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<?php


namespace Varunsridharan\WordPress;

use TheLeague\Database\Query_Builder;

if ( ! class_exists( '\Varunsridharan\WordPress\DB_Table' ) ) {
    /**
     * Class DB_Table
     *
     * @package Varunsridharan\WordPress
     * @author Varun Sridharan <varunsridharan23@gmail.com>
     *
     * A base WordPress database table class, which facilitates the creation of
     * and schema changes to individual database tables.
     *
     * This class is intended to be extended for each unique database table,
     * including global multisite tables and users tables.
     *
     * It exists to make managing database tables in WordPress as easy as possible.
     *
     * Extending this class comes with several automatic benefits:
     * - Activation hook makes it great for plugins
     * - Tables store their versions in the database independently
     * - Tables upgrade via independent upgrade abstract methods
     * - Multisite friendly - site tables switch on "switch_blog" action
     */
    abstract class DB_Table extends Query_Builder {

        /**
         * Table name, without the global table prefix
         *
         * @var string
         */
        protected $name = '';

        /**
         *  Database version
         *
         * @var int
         */
        protected $version = 0;

        /**
         * Is this table for a site, or global
         *
         * @var bool
         */
        protected $global = false;

        /**
         * Database version key (saved in _options or _sitemeta)
         *
         * @var string
         */
        protected $db_version_key = '';

        /**
         * Current database version
         *
         * @var int
         */
        protected $db_version = 0;

        /**
         * Table schema
         *
         * @var string
         */
        protected $schema = '';

        /**
         * @var string
         */
        protected $prefix = null;

        /**
         * Database character-set & collation for table
         *
         * @var string
         */
        protected $charset_collation = '';

        /**
         * WPDB Database object (usually $GLOBALS['wpdb'])
         *
         * @var \wpdb
         */
        protected $db = false;

        /**
         * Stores Multiple Class Instance.
         *
         * @var array
         */
        protected static $_instances = array();

        /**
         * DB_Table constructor.
         */
        public function __construct() {
            parent::__construct( false );
            $table_name = $this->table_name();
            if ( ! empty( $table_name ) ) {
                $this->name = $table_name;
            }

            $db_version = $this->table_version();
            if ( ! empty( $db_version ) ) {
                $this->db_version = $db_version;
            }

            $this->setup();
            if ( empty( $this->name ) || empty( $this->db_version_key ) ) {
                return;
            }
            $this->get_db_version();
            $this->set_wpdb_tables();

            $set_schema = $this->set_schema();
            if ( ! empty( $set_schema ) ) {
                $this->schema = $set_schema;
            }

            $this->add_hooks();
        }

        /**
         * Returns Current Instance / create a new instance
         *
         * @return self|static
         */
        public static function instance() {
            if ( ! isset( self::$_instances[ static::class ] ) ) {
                self::$_instances[ static::class ] = new static();
            }
            return self::$_instances[ static::class ];
        }

        /**
         * Setup this database table
         */
        protected abstract function set_schema();

        /**
         * Upgrade this database table
         */
        protected abstract function upgrade();

        /**
         * Provides Table Name.
         *
         * @return mixed
         */
        protected abstract function table_name();

        /**
         * Provides Table Version Number.
         *
         * @return mixed
         */
        protected abstract function table_version();

        /**
         * Update table version & references.
         *
         * Hooked to the "switch_blog" action.
         *
         * @param int $site_id The site being switched to
         */
        public function switch_blog( $site_id = 0 ) {
            if ( ! $this->is_global() ) {
                $this->db_version = \get_blog_option( $site_id, $this->db_version_key, false );
            }
            $this->set_wpdb_tables();
        }

        /**
         * Maybe upgrade the database table. Handles creation & schema changes.
         *
         * Hooked to the "admin_init" action.
         */
        public function maybe_upgrade() {
            if ( ! $this->exists() ) {
                $this->create();
            } else {
                $needs_upgrade = version_compare( $this->version, $this->db_version, '>=' );

                if ( true === $needs_upgrade ) {
                    return;
                }

                if ( $this->is_global() && ! \wp_should_upgrade_global_tables() ) {
                    return;
                }

                $this->exists() ? $this->upgrade() : $this->create();
            }

            if ( $this->exists() ) {
                $this->set_db_version();
            }
        }

        /**
         * Setup the necessary table variables
         */
        private function setup() {
            $this->db = isset( $GLOBALS['wpdb'] ) ? $GLOBALS['wpdb'] : false;

            if ( false === $this->db ) {
                return;
            }

            $this->prefix = $this->db->prefix;
            $this->name   = $this->sanitize_table_name( $this->name );

            if ( false === $this->name ) {
                return;
            }

            if ( empty( $this->db_version_key ) ) {
                $this->db_version_key = "wpdb_{$this->name}_version";
            }
        }

        /**
         * Modify the database object and add the table to it
         *
         * This must be done directly because WordPress does not have a mechanism
         * for manipulating them safely
         */
        private function set_wpdb_tables() {
            if ( $this->is_global() ) {
                $prefix                       = $this->db->get_blog_prefix( 0 );
                $this->db->{$this->name}      = "{$prefix}{$this->name}";
                $this->db->ms_global_tables[] = $this->name;
            } else {
                $prefix                  = $this->db->get_blog_prefix( null );
                $this->db->{$this->name} = "{$prefix}{$this->name}";
                $this->db->tables[]      = $this->name;
            }

            $this->table = $this->db->{$this->name};

            if ( ! empty( $this->db->charset ) ) {
                $this->charset_collation = "DEFAULT CHARACTER SET {$this->db->charset}";
            }

            if ( ! empty( $this->db->collate ) ) {
                $this->charset_collation .= " COLLATE {$this->db->collate}";
            }
        }

        /**
         * Set the database version for the table
         *
         * Global table version in "_sitemeta" on the main network
         */
        private function set_db_version() {
            $this->version = $this->db_version;
            $this->is_global() ? \update_network_option( null, $this->db_version_key, $this->version ) : \update_option( $this->db_version_key, $this->version );
        }

        /**
         * Get the table version from the database
         *
         * Global table version from "_sitemeta" on the main network
         */
        private function get_db_version() {
            $this->version = $this->is_global() ? \get_network_option( null, $this->db_version_key, false ) : \get_option( $this->db_version_key, false );
        }

        /**
         * Add class hooks to WordPress actions
         */
        private function add_hooks() {
            \add_action( 'switch_blog', array( $this, 'switch_blog' ) );
        }

        /**
         * Create the table
         */
        private function create() {
            if ( ! function_exists( 'dbDelta' ) ) {
                require_once ABSPATH . 'wp-admin/includes/upgrade.php';
            }

            if ( ! function_exists( 'dbDelta' ) ) {
                return false;
            }

            $query   = "CREATE TABLE {$this->table} ( {$this->schema} ) {$this->charset_collation};";
            $created = dbDelta( array( $query ) );
            if ( ! empty( $created ) ) {
                $this->after_table_created();
            }
            return ! empty( $created );
        }

        /**
         * Works As A Built In Hook To Provide a Option to run after table is created.
         */
        protected function after_table_created() {
        }

        /**
         * Check if table already exists
         *
         * @return bool
         */
        private function exists() {
            $query       = 'SHOW TABLES LIKE %s';
            $like        = $this->db->esc_like( $this->table );
            $prepared    = $this->db->prepare( $query, $like );
            $table_exist = $this->db->get_var( $prepared );
            return ! empty( $table_exist );
        }

        /**
         * Check if table is global
         *
         * @return bool
         */
        private function is_global() {
            return ( true === $this->global );
        }

        /**
         * Sanitize a table name string
         *
         * Applies the following formatting to a string:
         * - No accents
         * - No special characters
         * - No hyphens
         * - No double underscores
         * - No trailing underscores
         *
         * @param string $name The name of the database table
         *
         * @return string Sanitized database table name
         */
        private function sanitize_table_name( $name = '' ) {
            $accents = \remove_accents( $name );
            $lower   = \sanitize_key( $accents );
            $under   = str_replace( '-', '_', $lower );
            $single  = str_replace( '__', '_', $under );
            $clean   = trim( $single, '_' );
            return empty( $clean ) ? false : $clean;
        }
    }
}