<?php
/**
 * Main plugin class file.
 *
 * @package WordPress Plugin Template/Includes
 */

if ( ! defined( 'ABSPATH' ) ) {
  exit;
}

/**
 * Main plugin class.
 *
 * Only make one instance of this, please.
 */
class SQLite_Object_Cache {
  const CLEAN_EVENT_HOOK = 'sqlite_object_cache_clean';

  /**
   * Local instance of SQLite_Object_Cache_Admin_API
   *
   * @var SQLite_Object_Cache_Admin_API|null
   */
  public $admin;

  /**
   * Settings class object
   *
   * @var     object
   * @access  public
   * @since   1.0.0
   */
  public $settings;

  /**
   * The version number.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $_version;

  /**
   * The token.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $_token;

  /**
   * The main plugin file.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $file;

  /**
   * The main plugin directory.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $dir;

  /**
   * The plugin assets directory.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $assets_dir;

  /**
   * The plugin assets URL.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $assets_url;

  /**
   * Suffix for JavaScripts.
   *
   * @var     string
   * @access  public
   * @since   1.0.0
   */
  public $script_suffix;

  /**
   * Path for the drop-in when it is working.
   * @var string
   */
  public $dropinfiledest;

  /**
   * Path for the drop-in in the plugin tree.
   * @var string
   */
  public $dropinfilesource;

  /**
   * Minimum required sqlite version.
   *
   * @var string
   */
  public $minimum_sqlite_version = '3.7.0';

  /**
   * Constructor function.
   *
   * @param string $file File constructor.
   * @param string $version Plugin version.
   */
  public function __construct( $file = '', $version = '1.5.5' ) {
    $this->_version = $version;
    $this->_token   = 'sqlite_object_cache';

    // Load plugin environment variables.
    $this->file             = $file;
    $this->dir              =
      trailingslashit( dirname( WP_CONTENT_DIR . '/plugins/' . plugin_basename( $this->file ) ) );
    $this->assets_dir       = trailingslashit( $this->dir . 'assets' );
    $this->dropinfilesource = $this->assets_dir . 'drop-in/object-cache.php';
    $this->dropinfiledest   = trailingslashit( WP_CONTENT_DIR ) . 'object-cache.php';

    $this->assets_url = esc_url( trailingslashit( plugins_url( '/assets/', $this->file ) ) );

    $this->script_suffix = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? '' : '.min';

    register_activation_hook( $this->file, array( $this, 'on_activation' ) );
    register_deactivation_hook( $this->file, array( $this, 'on_deactivation' ) );

    if ( is_admin() ) {
      // Load API for generic admin functions.
      $this->admin = new SQLite_Object_Cache_Admin_API();
      // Suppress backups
      new SQLite_Backup_Exclusion();
    }

    add_action( 'admin_init', array( $this, 'maybe_update_dropin' ) );

    /* handle cron cache cleanup */
    add_action( self::CLEAN_EVENT_HOOK, array( $this, 'clean_job' ), 10, 0 );
    if ( ! wp_next_scheduled( self::CLEAN_EVENT_HOOK ) ) {
      wp_schedule_event( time() + HOUR_IN_SECONDS, 'hourly', self::CLEAN_EVENT_HOOK );
    }
    /* Handle probabilistic non-cron cleanup, one request in 2000. */
    if ( 1 === rand( 1, 2000 ) ) {
      add_action( 'shutdown', function () {
        $this->clean_job( 1.25 );
      }, 999, 0 );
    }
  }

  /**
   * WP_Cron task to clean cache entries.
   *
   * @param float $grace_factor Default 1.0
   *
   * @return void
   */
  public function clean_job( $grace_factor = 1.0 ) {
    $option         = get_option( $this->_token . '_settings', array() );
    $target_size    = empty ( $option['target_size'] ) ? 16 : $option['target_size'];
    $target_size    *= ( 1024 * 1024 );
    $threshold_size = (int) ( $target_size * $grace_factor );

    global $wp_object_cache;
    if ( ! method_exists( $wp_object_cache, 'sqlite_get_size' ) ) {
      return;
    }
    /* Clean up old statistics. Do this even when the cache is not over size. */
    $retention = empty ( $option['retainmeasurements'] ) ? 24 : $option['retainmeasurements'];
    $wp_object_cache->sqlite_reset_statistics( $retention * HOUR_IN_SECONDS );

    $current_size = $wp_object_cache->sqlite_get_size();
    /* Skip this if the current size is small enough. */
    if ( $current_size <= $threshold_size ) {
      return;
    }

    /* Remove expired items (transients mostly). */
    if ( $wp_object_cache->sqlite_remove_expired() ) {
      /* If anything was removed, get the size again. */
      $current_size = $wp_object_cache->sqlite_get_size();
    }

    /* Skip this if the size is small enough, after removing expired items. */
    if ( $current_size <= $threshold_size ) {
      return;
    }

    /* Delete the least-recently-updated items to get to the target size. */
    $wp_object_cache->sqlite_delete_old( $target_size, $current_size );
  }

  /**
   * Plugin activation hook
   *
   * @return void
   */
  public function on_activation() {

    $this->sync_apcu_global_to_option( true );
    if ( true === $this->has_sqlite() ) {
      add_action( 'shutdown', array( $this, 'update_dropin' ) );
    }
  }

  /**
   * Determine whether we can use SQLite3.
   *
   * @return bool|string true, or an error message.
   */
  public function has_sqlite() {
    if ( ! class_exists( 'SQLite3' ) || ! extension_loaded( 'sqlite3' ) ) {
      return __( 'You cannot use the SQLite Object Cache plugin. Your server does not have php\'s SQLite3 extension installed.', 'sqlite-object-cache' );
    }

    $sqlite_version = $this->sqlite_get_version();
    if ( version_compare( $sqlite_version, $this->minimum_sqlite_version ) < 0 ) {
      return sprintf(
      /* translators: 1 actual SQLite version. 2 required SQLite version) */
        __( 'You cannot use the SQLite Object Cache plugin. Your server only offers SQLite3 version %1$s, but at least %2$s is required.', 'sqlite-object-cache' ),
        $sqlite_version, $this->minimum_sqlite_version );
    }

    return true;
  }

  /**
   * Get the version number for the SQLite extension.
   *
   * @return string|false  SQLite's version number.
   */
  public function sqlite_get_version() {

    if ( class_exists( 'SQLite3' ) ) {
      $version = SQLite3::version();

      return $version['versionString'];
    }

    return false;
  }

  /**
   * Test if we can write in the WP_CONTENT_DIR and modify the `object-cache.php` drop-in
   *
   * @return true|WP_Error
   * @author Till Krüss
   *
   */
  public function test_filesystem_writing() {
    global $wp_filesystem;

    if ( ! $this->initialize_filesystem( '', true ) ) {
      return new WP_Error( 'fs', __( 'Could not initialize filesystem.', 'sqlite-object-cache' ) );
    }

    $testfiledest = WP_CONTENT_DIR . '/sqlite-write-test.tmp';

    if ( ! $wp_filesystem->exists( $this->dropinfilesource ) ) {
      return new WP_Error( 'exists', __( 'Object cache drop-in file doesn’t exist.', 'sqlite-object-cache' ) );
    }

    if ( $wp_filesystem->exists( $testfiledest ) && ! $wp_filesystem->delete( $testfiledest ) ) {
      return new WP_Error( 'delete', __( 'Test file exists, but couldn’t be deleted.', 'sqlite-object-cache' ) );
    }

    if ( ! $wp_filesystem->is_writable( WP_CONTENT_DIR ) ) {
      return new WP_Error( 'copy', __( 'Content directory is not writable.', 'sqlite-object-cache' ) );
    }

    if ( ! $wp_filesystem->copy( $this->dropinfilesource, $testfiledest, true, FS_CHMOD_FILE ) ) {
      return new WP_Error( 'copy', __( 'Failed to copy test file.', 'sqlite-object-cache' ) );
    }

    if ( ! $wp_filesystem->exists( $testfiledest ) ) {
      return new WP_Error( 'exists', __( 'Copied test file doesn’t exist.', 'sqlite-object-cache' ) );
    }

    $meta = get_file_data( $testfiledest, array( 'Version' => 'Version' ) );

    if ( $meta['Version'] !== $this->_version ) {
      return new WP_Error( 'version', __( 'Couldn’t verify test file contents.', 'sqlite-object-cache' ) );
    }

    if ( ! $wp_filesystem->delete( $testfiledest ) ) {
      return new WP_Error( 'delete', __( 'Copied test file couldn’t be deleted.', 'sqlite-object-cache' ) );
    }

    return true;
  }

  /**
   * Initializes the WP filesystem API to be ready for use
   *
   * @param string $url The URL to post the form to.
   * @param bool $silent Whether to ask the user for credentials if necessary or not.
   *
   * @return bool
   * @author Till Krüss
   *
   */
  public function initialize_filesystem( $url, $silent = false ) {
    require_once ABSPATH . 'wp-admin/includes/file.php';
    if ( $silent ) {
      ob_start();
    }

    $credentials = request_filesystem_credentials( $url );

    if ( false === $credentials ) {
      if ( $silent ) {
        ob_end_clean();
      }

      return false;
    }

    if ( ! WP_Filesystem( $credentials ) ) {
      request_filesystem_credentials( $url );

      if ( $silent ) {
        ob_end_clean();
      }

      return false;
    }

    return true;
  }

  /**
   * Calls the drop-in update method if necessary
   *
   * @return void
   * @author Till Krüss
   */
  public function maybe_update_dropin() {
    if ( defined( 'WP_SQLITE_OBJECT_CACHE_DISABLE_DROPIN_AUTOUPDATE' ) && WP_SQLITE_OBJECT_CACHE_DISABLE_DROPIN_AUTOUPDATE ) {
      return;
    }

    $has = $this->has_sqlite();
    if ( ( true === $has ) && $this->object_cache_dropin_needs_updating() ) {
      add_action( 'shutdown', array( $this, 'update_dropin' ) );
    }
  }

  /**
   * Checks if the `object-cache.php` drop-in is outdated
   * @return bool
   * @author Till Krüss
   *
   */
  public function object_cache_dropin_needs_updating() {
    global $wp_object_cache;
    if ( ! method_exists( $wp_object_cache, 'dropin_get_version' ) ) {
      return true;
    }
    return version_compare( $wp_object_cache->dropin_get_version(), $this->_version, '<' );
  }

  /**
   * Updates the `object-cache.php` drop-in
   *
   * @return void
   * @author Till Krüss
   */
  public function update_dropin() {
    global $wp_filesystem;
    $has = $this->has_sqlite();
    if ( true === $has && $this->initialize_filesystem( '', true ) ) {

      $this->delete_sqlite_files();
      $result = $wp_filesystem->copy( $this->dropinfilesource, $this->dropinfiledest, true, FS_CHMOD_FILE );
      /**
       * Fires on cache enable event
       *
       * @param bool $result Whether the filesystem event (copy of the `object-cache.php` file) was successful.
       *
       * @since 0.1.0
       */
      do_action( 'sqlite_object_cache_update_dropin', $result );
    }
  }

  /**
   * Validates the `object-cache.php` drop-in
   *
   * @return bool
   * @author Till Krüss
   */
  public function validate_object_cache_dropin() {
    global $wp_object_cache;

    if ( ! method_exists( $wp_object_cache, 'dropin_get_version' ) ) {
      return false;
    }

    $dropin = get_plugin_data( $this->dropinfiledest );
    $plugin = get_plugin_data( $this->dropinfilesource );

    /**
     * Filters the drop-in validation state
     *
     * @param bool $state The validation state of the drop-in.
     * @param string $dropin The `PluginURI` of the drop-in.
     * @param string $plugin The `PluginURI` of the plugin.
     *
     * @since 2.0.16
     */
    return apply_filters(
      'sqlite_object_cache_validate_dropin',
      $dropin['PluginURI'] === $plugin['PluginURI'],
      $dropin['PluginURI'],
      $plugin['PluginURI']
    );
  }

  /**
   * Plugin deactivation hook
   *
   * @param string $plugin Plugin basename.
   *
   * @return void
   * @author Till Krüss
   */
  public function on_deactivation( $plugin ) {

    wp_cache_flush();

    wp_unschedule_hook( self::CLEAN_EVENT_HOOK );
    $this->delete_sqlite_files();
    $this->delete_dropin();
  }

  private function delete_sqlite_files() {
    global $wp_filesystem;
    global $wp_object_cache;

    if ( method_exists( $wp_object_cache, 'sqlite_files' ) ) {
      if ( $this->initialize_filesystem( '', true ) ) {
        foreach ( $wp_object_cache->sqlite_files() as $file ) {
          $wp_filesystem->delete( $file );
        }
      }
    }
  }

  private function delete_dropin() {
    global $wp_filesystem;
    ob_start();

    if ( $this->validate_object_cache_dropin() && $this->initialize_filesystem( '', true ) ) {
      $wp_filesystem->delete( $this->dropinfiledest );
    }

    ob_end_clean();
  }

  /**
   * @return bool True if APCu support is activated for this plugin.
   */
  public function apcu_is_activated() {
    return defined( 'WP_SQLITE_OBJECT_CACHE_APCU' ) && WP_SQLITE_OBJECT_CACHE_APCU
           && $this->apcu_extension_is_enabled();
  }

  /**
   * @return bool True if the APCu extension is loaded and enabled.
   */
  public function apcu_extension_is_enabled() {
    return function_exists( 'apcu_enabled' ) && apcu_enabled();
  }

  /**
   *  Make sure WP_SQLITE_OBJECT_CACHE_APCU and $option['use_apcu'] match.
   *
   * @param bool $unconditional true if we should always change the option to match WP_SQLITE_OBJECT_CACHE_APCU.
   *
   * @return string 'on' or 'off': the current activation state of epcu.
   */
  public function sync_apcu_global_to_option( $unconditional = true ) {
    global $wp_object_cache;
    $option       = get_option( $this->_token . '_settings', array() );
    $option_dirty = false;
    $updated_flag = array_key_exists( 'use_apcu_updated', $option );
    $use_apcu     = array_key_exists( 'use_apcu', $option ) && 'on' === $option['use_apcu'] ? 'on' : 'off';
    if ( $updated_flag ) {
      unset ( $option['use_apcu_updated'] );
      $option_dirty = true;
    }
    $target_use_apcu = $this->apcu_is_activated() ? 'on' : 'off';
    if ( ! $unconditional && $updated_flag ) {
      $target_use_apcu = $use_apcu;
    }
    if ( $target_use_apcu !== $use_apcu ) {
      $option['use_apcu'] = $target_use_apcu;
      $option_dirty       = true;
    }
    if ( $option_dirty ) {
      if ( method_exists( $wp_object_cache, 'apcu-clear_cache' ) ) {
        $wp_object_cache->apcu_clear_cache();
      }
      update_option( $this->_token . '_settings', $option, true );
    }

    return $target_use_apcu;
  }


}