#!/usr/bin/python

import sys
import math
import xml.dom.minidom

class AppInfo(object):
	def __init__(self):
		self.infilename = None

def usageExit():
	sys.stderr.write("usage: gpxlen infile\n")
	sys.exit(1)

def parseCommandLine(argv):
	ai = AppInfo()

	argv.pop(0)

	while len(argv) > 0:
		if ai.infilename == None:
			ai.infilename = argv[0]
		else:
			usageExit()

		argv.pop(0)

	if ai.infilename == None:
		usageExit()

	return ai

def getSegmentLength(segmentNode):
	t = 0.0
	oldLat = None
	oldLon = None

	for pt in segmentNode.getElementsByTagName("trkpt"):
		lat = float(pt.getAttribute("lat")) * math.pi/180.0
		lon = float(pt.getAttribute("lon")) * math.pi/180.0

		if oldLat != None:
			#t += math.acos(
			#	math.cos(lat) * math.cos(lon) * math.cos(oldLat) * math.cos(oldLon) +
			#	math.cos(lat) * math.sin(lon) * math.cos(oldLat) * math.sin(oldLon) +
			#	math.sin(lat) * math.sin(oldLat)
			#) * 6378100.0

			cosa = (math.sin(lat) * math.sin(oldLat) +
				math.cos(lat) * math.cos(oldLat) *
				math.cos(oldLon - lon))

			if cosa > 1.0: cosa = 1.0

			t += math.acos(cosa) * 6378100.0

		oldLat = lat
		oldLon = lon

	return t

def getTrackLength(trackNode):
	t = 0.0
	for seg in trackNode.getElementsByTagName("trkseg"):
		t = t + getSegmentLength(seg)

	return t

def main(argv):
	ai = parseCommandLine(argv)

	dom = xml.dom.minidom.parse(ai.infilename)

	gpxNode = dom.firstChild

	for track in gpxNode.getElementsByTagName("trk"):
		nameNode = track.getElementsByTagName("name")
		if nameNode != None:
			name = nameNode[0].firstChild.data
		else:
			name = "<no name>"

		sys.stdout.write("Track: %s, " % name)
		sys.stdout.write("length: %.3f\n" % getTrackLength(track))

	return 0

if __name__ == "__main__": sys.exit(main(sys.argv))