<?php
/**
 * MainWP Warm Cache Helper.
 *
 * @package MainWP/Dashboard
 */

namespace MainWP\Dashboard;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

/**
 * Class MainWP_System
 *
 * @package MainWP\Dashboard
 */
class MainWP_Cache_Warm_Helper { // phpcs:ignore Generic.Classes.OpeningBraceSameLine.ContentAfterBrace -- NOSONAR.

    const WPC_VER = '1';

    /**
     * Private static variable to hold the single instance of the class.
     *
     * @var mixed Default null
     */
    private static $instance = null;

    /**
     * Private static variable to hold processed list of invalidated pages.
     *
     * @var mixed Default array
     */
    private static $invalidated_processed = array();

    /**
     * Method instance()
     *
     * Create a public static instance.
     *
     * @static
     * @return MainWP_System
     */
    public static function instance() {
        if ( null === static::$instance ) {
            static::$instance = new self();
        }
        return static::$instance;
    }

    /**
     * Constructor.
     *
     * Runs any time class is called.
     */
    public function __construct() { //phpcs:ignore -- NOSONAR - complex.
        add_action( 'current_screen', array( __CLASS__, 'init_no_cache_header' ), 999 );
        /**
         * Action to Invalide warm cache pages.
         *
         * @since 5.5.
         */
        add_action( 'mainwp_invalidate_warm_cache_pages', array( __CLASS__, 'hook_warm_cache_invalidate_pages' ), 10, 2 );
    }

    /**
     * Method init_no_cache_header()
     */
    public static function init_no_cache_header() {
        if ( MainWP_System::is_mainwp_pages() ) {
            $page = isset( $_GET['page'] ) ? wp_unslash( $_GET['page'] ) : ''; // phpcs:ignore WordPress.Security.NonceVerification,WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
            if ( ! headers_sent() && ! static::is_excluded_warm_cache_pages( $page ) ) {
                $maxage = get_option( 'mainwp_warm_cache_pages_ttl', 10 );
                if ( empty( $maxage ) ) {
                    return;
                }
                static::verify_current_page_no_cache_header();
            }
        }
    }

    /**
     * Method hook_warm_cache_invalidate_pages().
     *
     * @param array $pages List pages to invalidate.
     */
    public static function hook_warm_cache_invalidate_pages( $pages = array() ) {
        static::invalidate_manage_pages( $pages );
    }

    /**
     * Method invalidate_manage_pages().
     *
     * @param array $pages List pages to invalidate.
     */
    public static function invalidate_manage_pages( $pages = array() ) {
        if ( ! empty( $pages ) && is_array( $pages ) ) {
            foreach ( $pages as $page ) {
                static::invalidate_page_warm_cache( $page );
            }
        }
    }

    /**
     * Method invalidate_pages_by_site_actions().
     *
     * @param array $action Site actions.
     */
    public static function invalidate_pages_by_site_actions( $action ) {
        if ( 'stats' === $action ) {
            static::invalidate_manage_pages( array( 'mainwp_tab', 'managesites' ) );
        }
    }

    /**
     * Method maybe_invalidate_page_by_params().
     *
     * @param array $page pages to invalidate.
     * @param array $params Request params.
     */
    public static function maybe_invalidate_page_by_params( $page = '', $params = array() ) {
        if ( ! empty( $page ) ) {
            $page_key      = static::get_warm_cache_page_key( $page );
            $prefix_key    = static::get_page_warm_cache_key_prefix( $page_key );
            $prefix_params = static::generate_warm_cache_params_prefix( $params );
            MainWP_Logger::instance()->log_events( 'warm-cache', 'Maybe Invalidate :: [page=' . $page . '] :: [params=' . print_r( $params, true ) . '] :: [prefix_key=' . $prefix_key . '] :: [prefix_params=' . $prefix_params . ']' ); //phpcs:ignore -- ok.
            if ( $prefix_key !== $prefix_params ) {
                // set new prefix.
                static::set_page_warm_cache_key_prefix( $page_key, $prefix_params );
                // invalidate the cache.
                static::invalidate_page_warm_cache( $page );
            } else {
                MainWP_Logger::instance()->log_events( 'warm-cache', 'No Invalidate :: [page=' . $page . ']' );
            }
        }
    }

    /**
     * Method verify_current_page_no_cache_header()
     */
    private static function verify_current_page_no_cache_header() { // phpcs:ignore -- NOSONAR -complex method.

        $page = isset($_GET['page']) ? preg_replace('/[^a-z0-9_\-]/i', '', $_GET['page']) : ''; //phpcs:ignore -- ok.

        if ( empty( $page ) ) {
            return;
        }

        $method  = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( $_SERVER['REQUEST_METHOD'] ) : ''; //phpcs:ignore -- WPCS: sanitization ok.
        if ( ! in_array( $method, array( 'GET', 'HEAD' ) ) ) {
            return;
        }

        // Your real "last time this page's data changed" (must be stable until content changes!).
        $lastChangedTs = (int) static::get_current_page_warm_cache_last_changed();

        if ( empty( $lastChangedTs ) ) {
            return;
        }

        $etag = static::get_current_page_etag_header();

        $lastModified = gmdate( 'D, d M Y H:i:s', $lastChangedTs ) . ' GMT';

        // Clear conflicting headers first.
        header_remove( 'Pragma' );
        header_remove( 'Expires' );
        header_remove( 'Cache-Control' );

        // ====== Freshness policy ======
        // Always revalidate before use (keeps a cached copy, but checks each navigation).
        header( 'Cache-Control: private, no-cache' );
        // If you prefer a TTL, use e.g.: header('Cache-Control: private, max-age=60, must-revalidate');.

        header( "ETag: $etag" );
        header( "Last-Modified: $lastModified" );
        header( 'Vary: Accept-Encoding' ); // safe variant separation.

        // ====== Conditional handling (304 if unchanged) ======.
        $ifNoneMatch     = $_SERVER['HTTP_IF_NONE_MATCH'] ?? ''; //phpcs:ignore -- ok.
        $ifModifiedSince = $_SERVER['HTTP_IF_MODIFIED_SINCE'] ?? ''; //phpcs:ignore -- ok.

        $normalize = static function ( string $t ): string {
            $t = trim( $t );
            if ( strncasecmp( $t, 'W/', 2 ) === 0 ) {
                $t = substr( $t, 2 ); // ignore weak prefix.
            }
            return $t;
        };

        $etagMatch = false;
        if ( '' !== $ifNoneMatch ) {
            foreach ( explode( ',', $ifNoneMatch ) as $cand ) {
                if ( $normalize( $cand ) === $etag ) {
                    $etagMatch = true;
                    break;
                }
            }
        }

        $lmMatch = ( '' !== $ifModifiedSince ) && ( strtotime( $ifModifiedSince ) >= $lastChangedTs );

        // If either validator matches, nothing changed → 304.
        if ( $etagMatch || $lmMatch ) {
            http_response_code( 304 );
            // Re-send validators with 304.
            header( "ETag: $etag" );
            header( "Last-Modified: $lastModified" );
            exit;
        }
    }

    /**
     * Method get_page_warm_cache_last_change_key().
     *
     * @param string $page The page.
     *
     * @return string The key prefix.
     */
    public static function get_page_warm_cache_last_change_key( $page = '' ) {
        $page_key   = static::get_warm_cache_page_key( $page );
        $prefix_key = static::get_page_warm_cache_key_prefix( $page_key );
        if ( empty( $prefix_key ) ) {
            return '';
        }
        return 'mainwp_warm_cache_page_last_changed_key_' . $prefix_key;
    }

    /**
     * Method get_warm_cache_page_key().
     *
     * @param string $page The page.
     *
     * @return string The key.
     */
    public static function get_warm_cache_page_key( $page = '' ) {

        if ( empty( $page ) ) {
             $page = isset($_GET['page']) ? preg_replace('/[^a-z0-9_\-]/i', '', $_GET['page']) : ''; //phpcs:ignore -- ok.
            if ( empty( $page ) ) {
                return '';
            }
        }

        // Per-user id.
        if ( function_exists( 'get_current_user_id' ) ) {
            $userId = (int) get_current_user_id();
        } else {
            $userId = 0;
        }

        return sha1( 'v:' . static::WPC_VER . "|u:$userId|p:$page" ); // NOSONAR - is sufficient for keys.
    }


    /**
     * Method get_page_warm_cache_key_prefix().
     *
     * @param string $page_key The page key.
     *
     * @return string The key.
     */
    public static function get_page_warm_cache_key_prefix( $page_key = '' ) {

        if ( empty( $page_key ) ) {
            return '';
        }

        $prefix = get_transient( 'mainwp_warm_cache_last_changed_key_prefix_' . $page_key );

        if ( empty( $prefix ) ) {
            $prefix = static::set_page_warm_cache_key_prefix( $page_key ); // set default prefix.
        }

        return $prefix;
    }

    /**
     * Method set_page_warm_cache_key_prefix().
     *
     * @param string $page_key The page key.
     * @param string $prefix_params The params prefix.
     *
     * @return string The key.
     */
    public static function set_page_warm_cache_key_prefix( $page_key = '', $prefix_params = '' ) {

        if ( empty( $page_key ) ) {
            return '';
        }

        $maxage  = (int) get_option( 'mainwp_warm_cache_pages_ttl', 10 );
        $seconds = $maxage * 60;

        if ( ! empty( $prefix_params ) ) {
            $prefix_key = $prefix_params;
        } else {
            $prefix_key = $page_key;
        }

        set_transient( 'mainwp_warm_cache_last_changed_key_prefix_' . $page_key, $prefix_key, $seconds );

        return $prefix_key;
    }

    /**
     * Method generate_warm_cache_params_prefix().
     *
     * @param array $params The page params.
     *
     * @return string The key.
     */
    public static function generate_warm_cache_params_prefix( $params = array() ) {
        $key_params = 'params:';
        if ( ! empty( $params ) ) {
            $normalized_key = MainWP_Cache_Helper::get_params_key( $params );
            if ( ! empty( $normalized_key ) ) {
                $key_params .= $normalized_key;
            }
        }
        return sha1( $key_params ); // NOSONAR - is sufficient for keys.
    }


    /**
     * Method get_current_page_warm_cache_last_changed().
     *
     * @return int Last change timestamp.
     */
    public static function get_current_page_warm_cache_last_changed() {

        $lastchanged = (int) static::get_page_last_changed_cache();

        $maxage  = (int) get_option( 'mainwp_warm_cache_pages_ttl', 10 );
        $seconds = $maxage * 60;

        if ( empty( $lastchanged ) || (int) $lastchanged < time() - $seconds ) {
            $lastchanged      = time();
            $last_changed_key = static::get_page_warm_cache_last_change_key();
            if ( ! empty( $last_changed_key ) ) {
                set_transient( $last_changed_key, $lastchanged, $seconds );
            }
        }

        return $lastchanged;
    }


    /**
     * Method get_current_page_etag_header().
     *
     * @return string Etag.
     */
    public static function get_current_page_etag_header() {
        return static::get_page_etag_header();
    }

    /**
     * Method get_page_etag_header().
     *
     * @param string $page Page to get Etag header.
     *
     * @return string Etag.
     */
    public static function get_page_etag_header( $page = '' ) {

        if ( empty( $page ) ) {
             $page = isset($_GET['page']) ? preg_replace('/[^a-z0-9_\-]/i', '', $_GET['page']) : ''; //phpcs:ignore -- ok.
            if ( empty( $page ) ) {
                return '';
            }
        }

        $lastChangedTs = (int) static::get_page_last_changed_cache();
        // Per-user id.
        if ( function_exists( 'get_current_user_id' ) ) {
            $userId = (int) get_current_user_id();
        } else {
            $userId = 0;
        }
        // ====== Build ETag from user + page + last-modified ======.
        return '"mainwp_pages_' . sha1( "u:$userId|p:$page|ts:$lastChangedTs" ) . '"'; // NOSONAR - is sufficient for keys.
    }


    /**
     * Method get_page_last_changed_cache().
     *
     * @param string $page Page to get last changed cache.
     *
     * @return mixed Page last change.
     */
    public static function get_page_last_changed_cache( $page = '' ) {
        $last_changed_key = static::get_page_warm_cache_last_change_key( $page );
        if ( empty( $last_changed_key ) ) {
            return 0;
        }
        return get_transient( $last_changed_key );
    }

    /**
     * Method invalidate_page_warm_cache().
     *
     * @param string $page Page to invalidate.
     *
     * @return mixed Invalidate last change timestamp.
     */
    private static function invalidate_page_warm_cache( $page ) {

        if ( ! is_array( static::$invalidated_processed ) ) {
            static::$invalidated_processed = array();
        }

        if ( isset( static::$invalidated_processed[ $page ] ) ) {
            return false;
        }

        static::$invalidated_processed[ $page ] = 1;

        $last_changed_key = static::get_page_warm_cache_last_change_key( $page );
        MainWP_Logger::instance()->log_events( 'warm-cache', 'Invalidate :: [page=' . $page . '] :: [last_changed_key=' . $last_changed_key . ']' );
        return static::invalidate_warm_cache_key( $last_changed_key );
    }

    /**
     * Method invalidate_warm_cache_key().
     *
     * @param string $last_key Last key to invalidate.
     *
     * @return int Invalidate last change timestamp.
     */
    private static function invalidate_warm_cache_key( $last_key ) {
        $lastchanged = time();
        $maxage      = get_option( 'mainwp_warm_cache_pages_ttl', 10 );
        $seconds     = $maxage * 60;
        set_transient( $last_key, $lastchanged, $seconds );
        return $lastchanged;
    }

    /**
     * Method is_excluded_warm_cache_pages().
     *
     * @param mixed $page Check excluded pages or not.
     *
     * @return bool True|false, excluded or not.
     */
    public static function is_excluded_warm_cache_pages( $page = false ) {

        if ( empty( $page ) ) {
            $page = isset( $_GET['page'] ) ? sanitize_text_field( wp_unslash( $_GET['page'] ) ) : ''; //phpcs:ignore -- ok.
        }

        if ( empty( $page ) ) {
            return true;
        }

        /**
         * Excluded warm cache pages.
         *
         * @since 5.5.
         */
        $exclude_pages = apply_filters(
            'mainwp_warm_cache_excluded_pages',
            array(
                'ActionLogs',
                'mainwp-setup',
            )
        );
        return ! is_array( $exclude_pages ) || in_array( '_excluded_all', $exclude_pages ) || ! in_array( $page, $exclude_pages ) ? true : false;
    }
}