#!/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: radmonAgent.py
 #

 # Description: This module acts as an agent between the radiation monitoring
 # device and the Internet web server.  The agent periodically sends an http
 # request to the radiation monitoring device and processes the response from
 # the device and performs a number of operations:

 #     - conversion of data itemsq

 #     - update a round robin (rrdtool) database with the radiation data
 #     - periodically generate graphic charts for display in html documents
 #     - forward the radiation data to other services

 #     - write the processed weather data to a JSON file for use by html
 #       documents

 #

 # Copyright 2018 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

 #   * v20 released 15 Sep 2015 by J L Owrey; first release
 #   * v21 released 27 Nov 2017 by J L Owrey; bug fixes; updates

 #   * v22 released 03 Mar 2018 by J L Owrey; improved code readability;
 #         improved radmon device offline status handling

 #

 _MIRROR_SERVER = False

 import os

 import urllib2

 import sys
 import signal

 import subprocess
 import multiprocessing

 import time
 import calendar
 
 _USER = os.environ['USER']
 

    ### DEFAULT RADIATION MONITOR URL ###

 # ip address of radiation monitoring device

 _DEFAULT_RADIATION_MONITOR_URL = "{your radiation monitor url}"

 # url if this is a mirror server

 _PRIMARY_SERVER_URL = "{your primary server url}"

     ### FILE AND FOLDER LOCATIONS ###
 

 # folder for containing dynamic data objects

 _DOCROOT_PATH = "/home/%s/public_html/radmon/" % _USER

 # folder for charts and output data file

 _CHARTS_DIRECTORY = _DOCROOT_PATH + "dynamic/"
 # location of data input file

 _INPUT_DATA_FILE = _DOCROOT_PATH + "dynamic/radmonInputData.dat"

 # location of data output file

 _OUTPUT_DATA_FILE = _DOCROOT_PATH + "dynamic/radmonOutputData.js"

 # database that stores weather data
 _RRD_FILE = "/home/%s/database/radmonData.rrd" % _USER

 
     ### GLOBAL CONSTANTS ###

 # max number of failed data requests allowed
 _MAX_FAILED_DATA_REQUESTS = 2

 # interval in seconds between data requests to radiation monitor
 _DEFAULT_DATA_REQUEST_INTERVAL = 5
 # defines how often the charts get updated in seconds
 _CHART_UPDATE_INTERVAL = 300
 # defines how often the database gets updated
 _DATABASE_UPDATE_INTERVAL = 30
 # number seconds to wait for a response to HTTP request
 _HTTP_REQUEST_TIMEOUT = 3

 # standard chart width in pixels

 _CHART_WIDTH = 600

 # standard chart height in pixels

 _CHART_HEIGHT = 150

    ### GLOBAL VARIABLES ###
 

 # turn on or off of verbose debugging information

 debugOption = False

 # online status of radiation monitor

 radiationMonitorOnline = True

 # number of unsuccessful http requests

 failedDataRequestCount = 0

 # status of reset command to radiation monitor
 remoteDeviceReset = False

 # ip address of radiation monitor

 radiationMonitorUrl = _DEFAULT_RADIATION_MONITOR_URL

 # web update frequency
 dataRequestInterval = _DEFAULT_DATA_REQUEST_INTERVAL

   ###  PRIVATE METHODS  ###
 
 def getTimeStamp():
     """
     Sets the error message time stamp to the local system time.
     Parameters: none
     Returns string containing the time stamp.
     """

     return time.strftime( "%m/%d/%Y %T", time.localtime() )

 ##end def
 

 def setOfflineStatus(dData):
     """Set the status of the the upstream device to "offline" and sends

        blank data to the downstream clients.

        Parameters:
            dData - dictionary object containing weather data

        Returns nothing.
     """

     global radiationMonitorOnline, failedDataRequestCount

     if os.path.exists(_INPUT_DATA_FILE):
         os.remove(_INPUT_DATA_FILE)

     if failedDataRequestCount < _MAX_FAILED_DATA_REQUESTS - 1:
         failedDataRequestCount += 1

         return

 
     # If the radiation monitor was previously online, then send a message
     # that we are now offline.

     if radiationMonitorOnline:
         print "%s: radiation monitor offline" % getTimeStamp()
         radiationMonitorOnline = False

         if os.path.exists(_OUTPUT_DATA_FILE):
             os.remove(_OUTPUT_DATA_FILE)

     return
 ##end def
 

 def signal_term_handler(signal, frame):
     """Send message to log when process killed
        Parameters: signal, frame - sigint parameters
        Returns: nothing
     """
     print '%s terminating radmon agent process' % \
               (getTimeStamp())
     if os.path.exists(_OUTPUT_DATA_FILE):
         os.remove(_OUTPUT_DATA_FILE)
     if os.path.exists(_INPUT_DATA_FILE):
         os.remove(_INPUT_DATA_FILE)
     sys.exit(0)
 ##end def
 

   ###  PUBLIC METHODS  ###
 

 def getRadiationData():

     """Send http request to radiation monitoring device.  The response
        from the device contains the radiation data.  The data is formatted
        as an html document.
     Parameters: 

         radiationMonitorUrl - url of radiation monitoring device

         HttpRequesttimeout - how long to wait for device
                              to respond to http request
     Returns a string containing the radiation data, or None if
     not successful.
     """

     global radiationMonitorOnline, failedDataRequestCount, \

            remoteDeviceReset
 

     if _MIRROR_SERVER:
         sUrl = _PRIMARY_SERVER_URL
     else:

         sUrl = radiationMonitorUrl
         if remoteDeviceReset:
             sUrl += "/reset"
         else:
             sUrl += "/rdata"

 
     try:

         conn = urllib2.urlopen(sUrl, timeout=_HTTP_REQUEST_TIMEOUT)

 
         # Format received data into a single string.
         content = ""
         for line in conn:
             content += line.strip()
         del conn
 

     except Exception, exError:
         # If no response is received from the device, then assume that
         # the device is down or unavailable over the network.  In
         # that case set the status of the device to offline.
         if debugOption:

             print "http error: %s" % exError

         return None
 
     # If the radiation monitor was previously offline, then send a message
     # that we are now online.

     if not radiationMonitorOnline:
         print "%s radiation monitor online" % getTimeStamp()
         radiationMonitorOnline = True
 

     failedDataRequestCount = 0

     return content

 ##end def
 

 def parseDataString(sData, dData):

     """Parse the radiation data JSON string from the radiation 
        monitoring device into its component parts.  
        Parameters:
            sData - the string containing the data to be parsed
            dData - a dictionary object to contain the parsed data items
        Returns true if successful, false otherwise.
     """
     try:

         sTmp = sData[2:-2]

         lsTmp = sTmp.split(',')
     except Exception, exError:

         print "%s parseDataString: %s" % (getTimeStamp(), exError)

         return False
 
     # Load the parsed data into a dictionary for easy access.

     for item in lsTmp:

         if "=" in item:
             dData[item.split('=')[0]] = item.split('=')[1]

     dData['status'] = 'online'

     if len(dData) != 6:

         print "%s parse failed: corrupted data string" % getTimeStamp()

         return False;
 

     return True
 ##end def
 

 def convertData(dData):

     """Convert individual radiation data items as necessary.
        Parameters:
            lsData - a list object containing the radiation data
            dData - a dictionary object containing the radiation data
        Returns true if successful, false otherwise.
     """
     result = True
  
     try:

         # Convert the UTC timestamp provided by the radiation monitoring
         # device to epoch local time in seconds.

         ts_utc = time.strptime(dData['UTC'], "%H:%M:%S %m/%d/%Y")

         epoch_local_sec = calendar.timegm(ts_utc)
         dData['ELT'] = epoch_local_sec
 
         # Uncomment the code line below to use a timestamp generated by the
         # requesting server (this) instead of the timestamp provided by the
         # radiation monitoring device.  Using the server generated timestamp
         # prevents errors that occur when the radiation monitoring device
         # fails to synchronize with a valid NTP time server.
         #dData['ELT'] = time.time()

         dData['Mode'] = dData['Mode'].lower()

  
         dData['uSvPerHr'] = float(dData.pop('uSv/hr'))
         
         dData['CPM'] = int(dData.pop('CPM'))
 

         dData['CPS'] = int(dData.pop('CPS'))
 

     except Exception, exError:

         print "%s convert data failed: %s" % (getTimeStamp(), exError)

         result = False

 
     return result
 ##end def
 

 def writeOutputDataFile(dData):

     """Write radiation data items to a JSON formatted file for use by
        HTML documents.

        Parameters:
            lsData - a list object containing the data to be written
                     to the JSON file
        Returns true if successful, false otherwise.
     """

     # Set date to current time and data

     dData['date'] = time.strftime("%m/%d/%Y %T", time.localtime(dData['ELT']))

     # Format the weather data as string using java script object notation.
     sData = '[{'

     sData += "\"date\":\"%s\"," % dData['date']

     sData += "\"CPM\":\"%d\"," % dData['CPM']
     sData += "\"CPS\":\"%d\"," % dData['CPS']
     sData += "\"uSvPerHr\":\"%.2f\"," % dData['uSvPerHr']

     sData += "\"Mode\":\"%s\"," % dData['Mode']
     sData += "\"status\":\"%s\"," % dData['status']
     sData = sData[:-1] + '}]\n'

     # Write the string to the output data file for use by html documents.

     try:
         fc = open(_OUTPUT_DATA_FILE, "w")

         fc.write(sData)

         fc.close()
     except Exception, exError:

         print "%s writeOutputDataFile: %s" % (getTimeStamp(), exError)

         return False

     return True
 ## end def
 

 def writeInputDataFile(sData):

     """Write raw data from radiation monitor to file for use by mirror
        servers.
        Parameters:
            sData - a string object containing the data string from
                    the radiation monitor
        Returns true if successful, false otherwise.
     """

     sData += "\n"

     try:

         fc = open(_INPUT_DATA_FILE, "w")

         fc.write(sData)
         fc.close()
     except Exception, exError:
         print "%s writeOutputDataFile: %s" % (getTimeStamp(), exError)
         return False
 
     return True
 ##end def
 

 def updateDatabase(dData):
     """
     Updates the rrdtool database by executing an rrdtool system command.
     Formats the command using the data extracted from the radiation
     monitor response.   
     Parameters: dData - dictionary object containing data items to be
                         written to the rr database file
     Returns true if successful, false otherwise.
     """

     global remoteDeviceReset
 
     # The RR database stores whole units, so convert uSv to Sv.

     SvPerHr = dData['uSvPerHr'] * 1.0E-06 

 
     # Create the rrdtool update command.
     strCmd = "rrdtool update %s %s:%s:%s" % \

                        (_RRD_FILE, dData['ELT'], dData['CPM'], SvPerHr)

     if debugOption and False:

         print "%s" % strCmd # DEBUG

 
     # Run the command as a subprocess.
     try:
         subprocess.check_output(strCmd, shell=True,  \
                              stderr=subprocess.STDOUT)
     except subprocess.CalledProcessError, exError:
         print "%s: rrdtool update failed: %s" % \

                     (getTimeStamp(), exError.output)

         if exError.output.find("illegal attempt to update using time") > -1:
             remoteDeviceReset = True

             print "%s: rebooting radiation monitor" % (getTimeStamp())

         return False

     else:
         if debugOption:
             print 'database update sucessful'
         return True

 ##end def
 

 def createGraph(fileName, dataItem, gLabel, gTitle, gStart,
                 lower, upper, addTrend, autoScale):

     """Uses rrdtool to create a graph of specified weather data item.
        Parameters:
            fileName - name of graph image file
            dataItem - data item to be graphed

            gLabel - string containing a graph label for the data item
            gTitle - string containing a title for the graph
            lower - lower bound for graph ordinate #NOT USED
            upper - upper bound for graph ordinate #NOT USED
            addTrend - 0, show only graph data
                       1, show only a trend line
                       2, show a trend line and the graph data
            autoScale - if True, then use vertical axis auto scaling
                (lower and upper parameters are ignored), otherwise use
                lower and upper parameters to set vertical axis scale

        Returns true if successful, false otherwise.
     """

     gPath = _CHARTS_DIRECTORY + fileName + ".png"

     trendWindow = { 'end-1day': 7200,
                     'end-4weeks': 172800,
                     'end-12months': 604800 }
  
     # Format the rrdtool graph command.
 
     # Set chart start time, height, and width.
     strCmd = "rrdtool graph %s -a PNG -s %s -e now -w %s -h %s " \
              % (gPath, gStart, _CHART_WIDTH, _CHART_HEIGHT)
    

     # Set the range and scaling of the chart y-axis.

     if lower < upper:

         strCmd  +=  "-l %s -u %s -r " % (lower, upper)
     elif autoScale:
         strCmd += "-A "
     strCmd += "-Y "

 
     # Set the chart ordinate label and chart title. 
     strCmd += "-v %s -t %s " % (gLabel, gTitle)

     # Show the data, or a moving average trend line over
     # the data, or both.

     strCmd += "DEF:dSeries=%s:%s:LAST " % (_RRD_FILE, dataItem)
     if addTrend == 0:
         strCmd += "LINE1:dSeries#0400ff "
     elif addTrend == 1:
         strCmd += "CDEF:smoothed=dSeries,%s,TREND LINE3:smoothed#ff0000 " \
                   % trendWindow[gStart]
     elif addTrend == 2:
         strCmd += "LINE1:dSeries#0400ff "
         strCmd += "CDEF:smoothed=dSeries,%s,TREND LINE3:smoothed#ff0000 " \
                   % trendWindow[gStart]
      

     if debugOption and False:

         print "%s\n" % strCmd # DEBUG
     

     # Run the formatted rrdtool command as a subprocess.

     try:

         result = subprocess.check_output(strCmd, \
                      stderr=subprocess.STDOUT,   \

                      shell=True)
     except subprocess.CalledProcessError, exError:

         print "rrdtool graph failed: %s" % (exError.output)

         return False
 
     if debugOption:
         print "rrdtool graph: %s" % result
     return True

 ##end def
 

 def generateGraphs():
     """Generate graphs for display in html documents.
        Parameters: none
        Returns nothing.
     """
     autoScale = False
 

     createGraph('24hr_cpm', 'CPM', 'counts\ per\ minute', 

                 'CPM\ -\ Last\ 24\ Hours', 'end-1day', 0, 0, 2, autoScale)

     createGraph('24hr_svperhr', 'SvperHr', 'Sv\ per\ hour',

                 'Sv/Hr\ -\ Last\ 24\ Hours', 'end-1day', 0, 0, 2, autoScale)

     createGraph('4wk_cpm', 'CPM', 'counts\ per\ minute',

                 'CPM\ -\ Last\ 4\ Weeks', 'end-4weeks', 0, 0, 2, autoScale)

     createGraph('4wk_svperhr', 'SvperHr', 'Sv\ per\ hour',

                 'Sv/Hr\ -\ Last\ 4\ Weeks', 'end-4weeks', 0, 0, 2, autoScale)

     createGraph('12m_cpm', 'CPM', 'counts\ per\ minute',

                 'CPM\ -\ Past\ Year', 'end-12months', 0, 0, 2, autoScale)

     createGraph('12m_svperhr', 'SvperHr', 'Sv\ per\ hour',

                 'Sv/Hr\ -\ Past\ Year', 'end-12months', 0, 0, 2, autoScale)
 ##end def
 

 def getCLarguments():
     """Get command line arguments.  There are three possible arguments
           -d turns on debug mode
           -t sets the radiation device query interval
           -u sets the url of the radiation monitoring device
        Returns nothing.
     """

     global debugOption, dataRequestInterval, radiationMonitorUrl

 
     index = 1
     while index < len(sys.argv):
         if sys.argv[index] == '-d':
             debugOption = True
         elif sys.argv[index] == '-t':
             try:

                 dataRequestInterval = abs(int(sys.argv[index + 1]))

             except:
                 print "invalid polling period"
                 exit(-1)
             index += 1
         elif sys.argv[index] == '-u':

             radiationMonitorUrl = sys.argv[index + 1]

             index += 1
         else:
             cmd_name = sys.argv[0].split('/')

             print "Usage: %s [-d] [-t seconds] [-u url}" % cmd_name[-1]

             exit(-1)
         index += 1
 ##end def
 
 def main():

     """Handles timing of events and acts as executive routine managing
        all other functions.

        Parameters: none
        Returns nothing.
     """

     signal.signal(signal.SIGTERM, signal_term_handler)
 
     print '%s starting up radmon agent process' % \
                   (getTimeStamp())

     # last time output JSON file updated
     lastDataRequestTime = -1
     # last time charts generated
     lastChartUpdateTime = - 1
     # last time the rrdtool database updated
     lastDatabaseUpdateTime = -1
 

     ## Get command line arguments.
     getCLarguments()
 

     ## Exit with error if rrdtool database does not exist.

     if not os.path.exists(_RRD_FILE):

         print 'rrdtool database does not exist\n' \
               'use createWeatherRrd script to ' \
               'create rrdtool database\n'

         exit(1)
  
     ## main loop
     while True:
 

         currentTime = time.time() # get current time in seconds

         # Every web update interval request data from the radiation
         # monitor and process the received data.
         if currentTime - lastDataRequestTime > dataRequestInterval:
             lastDataRequestTime = currentTime

             dData = {}

             result = True
 
             # Get the data string from the device.

             sData = getRadiationData()

             if sData == None:

                 setOfflineStatus(dData)

                 result = False
 
             # If successful parse the data.
             if result:

                 result = parseDataString(sData, dData)

 
             # If parsing successful, convert the data.
             if result:

                 result = convertData(dData)

             # If conversion successful, write data to data files.

             if result:

                 writeInputDataFile(sData)

                 writeOutputDataFile(dData)

                 if debugOption:
                     print "http request successful"

                 # At the rrdtool database update interval, update the database.

                 if currentTime - lastDatabaseUpdateTime > \
                         _DATABASE_UPDATE_INTERVAL:   

                     lastDatabaseUpdateTime = currentTime
                     ## Update the round robin database with the parsed data.
                     result = updateDatabase(dData)

 
         # At the chart generation interval, generate charts.
         if currentTime - lastChartUpdateTime > _CHART_UPDATE_INTERVAL:
             lastChartUpdateTime = currentTime
             p = multiprocessing.Process(target=generateGraphs, args=())
             p.start()
 
         # Relinquish processing back to the operating system until
         # the next update interval.
 
         elapsedTime = time.time() - currentTime
         if debugOption:

             print "processing time: %6f sec\n" % elapsedTime
         remainingTime = dataRequestInterval - elapsedTime
         if remainingTime > 0.0:

             time.sleep(remainingTime)
     ## end while

     return

 ## end def
 
 if __name__ == '__main__':

     try:
         main()
     except KeyboardInterrupt:

         print '\n%s terminating radmon agent process' % \
               (getTimeStamp())

         if os.path.exists(_OUTPUT_DATA_FILE):
             os.remove(_OUTPUT_DATA_FILE)
         if os.path.exists(_INPUT_DATA_FILE):
             os.remove(_INPUT_DATA_FILE)