/**
 * Server-side Mapbox Directions call — used by `requestRide` to compute the
 * authoritative distance/duration a ride's price is based on. The client
 * shows its own local, unpersisted preview using the same public pricing
 * coefficients (see Firebase/lib/features/drive/providers/route_controller.dart);
 * only the value this function returns is ever written to a ride document, so
 * a tampered client can never write itself a discounted fare.
 */

interface RouteResult {
  distanceMeters: number;
  durationSeconds: number;
}

export async function fetchDrivingRoute(
  pickup: { lat: number; lng: number },
  dropoff: { lat: number; lng: number },
  accessToken: string,
): Promise<RouteResult> {
  const coordinates = `${pickup.lng},${pickup.lat};${dropoff.lng},${dropoff.lat}`;
  const url = `https://api.mapbox.com/directions/v5/mapbox/driving/${coordinates}` +
    `?overview=false&approaches=curb;curb&radiuses=120;120&access_token=${accessToken}`;

  const res = await fetch(url);
  if (!res.ok) {
    throw new Error(`Mapbox Directions request failed: ${res.status}`);
  }
  const json = (await res.json()) as {
    routes?: { distance: number; duration: number }[];
  };
  const route = json.routes?.[0];
  if (!route) {
    throw new Error("Mapbox Directions returned no route");
  }
  return {distanceMeters: route.distance, durationSeconds: route.duration};
}