MPH_REGIONS = ("US", "GB", "LR")
METRIC_REGION = "METRIC"
UNKNOWN_REGION = ""

_US_CONUS = [
  (-123.32, 49.00), (-117.03, 49.00), (-110.00, 49.00), (-104.05, 49.00), (-97.23, 49.00), (-95.15, 49.00),
  (-95.15, 49.38), (-94.82, 49.30), (-94.68, 48.77), (-93.85, 48.63), (-93.35, 48.62), (-92.72, 48.54),
  (-92.30, 48.24), (-91.55, 48.10), (-90.84, 48.24), (-89.99, 48.02), (-89.60, 48.02), (-89.10, 48.32),
  (-88.40, 48.30), (-87.00, 47.80), (-85.60, 47.15), (-84.60, 46.75), (-84.42, 46.56), (-84.30, 46.49),
  (-84.12, 46.28), (-83.90, 46.05), (-83.40, 45.75), (-82.90, 45.05), (-82.55, 44.00), (-82.42, 43.00),
  (-82.70, 42.47), (-82.93, 42.34), (-83.00, 42.33), (-83.05, 42.32), (-83.075, 42.312), (-83.13, 42.25),
  (-83.15, 42.18), (-83.11, 42.10), (-83.09, 42.02),
  (-82.50, 41.70), (-81.50, 42.00), (-80.20, 42.40), (-79.06, 42.85), (-79.05, 43.27), (-78.00, 43.45),
  (-77.00, 43.65), (-76.40, 44.10), (-75.80, 44.50), (-74.75, 45.00), (-73.35, 45.01), (-71.50, 45.01),
  (-71.29, 45.30), (-70.90, 45.30), (-70.72, 45.42), (-70.31, 45.86), (-70.05, 46.44), (-69.99, 46.70),
  (-69.24, 47.46), (-68.90, 47.20), (-68.38, 47.29), (-67.79, 47.07), (-67.78, 45.94), (-67.42, 45.60),
  (-67.03, 44.80), (-68.00, 44.30), (-69.06, 43.80), (-70.20, 43.60), (-70.80, 42.85), (-70.00, 41.90),
  (-70.00, 41.55), (-71.20, 41.30), (-72.00, 41.05), (-73.90, 40.55), (-74.20, 39.60), (-75.05, 38.45),
  (-75.90, 37.05), (-75.50, 35.20), (-78.50, 33.85), (-80.90, 32.00), (-81.40, 30.70), (-80.03, 26.80),
  (-80.15, 25.15), (-81.20, 24.55), (-82.00, 26.40), (-82.80, 27.80), (-83.00, 29.15), (-84.30, 29.90),
  (-85.30, 29.65), (-87.50, 30.25), (-89.00, 29.15), (-89.40, 28.95), (-91.30, 29.10), (-93.80, 29.65),
  (-95.00, 29.10), (-97.10, 27.80), (-97.14, 25.96), (-98.30, 26.05), (-99.10, 26.40), (-99.50, 27.60),
  (-100.40, 28.50), (-101.40, 29.77), (-102.30, 29.88), (-102.90, 29.30), (-103.30, 29.00), (-104.37, 29.56),
  (-104.68, 30.13), (-105.30, 30.80), (-105.85, 31.30), (-106.15, 31.50), (-106.30, 31.68), (-106.45, 31.755),
  (-106.53, 31.786), (-108.21, 31.783), (-108.21, 31.33), (-111.07, 31.33), (-114.72, 32.72),
  (-117.13, 32.53), (-118.40, 33.75), (-119.80, 34.40), (-120.65, 35.10), (-121.90, 36.60), (-122.52, 37.78),
  (-123.75, 39.40), (-124.20, 40.45), (-124.15, 42.00), (-124.05, 43.35), (-123.95, 46.25), (-124.75, 48.40),
  (-123.30, 48.25), (-123.15, 48.70),
]

_US_ALASKA = [
  (-141.00, 70.20), (-141.00, 60.30), (-139.05, 60.35), (-137.45, 58.95), (-136.47, 59.63), (-135.03, 59.57),
  (-134.30, 58.90), (-133.40, 58.20), (-132.20, 56.90), (-130.60, 56.20), (-130.01, 54.80), (-131.80, 54.70),
  (-133.80, 55.90), (-136.60, 58.20), (-140.00, 59.70), (-145.00, 60.00), (-149.20, 59.10), (-152.30, 57.30),
  (-155.20, 55.60), (-160.00, 54.60), (-164.50, 54.40), (-162.00, 57.50), (-165.00, 60.20), (-167.50, 62.50),
  (-164.00, 64.50), (-168.10, 65.60), (-166.00, 68.30), (-161.00, 70.30), (-156.50, 71.40), (-150.00, 70.50),
]

_US_ALEUTIANS_EAST = [(-180.00, 51.00), (-158.50, 51.00), (-158.50, 56.00), (-180.00, 56.00)]
_US_ALEUTIANS_WEST = [(172.00, 51.00), (180.00, 51.00), (180.00, 54.00), (172.00, 54.00)]
_US_HAWAII = [(-160.50, 18.80), (-154.70, 18.80), (-154.70, 22.30), (-160.50, 22.30)]
_US_PUERTO_RICO = [(-67.35, 17.85), (-64.55, 17.85), (-64.55, 18.55), (-67.35, 18.55)]
_US_MARIANAS = [(144.50, 13.10), (146.20, 13.10), (146.20, 20.60), (144.50, 20.60)]
_US_SAMOA = [(-171.20, -14.60), (-168.10, -14.60), (-168.10, -11.00), (-171.20, -11.00)]

_GB_BRITAIN = [
  (-5.72, 50.07), (-4.20, 50.32), (-3.41, 50.62), (-2.45, 50.52), (-1.80, 50.72), (-0.90, 50.77),
  (0.58, 50.85), (1.35, 51.13), (1.38, 51.38), (1.15, 51.79), (1.35, 51.95), (1.75, 52.48),
  (1.30, 52.94), (0.49, 52.94), (0.34, 53.15), (-0.08, 53.57), (-0.08, 54.12), (-0.61, 54.49),
  (-1.18, 54.69), (-1.38, 54.91), (-1.50, 55.13), (-2.00, 55.77), (-2.52, 56.00), (-2.62, 56.28),
  (-2.47, 56.55), (-2.21, 56.96), (-2.08, 57.14), (-1.77, 57.50), (-2.00, 57.70), (-2.96, 57.68),
  (-3.90, 57.60), (-4.22, 57.48), (-4.05, 57.81), (-3.85, 58.01), (-3.65, 58.12), (-3.09, 58.44),
  (-3.01, 58.67), (-3.35, 58.62), (-3.52, 58.60), (-4.99, 58.62), (-5.05, 58.45), (-5.16, 57.90), (-5.70, 57.72),
  (-5.72, 57.28), (-5.83, 57.00), (-5.72, 56.65), (-5.47, 56.41), (-5.79, 55.60), (-5.62, 55.31),
  (-4.82, 55.64), (-4.63, 55.46), (-4.85, 55.24), (-5.12, 54.84), (-4.86, 54.63), (-4.44, 54.87),
  (-4.05, 54.83), (-3.26, 54.98), (-3.05, 54.90), (-3.50, 54.72), (-3.23, 54.07), (-3.05, 53.82),
  (-3.40, 53.34), (-3.83, 53.33), (-4.63, 53.42), (-4.72, 53.28), (-4.35, 53.12), (-4.76, 52.80),
  (-4.06, 52.72), (-4.09, 52.41), (-4.66, 52.09), (-5.31, 51.88), (-5.06, 51.70), (-4.70, 51.67),
  (-4.30, 51.62), (-3.95, 51.56), (-3.70, 51.48), (-3.17, 51.45), (-2.99, 51.55), (-2.67, 51.62),
  (-2.48, 51.72), (-2.30, 51.85), (-2.70, 51.50), (-2.98, 51.35), (-3.00, 51.20), (-3.47, 51.21),
  (-4.12, 51.21), (-4.55, 50.83), (-5.08, 50.42), (-5.48, 50.21),
]

_GB_NORTHERN_IRELAND = [
  (-6.03, 54.05), (-6.28, 54.10), (-6.65, 54.17), (-6.86, 54.33), (-7.16, 54.34), (-7.31, 54.12),
  (-7.62, 54.14), (-8.00, 54.31), (-8.18, 54.47), (-8.20, 54.52), (-7.90, 54.55), (-7.85, 54.72), (-7.55, 54.75),
  (-7.44, 54.94), (-7.25, 55.06), (-6.95, 55.22), (-6.50, 55.25), (-6.25, 55.31), (-6.03, 55.22),
  (-5.43, 54.62), (-5.53, 54.24),
]

_GB_ISLE_OF_MAN = [(-4.85, 54.03), (-4.30, 54.03), (-4.30, 54.42), (-4.85, 54.42)]
_GB_CHANNEL_ISLANDS = [(-2.75, 49.15), (-1.95, 49.15), (-1.95, 49.80), (-2.75, 49.80)]
_GB_ISLE_OF_WIGHT = [(-1.60, 50.55), (-1.05, 50.55), (-1.05, 50.80), (-1.60, 50.80)]
_GB_OUTER_HEBRIDES = [(-7.75, 56.75), (-6.05, 56.75), (-6.05, 58.55), (-7.75, 58.55)]
_GB_INNER_HEBRIDES = [(-7.00, 55.45), (-5.55, 55.45), (-5.55, 57.85), (-7.00, 57.85)]
_GB_ORKNEY = [(-3.50, 58.70), (-2.35, 58.70), (-2.35, 59.45), (-3.50, 59.45)]
_GB_SHETLAND = [(-1.85, 59.80), (-0.65, 59.80), (-0.65, 60.90), (-1.85, 60.90)]

_LR_LIBERIA = [
  (-11.46, 6.77), (-11.30, 6.95), (-11.16, 7.15), (-11.05, 7.40), (-10.85, 7.75), (-10.60, 8.00),
  (-10.28, 8.49), (-9.70, 8.54), (-9.35, 7.80),
  (-8.85, 7.40), (-8.48, 7.55), (-8.30, 6.90), (-7.95, 6.20), (-7.60, 5.20), (-7.40, 4.55),
  (-7.74, 4.33), (-8.46, 4.61), (-9.06, 4.97), (-9.52, 5.36), (-10.08, 5.85), (-10.40, 6.11),
  (-10.83, 6.27),
]

_REGION_RINGS = {
  "US": (_US_CONUS, _US_ALASKA, _US_ALEUTIANS_EAST, _US_ALEUTIANS_WEST, _US_HAWAII, _US_PUERTO_RICO,
         _US_MARIANAS, _US_SAMOA),
  "GB": (_GB_BRITAIN, _GB_NORTHERN_IRELAND, _GB_ISLE_OF_MAN, _GB_CHANNEL_ISLANDS, _GB_ISLE_OF_WIGHT,
         _GB_OUTER_HEBRIDES, _GB_INNER_HEBRIDES, _GB_ORKNEY, _GB_SHETLAND),
  "LR": (_LR_LIBERIA,),
}


def _bounded(rings):
  out = []
  for ring in rings:
    lons = [p[0] for p in ring]
    lats = [p[1] for p in ring]
    out.append(((min(lons), min(lats), max(lons), max(lats)), ring))
  return tuple(out)


_REGIONS = tuple((region, _bounded(rings)) for region, rings in _REGION_RINGS.items())


def _point_in_ring(lat: float, lon: float, ring) -> bool:
  inside = False
  count = len(ring)
  j = count - 1
  for i in range(count):
    lon_i, lat_i = ring[i]
    lon_j, lat_j = ring[j]
    if (lat_i > lat) != (lat_j > lat):
      crossing = (lon_j - lon_i) * (lat - lat_i) / (lat_j - lat_i) + lon_i
      if lon < crossing:
        inside = not inside
    j = i
  return inside


def valid_position(lat: float, lon: float) -> bool:
  return abs(lat) <= 90.0 and abs(lon) <= 180.0 and (abs(lat) > 1e-4 or abs(lon) > 1e-4)


def region_for_position(lat: float, lon: float) -> str:
  if not valid_position(lat, lon):
    return UNKNOWN_REGION

  for region, rings in _REGIONS:
    for (min_lon, min_lat, max_lon, max_lat), ring in rings:
      if min_lon <= lon <= max_lon and min_lat <= lat <= max_lat and _point_in_ring(lat, lon, ring):
        return region

  return METRIC_REGION


def region_is_metric(region: str) -> bool:
  return bool(region) and region not in MPH_REGIONS