<?php
/**
 * Plugin Name: RESPILON Quick Buy
 * Description: Stable, product-ID-agnostic buy link for the static antiakne.no landing.
 *              GET https://kasse.antiakne.no/kjop  ->  empties cart, adds the Anti-Akne
 *              kur (by SKU), redirects to checkout. Optional ?antall=N for quantity.
 *
 * The static site links here so it never has to hardcode a WooCommerce product ID
 * (which changes if the store is re-provisioned). Must be a full browser navigation
 * to the kasse subdomain so the WooCommerce session cookie is first-party.
 */

defined( 'ABSPATH' ) || exit;

const RESPILON_QUICKBUY_SKU = 'ANTIAKNE-KUR-01';

add_action( 'wp_loaded', function () {
    $path = strtok( $_SERVER['REQUEST_URI'] ?? '', '?' );
    if ( rtrim( (string) $path, '/' ) !== '/kjop' ) {
        return;
    }

    // WooCommerce must be loaded with an initialised cart/session.
    if ( ! function_exists( 'WC' ) || ! function_exists( 'wc_get_product_id_by_sku' ) || ! WC()->cart ) {
        wp_safe_redirect( home_url( '/' ) );
        exit;
    }

    nocache_headers();

    $product_id = wc_get_product_id_by_sku( RESPILON_QUICKBUY_SKU );
    if ( ! $product_id ) {
        wp_safe_redirect( home_url( '/' ) );
        exit;
    }

    $qty = isset( $_GET['antall'] ) ? max( 1, absint( $_GET['antall'] ) ) : 1;

    // Single-product funnel: start clean so repeat clicks don't stack the cart.
    WC()->cart->empty_cart();
    WC()->cart->add_to_cart( $product_id, $qty );

    wp_safe_redirect( wc_get_checkout_url() );
    exit;
}, 20 );