#!/usr/bin/env python

import re

class GPSData:
	def __init__(self):
		self.reset()

	def reset(self):
		self.time = None
		self.lat = None
		self.lon = None
		self.quality = None
		self.nsat = None
		self.hdop = None
		self.ele = None

	def parse_nmea_string(self, string):
		try:
			string = string.lstrip('$')
			(data, dummy, csum) = string.rpartition('*')

			mycsum = 0
			for byte in data:
				mycsum ^= ord(byte)

			if mycsum != int(csum, 16): # can throw with invalid csum
				return

			data = data.split(',')

			if data[0] == 'GPGGA':
				self.reset()

				# time
				(temp, n) = re.subn('^(\d{2})(\d{2})(\d{2}\.\d+)$', '\\1:\\2:\\3', data[1])
				if n == 1:
					self.time = temp

				# latitude
				(temp, n) = re.subn('^(\d{2})(\d{2})\.(.*)$', '\\1.\\2\\3', data[2])
				if n == 1:
					self.lat = temp + data[3]

				# longitude
				(temp, n) = re.subn('^0?(\d{2,3}?)(\d{2})\.(.*)$', '\\1.\\2\\3', data[4])
				if n == 1:
					self.lon = temp + data[5]

				# quality
				if int(data[6]) == 0:
					self.quality = "none"
				elif int(data[6]) == 1:
					self.quality = "normal"
				elif int(data[6]) == 2:
					self.quality = "diff"
				elif int(data[6]) == 3:
					self.quality = "precision"
				else:
					self.quality = None

				# other params
				self.nsat = int(data[7])
				self.hdop = data[8]
				self.ele = data[9]
		except:
			return

	def dump(self):
		return "Time: %s\tQuality: %s\nLat: %s\tSat: %s\nLon: %s\tHDOP: %s\nEle: %s" % (self.time, self.quality, self.lat, self.nsat, self.lon, self.hdop, self.ele)