#!/usr/bin/env python

# GPX trimmer
# Copyright (C) 2008	Steve Hill <steve@nexusuk.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of version 3 of the GNU General Public License as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import sys
import xml.sax
import geolib

class gpx_handler(xml.sax.handler.ContentHandler):
	def __init__(self, outfile, exclude_boxes):
		self.outfile = outfile
		self.exclude_boxes = exclude_boxes
		self.point = None
		self.stack = None
	
	def startElement(self, name, attributes):
		if (self.point == None):
			if (name == "trkseg"):
				self.segment = []
			elif (name == "trkpt"):
				self.point = {
					"name":		name,
					"attributes":	attributes,
					"data":		None,
					"nodes":	[]
				}
				self.stack = [self.point]
			else:
				self.outfile.open(name, attributes)
		else:
			node = {
					"name":		name,
					"attributes":	attributes,
					"data":		None,
					"nodes":	[]
			}
			prevnode = self.stack[len(self.stack)-1]
			prevnode["nodes"].append(node)
			self.stack.append(node)

	def characters(self, data):
		if (self.point == None):
			return
		data = data.strip()
		if (data == ""):
			return
		node = self.stack[len(self.stack)-1]
		node["data"] = data
	
	def is_in_box(self,point,box):
		lat = float(point["attributes"]["lat"])
		lon = float(point["attributes"]["lon"])
		if (lat < box[0]):
			return False
		if (lon < box[1]):
			return False
		if (lat > box[2]):
			return False
		if (lon > box[3]):
			return False
		return True
	
	def trim_segment(self,points):
		outpoints = []
		pointbuff = []
		start_discard = 0
		mid = 0
		for p in points:
			in_box = False
			for b in exclude_boxes:
				if (self.is_in_box(p, b)):
					in_box = True
					break
			if (in_box):
				if (len(outpoints) <= 0):
					# Start of track - discard
					start_discard += 1
				else:
					# Middle or end of track - buffer
					pointbuff.append(p)
			else:
				mid += len(pointbuff)
				outpoints.extend(pointbuff)
				pointbuff = []
				outpoints.append(p)
		end_discard = len(pointbuff)
		if ((start_discard > 0) or (end_discard > 0) or (mid > 0)):
			print "Trimmed",start_discard,"points from start and",end_discard,"points from end. ",mid,"untrimmed points within the boxes."
		return outpoints

	def write_node(self,node):
		self.outfile.open(node["name"],node["attributes"])
		for n in node["nodes"]:
			self.write_node(n)
		if (node["data"] != None):
			self.outfile.data(node["data"])
		self.outfile.close(node["name"])

	def write_segment(self,points):
		if (len(points) > 0):
			self.outfile.open("trkseg")
			for p in points:
				self.write_node(p)
			self.outfile.close("trkseg")
			print "Wrote segment with",len(points),"points"

	def endElement(self, name):
		if (self.point == None):
			if (name == "trkseg"):
				trimmed = self.trim_segment(self.segment)
				self.write_segment(trimmed)
				self.segment = None
			else:
				self.outfile.close(name)
		else:
			if (name == "trkpt"):
				self.segment.append(self.point)
				self.point = None
				self.stack = None
			else:
				self.stack.pop()

args = sys.argv
progname = args.pop(0)

if (len(args) < 6):
	print "GPX trimmer"
	print "Removes the start and end of tracks if they are within a set of bounding boxes."
	print
	print "Usage:", progname, "<input file> <output file> <min lat> <min lon> <max lat> <max lon> [<min lat> <min lon> <max lat> <max lon> ...]"
	sys.exit(1)

infile = file(args.pop(0), "r")
outfile = geolib.xmlindent(args.pop(0), False)
exclude_boxes = []
while (len(args) >= 4):
	box = (
		float(args.pop(0)),
		float(args.pop(0)),
		float(args.pop(0)),
		float(args.pop(0))
	)
	print "Removing track starts and ends within",(box[0],box[1]),"-",(box[2],box[3])
	exclude_boxes.append(box)

parser = xml.sax.make_parser()
handler = gpx_handler(outfile, exclude_boxes)
parser.setContentHandler(handler)
parser.parse(infile)

del infile
del outfile