feat: limit subscription purchase for user with network membership

includes/class-initializer.php

@@ -58,6 +58,7 @@ public static function init() {
 		Woocommerce_Memberships\Admin::init();
 		Woocommerce_Memberships\Events::init();
 		Woocommerce_Memberships\Subscriptions_Integration::init();
+		Woocommerce_Memberships\Limit_Purchase::init();
 		Woocommerce\Events::init();
 
 		register_activation_hook( NEWSPACK_NETWORK_PLUGIN_FILE, [ __CLASS__, 'activation_hook' ] );

includes/woocommerce-memberships/class-limit-purchase.php

@@ -0,0 +1,108 @@
+<?php
+/**
+ * Newspack Network limiter for WooCommerce Subscriptions.
+ *
+ * @package Newspack
+ */
+
+namespace Newspack_Network\Woocommerce_Memberships;
+
+/**
+ * Handles limiting WooCommerce Subscriptions purchases
+ *
+ * If the subscription is tied to a membership, we check whether the user already has an active subscription that gives access to the same membership in another site in the network.
+ */
+class Limit_Purchase {
+
+	/**
+	 * Initializer.
+	 */
+	public static function init() {
+		add_filter( 'woocommerce_subscription_is_purchasable', [ __CLASS__, 'restrict_network_subscriptions' ], 10, 2 );
+		add_filter( 'woocommerce_cart_product_cannot_be_purchased_message', [ __CLASS__, 'woocommerce_cart_product_cannot_be_purchased_message' ], 10, 2 );
+	}
+
+	/**
+	 * Restricts subscription purchasing from a network-synchronized plan to one.
+	 *
+	 * @param bool                                                        $purchasable Whether the subscription product is purchasable.
+	 * @param \WC_Product_Subscription|\WC_Product_Subscription_Variation $subscription_product The subscription product.
+	 * @return bool
+	 */
+	public static function restrict_network_subscriptions( $purchasable, $subscription_product ) {
+		return self::get_network_equivalent_subscription_for_current_user( $subscription_product ) ? false : $purchasable;
+	}
+
+	/**
+	 * Given a product, check if the current user has an active subscription in another site that gives access to the same membership.
+	 *
+	 * @param \WC_Product $product Product data.
+	 */
+	private static function get_network_equivalent_subscription_for_current_user( \WC_Product $product ) {
+		$user_id = get_current_user_id();
+		if ( ! $user_id ) {
+			return;
+		}
+
+		// Get the membership plan related to the subscription.
+		$plans = self::get_plans_from_subscription_product( $product );
+		if ( empty( $plans ) ) {
+			return;
+		}
+
+		// Check if the user has an active subscription in another site that gives access to the same membership.
+		foreach ( $plans as $plan ) {
+			$user_subscription = Subscriptions_Integration::user_has_active_subscription_in_network( $user_id, $plan['network_id'] );
+			if ( $user_subscription ) {
+				return $user_subscription;
+			}
+		}
+	}
+
+	/**
+	 * Get the plan related to the subscription product.
+	 *
+	 * @param \WC_Product $product Product data.
+	 */
+	public static function get_plans_from_subscription_product( \WC_Product $product ) {
+		$membership_plans = [];
+		if ( ! function_exists( 'wc_memberships_get_membership_plans' ) ) {
+			return [];
+		}
+		$plans = array_filter(
+			wc_memberships_get_membership_plans(),
+			function( $plan ) use ( $product ) {
+				return in_array( $product->get_id(), $plan->get_product_ids() );
+			}
+		);
+		return array_map(
+			function( $plan ) {
+				return [
+					'id'         => $plan->get_id(),
+					'network_id' => get_post_meta( $plan->post->ID, Admin::NETWORK_ID_META_KEY, true ),
+				];
+			},
+			$plans
+		);
+	}
+
+	/**
+	 * Filters the error message shown when a product can't be added to the cart.
+	 *
+	 * @param string      $message Message.
+	 * @param \WC_Product $product_data Product data.
+	 *
+	 * @return string
+	 */
+	public static function woocommerce_cart_product_cannot_be_purchased_message( $message, \WC_Product $product_data ) {
+		$network_subscription = self::get_network_equivalent_subscription_for_current_user( $product_data );
+		if ( $network_subscription ) {
+			$message = sprintf(
+				/* translators: %s: Site URL */
+				__( "You can't buy this subscription because you already have it active on %s", 'newspack-network' ),
+				$network_subscription['site']
+			);
+		}
+		return $message;
+	}
+}