Add Smart Wayback Machine links to URLs', 'add-smart-wayback-machine-links-to-urls'),
            'manage_options',
            'add-smart-wayback-machine-links-to-urls',
            array($this, 'admin_page')
        );
    }

    /**
     * Register plugin settings
     */
    public function register_settings() {
        register_setting('wayback_filter_settings', 'wayback_filter_options', array(
            'type' => 'array',
            'sanitize_callback' => array($this, 'validate_options'),
            'default' => array()
        ));

        add_settings_section(
            'wayback_filter_main',
            __('Add Smart Wayback Machine links to URLs Settings', 'add-smart-wayback-machine-links-to-urls'),
            array($this, 'settings_section_callback'),
            'add-smart-wayback-machine-links-to-urls'
        );

        add_settings_field(
            'waybacklink_icon',
            __('Icon or text for the Wayback link', 'add-smart-wayback-machine-links-to-urls'),
            array($this, 'icon_field_callback'),
            'add-smart-wayback-machine-links-to-urls',
            'wayback_filter_main'
        );

        add_settings_field(
            'waybacklink_title',
            __('Link title for the Wayback link', 'add-smart-wayback-machine-links-to-urls'),
            array($this, 'title_field_callback'),
            'add-smart-wayback-machine-links-to-urls',
            'wayback_filter_main'
        );

        add_settings_field(
            'waybacklink_start',
            __('Place Wayback links on posts older than...', 'add-smart-wayback-machine-links-to-urls'),
            array($this, 'start_field_callback'),
            'add-smart-wayback-machine-links-to-urls',
            'wayback_filter_main'
        );

        add_settings_field(
            'field_types',
            __('Content types to apply filter to', 'add-smart-wayback-machine-links-to-urls'),
            array($this, 'field_types_callback'),
            'add-smart-wayback-machine-links-to-urls',
            'wayback_filter_main'
        );
    }

    /**
     * Settings section callback
     */
    public function settings_section_callback() {
        echo '<p>' . esc_html__('Configure how Wayback Machine links are added to your older posts.', 'add-smart-wayback-machine-links-to-urls') . '</p>';
    }


    /**
     * Renders the input field for the wayback link icon.
     *
     * This function is a callback for the WordPress Settings API (add_settings_field).
     * It displays a text input where users can set the icon/emoji and provides
     * helpful recommendations and links.
     *
     * @since 1.0.0
     *
     * @param array $args Arguments passed from add_settings_field. Not used in this function.
     */
    public function icon_field_callback( $args = array() ) {
        // 1. Define constants/variables for option names and defaults.
        $option_group = 'wayback_filter_options';
        $option_name  = 'waybacklink_icon';
        $default_icon = '🏛️';

        // 2. Get the saved option value, providing a default.
        $options = get_option( $option_group, [] );
        $value   = isset( $options[ $option_name ] ) && ! empty( $options[ $option_name ] ) ? $options[ $option_name ] : $default_icon;

        // 3. Prepare the description text for translation.
        $description_text = sprintf(
            /* translators: 1: A link to the 'building' emoji. 2: A link to the 'floppy disk' emoji. 3: A link to the 'circle arrow' unicode character. 4: The text for an example link. 5: A link to the Emojipedia website. */
            esc_html__( 'Enter an emoji, a unicode character or some text. %1$s We recommend %2$s (classical building), %3$s (floppy disk), %4$s (circle arrow) or simply the text %5$s. %1$s You can find more emojis at %6$s.', 'add-smart-wayback-machine-links-to-urls' ),
            '<br />', // Placeholder for line break.
            sprintf( '<a href="%s" target="_blank" rel="noopener">🏛️</a>', esc_url( 'https://emojipedia.org/classical-building/' ) ),
            sprintf( '<a href="%s" target="_blank" rel="noopener">💾</a>', esc_url( 'https://emojipedia.org/floppy-disk/' ) ),
            sprintf( '<a href="%s" target="_blank" rel="noopener">⟲</a>', esc_url( 'https://www.compart.com/en/unicode/U+27F2' ) ),
            '<em>[Wayback link]</em>',
            sprintf( '<a href="%s" target="_blank" rel="noopener">Emojipedia</a>', esc_url( 'https://emojipedia.org/' ) )
        );

        // 4. Define the allowed HTML for wp_kses.
        $allowed_html = [
            'a'  => [
                'href'   => [],
                'target' => [],
                'rel'    => [],
            ],
            'br' => [],
            'em' => [],
        ];

        // 5. Output the final HTML.
        ?>
        <input
            type="text"
            id="<?php echo esc_attr( $option_name ); ?>"
            name="<?php echo esc_attr( "{$option_group}[{$option_name}]" ); ?>"
            value="<?php echo esc_attr( $value ); ?>"
            class="regular-text"
            size="20"
        />
        <p class="description">
            <?php echo wp_kses( $description_text, $allowed_html ); ?>
        </p>
        <?php
    }

    /**
     * Title field callback
     */
    public function title_field_callback() {
        $options = get_option('wayback_filter_options', array());
        $value = isset($options['waybacklink_title']) ? $options['waybacklink_title'] : __('Click to see an archived version of the destination page.', 'add-smart-wayback-machine-links-to-urls');
        echo '<input type="text" id="waybacklink_title" name="wayback_filter_options[waybacklink_title]" value="' . esc_attr($value) . '" size="60" />';
        echo '<p class="description">' . esc_html__('This is what desktop users get to read when their cursor hovers over the Wayback link.', 'add-smart-wayback-machine-links-to-urls') . '</p>';
    }

    /**
     * Start field callback
     */
    public function start_field_callback() {
        $options = get_option('wayback_filter_options', array());
        $value = isset($options['waybacklink_start']) ? $options['waybacklink_start'] : 3;
        echo '<input type="number" id="waybacklink_start" name="wayback_filter_options[waybacklink_start]" value="' . esc_attr($value) . '" min="0" max="30" /> ' . esc_html__('years', 'add-smart-wayback-machine-links-to-urls');
        echo '<p class="description">' . esc_html__('Posts older than this many years will get trailing Wayback links.', 'add-smart-wayback-machine-links-to-urls') . '</p>';
    }

    /**
     * Field types callback
     */
    public function field_types_callback() {
        $options = get_option('wayback_filter_options', array());
        $post_types = get_post_types(array('public' => true), 'objects');
        $selected_types = isset($options['field_types']) ? $options['field_types'] : array('post');

        foreach ($post_types as $post_type) {
            $checked = in_array($post_type->name, $selected_types, true) ? 'checked="checked"' : '';
            echo '<label><input type="checkbox" name="wayback_filter_options[field_types][]" value="' . esc_attr($post_type->name) . '" ' . esc_attr($checked) . ' /> ' . esc_html($post_type->label) . '</label><br />';
        }
        echo '<p class="description">' . esc_html__('Select which post types should have Wayback links added to their content.', 'add-smart-wayback-machine-links-to-urls') . '</p>';
    }

    /**
     * Validate options
     */
    public function validate_options($input) {
        $validated = array();

        if (isset($input['waybacklink_icon'])) {
            $validated['waybacklink_icon'] = sanitize_text_field($input['waybacklink_icon']);
        }

        if (isset($input['waybacklink_title'])) {
            $validated['waybacklink_title'] = sanitize_text_field($input['waybacklink_title']);
        }

        if (isset($input['waybacklink_start'])) {
            $validated['waybacklink_start'] = absint($input['waybacklink_start']);
        }

        if (isset($input['field_types']) && is_array($input['field_types'])) {
            $validated['field_types'] = array_map('sanitize_key', $input['field_types']);
        }

        return $validated;
    }

    /**
     * Admin page
     */
    public function admin_page() {
        if (!current_user_can('manage_options')) {
            wp_die(esc_html__('You do not have sufficient permissions to access this page.', 'add-smart-wayback-machine-links-to-urls'));
        }
        ?>
        <div class="wrap">
            <h1><?php echo esc_html(get_admin_page_title()); ?></h1>

            <div class="wayback-preview">
                <h3><?php esc_html_e('Preview of a link with a trailing Wayback link', 'add-smart-wayback-machine-links-to-urls'); ?></h3>
                <p>
                    <a href="https://vertikal.dk/linkrot-solved-problem"><?php esc_html_e('Sample Link', 'add-smart-wayback-machine-links-to-urls'); ?></a>
                    <a href="https://web.archive.org/web/20160310202428/http://vertikal.dk/linkrot-solved-problem"
                       title="<?php echo esc_attr(__('Click to see an archived version of the destination page.', 'add-smart-wayback-machine-links-to-urls')); ?>"
                       class="wayback-link"
                       id="waybacklink_preview">🏛️</a>
                </p>
            </div>

            <form method="post" action="options.php">
                <?php
                settings_fields('wayback_filter_settings');
                do_settings_sections('add-smart-wayback-machine-links-to-urls');
                submit_button();
                ?>
            </form>

            <div class="wayback-help">
                <h3><?php esc_html_e('Advanced Help', 'add-smart-wayback-machine-links-to-urls'); ?></h3>
                <p><?php esc_html_e('Most people will be able to see emojis and unicode characters. Even if they differ a bit between platforms. Only desktop users will be able to see the link title and only when their cursor hovers over the Wayback link. The Wayback link can be styled by adding styles to the css class "wayback-link" (i.e .wayback-link {font-size: 0.8rem; color: red;} somewhere in your stylesheet will make the Wayback link small and red.)', 'add-smart-wayback-machine-links-to-urls'); ?></p>
            </div>
        </div>
        <?php
    }

    /**
     * Filter content to add Wayback links
     */
    public function filter_content($content) {
        global $post;

        // Only process single post/page views
        if (!is_single() && !is_page()) {
            return $content;
        }

        // Verify we have a valid post object
        if (!$post || !isset($post->post_type, $post->post_date)) {
            return $content;
        }

        $options = get_option('wayback_filter_options', array());
        $selected_types = isset($options['field_types']) ? $options['field_types'] : array('post');

        // Check if current post type should be processed
        if (!in_array($post->post_type, $selected_types, true)) {
            return $content;
        }

        // Check post age
        $waybacklink_start = isset($options['waybacklink_start']) ? $options['waybacklink_start'] : 3;
        $waybacklink_start_date = strtotime('-' . $waybacklink_start . ' years');

        if ($waybacklink_start === 0) {
            $waybacklink_start_date = 0; // Always show for 0 years
        }

        $post_date = strtotime($post->post_date);

        if ($post_date > $waybacklink_start_date) {
            return $content; // Post is too new
        }

        // Process links in content
        $waybacklink_icon = isset($options['waybacklink_icon']) ? $options['waybacklink_icon'] : '🏛️';
        $waybacklink_title = isset($options['waybacklink_title']) ? $options['waybacklink_title'] : __('Click to see an archived version of the destination page.', 'add-smart-wayback-machine-links-to-urls');

        $time = gmdate('YmdHis', $post_date);

        // Regular expression to find links
        $regexp = '/<a\s[^>]*href=(["\'`])([^"\' >]*?)\1[^>]*>(.*?)<\/a>/si';

        preg_match_all($regexp, $content, $matches, PREG_SET_ORDER);
        $processed_urls = array();

        foreach ($matches as $match) {
            $full_link = $match[0];
            $url = $match[2];

            // Skip if already a Wayback link
            if (strpos($url, 'web.archive.org') !== false) {
                continue;
            }

            // Skip if not http/https
            if (!preg_match('/^https?:\/\//', $url)) {
                continue;
            }

            // Skip if already processed
            if (isset($processed_urls[$url])) {
                continue;
            }

            $processed_urls[$url] = true;

            // Create Wayback link
            $wayback_url = 'https://web.archive.org/web/' . $time . '/' . $url;
            $wayback_link = ' <a title="' . esc_attr($waybacklink_title) . '" class="wayback-link" href="' . esc_url($wayback_url) . '" rel="noopener noreferrer" target="_blank"><span class="waybacklink_icon">' . esc_html($waybacklink_icon) . '</span></a>';

            // Replace the original link with link + wayback link
            $content = str_replace($full_link, $full_link . $wayback_link, $content);
        }

        return $content;
    }

    /**
     * Plugin activation
     */
    public function activate() {
        // Set default options
        $default_options = array(
            'waybacklink_icon' => '🏛️',
            'waybacklink_title' => __('Click to see an archived version of the destination page.', 'add-smart-wayback-machine-links-to-urls'),
            'waybacklink_start' => 3,
            'field_types' => array('post')
        );

        add_option('wayback_filter_options', $default_options);
    }

    /**
     * Plugin deactivation
     */
    public function deactivate() {
        // Clean up if needed
    }
}

// Initialize the plugin
new WaybackFilter();