ion( 'user_tokens', $tokens );

		return true;
	}

	/**
	 * Returns an array of user_id's that have user tokens for communicating with wpcom.
	 * Able to select by specific capability.
	 *
	 * @param string $capability The capability of the user.
	 * @return array Array of WP_User objects if found.
	 */
	public function get_connected_users( $capability = 'any' ) {
		$connected_users = array();
		$user_tokens     = Jetpack_Options::get_option( 'user_tokens' );

		if ( ! is_array( $user_tokens ) || empty( $user_tokens ) ) {
			return $connected_users;
		}
		$connected_user_ids = array_keys( $user_tokens );

		if ( ! empty( $connected_user_ids ) ) {
			foreach ( $connected_user_ids as $id ) {
				// Check for capability.
				if ( 'any' !== $capability && ! user_can( $id, $capability ) ) {
					continue;
				}

				$user_data = get_userdata( $id );
				if ( $user_data instanceof \WP_User ) {
					$connected_users[] = $user_data;
				}
			}
		}

		return $connected_users;
	}

	/**
	 * Fetches a signed token.
	 *
	 * @param object $token the token.
	 * @return WP_Error|string a signed token
	 */
	public function get_signed_token( $token ) {
		if ( ! isset( $token->secret ) || empty( $token->secret ) ) {
			return new WP_Error( 'invalid_token' );
		}

		list( $token_key, $token_secret ) = explode( '.', $token->secret );

		$token_key = sprintf(
			'%s:%d:%d',
			$token_key,
			Constants::get_constant( 'JETPACK__API_VERSION' ),
			$token->external_user_id
		);

		$timestamp = time();

		if ( function_exists( 'wp_generate_password' ) ) {
			$nonce = wp_generate_password( 10, false );
		} else {
			$nonce = substr( sha1( wp_rand( 0, 1000000 ) ), 0, 10 );
		}

		$normalized_request_string = join(
			"\n",
			array(
				$token_key,
				$timestamp,
				$nonce,
			)
		) . "\n";

		// phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode
		$signature = base64_encode( hash_hmac( 'sha1', $normalized_request_string, $token_secret, true ) );

		$auth = array(
			'token'     => $token_key,
			'timestamp' => $timestamp,
			'nonce'     => $nonce,
			'signature' => $signature,
		);

		$header_pieces = array();
		foreach ( $auth as $key => $value ) {
			$header_pieces[] = sprintf( '%s="%s"', $key, $value );
		}

		return join( ' ', $header_pieces );
	}
}