<?php

/**

 * Abstract class for managing user session tokens.

 *

 * @since 4.0.0

 */

abstract class WP_Session_Tokens {

	/**

	 * User ID.

	 *

	 * @since 4.0.0

	 * @access protected

	 * @var int User ID.

	 */

	protected $user_id;

	/**

	 * Protected constructor.

	 *

	 * @since 4.0.0

	 *

	 * @param int $user_id User whose session to manage.

	 */

	protected function __construct( $user_id ) {

		$this->user_id = $user_id;

	}

	/**

	 * Get a session token manager instance for a user.

	 *

	 * This method contains a filter that allows a plugin to swap out

	 * the session manager for a subclass of WP_Session_Tokens.

	 *

	 * @since 4.0.0

	 * @access public

	 * @static

	 *

	 * @param int $user_id User whose session to manage.

	 */

	final public static function get_instance( $user_id ) {

		/**

		 * Filter the session token manager used.

		 *

		 * @since 4.0.0

		 *

		 * @param string $session Name of class to use as the manager.

		 *                        Default 'WP_User_Meta_Session_Tokens'.

		 */

		$manager = apply_filters( 'session_token_manager', 'WP_User_Meta_Session_Tokens' );

		return new $manager( $user_id );

	}

	/**

	 * Hashes a session token for storage.

	 *

	 * @since 4.0.0

	 * @access private

	 *

	 * @param string $token Session token to hash.

	 * @return string A hash of the session token (a verifier).

	 */

	final private function hash_token( $token ) {

		// If ext/hash is not present, use sha1() instead.

		if ( function_exists( 'hash' ) ) {

			return hash( 'sha256', $token );

		} else {

			return sha1( $token );

		}

	}

	/**

	 * Get a user's session.

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @param string $token Session token

	 * @return array User session

	 */

	final public function get( $token ) {

		$verifier = $this->hash_token( $token );

		return $this->get_session( $verifier );

	}

	/**

	 * Validate a user's session token as authentic.

	 *

	 * Checks that the given token is present and hasn't expired.

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @param string $token Token to verify.

	 * @return bool Whether the token is valid for the user.

	 */

	final public function verify( $token ) {

		$verifier = $this->hash_token( $token );

		return (bool) $this->get_session( $verifier );

	}

	/**

	 * Generate a session token and attach session information to it.

	 *

	 * A session token is a long, random string. It is used in a cookie

	 * link that cookie to an expiration time and to ensure the cookie

	 * becomes invalidated upon logout.

	 *

	 * This function generates a token and stores it with the associated

	 * expiration time (and potentially other session information via the

	 * `attach_session_information` filter).

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @param int $expiration Session expiration timestamp.

	 * @return string Session token.

	 */

	final public function create( $expiration ) {

		/**

		 * Filter the information attached to the newly created session.

		 *

		 * Could be used in the future to attach information such as

		 * IP address or user agent to a session.

		 *

		 * @since 4.0.0

		 *

		 * @param array $session Array of extra data.

		 * @param int   $user_id User ID.

		 */

		$session = apply_filters( 'attach_session_information', array(), $this->user_id );

		$session['expiration'] = $expiration;

		// IP address.

		if ( !empty( $_SERVER['REMOTE_ADDR'] ) ) {

			$session['ip'] = $_SERVER['REMOTE_ADDR'];

		}

		// User-agent.

		if ( ! empty( $_SERVER['HTTP_USER_AGENT'] ) ) {

			$session['ua'] = wp_unslash( $_SERVER['HTTP_USER_AGENT'] );

		}

		// Timestamp

		$session['login'] = time();

		$token = wp_generate_password( 43, false, false );

		$this->update( $token, $session );

		return $token;

	}

	/**

	 * Update a session token.

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @param string $token Session token to update.

	 * @param array  $session Session information.

	 */

	final public function update( $token, $session ) {

		$verifier = $this->hash_token( $token );

		$this->update_session( $verifier, $session );

	}

	/**

	 * Destroy a session token.

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @param string $token Session token to destroy.

	 */

	final public function destroy( $token ) {

		$verifier = $this->hash_token( $token );

		$this->update_session( $verifier, null );

	}

	/**

	 * Destroy all session tokens for this user,

	 * except a single token, presumably the one in use.

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @param string $token_to_keep Session token to keep.

	 */

	final public function destroy_others( $token_to_keep ) {

		$verifier = $this->hash_token( $token_to_keep );

		$session = $this->get_session( $verifier );

		if ( $session ) {

			$this->destroy_other_sessions( $verifier );

		} else {

			$this->destroy_all_sessions();

		}

	}

	/**

	 * Determine whether a session token is still valid,

	 * based on expiration.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param array $session Session to check.

	 * @return bool Whether session is valid.

	 */

	final protected function is_still_valid( $session ) {

		return $session['expiration'] >= time();

	}

	/**

	 * Destroy all session tokens for a user.

	 *

	 * @since 4.0.0

	 * @access public

	 */

	final public function destroy_all() {

		$this->destroy_all_sessions();

	}

	/**

	 * Destroy all session tokens for all users.

	 *

	 * @since 4.0.0

	 * @access public

	 * @static

	 */

	final public static function destroy_all_for_all_users() {

		$manager = apply_filters( 'session_token_manager', 'WP_User_Meta_Session_Tokens' );

		call_user_func( array( $manager, 'drop_sessions' ) );

	}

	/**

	 * Retrieve all sessions of a user.

	 *

	 * @since 4.0.0

	 * @access public

	 *

	 * @return array Sessions of a user.

	 */

	final public function get_all() {

		return array_values( $this->get_sessions() );

	}

	/**

	 * This method should retrieve all sessions of a user, keyed by verifier.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @return array Sessions of a user, keyed by verifier.

	 */

	abstract protected function get_sessions();

	/**

	 * This method should look up a session by its verifier (token hash).

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param string $verifier Verifier of the session to retrieve.

	 * @return array|null The session, or null if it does not exist.

	 */

	abstract protected function get_session( $verifier );

	/**

	 * This method should update a session by its verifier.

	 *

	 * Omitting the second argument should destroy the session.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param string $verifier Verifier of the session to update.

	 */

	abstract protected function update_session( $verifier, $session = null );

	/**

	 * This method should destroy all session tokens for this user,

	 * except a single session passed.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param string $verifier Verifier of the session to keep.

	 */

	abstract protected function destroy_other_sessions( $verifier );

	/**

	 * This method should destroy all sessions for a user.

	 *

	 * @since 4.0.0

	 * @access protected

	 */

	abstract protected function destroy_all_sessions();

	/**

	 * This static method should destroy all session tokens for all users.

	 *

	 * @since 4.0.0

	 * @access public

	 * @static

	 */

	public static function drop_sessions() {}

}

/**

 * Meta-based user sessions token manager.

 *

 * @since 4.0.0

 */

class WP_User_Meta_Session_Tokens extends WP_Session_Tokens {

	/**

	 * Get all sessions of a user.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @return array Sessions of a user.

	 */

	protected function get_sessions() {

		$sessions = get_user_meta( $this->user_id, 'session_tokens', true );

		if ( ! is_array( $sessions ) ) {

			return array();

		}

		$sessions = array_map( array( $this, 'prepare_session' ), $sessions );

		return array_filter( $sessions, array( $this, 'is_still_valid' ) );

	}

	/**

	 * Converts an expiration to an array of session information.

	 *

	 * @param mixed $session Session or expiration.

	 * @return array Session.

	 */

	protected function prepare_session( $session ) {

		if ( is_int( $session ) ) {

			return array( 'expiration' => $session );

		}

		return $session;

	}

	/**

	 * Retrieve a session by its verifier (token hash).

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param string $verifier Verifier of the session to retrieve.

	 * @return array|null The session, or null if it does not exist

	 */

	protected function get_session( $verifier ) {

		$sessions = $this->get_sessions();

		if ( isset( $sessions[ $verifier ] ) ) {

			return $sessions[ $verifier ];

		}

		return null;

	}

	/**

	 * Update a session by its verifier.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param string $verifier Verifier of the session to update.

	 * @param array  $session  Optional. Session. Omitting this argument destroys the session.

	 */

	protected function update_session( $verifier, $session = null ) {

		$sessions = $this->get_sessions();

		if ( $session ) {

			$sessions[ $verifier ] = $session;

		} else {

			unset( $sessions[ $verifier ] );

		}

		$this->update_sessions( $sessions );

	}

	/**

	 * Update a user's sessions in the usermeta table.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param array $sessions Sessions.

	 */

	protected function update_sessions( $sessions ) {

		if ( $sessions ) {

			update_user_meta( $this->user_id, 'session_tokens', $sessions );

		} else {

			delete_user_meta( $this->user_id, 'session_tokens' );

		}

	}

	/**

	 * Destroy all session tokens for a user, except a single session passed.

	 *

	 * @since 4.0.0

	 * @access protected

	 *

	 * @param string $verifier Verifier of the session to keep.

	 */

	protected function destroy_other_sessions( $verifier ) {

		$session = $this->get_session( $verifier );

		$this->update_sessions( array( $verifier => $session ) );

	}

	/**

	 * Destroy all session tokens for a user.

	 *

	 * @since 4.0.0

	 * @access protected

	 */

	protected function destroy_all_sessions() {

		$this->update_sessions( array() );

	}

	/**

	 * Destroy all session tokens for all users.

	 *

	 * @since 4.0.0

	 * @access public

	 * @static

	 */

	public static function drop_sessions() {

		delete_metadata( 'user', 0, 'session_tokens', false, true );

	}

}