from xml.dom.minidom import *
from datetime import datetime
from numpy import *
from math import sin,cos,radians

#
def readtv(filename):
  t=[]
  v=[];
  tvfile=open(filename,'r')
  for line in tvfile:
    tandv=line.strip().split(",")
    t.append(float(tandv[0]))
    v.append(float(tandv[1]))
  tvfile.close()
  return t,v

# Reads a gpx file with a given name, and computes time and speed values from this. theses values are stored in the comma separated output file with a given name
def gpxtotv(filenamein,filenameout):
  doc=parse(filenamein)
  lat=[]
  lon=[]
  elev=[]
  t=[]
  childnodes=doc.getElementsByTagName('trkpt')
  for nexttrkpt in childnodes:
      nextlat=float(nexttrkpt.getAttribute('lat'))
      nextlon=float(nexttrkpt.getAttribute('lon'))
      
      nextelev=[];
      nextelevs=nexttrkpt.getElementsByTagName('ele')
      if nextelevs.length>=1:
          nextelev=float(nextelevs[0].firstChild.data)
      
      nexttime=[]
      nexttimes=nexttrkpt.getElementsByTagName('time')
      if nexttimes.length>=1:
          try:
              timeStr=nexttimes[0].firstChild.data
              timeStr=timeStr.replace('T',' ')      
              timeStr=timeStr.replace('Z', '')
              dt=datetime.strptime(timeStr, "%Y-%m-%d %H:%M:%S")
              nexttime=dt.hour*3600 + dt.minute*60 + dt.second
          except:
            print 'Something went wrong'
      
      if nextlat!=0 and nextlon!=0 and  nextelev!=0 and nexttime!=0:
          lat.append(nextlat)
          lon.append(nextlon)
          elev.append(nextelev)
          t.append(nexttime)
  
  coords=zeros((3,len(lat)))
  r=6378500
  elev=array(elev)
  lat=array(lat)
  lon=array(lon)
  t=array(t)

  coordsx=zeros((len(lat)))
  coordsy=zeros((len(lat)))
  coordsz=zeros((len(lat)))
  for k in range(len(lat)):
    coordsx[k]=(r+elev[k])*cos(radians(lon[k]))*sin(radians(90-lat[k]))
    coordsy[k]=(r+elev[k])*sin(radians(lon[k]))*sin(radians(90-lat[k]))
    coordsz[k]=(r+elev[k])*cos(radians(90-lat[k]))
  
  v=zeros((len(lat)-1));
  for k in range(len(lat)-1):
    v[k]=sqrt((coordsx[k+1]-coordsx[k])**2 + (coordsy[k+1]-coordsy[k])**2 + (coordsz[k+1]-coordsz[k])**2)/(t[k+1]-t[k])


  tvfile=open(filenameout,'w')
  for k in range(len(lat)-1):
    tvfile.write(str(t[k]) + ',' + str(v[k]) + '\n')
  tvfile.close()