Add a delivery note to shipping option names

api_version = "2026-10"

[[extensions]]
name = "Add a delivery note to shipping options"
handle = "shipping-option-delivery-note"
type = "function"

  [[extensions.targeting]]
  target = "cart.delivery-options.transform.run"
  input_query = "src/cart_delivery_options_transform_run.graphql"
  export = "cart-delivery-options-transform-run"

  [extensions.build]
  command = ""
  path = "dist/function.wasm"

query CartDeliveryOptionsTransformRunInput {
  cart {
    deliveryGroups {
      deliveryAddress {
        countryCode
      }
      deliveryOptions {
        handle
        title
      }
    }
  }
  deliveryCustomization {
    metafield(namespace: "$app", key: "function-configuration") {
      jsonValue
    }
  }
}

// @ts-check

/**
 * @typedef {import("../generated/api").CartDeliveryOptionsTransformRunInput} CartDeliveryOptionsTransformRunInput
 * @typedef {import("../generated/api").CartDeliveryOptionsTransformRunResult} CartDeliveryOptionsTransformRunResult
 */

/**
 * Settings stored as JSON in the customization's metafield, so delivery
 * promises can change (holidays, carrier delays) without a deploy.
 */
const DEFAULT_CONFIG = {
  /**
   * Rules checked in order; the first one whose title matches wins.
   * `title` is matched case-insensitively against the start of the option
   * title; `countries` (optional) limits the rule to delivery addresses there.
   * @type {{title: string, note: string, countries?: string[]}[]}
   */
  rules: [],
  // Placed between the original title and the note.
  separator: " · ",
};

/**
 * @param {CartDeliveryOptionsTransformRunInput} input
 * @returns {CartDeliveryOptionsTransformRunResult}
 */
export function cartDeliveryOptionsTransformRun(input) {
  const config = { ...DEFAULT_CONFIG, ...input.deliveryCustomization?.metafield?.jsonValue };
  const operations = [];

  for (const group of input.cart.deliveryGroups) {
    const country = group.deliveryAddress?.countryCode ?? null;
    for (const option of group.deliveryOptions) {
      const title = option.title ?? "";
      const rule = config.rules.find(
        (r) =>
          title.toLowerCase().startsWith(r.title.toLowerCase()) &&
          (!r.countries?.length || (country !== null && r.countries.some((code) => code.toUpperCase() === country))),
      );
      // Keep the original title in front: Shopify adds the carrier name before
      // it anyway, and customers recognise the rate they saw on the cart page.
      if (rule) {
        operations.push({
          deliveryOptionRename: { deliveryOptionHandle: option.handle, title: `${title}${config.separator}${rule.note}` },
        });
      }
    }
  }

  return { operations };
}