Apply Shipping Discounts if cart's items are from different locations

Retired Boards Appdev Functions
1

I am writing a Shipping Discount Shopify function. If a customer buy two items which are from different locations, e.g. item A from location X and item B from location Y, I want to give 50% discount on shipping fee.

But how to detect if the cart’s items are from multiple locations?

I am using input.cart.deliveryGroups.length.

It seems not correct as it always returns one.

Can anyone help?

Here is my code (run.js):

const EMPTY_DISCOUNT = {
  discounts: [],
};

export function run(input) {

  const deliveryGroupCount = input.cart.deliveryGroups.length;
  if (deliveryGroupCount === 1) {
    return EMPTY_DISCOUNT;
  }

  const discountPercentage = 100 / deliveryGroupCount;

  const deliveryOptions = [];

  for(const deliveryGroup of input.cart.deliveryGroups) {
    for (const option of deliveryGroup.deliveryOptions) {
      deliveryOptions.push({
        deliveryOption: {
          handle: option.handle
        }
      })
    }
  }

  return {
    discounts: [
      {
        targets: deliveryOptions,
        value: {
          percentage: {
            value: discountPercentage
          }
        }
      }
    ]
  }
};

Here is run.graphql

query RunInput {
  cart {
    deliveryGroups {
      deliveryOptions {
        title
        handle
      }
    }
  }
}