#!/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 items
 #     - 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 2015 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
 #

 
 import os

 import urllib2

 import sys   

 import subprocess
 import multiprocessing

 import time
 import calendar
 
 _USER = os.environ['USER']
 
    ### DEFAULT WEATHER STATION URL ###
 
 _DEFAULT_RADIATION_MONITOR_URL = "{your weather station url}"
 _DATA_FORWARDING_FILE = "/home/%s/public_html/radmon/dynamic/rad.dat" % _USER

     ### FILE AND FOLDER LOCATIONS ###
 
 _TMP_DIRECTORY = "/tmp/radmon" # folder for charts and output data file

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

 _OUTPUT_DATA_FILE = "/tmp/radmon/radmonData.js" # output file used by HTML docs
 
     ### GLOBAL CONSTANTS ###
 

 _DEFAULT_DATA_REQUEST_INTERVAL = 10 # interval between data requests to radiation monitor

 _CHART_UPDATE_INTERVAL = 300 # defines how often the charts get updated in seconds

 _DATABASE_UPDATE_INTERVAL = 30 # defines how often the database gets updated

 _HTTP_REQUEST_TIMEOUT = 3 # number seconds to wait for a response to HTTP request
 _MAX_RADIATION_MONITOR_OFFLINE_COUNT = 2 # max number of failed data requests allowed

 _CHART_WIDTH = 600
 _CHART_HEIGHT = 150

    ### GLOBAL VARIABLES ###
 

 debugOption = False

 radiationMonitorOnline = True
 radiationMonitorOfflineCount = 0
 dataRequestInterval = _DEFAULT_DATA_REQUEST_INTERVAL  # web update frequency
 radiationMonitorUrl = _DEFAULT_RADIATION_MONITOR_URL  # radiation monitor network address

   ###  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, radiationMonitorOfflineCount
 
     radiationMonitorOfflineCount += 1
 
     if radiationMonitorOfflineCount < _MAX_RADIATION_MONITOR_OFFLINE_COUNT:
         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

 
     # Set data items to blank.
     dData['UTC'] = ''
     dData['CPM'] = ''
     dData['CPS'] = ''
     dData['uSvPerHr'] = ''
     dData['Mode'] = ''
     dData['status'] = 'offline'
 
     writeOutputDataFile(dData)

     return
 ##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, radiationMonitorOfflineCount

 
     try:

         conn = urllib2.urlopen(radiationMonitorUrl,

                                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
 

     radiationMonitorOfflineCount = 0
 

     # 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
 
     if debugOption:
         #print content

         pass
 

     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'

 
     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 UTC from radiation monitoring device to local time.
         ts_utc = time.strptime(dData['UTC'], "%H:%M:%S %m/%d/%Y")
         local_sec = calendar.timegm(ts_utc)
         dData['UTC'] = local_sec
 

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

         dData['uSvPerHr'] = dData.pop('uSv/hr')
     except Exception, exError:
         print "%s convertData: %s" % (getTimeStamp(), exError)
         result = False

 
     return result
 ##end def
 

 def writeOutputDataFile(dData):

     """Convert individual weather string data items as necessary.
        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'] = getTimeStamp()

     # Format the weather data as string using java script object notation.
     sData = '[{'
     for key in dData:
         sData += "\"%s\":\"%s\"," % (key, dData[key])

     sData = sData[:-1] + '}]'

     # 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

     if debugOption and 0:

         print sData
 

     return True
 ## end def
 

 def writeForwardingFile(sData):
     """Write weather station response string to a forwarding file for use
        by down stream servers that mirror this site.
     """
     # Write the string to the output data file for use by html documents.
     try:
         fc = open(_DATA_FORWARDING_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.
     """
     # The RR database stores whole units, so convert uSv to Sv.   

     Svvalue = float(dData['uSvPerHr']) * 1.0E-06 # convert micro-Sieverts to Sieverts

 
     # Create the rrdtool update command.
     strCmd = "rrdtool update %s %s:%s:%s" % \
                        (_RRD_FILE, dData['UTC'], dData['CPM'], Svvalue)
     if debugOption:

         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)
         return False
 
     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 = _TMP_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:
         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.
     """

     lastDataRequestTime = -1 # last time output JSON file updated

     lastChartUpdateTime = - 1 # last time charts generated
     lastDatabaseUpdateTime = -1 # last time the rrdtool database updated
     dData = {}  # dictionary object for temporary data storage
 
     ## Get command line arguments.
     getCLarguments()
 
     ## Create www data folder if it does not already exist.
     if not os.path.isdir(_TMP_DIRECTORY):
         os.makedirs(_TMP_DIRECTORY)
 

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

     if not os.path.exists(_RRD_FILE):

         print "cannot find rrdtool database\nuse 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

             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 output file.

             if result:

                 writeForwardingFile(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__':
     main()