export interface Location {
  latitude: number;
  longitude: number;
}

export function inArea(bounds: Array<Location>, point: Location): boolean {
  let lonA: number;
  let latA: number;
  let lonB: number;
  let latB: number;
  let inside = 0;
  for (let i = 0; i < bounds.length; i++) {
    lonA = bounds[i].longitude - point.longitude;
    latA = bounds[i].latitude - point.latitude;
    lonB = bounds[(i + 1) % bounds.length].longitude - point.longitude;
    latB = bounds[(i + 1) % bounds.length].latitude - point.latitude;
    const check = polygonPointCheck(lonA, latA, lonB, latB);
    if (check === 4) {
      return true;
    }
    inside += check;
  }
  return inside !== 0;
}

export function polygonPointCheck(
  lonA: number,
  latA: number,
  lonB: number,
  latB: number,
): number {
  if (latA * latB > 0) {
    return 0;
  }
  if (lonA * latB !== lonB * latA || lonA * lonB > 0) {
    if (latA * latB < 0) {
      if (latA > 0) {
        if (latA * lonB >= lonA * latB) {
          return 0;
        }
        return -2;
      }
      if (lonA * latB >= latA * lonB) {
        return 0;
      }
      return 2;
    }
    if (latB === 0) {
      if (latA === 0) {
        return 0;
      } else if (lonB > 0) {
        return 0;
      } else if (latA > 0) {
        return -1;
      }
      return 1;
    } else if (lonA > 0) {
      return 0;
    } else if (latB > 0) {
      return 1;
    }
    return -1;
  }
  return 4;
}