Custom shipping plugin (Packeta)

public function onShippingDisplay(&$order, &$dbrates, &$usable_rates, &$messages)
	{
		// look in the cache first, maybe this has been done already
		if ($this->loadShippingCache($order, $usable_rates, $messages)) {
			return true;
		}
	
		$local_usable_rates = [];
		$local_messages = [];
		$ret = parent::onShippingDisplay($order, $dbrates, $local_usable_rates, $local_messages);
		if ($ret === false) {
			return false;
		}
	
		// we get a list of ALL rates, but only want to work with packeta
		foreach ($local_usable_rates as $rate) {
			if ($rate->shipping_type !== 'packeta') {
				continue;
			}
	
			$pickupPointInputName = 'checkout[shipping][custom]';
			if (isset($order->shipping_warehouse_id)) {
				$pickupPointInputName .= '[' . $order->shipping_warehouse_id . ']';
			}
			$pickupPointInputName .= '[' . $rate->shipping_id . ']';

                        // dirty load the script for now, better solution might be needed in production
			$rate->custom_html .= '<script src="https://widget.packeta.com/v6/www/js/library.js"></script>';
			
			// show the "select a pickup point" button including its functionality
			$rate->custom_html .= '
			<div class="packeta-widget-container" style="margin-top:8px;">
				<button type="button"
					class="btn hikashopPickupBtn packeta-selector-open"
					data-shipping-id="' . $rate->shipping_id . '">
					Select your pickup point
				</button>
				<input type="hidden"
					name="' . $pickupPointInputName . '"
					id="pickup_point_' . $rate->shipping_id . '"
					value="" />
				<div class="packeta-selector-value" id="pickup_display_' . $rate->shipping_id . '"></div>
			</div>
		
			<script>
				const packetaApiKey = "your_public_key";

				// generated from Packeta widget configurator
				const packetaOptions = {
					language: "cs",
					valueFormat: "name,city,street",
					view: "modal"
				};
		
				// mostly provided by Packeta, just make sure every shipping_id has its own function
				function showSelectedPickupPoint_' . $rate->shipping_id . '(point) {
					if (point) {
						const display = document.getElementById("pickup_display_' . $rate->shipping_id . '");
						const input = document.getElementById("pickup_point_' . $rate->shipping_id . '");
						display.innerText = "Address: " + point.formatedValue;
						input.value = point.id;
					}
				}
		
				document.addEventListener("DOMContentLoaded", function () {
					const btn = document.querySelector(".packeta-selector-open[data-shipping-id=\'' . $rate->shipping_id . '\']");
					if (btn) {
						btn.addEventListener("click", function () {
							Packeta.Widget.pick(packetaApiKey, showSelectedPickupPoint_' . $rate->shipping_id . ', packetaOptions);
						});
					}
				});
			</script>';
	
			$rate->custom_html_no_btn = true;
			$usable_rates[$rate->shipping_id] = $rate;
		}
	
		// save the processed methods into the cache
		$this->setShippingCache($order, $usable_rates, $messages);
	
		return true;
	}