#!/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: createRadmonRrd.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 2014 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 15 Sep 2015 by J L Owrey
#
import os
import time
import subprocess

    ### DEFINE FILE LOCATIONS ###

_RRD_FILE = "/home/{user}/database/radmonData.rrd"  # the file that stores the data
_RRD_SIZE_IN_DAYS = 370 # days
_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 "rrdtool radiation database file already exists"
        return True

    dbUpdateInterval = _DATABASE_UPDATE_INTERVAL  # rrd update step in seconds
    rrd1yearSteps = 30 # steps per day for longer time periods

    dataItemEpochTime = long(time.mktime(time.localtime())) 
    rrdfileStartTime = dataItemEpochTime - 10
    heartBeat = 2 * dbUpdateInterval
    rrd24hrRows = int(86400 / dbUpdateInterval)
    rrd1yearRows = int(3600 * 24 * _RRD_SIZE_IN_DAYS / (dbUpdateInterval * rrd1yearSteps))
       
    strFmt = ("rrdtool create %s --start %s --step %s "
               "DS:CPM:GAUGE:%s:U:U DS:SvperHr:GAUGE:%s:U:U "
               "RRA:AVERAGE:0.5:1:%s RRA:AVERAGE:0.5:%s:%s")

    strCmd = strFmt % (_RRD_FILE, rrdfileStartTime, dbUpdateInterval, \
                heartBeat, heartBeat, rrd24hrRows, rrd1yearSteps, rrd1yearRows)

    print "creating rrdtool radiation 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 "%s rrdtool create failed: %s" % \
                            (getTimeStamp(), exError.output)
        return False
    return True
##end def

def main():
    createRrdFile()
## end def

if __name__ == '__main__':
    main()