#!/usr/bin/python3 -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: createPowerRrd.py
 #
 # Description: Creates a rrdtool database for use by the power agent to
 # store the data from the power and temperature sensors.  The agent uses
 # the data in the database to generate graphic charts for display in the

 # weather station web page.

 #
 # Copyright 2021 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 01 Jun 2021 by J L Owrey
 #
 #2345678901234567890123456789012345678901234567890123456789012345678901234567890
 
 import os
 import time
 import subprocess
 
     ### DEFINE DATABASE FILE LOCATION ###
 
 _USER = os.environ['USER']
 # the file that stores the data
 _RRD_FILE = "/home/%s/database/powerData.rrd" % _USER
 
    ### DEFINE DATABASE SIZE AND GRANULARITY
 
 _RRD_SIZE_IN_DAYS = 740 # days
 _1YR_RRA_STEPS_PER_DAY = 1440
 _DATABASE_UPDATE_INTERVAL = 30
 
 def createRrdFile():
     """Create the rrd file if it does not exist.
        Parameters: none
        Returns: True, if successful
     """
 
     if os.path.exists(_RRD_FILE):

         print("power 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:CUR:GAUGE:%s:U:U DS:VOLT:GAUGE:%s:U:U "
               "DS:PWR:GAUGE:%s:U:U DS:BTMP:GAUGE:%s:U:U "
               "DS:ATMP: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, \
                 rrd24hrNumRows, rra1yrNumPDP, rrd1yearNumRows)
 

     print("creating power 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 as exError:
         print("rrdtool create failed: %s" % (exError.output))

         return False
     return True
 ##end def
 
 def main():
     createRrdFile()
 ## end def
 
 if __name__ == '__main__':
     main()