#!/usr/bin/python -u
 ## The -u option above turns off block buffering of python output. This assures
 ## that each error message gets individually printed to the log file.
 #
 # Module: createArednsigRrd.py
 #
 # Description: Creates a rrdtool database for use by the weather agent to
 # store the data from the weather station.  The agent uses the data in the
 # database to generate graphic charts for display in the weather station
 # web page.
 #
 # Copyright 2020 Jeff Owrey
 #    This program is free software: you can redistribute it and/or modify
 #    it under the terms of the GNU General Public License as published by
 #    the Free Software Foundation, either version 3 of the License, or
 #    (at your option) any later version.
 #
 #    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/license.
 #
 # Revision History
 #   * v10 released 11 Jan 2020 by J L Owrey
 #
 import os
 import time
 import subprocess
 
     ### DEFINE FILE LOCATIONS ###
 
 _USER = os.environ['USER']
 # the file that stores the data
 _RRD_FILE = "/home/%s/database/arednsigData.rrd" % _USER
 _RRD_SIZE_IN_DAYS = 370 # days
 _1YR_RRA_STEPS_PER_DAY = 96
 _DATABASE_UPDATE_INTERVAL = 60
 
 def createRrdFile():
     """Create the rrd file if it does not exist.
        Parameters: none
        Returns: True, if successful
     """
 
     if os.path.exists(_RRD_FILE):
         print "aredn node database already exists"
         return True
 
      ## Calculate database size
  
     heartBeat = 2 * _DATABASE_UPDATE_INTERVAL
     rra1yrNumPDP =  int(round(86400 / (_1YR_RRA_STEPS_PER_DAY * \
                     _DATABASE_UPDATE_INTERVAL)))
     rrd24hrNumRows = int(round(86400 / _DATABASE_UPDATE_INTERVAL))
     rrd1yearNumRows = _1YR_RRA_STEPS_PER_DAY * _RRD_SIZE_IN_DAYS
        
     strFmt = ("rrdtool create %s --start now-1day --step %s "
               "DS:S:GAUGE:%s:U:U DS:N:GAUGE:%s:U:U DS:SNR:GAUGE:%s:U:U "
               "DS:RX_MCS:GAUGE:%s:U:U DS:TX_MCS:GAUGE:%s:U:U "
               "DS:RX_RATE:GAUGE:%s:U:U DS:TX_RATE:GAUGE:%s:U:U "
               "RRA:LAST:0.5:1:%s RRA:LAST:0.5:%s:%s")
 
     strCmd = strFmt % (_RRD_FILE, _DATABASE_UPDATE_INTERVAL, \
                 heartBeat, heartBeat, heartBeat, heartBeat,  \
                 heartBeat,  heartBeat, heartBeat,            \
                 rrd24hrNumRows, rra1yrNumPDP, rrd1yearNumRows)
 
     print "creating aredn node database...\n\n%s\n" % strCmd
 
     # Spawn a sub-shell and run the command
     try:
         subprocess.check_output(strCmd, stderr=subprocess.STDOUT, \
                                 shell=True)
     except subprocess.CalledProcessError, exError:
         print "rrdtool create failed: %s" % (exError.output)
         return False
     return True
 ##end def
 
 def main():
     createRrdFile()
 ## end def
 
 if __name__ == '__main__':
     main()