<?php
/**
 * The wallet-auth REST surface.
 *
 * Two audiences. Themes and front-end code that want a sign-in form somewhere
 * other than `wp-login.php`, and other plugins that want to demand a fresh
 * signature before doing something irreversible — deleting a site, moving
 * money, transferring a name. The second is the reason `confirm` exists: a
 * capability check proves what a session is allowed to do, but it cannot
 * prove that the person holding the key is still at the keyboard. A fresh
 * signature can.
 *
 * Everything here is unauthenticated by design except `confirm`, and every
 * endpoint that does curve maths is rate limited, because signature recovery
 * is the most expensive thing a stranger can make this server do.
 *
 * @package SiriusPress
 */

defined( 'ABSPATH' ) || exit;

final class SPA_REST {

	const NS = 'sirius-press/v1';

	public static function hooks() {
		add_action( 'rest_api_init', array( __CLASS__, 'register_routes' ) );
	}

	public static function register_routes() {
		register_rest_route(
			self::NS,
			'/challenge',
			array(
				'methods'             => WP_REST_Server::READABLE,
				'permission_callback' => '__return_true',
				'callback'            => array( __CLASS__, 'challenge' ),
				'args'                => array(
					'purpose' => array(
						'type'    => 'string',
						'default' => SPA_Challenge::PURPOSE_LOGIN,
					),
				),
			)
		);

		register_rest_route(
			self::NS,
			'/login',
			array(
				'methods'             => WP_REST_Server::CREATABLE,
				'permission_callback' => '__return_true',
				'callback'            => array( __CLASS__, 'login' ),
				'args'                => self::signature_args(),
			)
		);

		register_rest_route(
			self::NS,
			'/register',
			array(
				'methods'             => WP_REST_Server::CREATABLE,
				'permission_callback' => '__return_true',
				'callback'            => array( __CLASS__, 'register' ),
				'args'                => self::signature_args(),
			)
		);

		register_rest_route(
			self::NS,
			'/confirm',
			array(
				'methods'             => WP_REST_Server::CREATABLE,
				'permission_callback' => function () {
					return is_user_logged_in();
				},
				'callback'            => array( __CLASS__, 'confirm' ),
				'args'                => self::signature_args(),
			)
		);
	}

	private static function signature_args() {
		return array(
			'nonce'     => array(
				'type'     => 'string',
				'required' => true,
			),
			'signature' => array(
				'type'     => 'string',
				'required' => true,
			),
		);
	}

	/** Hand out something to sign. */
	public static function challenge( WP_REST_Request $request ) {
		$limited = SPA_Challenge::check_rate_limit( 'challenge', 60, 300 );
		if ( is_wp_error( $limited ) ) {
			return $limited;
		}
		$purpose = (string) $request->get_param( 'purpose' );
		if ( ! SPA_Challenge::is_known_purpose( $purpose ) ) {
			return new WP_Error( 'sirius_bad_purpose', __( 'Unknown purpose.', 'sirius-press' ), array( 'status' => 400 ) );
		}
		if ( SPA_Challenge::PURPOSE_REGISTER === $purpose && ! SP_Settings::open_registration() ) {
			return new WP_Error( 'sirius_closed', __( 'This site is not accepting new accounts.', 'sirius-press' ), array( 'status' => 403 ) );
		}
		$nonce = SPA_Challenge::issue();
		return rest_ensure_response(
			array(
				'nonce'      => $nonce,
				'message'    => SPA_Challenge::message( $nonce, $purpose ),
				'purpose'    => $purpose,
				'expires_in' => SPA_Challenge::TTL,
				'prefix'     => SP_Settings::prefix(),
			)
		);
	}

	public static function login( WP_REST_Request $request ) {
		$limited = SPA_Challenge::check_rate_limit( 'login' );
		if ( is_wp_error( $limited ) ) {
			return $limited;
		}
		$address = SPA_Challenge::verify(
			(string) $request->get_param( 'nonce' ),
			(string) $request->get_param( 'signature' ),
			SPA_Challenge::PURPOSE_LOGIN
		);
		if ( is_wp_error( $address ) ) {
			return self::with_status( $address, 401 );
		}
		$user = SP_Identity::user_by_address( $address );
		if ( ! $user ) {
			return new WP_Error(
				'sirius_no_account',
				__( 'No account on this site uses that wallet.', 'sirius-press' ),
				array(
					'status'  => 404,
					'address' => $address,
				)
			);
		}

		$remember = (bool) $request->get_param( 'remember' );
		wp_set_current_user( $user->ID );
		wp_set_auth_cookie( $user->ID, $remember );
		do_action( 'wp_login', $user->user_login, $user );
		do_action( 'sirius_press_wallet_authenticated', $user, $address );

		return rest_ensure_response(
			array(
				'ok'       => true,
				'user_id'  => (int) $user->ID,
				'address'  => $address,
				'redirect' => user_can( $user, 'read' ) ? admin_url() : home_url( '/' ),
			)
		);
	}

	public static function register( WP_REST_Request $request ) {
		if ( ! SP_Settings::open_registration() ) {
			return new WP_Error( 'sirius_closed', __( 'This site is not accepting new accounts.', 'sirius-press' ), array( 'status' => 403 ) );
		}
		$limited = SPA_Challenge::check_rate_limit( 'register', 10, 900 );
		if ( is_wp_error( $limited ) ) {
			return $limited;
		}
		// Required, for the reason set out in class-spa-challenge.php: recovery
		// alone would happily mint an account for an address the caller cannot
		// sign with.
		$claimed = (string) $request->get_param( 'address' );
		if ( '' === $claimed ) {
			return new WP_Error(
				'sirius_missing_address',
				__( 'Send the address you signed with, so the signature can be checked against it.', 'sirius-press' ),
				array( 'status' => 400 )
			);
		}
		$address = SPA_Challenge::verify(
			(string) $request->get_param( 'nonce' ),
			(string) $request->get_param( 'signature' ),
			SPA_Challenge::PURPOSE_REGISTER,
			$claimed
		);
		if ( is_wp_error( $address ) ) {
			return self::with_status( $address, 400 );
		}
		$user_id = SP_Identity::create_user( $address, (string) $request->get_param( 'user_login' ) );
		if ( is_wp_error( $user_id ) ) {
			return self::with_status( $user_id, 409 );
		}
		wp_set_current_user( $user_id );
		wp_set_auth_cookie( $user_id, false );
		return rest_ensure_response(
			array(
				'ok'      => true,
				'user_id' => (int) $user_id,
				'address' => $address,
			)
		);
	}

	/**
	 * Re-prove the current user's key.
	 *
	 * Returns 403 rather than 200-with-false when the signature belongs to
	 * somebody else's wallet, so a caller that forgets to check the body still
	 * fails closed.
	 */
	public static function confirm( WP_REST_Request $request ) {
		$limited = SPA_Challenge::check_rate_limit( 'confirm', 30, 300 );
		if ( is_wp_error( $limited ) ) {
			return $limited;
		}
		$address = SPA_Challenge::verify(
			(string) $request->get_param( 'nonce' ),
			(string) $request->get_param( 'signature' ),
			SPA_Challenge::PURPOSE_CONFIRM
		);
		if ( is_wp_error( $address ) ) {
			return self::with_status( $address, 400 );
		}
		$mine = SP_Identity::address_of( get_current_user_id() );
		if ( '' === $mine || ! hash_equals( $mine, $address ) ) {
			return new WP_Error(
				'sirius_wrong_wallet',
				__( 'That signature is from a different wallet than the one signed in.', 'sirius-press' ),
				array( 'status' => 403 )
			);
		}
		/**
		 * Fires when a signed-in user re-proves their key.
		 *
		 * @param int    $user_id
		 * @param string $address
		 */
		do_action( 'sirius_press_wallet_confirmed', get_current_user_id(), $address );
		return rest_ensure_response(
			array(
				'ok'      => true,
				'address' => $address,
			)
		);
	}

	/** Attach an HTTP status to a WP_Error that was created without one. */
	private static function with_status( WP_Error $error, $status ) {
		$data = $error->get_error_data();
		if ( ! is_array( $data ) ) {
			$data = array();
		}
		if ( empty( $data['status'] ) ) {
			$data['status'] = $status;
		}
		$error->add_data( $data, $error->get_error_code() );
		return $error;
	}
}