source: jetpack/trunk/jetpack_vendor/automattic/jetpack-abtest/src/class-abtest.php @ 3068647

<?php
/**
 * A class that interacts with WP.com A/B tests.
 *
 * @package automattic/jetpack-abtest
 */

namespace Automattic\Jetpack;

use Automattic\Jetpack\Connection\Client;

/**
 * This class provides an interface to the WP.com A/B tests.
 */
class Abtest {
        /**
         * A variable to hold the tests we fetched, and their variations for the current user.
         *
         * @access private
         *
         * @var array
         */
        private $tests = array();

        /**
         * Retrieve the test variation for a provided A/B test.
         *
         * @access public
         *
         * @param string $test_name Name of the A/B test.
         * @return mixed|null A/B test variation, or null on failure.
         */
        public function get_variation( $test_name ) {
                $variation = $this->fetch_variation( $test_name );

                // If there was an error retrieving a variation, conceal the error for the consumer.
                if ( is_wp_error( $variation ) ) {
                        return null;
                }

                return $variation;
        }

        /**
         * Fetch and cache the test variation for a provided A/B test from WP.com.
         *
         * @access protected
         *
         * @param string $test_name Name of the A/B test.
         * @return mixed|Automattic\Jetpack\Error A/B test variation, or Automattic\Jetpack\Error on failure.
         */
        protected function fetch_variation( $test_name ) {
                // Make sure test name exists.
                if ( ! $test_name ) {
                        return new Error( 'test_name_not_provided', 'A/B test name has not been provided.' );
                }

                // Make sure test name is a valid one.
                if ( ! preg_match( '/^[A-Za-z0-9_]+$/', $test_name ) ) {
                        return new Error( 'invalid_test_name', 'Invalid A/B test name.' );
                }

                // Return cached test variations.
                if ( isset( $this->tests[ $test_name ] ) ) {
                        return $this->tests[ $test_name ];
                }

                // Make the request to the WP.com API.
                $response = $this->request_variation( $test_name );

                // Bail if there was an error or malformed response.
                if ( is_wp_error( $response ) || ! is_array( $response ) || ! isset( $response['body'] ) ) {
                        return new Error( 'failed_to_fetch_data', 'Unable to fetch the requested data.' );
                }

                // Decode the results.
                $results = json_decode( $response['body'], true );

                // Bail if there were no results or there is no test variation returned.
                if ( ! is_array( $results ) || empty( $results['variation'] ) ) {
                        return new Error( 'unexpected_data_format', 'Data was not returned in the expected format.' );
                }

                // Store the variation in our internal cache.
                $this->tests[ $test_name ] = $results['variation'];

                return $results['variation'];
        }

        /**
         * Perform the request for a variation of a provided A/B test from WP.com.
         *
         * @access protected
         *
         * @param string $test_name Name of the A/B test.
         * @return mixed|Automattic\Jetpack\Error A/B test variation, or Automattic\Jetpack\Error on failure.
         */
        protected function request_variation( $test_name ) {
                return Client::wpcom_json_api_request_as_blog( sprintf( '/abtest/%s', $test_name ), '2', array(), null, 'wpcom' );
        }
}