#!/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: arednsigAgent.py
 #
 # Description: This module acts as an agent between the aredn node
 # and aredn mest services.  The agent periodically sends an http
 # request to the aredn node, processes the response from
 # the node, and performs a number of operations:
 #     - conversion of data items
 #     - update a round robin (rrdtool) database with the node data
 #     - periodically generate graphic charts for display in html documents
 #     - write the processed node status to a JSON file for use by html
 #       documents
 #
 # 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
 #   * v20 released 11 Jan 2020 by J L Owrey; first release
 #   * v21 released 13 Feb 2020 by J L Owrey; fixed bug occuring when node
 #     powers on and signal data memory is empty.  Data points with N/A data
 #     are discarded.
 #   * v22 released 31 Mar 2020 by J L Owrey; upgraded for compatibility with
 #     Aredn firmware version 3.20.3.0.  This agent now downloads the node's
 #     status page and parsed the signal data from the html.

 #   * v23 released 11 Jun 2021 by J L Owrey; remove unused code.
 #   * v24 released 14 Jun 2021 by J L Owrey; minor revisions

 #   * v25 released 9 Jul 2021 by J L Owrey; improved handling of
 #         node status function

 #
 #2345678901234567890123456789012345678901234567890123456789012345678901234567890
 
 import os
 import sys
 import signal
 import subprocess
 import multiprocessing
 import time

 import json
 from urllib.request import urlopen
 
    ### ENVIRONMENT ###

 
 _USER = os.environ['USER']

 _SERVER_MODE = "primary"

 
    ### DEFAULT AREDN NODE URL ###
 
 # set url of the aredn node
 

 _DEFAULT_AREDN_NODE_URL = \
     "{your node url}"

 
     ### FILE AND FOLDER LOCATIONS ###
 
 # folder for containing dynamic data objects
 _DOCROOT_PATH = "/home/%s/public_html/arednsig/" % _USER
 # folder for charts and output data file
 _CHARTS_DIRECTORY = _DOCROOT_PATH + "dynamic/"
 # location of data output file

 _OUTPUT_DATA_FILE = _DOCROOT_PATH + "dynamic/arednsigData.js"

 # database that stores node data
 _RRD_FILE = "/home/%s/database/arednsigData.rrd" % _USER
 
     ### GLOBAL CONSTANTS ###
 

 # max number of failed data requests allowed
 _MAX_FAILED_DATA_REQUESTS = 2

 # AREDN node data request interval in seconds

 _DEFAULT_DATA_REQUEST_INTERVAL = 60

 # number seconds to wait for a response to HTTP request
 _HTTP_REQUEST_TIMEOUT = 5
 

 # chart update interval in seconds

 _CHART_UPDATE_INTERVAL = 600
 # standard chart width in pixels
 _CHART_WIDTH = 600
 # standard chart height in pixels
 _CHART_HEIGHT = 150
 # Set this to True only if this server is intended to relay raw
 
    ### GLOBAL VARIABLES ###
 
 # turn on or off of verbose debugging information

 verboseMode = False
 debugMode = False

 
 # The following two items are used for detecting system faults
 # and aredn node online or offline status.
 
 # count of failed attempts to get data from aredn node
 failedUpdateCount = 0
 # detected status of aredn node device

 nodeOnline = False

 
 # ip address of aredn node
 arednNodeUrl = _DEFAULT_AREDN_NODE_URL
 # frequency of data requests to aredn node
 dataRequestInterval = _DEFAULT_DATA_REQUEST_INTERVAL
 # chart update interval
 chartUpdateInterval = _CHART_UPDATE_INTERVAL
 
   ###  PRIVATE METHODS  ###
 
 def getTimeStamp():
     """
     Set 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 getEpochSeconds(sTime):

     """Convert the time stamp supplied in the supplied string

        to seconds since 1/1/1970 00:00:00.
        Parameters: 
            sTime - the time stamp to be converted must be formatted
                    as %m/%d/%Y %H:%M:%S
        Returns: epoch seconds
     """
     try:
         t_sTime = time.strptime(sTime, '%m/%d/%Y %H:%M:%S')

     except Exception as exError:
         print('%s getEpochSeconds: %s' % (getTimeStamp(), exError))

         return None
     tSeconds = int(time.mktime(t_sTime))
     return tSeconds
 ##end def
 
 def setStatusToOffline():
     """Set the detected status of the aredn node to
        "offline" and inform downstream clients by removing input
        and output data files.
        Parameters: none
        Returns: nothing
     """
     global nodeOnline
 
     # Inform downstream clients by removing output data file.
     if os.path.exists(_OUTPUT_DATA_FILE):
        os.remove(_OUTPUT_DATA_FILE)
     # If the aredn node was previously online, then send
     # a message that we are now offline.
     if nodeOnline:

         print('%s aredn node offline' % getTimeStamp())

     nodeOnline = False
 ##end def
 
 def terminateAgentProcess(signal, frame):
     """Send a message to log when the agent process gets killed
        by the operating system.  Inform downstream clients
        by removing input and output data files.
        Parameters:
            signal, frame - dummy parameters
        Returns: nothing
     """

     print('%s terminating arednsig agent process' % getTimeStamp())

     setStatusToOffline()

     sys.exit(0)
 ##end def
 
   ###  PUBLIC METHODS  ###
 

 def getNodeData(dData):

     """Send http request to aredn node.  The response from the
        node contains the node signal data as unformatted ascii text.
        Parameters: none

        Returns: True if successful,
                 or False if not successful

     """
     try:

         currentTime = time.time()
         response = urlopen(arednNodeUrl, timeout=_HTTP_REQUEST_TIMEOUT)

         requestTime = time.time() - currentTime

 
         content = response.read().decode('utf-8')
         content = content.replace('\n', '')
         content = content.replace('\r', '')
         if content == "":
             raise Exception("empty response")
         
     except Exception as exError:

         # If no response is received from the device, then assume that
         # the device is down or unavailable over the network.  In
         # that case return None to the calling function.

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

         return False

     ##end try

     if debugMode:

         print(content)

     if verboseMode:
         print("http request successful: %.4f sec" % requestTime)

 
     dData['content'] = content
     return True

 ##end def
 

 def parseDataString(dData):

     """Parse the node signal data JSON string from the aredn node

        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
     """

     sData = dData.pop('content')

     try:
         strBeginSearch = '<nobr>Signal/Noise/Ratio</nobr></th>' \
                          '<td valign=middle><nobr><big><b>'

         strEndSearch = 'dB</b>'

 
         iBeginIndex = sData.find(strBeginSearch) + len(strBeginSearch)
         iEndIndex = sData.find(strEndSearch, iBeginIndex)

         #print("search params: %d, %d" % (iBeginIndex, iEndIndex))

 
         if iBeginIndex == -1 or iEndIndex == -1:
             raise Exception("signal data not found in status page")
 
         snr = sData[iBeginIndex:iEndIndex]
         snr = snr.replace(' ','')
         lsnr = snr.split('/')
 
         dData['signal'] = lsnr[0]
         dData['noise'] = lsnr[1]
         dData['snr'] = lsnr[2]

     except Exception as exError:
         print("%s parse failed: %s" % (getTimeStamp(), exError))

         return False

     ## end try
 
     # Add status information to dictionary object.
     dData['date'] = getTimeStamp()
     dData['chartUpdateInterval'] = chartUpdateInterval
     dData['dataRequestInterval'] = dataRequestInterval
     dData['serverMode'] = _SERVER_MODE

 
     return True
 ##end def
 

 def writeOutputFile(dData):

     """Write node data items to the output data file, formatted as 
        a Javascript file.  This file may then be accessed and used by
        by downstream clients, for instance, in HTML documents.
        Parameters:
            sData - a string object containing the data to be written
                    to the output data file
        Returns: True if successful, False otherwise
     """
     # Write file for use by html clients.  The following two
     # data items are sent to the client file.
     #    * The last database update date and time
     #    * The data request interval

 
     # Format data into a JSON string.

     jsData = json.loads("{}")

     try:

         for key in dData:
             jsData.update({key:dData[key]})

         sData = "[%s]" % json.dumps(jsData)
     except Exception as exError:
         print("%s writeOutputFile: %s" % (getTimeStamp(), exError))

         return False
 

     if debugMode:

         print(sData)
 
     try:
         fc = open(_OUTPUT_DATA_FILE, "w")
         fc.write(sData)
         fc.close()
     except Exception as exError:
         print("%s write output file failed: %s" % (getTimeStamp(), exError))
         return False

 
     return True
 ## end def
 

 def setNodeStatus(updateSuccess):
     """Detect if aredn node is offline or not available on
        the network. After a set number of attempts to get data
        from the node set a flag that the node is offline.
        Parameters:
            updateSuccess - a boolean that is True if data request
                            successful, False otherwise
        Returns: nothing
     """
     global failedUpdateCount, nodeOnline
 
     if updateSuccess:
         failedUpdateCount = 0
         # Set status and send a message to the log if the device
         # previously offline and is now online.
         if not nodeOnline:
             print('%s node online' % getTimeStamp())
             nodeOnline = True
         return
     elif failedUpdateCount == _MAX_FAILED_DATA_REQUESTS - 1:
         # Max number of failed data requests, so set
         # device status to offline.
         setStatusToOffline()
     ## end if
     failedUpdateCount += 1
 ##end def
 
     ### DATABASE FUNCTIONS ###
 

 def updateDatabase(dData):
     """
     Update the rrdtool database by executing an rrdtool system command.
     Format the command using the data extracted from the aredn node
     response.   
     Parameters: dData - dictionary object containing data items to be
                         written to the rr database file
     Returns: True if successful, False otherwise
     """

     
     time = getEpochSeconds(dData['date'])
 

     # Format the rrdtool update command.
     strFmt = "rrdtool update %s %s:%s:%s:%s:%s:%s:%s:%s"

     strCmd = strFmt % (_RRD_FILE, time, dData['signal'], \

              dData['noise'], dData['snr'], '0', \
              '0', '0', '0')
 
     if debugMode:
         print("%s" % strCmd) # DEBUG
 
     # Run the command as a subprocess.
     try:
         subprocess.check_output(strCmd, shell=True,  \
                              stderr=subprocess.STDOUT)
     except subprocess.CalledProcessError as exError:
         print("%s: rrdtool update failed: %s" % \
                     (getTimeStamp(), exError.output))
         return False
 
     if verboseMode and not debugMode:

         print("database update successful")

 
     return True
 ##end def
 

 def createGraph(fileName, dataItem, gLabel, gTitle, gStart,
                 lower, upper, addTrend, autoScale):
     """Uses rrdtool to create a graph of specified node data item.
        Parameters:
            fileName - name of file containing the graph
            dataItem - data item to be graphed
            gLabel - string containing a graph label for the data item
            gTitle - string containing a title for the graph
            gStart - beginning time of the graphed data
            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 LINE2:smoothed#006600 " \

                   % trendWindow[gStart]
     elif addTrend == 2:
         strCmd += "LINE1:dSeries#0400ff "

         strCmd += "CDEF:smoothed=dSeries,%s,TREND LINE2:smoothed#006600 " \

                   % trendWindow[gStart]
      

     if debugMode:

         print("%s" % strCmd) # DEBUG

     
     # Run the formatted rrdtool command as a subprocess.
     try:
         result = subprocess.check_output(strCmd, \
                      stderr=subprocess.STDOUT,   \
                      shell=True)

     except subprocess.CalledProcessError as exError:
         print("rrdtool graph failed: %s" % (exError.output))

         return False
 

     if verboseMode:

         print("rrdtool graph: %s\n" % result.decode('utf-8'), end='')

     return True
 
 ##end def
 
 def generateGraphs():
     """Generate graphs for display in html documents.
        Parameters: none
        Returns: nothing
     """
     autoScale = False
 
     # The following will force creation of charts
     # of only signal strength and S/N charts.  Note that the following
     # data items appear constant and do not show variation with time:
     # noise level, rx mcs, rx rate, tx mcs, tx rate.  Therefore, until
     # these parameters are demonstrated to vary in time, there is no point
     # in creating the charts for these data items.
     createAllCharts = False
 
     # 24 hour stock charts
 
     createGraph('24hr_signal', 'S', 'dBm', 
                 'RSSI\ -\ Last\ 24\ Hours', 'end-1day', 0, 0, 2, autoScale)
     createGraph('24hr_snr', 'SNR', 'dB', 
                 'SNR\ -\ Last\ 24\ Hours', 'end-1day', 0, 0, 2, autoScale)
 
     # 4 week stock charts
 
     createGraph('4wk_signal', 'S', 'dBm', 
                 'RSSI\ -\ Last\ 4\ Weeks', 'end-4weeks', 0, 0, 2, autoScale)
     createGraph('4wk_snr', 'SNR', 'dB', 
                 'SNR\ -\ Last\ 4\ Weeks', 'end-4weeks', 0, 0, 2, autoScale)
 
     # 12 month stock charts
 
     createGraph('12m_signal', 'S', 'dBm', 
                 'RSSI\ -\ Past\ Year', 'end-12months', 0, 0, 2, autoScale)
     createGraph('12m_snr', 'SNR', 'dB', 
                 'SNR\ -\ Past\ Year', 'end-12months', 0, 0, 2, autoScale)
 

     if verboseMode:

         #print() # print a blank line to improve readability when in debug mode

         pass
 ##end def
 
 def getCLarguments():
     """Get command line arguments.  There are four possible arguments
           -d turns on debug mode
           -v turns on verbose debug mode
           -t sets the aredn node query interval
           -u sets the url of the aredn nodeing device
        Returns: nothing
     """

     global verboseMode, debugMode, dataRequestInterval, \

            arednNodeUrl
 
     index = 1
     while index < len(sys.argv):

         if sys.argv[index] == '-v':
             verboseMode = True
         elif sys.argv[index] == '-d':
             verboseMode = True
             debugMode = True

         elif sys.argv[index] == '-p':
             try:
                 dataRequestInterval = abs(int(sys.argv[index + 1]))
             except:

                 print("invalid polling period")

                 exit(-1)
             index += 1
         elif sys.argv[index] == '-u':
             arednNodeUrl = sys.argv[index + 1]

             if arednNodeUrl.find('http://') < 0:
                 arednNodeUrl = 'http://' + arednNodeUrl

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

             print("Usage: %s [-d] [-v] [-p 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
     """
     global dataRequestInterval
 
     signal.signal(signal.SIGTERM, terminateAgentProcess)

     signal.signal(signal.SIGINT, terminateAgentProcess)

     print('===================')

     print('%s starting up arednsig 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 createArednsigRrd 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 aredn
         # node and process the received data.
         if currentTime - lastDataRequestTime > dataRequestInterval:
             lastDataRequestTime = currentTime
             dData = {}
 
             # Get the data string from the device.

             result = getNodeData(dData)

             # If successful parse the data.
             if result:

                 result = parseDataString(dData)

 
             # If parse successful, write data output data file.

             if result:

                 writeOutputFile(dData)

             # If write output file successful, update the database.

             if result:

                 result = updateDatabase(dData)

 
             # Set the node status to online or offline depending on the
             # success or failure of the above operations.
             setNodeStatus(result)
 
 
         # At the chart generation interval, generate charts.
         if currentTime - lastChartUpdateTime > chartUpdateInterval:
             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 verboseMode:

             if result:

                 print("update successful: %s sec\n" % elapsedTime)

             else:

                 print("update failed: %s sec\n" % elapsedTime)

         remainingTime = dataRequestInterval - elapsedTime
         if remainingTime > 0.0:
             time.sleep(remainingTime)
     ## end while
     return
 ## end def
 
 if __name__ == '__main__':

     main()