Add experimental abtest class and use it in WCPayPromotion

includes/class-experimental-abtest.php

@@ -0,0 +1,173 @@
+<?php
+/**
+ * A class that interacts with Explat A/B tests.
+ *
+ * This class is experimental. It is a fork of the jetpack-abtest package and
+ * updated for use with ExPlat. These changes are planned to be contributed
+ * back to the upstream Jetpack package. If accepted, this class should then
+ * be superseded by the Jetpack class using Composer.
+ *
+ * This class should not be used externally.
+ *
+ * @package WooCommerce\Admin
+ * @link https://packagist.org/packages/automattic/jetpack-abtest
+ */
+
+namespace WooCommerce\Admin;
+
+/**
+ * This class provides an interface to the Explat A/B tests.
+ *
+ * @internal This class is experimental and should not be used externally due to planned breaking changes.
+ */
+final class Experimental_Abtest {
+
+	/**
+	 * A variable to hold the tests we fetched, and their variations for the current user.
+	 *
+	 * @var array
+	 */
+	private $tests = array();
+
+	/**
+	 * ExPlat Anonymous ID.
+	 *
+	 * @var string
+	 */
+	private $anon_id = null;
+
+	/**
+	 * ExPlat Platform name.
+	 *
+	 * @var string
+	 */
+	private $platform = 'woocommerce';
+
+	/**
+	 * Whether trcking consent is given.
+	 *
+	 * @var bool
+	 */
+	private $consent = false;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param string $anon_id ExPlat anonymous ID.
+	 * @param string $platform ExPlat platform name.
+	 * @param bool   $consent Whether tracking consent is given.
+	 */
+	public function __construct( string $anon_id, string $platform, bool $consent ) {
+		$this->anon_id  = $anon_id;
+		$this->platform = $platform;
+		$this->consent  = $consent;
+	}
+
+	/**
+	 * Retrieve the test variation for a provided A/B test.
+	 *
+	 * @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 ) {
+		// Default to the control variation when users haven't consented to tracking.
+		if ( ! $this->consent ) {
+			return 'control';
+		}
+
+		$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 'control';
+		}
+
+		return $variation;
+	}
+
+	/**
+	 * Fetch and cache the test variation for a provided A/B test from WP.com.
+	 *
+	 * ExPlat returns a null value when the assigned variation is control or
+	 * an assignment has not been set. In these instances, this method returns
+	 * a value of "control".
+	 *
+	 * @param string $test_name Name of the A/B test.
+	 * @return array|\WP_Error A/B test variation, or error on failure.
+	 */
+	protected function fetch_variation( $test_name ) {
+		// Make sure test name exists.
+		if ( ! $test_name ) {
+			return new \WP_Error( 'test_name_not_provided', 'A/B test name has not been provided.' );
+		}
+
+		// Make sure test name is a valid one.
+		if ( ! preg_match( '/^[A-Za-z0-9_]+$/', $test_name ) ) {
+			return new \WP_Error( 'invalid_test_name', 'Invalid A/B test name.' );
+		}
+
+		// Return internal-cached test variations.
+		if ( isset( $this->tests[ $test_name ] ) ) {
+			return $this->tests[ $test_name ];
+		}
+
+		// Return external-cached test variations.
+		if ( ! empty( get_transient( 'abtest_variation_' . $test_name ) ) ) {
+			return get_transient( 'abtest_variation_' . $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 \WP_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['variations'] ) ) {
+			return new \WP_Error( 'unexpected_data_format', 'Data was not returned in the expected format.' );
+		}
+
+		// Store the variation in our internal cache.
+		$this->tests[ $test_name ] = $results['variations'][ $test_name ];
+
+		$variation = $results['variations'][ $test_name ] ?? 'control';
+
+		// Store the variation in our external cache.
+		if ( ! empty( $results['ttl'] ) ) {
+			set_transient( 'abtest_variation_' . $test_name, $variation, $results['ttl'] );
+		}
+
+		return $variation;
+	}
+
+	/**
+	 * Perform the request for a variation of a provided A/B test from WP.com.
+	 *
+	 * @param string $test_name Name of the A/B test.
+	 * @return array|\WP_Error A/B test variation error on failure.
+	 */
+	protected function request_variation( $test_name ) {
+		$args = array(
+			'experiment_name' => $test_name,
+			'anon_id'         => $this->anon_id,
+		);
+
+		$url = add_query_arg(
+			$args,
+			sprintf(
+				'https://public-api.wordpress.com/wpcom/v2/experiments/0.1.0/assignments/%s',
+				$this->platform
+			)
+		);
+
+		$get = wp_remote_get( $url );
+
+		return $get;
+	}
+}
+

src/FeaturePlugin.php

@@ -68,6 +68,7 @@ public function init() {
 		require_once WC_ADMIN_ABSPATH . '/includes/core-functions.php';
 		require_once WC_ADMIN_ABSPATH . '/includes/feature-config.php';
 		require_once WC_ADMIN_ABSPATH . '/includes/wc-admin-update-functions.php';
+		require_once WC_ADMIN_ABSPATH . '/includes/class-experimental-abtest.php';
 
 		register_activation_hook( WC_ADMIN_PLUGIN_FILE, array( $this, 'on_activation' ) );
 		register_deactivation_hook( WC_ADMIN_PLUGIN_FILE, array( $this, 'on_deactivation' ) );

src/Features/WcPayPromotion/Init.php

@@ -104,7 +104,22 @@ public static function should_register_pre_install_wc_pay_promoted_gateway() {
 		if ( ! $wc_pay_spec ) {
 			return false;
 		}
-		return true;
+
+		$anon_id        = isset( $_COOKIE['tk_ai'] ) ? sanitize_text_field( wp_unslash( $_COOKIE['tk_ai'] ) ) : null;
+		$allow_tracking = 'yes' === get_option( 'woocommerce_allow_tracking' );
+		$abtest         = new \WooCommerce\Admin\Experimental_Abtest(
+			$anon_id,
+			'woocommerce',
+			$allow_tracking
+		);
+
+		$variation_name = $abtest->get_variation( 'woocommerce_wc_pay_promotion_payment_methods_table_' . $wc_pay_spec->version );
+
+		if ( 'treatment' === $variation_name ) {
+			return true;
+		}
+
+		return false;
 	}
 
 	/**