1 files changed, 120 insertions, 0 deletions
diff --git a/includes/class-cepis-woo-rest.php b/includes/class-cepis-woo-rest.php
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+++ b/includes/class-cepis-woo-rest.php
@@ -0,0 +1,120 @@
+<?php
+/**
+ * The optional server-side proxy route.
+ *
+ * @package CepisWooCommerce
+ */
+
+declare(strict_types=1);
+
+defined( 'ABSPATH' ) || exit;
+
+/**
+ * Exposes `GET /wp-json/cepis/v1/lookup/{token}/{cep}`, which answers exactly
+ * what cep.is answers.
+ *
+ * The route is only registered when the store has turned proxy mode on. It is
+ * off by default because the browser can reach cep.is directly in about twenty
+ * milliseconds against a Cloudflare edge cache, and putting a WordPress
+ * bootstrap in front of that — on the checkout page, once per settled CEP —
+ * spends latency where a store can least afford it. Turn it on when a
+ * Content-Security-Policy forbids external XHR, or to get the server-side
+ * cache in {@see Cepis_Woo_Lookup}.
+ *
+ * The token is a path segment rather than a header because the widget's
+ * request is a plain cross-origin-safe GET with no custom headers.
+ * {@see Cepis_Woo_Token} explains why it is not a session-bound nonce.
+ */
+final class Cepis_Woo_Rest {
+
+	/**
+	 * REST namespace for the proxy.
+	 */
+	public const NAMESPACE_V1 = 'cepis/v1';
+
+	/**
+	 * Register the route, when the store asked for it.
+	 */
+	public static function init(): void {
+		if ( ! Cepis_Woo_Options::enabled() || 'proxy' !== Cepis_Woo_Options::mode() ) {
+			return;
+		}
+
+		add_action( 'rest_api_init', array( self::class, 'register' ) );
+	}
+
+	/**
+	 * Declare the route.
+	 */
+	public static function register(): void {
+		register_rest_route(
+			self::NAMESPACE_V1,
+			'/lookup/(?P<token>[A-Za-z0-9]{1,64})/(?P<cep>[0-9]{8})',
+			array(
+				'methods'             => WP_REST_Server::READABLE,
+				'callback'            => array( self::class, 'lookup' ),
+				'permission_callback' => array( self::class, 'permitted' ),
+				'args'                => array(
+					'token' => array(
+						'type'              => 'string',
+						'required'          => true,
+						'sanitize_callback' => 'sanitize_key',
+					),
+					'cep'   => array(
+						'type'              => 'string',
+						'required'          => true,
+						'sanitize_callback' => 'sanitize_key',
+						'validate_callback' => static fn( $value ): bool => 1 === preg_match( '/^[0-9]{8}$/', (string) $value ),
+					),
+				),
+			)
+		);
+	}
+
+	/**
+	 * Reject anything that does not carry a live token.
+	 *
+	 * @param WP_REST_Request $request Incoming request.
+	 *
+	 * @return true|WP_Error True when the token checks out.
+	 */
+	public static function permitted( WP_REST_Request $request ): bool|WP_Error {
+		if ( Cepis_Woo_Token::verify( (string) $request['token'] ) ) {
+			return true;
+		}
+
+		return new WP_Error(
+			'cepis_invalid_token',
+			__( 'Lookup token missing, invalid or expired. Reload the page.', 'cepis-woocommerce' ),
+			array( 'status' => 403 )
+		);
+	}
+
+	/**
+	 * Answer one lookup.
+	 *
+	 * @param WP_REST_Request $request Incoming request.
+	 */
+	public static function lookup( WP_REST_Request $request ): WP_REST_Response {
+		$result = Cepis_Woo_Lookup::resolve( (string) $request['cep'] );
+
+		$response = new WP_REST_Response( $result['body'], $result['status'] );
+		$response->header( 'Cache-Control', 'no-store' );
+
+		if ( null !== $result['retry_after'] ) {
+			$response->header( 'Retry-After', (string) $result['retry_after'] );
+		}
+
+		return $response;
+	}
+
+	/**
+	 * The API root to hand the browser, with a live token already in it.
+	 *
+	 * Shaped so that appending `/{cep}` to it reaches this route, which is what
+	 * the widget does with its `baseUrl`.
+	 */
+	public static function base_url(): string {
+		return untrailingslashit( rest_url( self::NAMESPACE_V1 . '/lookup/' . Cepis_Woo_Token::create() ) );
+	}
+}