import string, os
from copy import *
from math import sqrt
from sets import *

class OffMap:
	pass

class Grid:
	def __init__(self):
		self.names = (("SV", "SW", "SX", "SY", "SZ", "TV", "TW"),
				("SQ", "SR", "SS", "ST", "SU", "TQ", "TR"),
				("SL", "SM", "SN", "SO", "SP", "TL", "TM"),
				("SF", "SG", "SH", "SJ", "SK", "TF", "TG"),
				("SA", "SB", "SC", "SD", "SE", "TA", "TB"),
				("NV", "NW", "NX", "NY", "NZ", "OV", "OW"),
				("NQ", "NR", "NS", "NT", "NU", "OQ", "OR"),
				("NL", "NM", "NN", "NO", "NP", "OL", "OM"),
				("NF", "NG", "NH", "NJ", "NK", "OF", "OG"),
				("NA", "NB", "NC", "ND", "NE", "OA", "OB"),
				("HV", "HW", "HX", "HY", "HZ", "JV", "JW"),
				("HQ", "HR", "HS", "HT", "HU", "JQ", "JR"),
				("HL", "HM", "HN", "HO", "HP", "JL", "JM"))

		self.squares = {}
		self.letters = {}
		self.width = 7

		self.scale = 1000 # number of 'tenths' in a 100km square side

		for i, row in enumerate(self.names):
			for j, sq in enumerate(row):
				self.squares[sq] = (j * self.scale, i * self.scale)
				self.letters[i * self.width + j] = sq

		self.Load()

	def Load(self, filename = os.environ['HOME'] + '/.makemaprc'):
		self.places = {}

		try:
			file = open(filename)
			lines = file.readlines()
			file.close()

			for line in lines[1:]:
				place, string_rep = string.split(line, ":")
				self.places[string.strip(place)] = string.strip(string_rep)

		except IOError:
			pass

	def NumRep(self, place):
		if place in self.places:
			string_rep = self.places[place]
		else:
			string_rep = place

		try:
			num_rep = self.squares[string.upper(string_rep[0:2])]
			num_rep = [num_rep[0], num_rep[1]] 

			easting = string.lstrip(string_rep[2:5], '0')
			northing = string.lstrip(string_rep[5:8], '0')

			if easting == "": easting = "0"
			if northing == "": northing = "0"

			num_rep[0] += int(easting)
			num_rep[1] += int(northing)

		except:
			raise OffMap()

		return num_rep

	def StringRep(self, num_rep):
		i = num_rep[0] / self.scale
		j = num_rep[1] / self.scale

		easting = num_rep[0] - i * self.scale
		northing = num_rep[1] - j * self.scale

		try:
			string_rep = self.letters[j * self.width + i] + \
					string.zfill(easting, 3) + string.zfill(northing, 3)
		except KeyError:
			raise OffMap()

		return string_rep

grid = Grid()

class Mapref:
	def __init__(self, rep):
		# No overloaded constructors, so use 'RTTI' to construct on variable
		# types. This is the right way to do it.
		if type(rep) == type('str'):
			self.num_rep = grid.NumRep(rep)
		else:
			self.num_rep = rep

	def __add__(self, mapref):
		m = deepcopy(self)
		m.num_rep[0] += mapref.num_rep[0]
		m.num_rep[1] += mapref.num_rep[1]
		return m

	def __sub__(self, mapref):
		num_rep = [self.num_rep[i] - mapref.num_rep[i] for i in range(2)]

		if mapref.__class__ == Mapref:
			return MaprefDelta(num_rep)
		elif mapref.__class__ == MaprefDelta:
			return Mapref(num_rep)
		else:
			assert(False)

	def __repr__(self):
		return grid.StringRep(self.num_rep)

class MaprefDelta:
	def __init__(self, num_rep):
		self.num_rep = num_rep

	def __mul__(self, s):
		"Integer multiply"
		m = deepcopy(self)
		m.num_rep[0] *= s
		m.num_rep[1] *= s
		return m

	def __div__(self, s):
		"Floating point divide"
		m = deepcopy(self)

		e = float(m.num_rep[0])
		n = float(m.num_rep[1])
		e /= s
		n /= s

		m.num_rep[0] = int(e)
		m.num_rep[1] = int(n)

		return m

	def __repr__(self):
		return "MaprefDelta " + repr(self.num_rep)

	def Length(self):
		"Length in kilometres"
		return sqrt(float(self.num_rep[0] ** 2 + self.num_rep[1] ** 2)) / 10.0

def main():
	try:
		house = Mapref("SP512098")
		coop = Mapref("Coop")
		delta = coop - house
		print delta.Length()
	except OffMap:
		print "off map"

if __name__ == '__main__':
	main()