Rate shop with delivery dates

curl --request POST \
  --url https://api.goshippo.com/v2/estimates \
  --header 'Authorization: ShippoToken <API_TOKEN>' \
  --header 'Content-Type: application/json' \
  --data '{
    "origin": {
      "zip": "95122"
    },
    "destination": {
      "zip": "94103"
    },
    "parcel": {
      "length": 10,
      "width": 8,
      "height": 4,
      "distance_unit": "in",
      "weight": 2,
      "mass_unit": "lb"
    },
    "planned_ship_date": "2026-05-01T17:00:00Z"
  }'

curl --request POST \
  --url https://api.goshippo.com/shipments/ \
  --header 'Authorization: ShippoToken <API_TOKEN>' \
  --header 'Content-Type: application/json' \
  --data '{
    "address_from": {
      "street1": "1092 Indian Summer Ct",
      "city": "San Jose",
      "state": "CA",
      "zip": "95122",
      "country": "US"
    },
    "address_to": {
      "street1": "965 Mission St",
      "city": "San Francisco",
      "state": "CA",
      "zip": "94103",
      "country": "US"
    },
    "parcels": [{
      "length": "10",
      "width": "8",
      "height": "4",
      "distance_unit": "in",
      "weight": "2",
      "mass_unit": "lb"
    }],
    "async": false
  }'

const DESTINATION_TIMEZONE = "America/Los_Angeles";

// Build a lookup map from the Estimate response
const estimatesByToken = {};
for (const prediction of estimatesResponse.predictions) {
  estimatesByToken[prediction.servicelevel.token] = prediction;
}

// Merge with Shipments rates
const combined = shipmentsResponse.rates
  .map(rate => {
    const estimate = estimatesByToken[rate.servicelevel.token];
    if (!estimate) return null; // no Estimate data for this service level

    const localDeliveryDate = new Date(estimate.estimated_delivery_date_utc)
      .toLocaleDateString("en-US", {
        timeZone: DESTINATION_TIMEZONE,
        weekday: "long",
        month: "long",
        day: "numeric"
      });

    return {
      provider: rate.provider,
      service: rate.servicelevel.name,
      token: rate.servicelevel.token,
      price: parseFloat(rate.amount),
      currency: rate.currency,
      deliveryDate: localDeliveryDate,
      transitDays: estimate.estimated_transit_days,
      rateId: rate.object_id,
    };
  })
  .filter(Boolean)
  .sort((a, b) => a.price - b.price); // cheapest first

// Example output:
// { provider: "UPS",   service: "Ground",           price: 5.80, deliveryDate: "Tuesday, May 5",   transitDays: 4 }
// { provider: "FedEx", service: "Ground",            price: 6.20, deliveryDate: "Monday, May 4",    transitDays: 3 }
// { provider: "USPS",  service: "Priority Mail",     price: 8.50, deliveryDate: "Sunday, May 3",    transitDays: 2 }
// { provider: "FedEx", service: "Priority Overnight",price: 26.35,deliveryDate: "Saturday, May 2",  transitDays: 1 }