<?php
/**
 * Sensor: Database
 *
 * Database sensor class file.
 *
 * @since     4.6.0
 * @package   wsal
 * @subpackage sensors
 */

declare(strict_types=1);

namespace WSAL\WP_Sensors;

use WSAL\Helpers\WP_Helper;
use WSAL\Helpers\Settings_Helper;
use WSAL\Controllers\Alert_Manager;

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

if ( ! class_exists( '\WSAL\WP_Sensors\WP_Database_Sensor' ) ) {
	/**
	 * Database sensor.
	 *
	 * 5010 Plugin created table
	 * 5011 Plugin modified table structure
	 * 5012 Plugin deleted table
	 * 5013 Theme created tables
	 * 5014 Theme modified tables structure
	 * 5015 Theme deleted tables
	 * 5016 Unknown component created tables
	 * 5017 Unknown component modified tables structure
	 * 5018 Unknown component deleted tables
	 * 5022 WordPress created tables
	 * 5023 WordPress modified tables structure
	 * 5024 WordPress deleted tables
	 *
	 * @package    wsal
	 * @subpackage sensors
	 */
	class WP_Database_Sensor {

		/**
		 * Local cache for basename of current script. It is used to improve performance
		 * of determining the actor of current action.
		 *
		 * @var string|bool
		 */
		private static $script_basename = null;

		/**
		 * If true, database events are being logged. This is used by the plugin's update process to temporarily disable
		 * the database sensor to prevent errors (events are registered after the upgrade process is run).
		 *
		 * @var bool
		 *
		 * @since 4.5.0
		 */
		private static $enabled = true;

		/**
		 * List of already logged operation during current request. It is used to prevent duplicate events. Values in the
		 * array are strings in form of "{operation type}_{table name}".
		 *
		 * @var string[]
		 *
		 * @since 4.5.0
		 */
		private static $already_logged = array();

		/**
		 * Inits the main hooks
		 *
		 * @return void
		 *
		 * @since 4.5.0
		 */
		public static function init() {
			if ( self::is_sensor_enabled() ) {
				add_action( 'dbdelta_queries', array( __CLASS__, 'event_db_delta_query' ) );
				add_filter( 'query', array( __CLASS__, 'event_drop_query' ) );
			}
		}

		/**
		 * Walks through the disabled alerts (for the given installation or current user settings) and checks always disabled events against them.
		 * If always disabled alerts (which are DB related alert), are currently disabled in the user configuration (all of them), then there is no need to init this sensor - the result from that will be false.
		 * If any of the events is enabled result will be true - that Sensor should be fired.
		 *
		 * @return boolean
		 *
		 * @since 4.5.0
		 */
		private static function is_sensor_enabled(): bool {
			$current_disabled_alerts = Settings_Helper::get_disabled_alerts();
			$res                     = empty( array_diff( Settings_Helper::get_default_always_disabled_alerts(), $current_disabled_alerts ) );

			return ! $res;
		}

		/**
		 * Sets the sensor as disabled.
		 *
		 * @return void
		 *
		 * @since 4.6.0
		 */
		public static function set_disabled() {
			self::$enabled = false;
		}

		/**
		 * Checks for drop query.
		 *
		 * @param string $query - Database query string.
		 *
		 * @return string
		 */
		public static function event_drop_query( $query ) {
			if ( ! self::$enabled ) {
				return $query;
			}

			$query_begins = \substr( trim( $query ), 0, 8 );

			if ( false === stripos( $query_begins, 'drop ' ) && false === stripos( $query_begins, 'create ' ) && false === stripos( $query_begins, 'alter ' ) ) {
				return $query;
			}

			$table_names = array();
			$str         = explode( ' ', $query );
			$query_type  = '';
			if ( preg_match( '|DROP TABLE( IF EXISTS)? ([^ ]*)|', $query ) ) {
				$table_name = empty( $str[4] ) ? $str[2] : $str[4];
				// Only log when the table exists as some plugins try to delete tables even if they don't exist.
				if ( self::is_table_operation_check_enabled( $table_name, 'delete' )
				&& self::check_if_table_exists( $table_name ) ) {
					array_push( $table_names, $table_name );
					$query_type = 'delete';
				}
			} elseif ( preg_match( '/CREATE TABLE( IF NOT EXISTS)? ([^ ]*)/i', $query, $matches ) || preg_match( '/CREATE TABLE ([^ ]*)/i', $query, $matches ) || preg_match( '/CREATE TEMPORARY TABLE ([^ ]*)/i', $query, $matches ) ) {
				$table_name = $matches[ count( $matches ) - 1 ];
				if ( self::is_table_operation_check_enabled( $table_name, 'create' )
				&& ! self::check_if_table_exists( $table_name ) ) {
					/**
					 * Some plugins keep trying to create tables even
					 * when they already exist - would result in too
					 * many alerts.
					 */
					array_push( $table_names, $table_name );
					$query_type = 'create';
				}
			} elseif ( preg_match( '/ALTER TABLE ([^ ]*)/i', $query, $matches ) ) {
				$table_name = $matches[ count( $matches ) - 1 ];
				if ( self::is_table_operation_check_enabled( $table_name, 'update' )
				&& self::check_if_table_exists( $table_name ) ) {
					/**
					 * Some plugins keep trying to create tables even
					 * when they already exist - would result in too
					 * many alerts.
					 */
					array_push( $table_names, $table_name );
					$query_type = 'update';
				}
			}

			self::maybe_trigger_event( $query_type, $table_names );

			return $query;
		}

		/**
		 * Triggers an event if the list of tables is not empty. It also checks if
		 * the event should be logged for events originated by WordPress.
		 *
		 * @param string   $query_type  Query type.
		 * @param string[] $table_names Table names.
		 */
		private static function maybe_trigger_event( $query_type, $table_names ) {
			if ( ! empty( $table_names ) ) {
				$actor = self::get_actor( $table_names );
				if ( 'WordPress' === $actor && ! Settings_Helper::get_boolean_option_value( 'wp-backend' ) ) {
					// Event is not fired if the monitoring of background events is disabled.
					return;
				}

				// Loop through each item to report event per table.
				foreach ( $table_names as $table_name ) {
					$alert_options = self::get_event_options( $actor );
					$event_code    = self::get_event_code( $actor, $query_type );
					$db_op_key     = $query_type . '_' . $table_name;
					if ( in_array( $db_op_key, self::$already_logged, true ) ) {
						continue;
					}

					$alert_options['TableNames'] = $table_name;
					Alert_Manager::trigger_event( $event_code, $alert_options );
					array_push( self::$already_logged, $db_op_key );
				}
			}
		}

		/**
		 * Determine the actor of database change.
		 *
		 * @param string[] $table_names Names of the tables that are being changed.
		 *
		 * @return bool|string Theme, plugin or false if unknown.
		 */
		private static function get_actor( $table_names ) {
			// Default actor (treated as an unknown component).
			$result = false;

			// Use current script name to determine if the actor is theme or a plugin.
			if ( is_null( self::$script_basename ) ) {
				self::$script_basename = isset( $_SERVER['SCRIPT_NAME'] ) ? basename( sanitize_text_field( wp_unslash( $_SERVER['SCRIPT_NAME'] ) ), '.php' ) : false;
			}

			$result = self::$script_basename;

			// Check table names for default WordPress table names (including network tables).
			if ( self::contains_wordpress_table( $table_names ) ) {
				$result = 'WordPress';
			}

			return $result;
		}

		/**
		 * Checks if the list of tables contains a WordPress table.
		 *
		 * @param array $tables List of table names.
		 *
		 * @return bool True if the list contains a WordPress table.
		 */
		private static function contains_wordpress_table( $tables ) {
			if ( ! empty( $tables ) ) {

				$wp_tables_array = array(
					'commentmeta',
					'comments',
					'links',
					'options',
					'postmeta',
					'posts',
					'terms',
					'termmeta',
					'term_relationships',
					'term_taxonomy',
					'usermeta',
					'users',
					'blogs',
					'blog_versions',
					'registration_log',
					'signups',
					'site',
					'sitemeta',
					'usermeta',
				);

				foreach ( $tables as $table ) {
					// 'wp_term_relationships' .
					// 'wp_1_term_relationships' .
					// 'wp_' .

					global $wpdb;

					$current_db_prefix = $wpdb->base_prefix;

					$table = trim( $table, '`' );
					$table = trim( $table, "'" );

					if ( 0 === \mb_strpos( $table, $current_db_prefix ) ) {

						$table = substr_replace( $table, '', 0, strlen( $current_db_prefix ) );

						if ( WP_Helper::is_multisite() ) {

							$table_name_chunks = \mb_split( '_', $table );
							$possible_index    = reset( $table_name_chunks );

							if ( false !== filter_var( $possible_index, FILTER_VALIDATE_INT ) ) {
								$table = substr_replace( $table, '', 0, strlen( $possible_index . '_' ) );
							}
						}
						if ( \in_array( $table, $wp_tables_array, true ) ) {
							// Stop as soon as the first WordPress table is found.
							return true;
						}
					} else {
						return false;
					}
				}
			}

			return false;
		}

		/**
		 * Get event options by actor.
		 *
		 * @param string $actor - Plugins, themes, WordPress or unknown.
		 *
		 * @return array
		 *
		 * phpcs:disable WordPress.Security.NonceVerification.Recommended
		 * phpcs:disable WordPress.Security.ValidatedSanitizedInput.InputNotValidated
		 */
		private static function get_event_options( $actor ) {
			// Check the actor.
			$alert_options = array();
			switch ( $actor ) {
				case 'plugins':
					// Action Plugin Component.
					$plugin_file = '';

					if ( isset( $_GET['plugin'] ) ) {
						$plugin_file = sanitize_text_field( wp_unslash( $_GET['plugin'] ) );
					} elseif ( isset( $_GET['checked'] ) && isset( $_GET['checked'][0] ) ) {
						$plugin_file = sanitize_text_field( wp_unslash( $_GET['checked'][0] ) );
					} else {

						global $wp_current_filter;
						if ( isset( $wp_current_filter ) && ! empty( $wp_current_filter ) ) {
							foreach ( $wp_current_filter as $key => $value ) {
								if ( 0 === strpos( $value, 'activate_' ) && 'activate_plugin' !== $value ) {

									$pos = strpos( $value, 'activate_' );
									if ( false !== $pos ) {
										$plugin_file = substr_replace( $value, '', $pos, strlen( 'activate_' ) );
									}

									break;
								}
							}
						}
						if ( empty( $plugin_file ) ) {
							if ( isset( $GLOBALS['plugin'] ) && '' !== trim( wp_unslash( $GLOBALS['plugin'] ) ) ) {
								$plugin_file = sanitize_text_field( wp_unslash( $GLOBALS['plugin'] ) );
							}
						}
					}
					// Get plugin data.
					$plugins = get_plugins();
					if ( isset( $plugins[ $plugin_file ] ) ) {
						$plugin = $plugins[ $plugin_file ];

						// Set alert options.
						$alert_options['Plugin'] = (object) array(
							'Name'      => $plugin['Name'],
							'PluginURI' => $plugin['PluginURI'],
							'Version'   => $plugin['Version'],
						);
					} else {
						$plugin_name = basename( $plugin_file, '.php' );
						$plugin_name = str_replace( array( '_', '-', '  ' ), ' ', $plugin_name );
						$plugin_name = ucwords( $plugin_name );

						// If this is still empty at this point, lets check recent events.
						if ( empty( $plugin_file ) ) {
							$plugin_name = self::determine_recently_activated_plugin();
						}

						$alert_options['Plugin'] = (object) array( 'Name' => $plugin_name );
					}
					break;
				case 'themes':
					// Action Theme Component.
					$theme_name = '';
					if ( isset( $_GET['theme'] ) ) {
						$theme_name = sanitize_text_field( wp_unslash( $_GET['theme'] ) );
					} elseif ( isset( $_GET['checked'] ) ) {
						$theme_name = sanitize_text_field( wp_unslash( $_GET['checked'][0] ) );
					}

					$theme_name             = str_replace( array( '_', '-', '  ' ), ' ', $theme_name );
					$theme_name             = ucwords( $theme_name );
					$alert_options['Theme'] = (object) array( 'Name' => $theme_name );
					break;

				case 'WordPress':
					$alert_options['Component'] = 'WordPress';
					break;

				default:
					// Action Unknown Component.
					$alert_options['Component'] = 'Unknown';

			}

			return $alert_options;
		}

		/**
		 * Get alert code by actor and query type.
		 *
		 * @param string $actor - Plugins, themes, WordPress or unknown.
		 * @param string $query_type - Create, update or delete.
		 *
		 * @return int Event code.
		 */
		protected static function get_event_code( $actor, $query_type ) {
			switch ( $actor ) {
				case 'plugins':
					if ( 'create' === $query_type ) {
						return 5010;
					} elseif ( 'update' === $query_type ) {
						return 5011;
					} elseif ( 'delete' === $query_type ) {
						return 5012;
					}
					break;

				case 'themes':
					if ( 'create' === $query_type ) {
						return 5013;
					} elseif ( 'update' === $query_type ) {
						return 5014;
					} elseif ( 'delete' === $query_type ) {
						return 5015;
					}
					break;

				case 'WordPress':
					if ( 'create' === $query_type ) {
						return 5022;
					} elseif ( 'update' === $query_type ) {
						return 5023;
					} elseif ( 'delete' === $query_type ) {
						return 5024;
					}
					break;
				default:
					if ( 'create' === $query_type ) {
						return 5016;
					} elseif ( 'update' === $query_type ) {
						return 5017;
					} elseif ( 'delete' === $query_type ) {
						return 5018;
					}
					break;
			}
		}

		/**
		 * Checks DB Delta queries.
		 *
		 * @param array $queries - Array of queries.
		 *
		 * @return array
		 */
		public static function event_db_delta_query( $queries ) {
			if ( ! self::$enabled ) {
				return $queries;
			}

			$query_types = array(
				'create' => array(),
				'update' => array(),
				'delete' => array(),
			);

			foreach ( $queries as $qry ) {
				$qry = str_replace( '`', '', $qry );
				$str = explode( ' ', $qry );
				if ( preg_match( '/CREATE TABLE( IF NOT EXISTS)? ([^ ]*)/i', $qry, $matches ) ) {
					$table_name = $matches[ count( $matches ) - 1 ];
					if ( self::is_table_operation_check_enabled( $table_name, 'create' )
					&& ! self::check_if_table_exists( $table_name ) ) {
						/**
						 * Some plugins keep trying to create tables even
						 * when they already exist- would result in too
						 * many alerts.
						 */
						array_push( $query_types['create'], $table_name );
					}
				} elseif ( preg_match( '|ALTER TABLE ([^ ]*)|', $qry ) ) {
					array_push( $query_types['update'], $str[2] );
				} elseif ( preg_match( '|DROP TABLE( IF EXISTS)? ([^ ]*)|', $qry ) ) {
					$table_name = empty( $str[4] ) ? $str[2] : $str[4];
					// Only log when the table exists as some plugins try to delete tables even if they don't exist.
					if ( self::is_table_operation_check_enabled( $table_name, 'delete' )
					&& self::check_if_table_exists( $table_name ) ) {
						array_push( $query_types['delete'], $table_name );
					}
				}
			}

			if ( ! empty( $query_types['create'] ) || ! empty( $query_types['update'] ) || ! empty( $query_types['delete'] ) ) {
				foreach ( $query_types as $query_type => $table_names ) {
					self::maybe_trigger_event( $query_type, $table_names );
				}
			}

			return $queries;
		}

		/**
		 * Sets the sensor as enabled / disabled
		 *
		 * @param boolean $enabled - Boolean value.
		 *
		 * @return void
		 *
		 * @since 4.5.0
		 */
		public static function set_enabled( bool $enabled ) {
			self::$enabled = (bool) $enabled;
		}

		/**
		 * Last resort to determine the name of a plugin performing the action.
		 *
		 * @return string Name, taken from recent event.
		 */
		private static function determine_recently_activated_plugin() {
			$alert_id = 5001;

			$latest_events = Alert_Manager::get_latest_events( 25, true );

			$plugin_name = false;

			if ( \is_array( $latest_events ) ) {
				foreach ( $latest_events as $latest_event ) {
					if ( intval( $latest_event['alert_id'] ) === $alert_id ) {
						$event_meta  = $latest_event ? $latest_event['meta_values'] : false;
						$plugin_name = $event_meta['PluginData']->Name;

						break;
					}
				}
			}

			if ( $plugin_name ) {
				return $plugin_name;
			}
		}

		/**
		 * Checks if a table exists in the WordPress database by running a SELECT query instead of former solution using
		 * SHOW TABLES. The previous solution has proven to be memory intense in shared hosting environments.
		 *
		 * @param string $table_name Table name.
		 *
		 * @return bool True if the table exists. False otherwise.
		 *
		 * @since 4.5.0
		 */
		private static function check_if_table_exists( $table_name ) {
			try {
				global $wpdb;

				$wpdb->suppress_errors( true );

				// Output buffering is here to prevent from error log messages that would be fired if the table didn't exist.
				ob_start();
				$db_result = $wpdb->query( "SELECT COUNT(1) FROM {$table_name};" ); // phpcs:ignore
				ob_clean();

				$wpdb->suppress_errors( false );

				return ( 1 === $db_result );
			} catch ( \Exception $e ) {
				$wpdb->suppress_errors( false );
				return false;
			}
		}

		/**
		 * Checks if alerts for certain query type are enabled or not.
		 *
		 * This is used to prevent unnecessary table existence checks. These checks should not take place
		 * if a specific alert is not enabled. Unfortunately if the alert is enabled or not is being checked
		 * too late.
		 *
		 * @param string $table_name Table name.
		 * @param string $query_type Query type.
		 *
		 * @return bool
		 *
		 * @since 4.5.0
		 */
		private static function is_table_operation_check_enabled( $table_name, $query_type ) {
			$actor      = self::get_actor( array( $table_name ) );
			$event_code = self::get_event_code( $actor, $query_type );

			return Alert_manager::is_enabled( $event_code );
		}
	}
}