/** Geo helpers for reconciliation (bounding boxes, precision comparisons). */
import { haversineKm, PRECISION_RANK, validLatLng, type GeoPoint, type GeoPrecision } from "@dci/core";

export interface BBox {
  minLat: number;
  maxLat: number;
  minLng: number;
  maxLng: number;
}

/** Bounding box around a point for a radius in km (cheap pre-filter before haversine). */
export function bboxAround(lat: number, lng: number, radiusKm: number): BBox {
  const dLat = radiusKm / 111.32;
  const cos = Math.max(0.05, Math.cos((lat * Math.PI) / 180));
  const dLng = radiusKm / (111.32 * cos);
  return { minLat: Math.max(-90, lat - dLat), maxLat: Math.min(90, lat + dLat), minLng: Math.max(-180, lng - dLng), maxLng: Math.min(180, lng + dLng) };
}

export function distanceKm(a: { lat: number; lng: number }, b: { lat: number; lng: number }): number {
  return haversineKm(a.lat, a.lng, b.lat, b.lng);
}

export function asPrecision(p: string | null | undefined): GeoPrecision {
  return p && p in PRECISION_RANK ? (p as GeoPrecision) : "unknown";
}

/** True when the incoming point may replace the stored one (never degrade precision). */
export function mayReplaceGeo(incoming: GeoPoint | null | undefined, storedPrecision: string | null | undefined, storedHasCoords: boolean): boolean {
  if (!incoming || !validLatLng(incoming.lat, incoming.lng)) return false;
  if (!storedHasCoords) return true;
  return PRECISION_RANK[incoming.precision] >= PRECISION_RANK[asPrecision(storedPrecision)];
}

export function validGeo(g: GeoPoint | null | undefined): g is GeoPoint {
  return !!g && validLatLng(g.lat, g.lng);
}