Initial commit
diff --git a/includes/compat/trait-wc-stripe-pre-orders.php b/includes/compat/trait-wc-stripe-pre-orders.php
new file mode 100644
index 0000000..b3a8a6a
--- /dev/null
+++ b/includes/compat/trait-wc-stripe-pre-orders.php
@@ -0,0 +1,268 @@
+<?php
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * Trait for Pre-Orders compatibility.
+ */
+trait WC_Stripe_Pre_Orders_Trait {
+
+	/**
+	 * Initialize pre-orders hook.
+	 *
+	 * @since 5.8.0
+	 */
+	public function maybe_init_pre_orders() {
+		if ( ! $this->is_pre_orders_enabled() ) {
+			return;
+		}
+
+		$this->supports[] = 'pre-orders';
+
+		add_action( 'wc_pre_orders_process_pre_order_completion_payment_' . $this->id, [ $this, 'process_pre_order_release_payment' ] );
+	}
+
+	/**
+	 * Checks if pre-orders are enabled on the site.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return bool
+	 */
+	public function is_pre_orders_enabled() {
+		return class_exists( 'WC_Pre_Orders' );
+	}
+
+	/**
+	 * Is $order_id a pre-order?
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param  int $order_id
+	 * @return bool
+	 */
+	public function has_pre_order( $order_id ) {
+		return $this->is_pre_orders_enabled() && class_exists( 'WC_Pre_Orders_Order' ) && WC_Pre_Orders_Order::order_contains_pre_order( $order_id );
+	}
+
+	/**
+	 * Returns boolean on whether current cart contains a pre-order item.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return bool
+	 */
+	public function is_pre_order_item_in_cart() {
+		return $this->is_pre_orders_enabled() && class_exists( 'WC_Pre_Orders_Cart' ) && WC_Pre_Orders_Cart::cart_contains_pre_order();
+	}
+
+	/**
+	 * Returns pre-order product from cart.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return object|null
+	 */
+	public function get_pre_order_product_from_cart() {
+		if ( ! $this->is_pre_orders_enabled() || ! class_exists( 'WC_Pre_Orders_Cart' ) ) {
+			return false;
+		}
+		return WC_Pre_Orders_Cart::get_pre_order_product();
+	}
+
+	/**
+	 * Returns pre-order product from order.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param int $order_id
+	 *
+	 * @return object|null
+	 */
+	public function get_pre_order_product_from_order( $order_id ) {
+		if ( ! $this->is_pre_orders_enabled() || ! class_exists( 'WC_Pre_Orders_Order' ) ) {
+			return false;
+		}
+		return WC_Pre_Orders_Order::get_pre_order_product( $order_id );
+	}
+
+	/**
+	 * Returns boolean on whether product is charged upon release.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param object $product
+	 *
+	 * @return bool
+	 */
+	public function is_pre_order_product_charged_upon_release( $product ) {
+		return $this->is_pre_orders_enabled() && class_exists( 'WC_Pre_Orders_Product' ) && WC_Pre_Orders_Product::product_is_charged_upon_release( $product );
+	}
+
+	/**
+	 * Returns boolean on whether product is charged upfront.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param object $product
+	 *
+	 * @return bool
+	 */
+	public function is_pre_order_product_charged_upfront( $product ) {
+		return $this->is_pre_orders_enabled() && class_exists( 'WC_Pre_Orders_Product' ) && WC_Pre_Orders_Product::product_is_charged_upfront( $product );
+	}
+
+	/**
+	 * Checks if we need to process pre-orders when
+	 * a pre-order product is in the cart.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param int $order_id
+	 *
+	 * @return bool
+	 */
+	public function maybe_process_pre_orders( $order_id ) {
+		return (
+			$this->has_pre_order( $order_id ) &&
+			WC_Pre_Orders_Order::order_requires_payment_tokenization( $order_id ) &&
+			! is_wc_endpoint_url( 'order-pay' )
+		);
+	}
+
+	/**
+	 * Remove order meta.
+	 *
+	 * @param object $order
+	 */
+	public function remove_order_source_before_retry( $order ) {
+		$order->delete_meta_data( '_stripe_source_id' );
+		$order->delete_meta_data( '_stripe_card_id' );
+		$order->save();
+	}
+
+	/**
+	 * Marks the order as pre-ordered.
+	 * The native function is wrapped so we can call it separately and more easily mock it in our tests.
+	 *
+	 * @param object $order
+	 */
+	public function mark_order_as_pre_ordered( $order ) {
+		if ( ! class_exists( 'WC_Pre_Orders_Order' ) ) {
+			return;
+		}
+		WC_Pre_Orders_Order::mark_order_as_pre_ordered( $order );
+	}
+
+	/**
+	 * Process the pre-order when pay upon release is used.
+	 *
+	 * @param int $order_id
+	 *
+	 * @return array
+	 */
+	public function process_pre_order( $order_id ) {
+		try {
+			$order = wc_get_order( $order_id );
+
+			// This will throw exception if not valid.
+			$this->validate_minimum_order_amount( $order );
+
+			$prepared_source = $this->prepare_source( get_current_user_id(), true );
+
+			// We need a source on file to continue.
+			if ( empty( $prepared_source->customer ) || empty( $prepared_source->source ) ) {
+				throw new WC_Stripe_Exception( __( 'Unable to store payment details. Please try again.', 'woocommerce-gateway-stripe' ) );
+			}
+
+			// Setup the response early to allow later modifications.
+			$response = [
+				'result'   => 'success',
+				'redirect' => $this->get_return_url( $order ),
+			];
+
+			$this->save_source_to_order( $order, $prepared_source );
+
+			// Try setting up a payment intent.
+			$intent_secret = $this->setup_intent( $order, $prepared_source );
+			if ( ! empty( $intent_secret ) ) {
+				$response['setup_intent_secret'] = $intent_secret;
+				return $response;
+			}
+
+			// Remove cart.
+			WC()->cart->empty_cart();
+
+			// Is pre ordered!
+			$this->mark_order_as_pre_ordered( $order );
+
+			// Return thank you page redirect
+			return $response;
+		} catch ( WC_Stripe_Exception $e ) {
+			wc_add_notice( $e->getLocalizedMessage(), 'error' );
+			WC_Stripe_Logger::log( 'Pre Orders Error: ' . $e->getMessage() );
+
+			return [
+				'result'   => 'success',
+				'redirect' => $order->get_checkout_payment_url( true ),
+			];
+		}
+	}
+
+	/**
+	 * Process a pre-order payment when the pre-order is released.
+	 *
+	 * @param WC_Order $order
+	 * @param bool     $retry
+	 *
+	 * @return void
+	 */
+	public function process_pre_order_release_payment( $order, $retry = true ) {
+		try {
+			$source   = $this->prepare_order_source( $order );
+			$response = $this->create_and_confirm_intent_for_off_session( $order, $source );
+
+			$is_authentication_required = $this->is_authentication_required_for_payment( $response );
+
+			if ( ! empty( $response->error ) && ! $is_authentication_required ) {
+				if ( ! $retry ) {
+					throw new Exception( $response->error->message );
+				}
+				$this->remove_order_source_before_retry( $order );
+				$this->process_pre_order_release_payment( $order, false );
+			} elseif ( $is_authentication_required ) {
+				$charge = end( $response->error->payment_intent->charges->data );
+				$id     = $charge->id;
+
+				$order->set_transaction_id( $id );
+				/* translators: %s is the charge Id */
+				$order->update_status( 'failed', sprintf( __( 'Stripe charge awaiting authentication by user: %s.', 'woocommerce-gateway-stripe' ), $id ) );
+				if ( is_callable( [ $order, 'save' ] ) ) {
+					$order->save();
+				}
+
+				WC_Emails::instance();
+
+				do_action( 'wc_gateway_stripe_process_payment_authentication_required', $order );
+
+				throw new WC_Stripe_Exception( print_r( $response, true ), $response->error->message );
+			} else {
+				// Successful
+				$this->process_response( end( $response->charges->data ), $order );
+			}
+		} catch ( Exception $e ) {
+			$error_message = is_callable( [ $e, 'getLocalizedMessage' ] ) ? $e->getLocalizedMessage() : $e->getMessage();
+			/* translators: error message */
+			$order_note = sprintf( __( 'Stripe Transaction Failed (%s)', 'woocommerce-gateway-stripe' ), $error_message );
+
+			// Mark order as failed if not already set,
+			// otherwise, make sure we add the order note so we can detect when someone fails to check out multiple times
+			if ( ! $order->has_status( 'failed' ) ) {
+				$order->update_status( 'failed', $order_note );
+			} else {
+				$order->add_order_note( $order_note );
+			}
+		}
+	}
+}