/**
 * Approximate centroids for Vietnam's 63 provinces / centrally-administered
 * cities, used as a fallback when OSM `addr:state` / `addr:province` tags
 * are missing (which is the common case for industrial-park polygons in VN).
 *
 * The coords are public-domain capital-city centroids (good enough for a
 * "which province does this point land in?" nearest-neighbour lookup at
 * the +/- few-km level — the long shape of some provinces means the
 * nearest centroid will occasionally pick the wrong neighbour, but admin
 * can correct on promote.
 *
 * Province name canonical form = display name in Vietnamese (no diacritics
 * stripped) so it matches what the seed data + UI already uses.
 */

export interface ProvinceCentroid {
  name: string;
  lat: number;
  lng: number;
}

export const VN_PROVINCE_CENTROIDS: ProvinceCentroid[] = [
  { name: 'Hà Nội', lat: 21.028511, lng: 105.804817 },
  { name: 'Hồ Chí Minh', lat: 10.762622, lng: 106.660172 },
  { name: 'Hải Phòng', lat: 20.844912, lng: 106.688084 },
  { name: 'Đà Nẵng', lat: 16.054407, lng: 108.202167 },
  { name: 'Cần Thơ', lat: 10.045162, lng: 105.746857 },
  { name: 'An Giang', lat: 10.521583, lng: 105.125896 },
  { name: 'Bà Rịa - Vũng Tàu', lat: 10.541136, lng: 107.242851 },
  { name: 'Bạc Liêu', lat: 9.294085, lng: 105.721787 },
  { name: 'Bắc Giang', lat: 21.281932, lng: 106.197658 },
  { name: 'Bắc Kạn', lat: 22.147291, lng: 105.834160 },
  { name: 'Bắc Ninh', lat: 21.186080, lng: 106.076371 },
  { name: 'Bến Tre', lat: 10.243519, lng: 106.375140 },
  { name: 'Bình Dương', lat: 11.325237, lng: 106.477017 },
  { name: 'Bình Định', lat: 13.782250, lng: 109.219574 },
  { name: 'Bình Phước', lat: 11.751888, lng: 106.723917 },
  { name: 'Bình Thuận', lat: 11.090668, lng: 108.072094 },
  { name: 'Cà Mau', lat: 9.176790, lng: 105.150253 },
  { name: 'Cao Bằng', lat: 22.665684, lng: 106.257549 },
  { name: 'Đắk Lắk', lat: 12.710017, lng: 108.237633 },
  { name: 'Đắk Nông', lat: 12.264144, lng: 107.609794 },
  { name: 'Điện Biên', lat: 21.386073, lng: 103.016510 },
  { name: 'Đồng Nai', lat: 11.066000, lng: 107.166700 },
  { name: 'Đồng Tháp', lat: 10.493333, lng: 105.688200 },
  { name: 'Gia Lai', lat: 13.808078, lng: 108.109375 },
  { name: 'Hà Giang', lat: 22.823453, lng: 104.978573 },
  { name: 'Hà Nam', lat: 20.541127, lng: 105.913303 },
  { name: 'Hà Tĩnh', lat: 18.342745, lng: 105.905499 },
  { name: 'Hải Dương', lat: 20.940981, lng: 106.330156 },
  { name: 'Hậu Giang', lat: 9.757897, lng: 105.641110 },
  { name: 'Hòa Bình', lat: 20.817192, lng: 105.337720 },
  { name: 'Hưng Yên', lat: 20.852241, lng: 106.015511 },
  { name: 'Khánh Hòa', lat: 12.258515, lng: 109.052528 },
  { name: 'Kiên Giang', lat: 10.012103, lng: 105.080921 },
  { name: 'Kon Tum', lat: 14.349953, lng: 108.000534 },
  { name: 'Lai Châu', lat: 22.396519, lng: 103.471370 },
  { name: 'Lâm Đồng', lat: 11.940419, lng: 108.458313 },
  { name: 'Lạng Sơn', lat: 21.853708, lng: 106.761525 },
  { name: 'Lào Cai', lat: 22.485198, lng: 103.974845 },
  { name: 'Long An', lat: 10.535359, lng: 106.405460 },
  { name: 'Nam Định', lat: 20.438822, lng: 106.162106 },
  { name: 'Nghệ An', lat: 18.679585, lng: 105.681753 },
  { name: 'Ninh Bình', lat: 20.250716, lng: 105.974623 },
  { name: 'Ninh Thuận', lat: 11.673911, lng: 108.864225 },
  { name: 'Phú Thọ', lat: 21.398716, lng: 105.151787 },
  { name: 'Phú Yên', lat: 13.088067, lng: 109.092876 },
  { name: 'Quảng Bình', lat: 17.478366, lng: 106.621288 },
  { name: 'Quảng Nam', lat: 15.539353, lng: 108.019047 },
  { name: 'Quảng Ngãi', lat: 15.120137, lng: 108.804340 },
  { name: 'Quảng Ninh', lat: 21.006382, lng: 107.292514 },
  { name: 'Quảng Trị', lat: 16.745360, lng: 107.187462 },
  { name: 'Sóc Trăng', lat: 9.602522, lng: 105.973797 },
  { name: 'Sơn La', lat: 21.328228, lng: 103.914400 },
  { name: 'Tây Ninh', lat: 11.310300, lng: 106.098046 },
  { name: 'Thái Bình', lat: 20.446016, lng: 106.336445 },
  { name: 'Thái Nguyên', lat: 21.594280, lng: 105.844866 },
  { name: 'Thanh Hóa', lat: 19.806692, lng: 105.785182 },
  { name: 'Thừa Thiên Huế', lat: 16.467397, lng: 107.590533 },
  { name: 'Tiền Giang', lat: 10.449334, lng: 106.342120 },
  { name: 'Trà Vinh', lat: 9.812741, lng: 106.299250 },
  { name: 'Tuyên Quang', lat: 21.778812, lng: 105.218015 },
  { name: 'Vĩnh Long', lat: 10.253938, lng: 105.972456 },
  { name: 'Vĩnh Phúc', lat: 21.308690, lng: 105.604813 },
  { name: 'Yên Bái', lat: 21.722733, lng: 104.911289 },
];

/**
 * Find the nearest province centroid for a given lat/lng. Uses naive squared
 * distance — fine for VN's ~1500-km north-south extent. Always returns a
 * province (the dataset covers the country); callers can fall back to
 * "Chưa xác định" if they need to.
 */
export function nearestProvince(lat: number, lng: number): string {
  let best = VN_PROVINCE_CENTROIDS[0];
  let bestD = Infinity;
  for (const p of VN_PROVINCE_CENTROIDS) {
    const dLat = lat - p.lat;
    const dLng = lng - p.lng;
    const d = dLat * dLat + dLng * dLng;
    if (d < bestD) {
      bestD = d;
      best = p;
    }
  }
  return best.name;
}