<?php
/**
 * Talks to the FlatRateChat service (server-to-server) and stores the connection.
 *
 * Only three calls exist: exchanging the one-time connect code for the site key (once, after Connect), reading
 * plan + usage for the settings page (only while connected, cached 5 minutes), and telling the service to invalidate
 * the status token on Disconnect. Nothing is sent before Connect.
 *
 * @package FlatRateChat
 */

defined( 'ABSPATH' ) || exit;

/**
 * Service client and option storage.
 */
class FlatRateChat_Service {

	const OPT_KEY       = 'flatratechat_site_key';
	const OPT_TOKEN     = 'flatratechat_site_token';
	const OPT_HOST      = 'flatratechat_site_host';
	const OPT_CONNECTED = 'flatratechat_connected_at';
	const TR_STATE      = 'flatratechat_connect_state';
	const TR_STATUS     = 'flatratechat_status_cache';

	/**
	 * Public site key used by the widget script (pk_…), or '' when not connected.
	 *
	 * @return string
	 */
	public static function site_key() {
		$key = (string) get_option( self::OPT_KEY, '' );
		return preg_match( '/^(pk_|wk)[A-Za-z0-9]{10,40}$/', $key ) ? $key : '';
	}

	/**
	 * Whether the site is connected.
	 *
	 * @return bool
	 */
	public static function is_connected() {
		return '' !== self::site_key() && '' !== (string) get_option( self::OPT_TOKEN, '' );
	}

	/**
	 * Base URL of the service without a trailing slash.
	 *
	 * @return string
	 */
	public static function base_url() {
		return untrailingslashit( FLATRATECHAT_SERVICE_URL );
	}

	/**
	 * URL of the connect page on flatratechat.com for this site.
	 *
	 * @param string $state One-time state token generated by the plugin.
	 * @return string
	 */
	public static function connect_url( $state ) {
		return add_query_arg(
			array(
				'site'   => rawurlencode( home_url( '/' ) ),
				'state'  => rawurlencode( $state ),
				'return' => rawurlencode( admin_url( 'options-general.php?page=flatratechat' ) ),
			),
			self::base_url() . '/connect-wordpress'
		);
	}

	/**
	 * Exchange the one-time connect code for the site key and the read token; store them.
	 *
	 * @param string $code Signed one-time code from the service.
	 * @return true|WP_Error
	 */
	public static function exchange_code( $code ) {
		$code = trim( (string) $code );
		if ( ! preg_match( '/^[A-Za-z0-9_\-.]{20,2000}$/', $code ) ) {
			return new WP_Error( 'frc_bad_code', __( 'That connection code does not look right. Click Connect again, or copy the whole code.', 'flatratechat' ) );
		}
		$res = self::request( 'POST', '/api/wp/exchange', array( 'code' => $code ) );
		if ( is_wp_error( $res ) ) {
			return $res;
		}
		if ( empty( $res['ok'] ) || empty( $res['key'] ) || empty( $res['token'] ) || ! preg_match( '/^(pk_|wk)[A-Za-z0-9]{10,40}$/', (string) $res['key'] ) ) {
			return new WP_Error( 'frc_bad_response', __( 'FlatRateChat did not return a site key. Click Connect again.', 'flatratechat' ) );
		}
		update_option( self::OPT_KEY, sanitize_text_field( (string) $res['key'] ), false );
		update_option( self::OPT_TOKEN, sanitize_text_field( (string) $res['token'] ), false );
		update_option( self::OPT_HOST, sanitize_text_field( isset( $res['host'] ) ? (string) $res['host'] : '' ), false );
		update_option( self::OPT_CONNECTED, time(), false );
		delete_transient( self::TR_STATUS );
		if ( isset( $res['status'] ) && is_array( $res['status'] ) ) {
			set_transient( self::TR_STATUS, $res['status'], 5 * MINUTE_IN_SECONDS );
		}
		return true;
	}

	/**
	 * Plan + usage for the settings page (read with the site token; cached 5 minutes).
	 *
	 * @param bool $force Skip the cache.
	 * @return array|WP_Error
	 */
	public static function status( $force = false ) {
		if ( ! self::is_connected() ) {
			return new WP_Error( 'frc_not_connected', __( 'Not connected.', 'flatratechat' ) );
		}
		if ( ! $force ) {
			$cached = get_transient( self::TR_STATUS );
			if ( is_array( $cached ) ) {
				return $cached;
			}
		}
		$res = self::request( 'GET', '/api/wp/status', null, (string) get_option( self::OPT_TOKEN, '' ) );
		if ( is_wp_error( $res ) ) {
			if ( self::is_stale_error( $res ) ) {
				// The service no longer accepts this connection (token revoked or replaced, or the site was deleted
				// in the dashboard): stop loading the bubble and ask for a new Connect. The host is kept for the notice.
				self::mark_stale();
			}
			return $res;
		}
		if ( empty( $res['ok'] ) ) {
			return new WP_Error( 'frc_status', isset( $res['message'] ) ? (string) $res['message'] : __( 'FlatRateChat could not return the status of this site.', 'flatratechat' ) );
		}
		if ( ! empty( $res['token'] ) && is_string( $res['token'] ) ) {
			// The service refreshes the status token when it is in its last months; keep the new one, never cache it.
			update_option( self::OPT_TOKEN, sanitize_text_field( $res['token'] ), false );
			unset( $res['token'] );
		}
		set_transient( self::TR_STATUS, $res, 5 * MINUTE_IN_SECONDS );
		return $res;
	}

	/**
	 * Whether a status error means the connection itself is gone (401 revoked/unauthorized, 404 no_site), as opposed
	 * to a temporary problem (network, 5xx, rate limit).
	 *
	 * @param WP_Error $err Error from request().
	 * @return bool
	 */
	public static function is_stale_error( $err ) {
		$data = $err->get_error_data();
		if ( ! is_array( $data ) ) {
			return false;
		}
		$code   = isset( $data['error'] ) ? (string) $data['error'] : '';
		$status = isset( $data['status'] ) ? (int) $data['status'] : 0;
		return ( 401 === $status && in_array( $code, array( 'revoked', 'unauthorized' ), true ) ) || ( 404 === $status && 'no_site' === $code );
	}

	/**
	 * Drop the key and token (the bubble stops loading, the settings page shows the Connect button) but keep the host
	 * and connection time, so the page can say "Disconnected, please Connect again".
	 */
	public static function mark_stale() {
		delete_option( self::OPT_KEY );
		delete_option( self::OPT_TOKEN );
		delete_transient( self::TR_STATUS );
	}

	/**
	 * A host is remembered but no key/token: the service ended the connection (see mark_stale()).
	 *
	 * @return bool
	 */
	public static function is_stale() {
		return ! self::is_connected() && '' !== (string) get_option( self::OPT_HOST, '' );
	}

	/**
	 * Forget the connection on this site. The FlatRateChat account itself is managed at flatratechat.com.
	 *
	 * Tells the service to invalidate the status token first (best effort: a failed call never blocks the local
	 * clean-up; connecting again issues a new token anyway).
	 */
	public static function disconnect() {
		$token = (string) get_option( self::OPT_TOKEN, '' );
		if ( '' !== $token ) {
			self::request( 'POST', '/api/wp/revoke', array(), $token );
		}
		delete_option( self::OPT_KEY );
		delete_option( self::OPT_TOKEN );
		delete_option( self::OPT_HOST );
		delete_option( self::OPT_CONNECTED );
		delete_transient( self::TR_STATUS );
		delete_transient( self::TR_STATE );
	}

	/**
	 * One HTTP call to the service.
	 *
	 * @param string      $method GET or POST.
	 * @param string      $path   Path starting with /api/.
	 * @param array|null  $body   JSON body for POST.
	 * @param string|null $token  Bearer token for authenticated reads.
	 * @return array|WP_Error Decoded JSON.
	 */
	private static function request( $method, $path, $body = null, $token = null ) {
		$args = array(
			'method'  => $method,
			'timeout' => 15,
			'headers' => array(
				'accept'     => 'application/json',
				'user-agent' => 'FlatRateChat-WordPress/' . FLATRATECHAT_VERSION . '; ' . home_url( '/' ),
			),
		);
		if ( null !== $body ) {
			$args['headers']['content-type'] = 'application/json';
			$args['body']                    = wp_json_encode( $body );
		}
		if ( $token ) {
			$args['headers']['authorization'] = 'Bearer ' . $token;
		}
		$res = wp_remote_request( self::base_url() . $path, $args );
		if ( is_wp_error( $res ) ) {
			return new WP_Error( 'frc_http', __( 'Could not reach FlatRateChat. Please try again in a minute.', 'flatratechat' ) );
		}
		$data = json_decode( (string) wp_remote_retrieve_body( $res ), true );
		if ( ! is_array( $data ) ) {
			return new WP_Error( 'frc_http', __( 'FlatRateChat returned an unexpected answer. Please try again in a minute.', 'flatratechat' ) );
		}
		if ( wp_remote_retrieve_response_code( $res ) >= 400 && empty( $data['ok'] ) ) {
			$msg = isset( $data['message'] ) ? (string) $data['message'] : __( 'FlatRateChat refused the request.', 'flatratechat' );
			return new WP_Error(
				'frc_api',
				$msg,
				array(
					'error'  => isset( $data['error'] ) ? sanitize_key( (string) $data['error'] ) : '',
					'status' => (int) wp_remote_retrieve_response_code( $res ),
				)
			);
		}
		return $data;
	}
}