onse_data        Object of data returned from request.
	 * @param string   $url                  Url for the web page to be checked.
	 * @param bool     $is_mobile            Optional. Flag for if this is cpcss for mobile or not. Default: false.
	 * @param string   $item_type Optional. Type for this item if it's custom or specific type. Default: custom.
	 *
	 * @return string
	 */
	private function get_response_message( $response_status_code, $response_data, $url, $is_mobile = false, $item_type = 'custom' ) {
		$message = '';

		switch ( $response_status_code ) {
			case 200:
				if ( ! isset( $response_data->data->id ) ) {
					$message .= sprintf(
						$is_mobile
							?
							// translators: %s = item URL.
							__( 'Critical CSS for %1$s on mobile not generated. Error: The API returned an empty response.', 'rocket' )
							:
							// translators: %s = item URL.
							__( 'Critical CSS for %1$s not generated. Error: The API returned an empty response.', 'rocket' ),
						( 'custom' === $item_type ) ? $url : $item_type
					);
				}
				break;
			case 400:
			case 440:
			case 404:
				// translators: %s = item URL.
				$message .= sprintf(
					$is_mobile
						// translators: %s = item URL.
						? __( 'Critical CSS for %1$s on mobile not generated.', 'rocket' )
						// translators: %s = item URL.
						: __( 'Critical CSS for %1$s not generated.', 'rocket' ),
					( 'custom' === $item_type ) ? $url : $item_type
					);
				break;
			default:
				$message .= sprintf(
					$is_mobile
						// translators: %s = URL.
						? __( 'Critical CSS for %1$s on mobile not generated. Error: The API returned an invalid response code.', 'rocket' )
						// translators: %s = URL.
						: __( 'Critical CSS for %1$s not generated. Error: The API returned an invalid response code.', 'rocket' ),
					( 'custom' === $item_type ) ? $url : $item_type
				);
				break;
		}

		if ( isset( $response_data->message ) ) {
			// translators: %1$s = error message.
			$message .= ' ' . sprintf( __( 'Error: %1$s', 'rocket' ), $response_data->message );
		}

		return $message;
	}

	/**
	 * Get response data from the API.
	 *
	 * @since 3.6
	 *
	 * @param array|WP_Error $response The response or WP_Error on failure.
	 *
	 * @return mixed response of API.
	 */
	private function get_response_data( $response ) {
		return json_decode( wp_remote_retrieve_body( $response ) );
	}

	/**
	 * Get our internal response code [Not the standard HTTP codes].
	 *
	 * @since 3.6
	 *
	 * @param array|WP_Error $response The response or WP_Error on failure.
	 *
	 * @return string response code.
	 */
	private function get_response_code( $response ) {
		// Todo: we can return code based on the response status number, for example 404 not_found.
		return 'cpcss_generation_failed';
	}

	/**
	 * Get job details by calling API with job ID.
	 *
	 * @since 3.6
	 *
	 * @param string $job_id    ID for the job to get details.
	 * @param string $url       URL to be used in error messages.
	 * @param bool   $is_mobile Optional. Flag for if this is cpcss for mobile or not. Default: false.
	 * @param string $item_type Optional. Type for this item if it's custom or specific type. Default: custom.
	 *
	 * @return mixed|WP_Error Details for job.
	 */
	public function get_job_details( $job_id, $url, $is_mobile = false, $item_type = 'custom' ) {
		$response = wp_remote_get(
			self::API_URL . "{$job_id}/"
		);

		return $this->prepare_response( $response, $url, $is_mobile, $item_type );
	}
}