#!/usr/bin/env python

# Mail Flow Checker version 2.3.

#Copyright (C) 2017 by National Board of eHealth, Denmark, and Troels Arvin.
#
#Permission is hereby granted, free of charge, to any person obtaining a copy
#of this software and associated documentation files (the "Software"), to deal
#in the Software without restriction, including without limitation the rights
#to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#copies of the Software, and to permit persons to whom the Software is
#furnished to do so, subject to the following conditions:
#
#The above copyright notice and this permission notice shall be included in
#all copies or substantial portions of the Software.
#
#THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
#THE SOFTWARE.

# wrapping in gigantic try-block to be able to return 3 if something
# unexpected goes wrong
try:
    import os
    import sys
    import getopt
    from ConfigParser import SafeConfigParser
    import psycopg2

    # policy
    default_warning_minutes = 30
    default_critical_minutes = 300
    default_unknown_minutes = 30
    default_giveup_minutes = 0

    # preparing to parse config file
    default_config_path_basename = 'mail_flow.cfg'
    default_config_path = '/etc/' + default_config_path_basename
    alt_config_path = os.path.dirname(__file__)+'/'+default_config_path_basename
    config_file = None
    # the above paths may be overridden by the -C argument

    # don't let database connection attempts run for more than 10 seconds:
    connect_timeout = 10

    # default db settings
    default_mail_smtp_server = None
    default_to_addr = 'nagios'
    default_subj = 'Mail flow test'
    default_db_name = 'nagios'
    default_db_schema = 'mail_flow'
    default_db_message_table = 'messages'
    default_db_check_view = 'check_view'
    default_db_receive_execution_table = 'receive_script_execution'

    this_script = os.path.basename(__file__) 
    default_critical_hours = int(default_critical_minutes/60)
    default_giveup_hours = int(default_giveup_minutes/60)
    default_unknown_hours = int(default_unknown_minutes/60)

    def usage():
        print """Usage: %s [-h|--help] [-w|--warning <minutes>] [-c|--critical <minutes>] 
                  [-g|--giveupafter <minutes>] [ -u|--unknownafter <minutes> ] 
                  [-C|--config_file <cfg_file>]

    warning minutes:      Number of minutes that a mail may be missing before
                          yielding a warning status; default: %d

    critical minutes:     Number of minutes that a mail may be missing before
                          yielding a critical status; default: %d (%d hours)

    giveupafter minutes:  Number of minutes after which to give up. 0 = forever.
                          Default: %d (%d hours).

    unknownafter minutes: Return UNKNOWN, if there has not been a sent probe mail
                          for this amount of minutes, or if message-receiving has
                          not happened for this amount of minutes. This could happen,
                          if the related cron jobs are not running, or if they 
                          keep failing. The implication os this is that the cron-job
                          which runs the mail_flow_sender script should run more
                          often than this value.
                          Default: %d (%d hours).

    cfg_file:             Where to read database configuration information from;
                          Defaults to %s (preferred) or %s. If no configuration file
                          is indicated, and no configuration file exists at default
                          paths, the following database defaults are used:
                          name=%s; schema=%s;
                          message_table=%s; check_view: %s

    Note: The following must hold:
        warning < critical < giveupafter""" % (
                            this_script,
                            default_warning_minutes,
                            default_critical_minutes, default_critical_hours,
                            default_giveup_minutes, default_giveup_hours,
                            default_unknown_minutes, default_unknown_hours,
                            default_config_path, alt_config_path,
                            default_db_name,default_db_schema,default_db_message_table,
                            default_db_check_view
                        )
        sys.exit(3)

    try:
        options, args = getopt.getopt \
        (
            sys.argv[1:],
            "h:w:c:g:u:C:",
            [
                "help",
                "warning=",
                "critical=",
                "giveupafter=",
                "unknownafter=",
                "config_file="
            ]
        )
    except getopt.GetoptError:
        usage()
        sys.exit(3)

    warning_minutes = default_warning_minutes
    critical_minutes = default_critical_minutes
    giveup_minutes = default_giveup_minutes
    unknown_minutes = default_unknown_minutes

    for name, value in options:
        if name in ("-h", "--help"):
            usage()
        if name in ("-w", "--warning"):
            try:
                warning_minutes = int(value)
            except Exception:
                print "ERROR: Unable to convert warning_minutes to integer.\n"
                print
                usage()
        if name in ("-c", "--critical"):
            try:
                critical_minutes = int(value)
            except Exception:
                print "ERROR: Unable to convert critical_minutes to integer.\n"
                print
                usage()
        if name in ("-g", "--giveupafter"):
            try:
                giveup_minutes = int(value)
            except Exception:
                print "ERROR: Unable to convert giveup_minutes to integer.\n"
                print
                usage()
        if name in ("-u", "--unknownafter"):
            try:
                unknown_minutes = int(value)
            except Exception:
                print "ERROR: Unable to convert unknown_minutes to integer.\n"
                print
                usage()
        if name in ("-C", "--config_file"):
            config_file = value
            if not os.path.exists(config_file):
                print "ERROR: No such file '%s'." % config_file
                print
                usage()

    if config_file is None:
        if os.path.exists(default_config_path):
            config_file = default_config_path
        else:
            if os.path.exists(alt_config_path):
                config_file = alt_config_path

    if not (warning_minutes < critical_minutes):
        print "ERROR: The 'warning < critical' precondition is violated."
        print
        usage()
    if giveup_minutes != 0 and not (critical_minutes < giveup_minutes):
        print "ERROR: The 'critical < giveup' precondition is violated."
        print
        usage()

    if config_file is None:
        mail_smtp_server           = default_mail_smtp_server
        to_addr                    = default_to_addr
        subj                       = default_subj
        db_name                    = default_db_name
        db_schema                  = default_db_schema
        db_message_table           = default_db_message_table
        db_check_view              = default_db_check_view
        db_receive_execution_table = default_db_receive_execution_table
    else:
        config = SafeConfigParser(
            {
                'smtp_server':             default_mail_smtp_server,
                'subject':                 default_subj,
                'name':                    default_db_name,
                'schema':                  default_db_schema,
                'message_table':           default_db_message_table,
                'check_view':              default_db_check_view,
                'receive_execution_table': default_db_receive_execution_table
            }
        )
        config.read(config_file)
        mail_smtp_server           = config.get('mail','smtp_server')
        to_addr                    = config.get('mail','to_addr')
        subj                       = config.get('mail','subject')
        db_name                    = config.get('db','name')
        db_schema                  = config.get('db','schema')
        db_message_table           = config.get('db','message_table')
        db_check_view              = config.get('db','check_view')
        db_receive_execution_table = config.get('db','receive_execution_table')

    try:
        # prepare db
        os.environ['PGCONNECT_TIMEOUT'] = str(connect_timeout)
        conn = psycopg2.connect("dbname='%s'" % db_name);
        cursor = conn.cursor()

        inject_sql_smtp_and_subj = ''
        if mail_smtp_server is not None:
            inject_sql_smtp_and_subj = " AND smtp_server = '%s' AND subj = %%(subj)s " % \
                (mail_smtp_server)

        inject_sql_giveup = ''
        if giveup_minutes != 0:
            inject_sql_giveup = " AND sent + INTERVAL '%d minutes' > CURRENT_TIMESTAMP " % \
                giveup_minutes

        # query and pull out result
        sql = """
            SELECT * FROM
            (
                SELECT COUNT(*) AS num_intransit
                FROM %s.%s
                WHERE received IS NULL
                  AND to_addr='%s'
                    %s
                    %s
            ) AS num_intransit,
            (
                SELECT COUNT(*) AS warncount
                FROM %s.%s
                WHERE received IS NULL
                  AND to_addr='%s'
                    %s
                    %s
                    AND sent + INTERVAL '%d minutes' < CURRENT_TIMESTAMP
            ) AS warncount,
            (
                SELECT COUNT(*) AS critcount
                FROM %s.%s
                WHERE received IS NULL
                  AND to_addr='%s'
                    %s
                    %s
                    AND sent + INTERVAL '%d minutes' < CURRENT_TIMESTAMP
            ) AS critcount,
            (
                SELECT CURRENT_TIMESTAMP-max(sent) AS interval_since_last_send
                FROM %s.%s
                WHERE to_addr='%s'
                    %s
            ) AS interval_since_last_send
        """ % (
            db_schema,db_check_view,to_addr,inject_sql_smtp_and_subj,inject_sql_giveup,
            db_schema,db_check_view,to_addr,inject_sql_smtp_and_subj,inject_sql_giveup,warning_minutes,
            db_schema,db_check_view,to_addr,inject_sql_smtp_and_subj,inject_sql_giveup,critical_minutes,
            db_schema,db_message_table,to_addr,inject_sql_smtp_and_subj
        )
        cursor.execute(sql,{'subj':subj,'subj':subj,'subj':subj,'subj':subj})
        msg_row = cursor.fetchone()
        if msg_row:
            num_intransit,num_warn,num_crit,interval_since_last_send = msg_row

            interval_since_last_send_minutes = None
            if interval_since_last_send:
                interval_since_last_send_minutes = (
                    interval_since_last_send.days*(24*60*60) +
                    interval_since_last_send.seconds/60
                )

            lookfor_age = None
            output_num = None
            if num_warn > 0:
                lookfor_age = warning_minutes
                output_num = num_warn
            if num_crit > 0:
                lookfor_age = critical_minutes
                output_num = num_crit

            # obtain an example of a message id which is missing
            if lookfor_age is not None:
                sql = """
                    SELECT   msg_id,sent
                    FROM     %s.%s
                    WHERE    sent = (
                        SELECT MIN(sent)
                        FROM   %s.%s
                        WHERE  received IS NULL
                          AND  to_addr='%s' %s %s
                    )
                      AND    to_addr='%s' %s %s
                    ORDER BY msg_id
                    LIMIT 1
                """ % (
                    db_schema,
                    db_message_table,
                    db_schema,
                    db_message_table,
                    to_addr,
                    inject_sql_smtp_and_subj,
                    inject_sql_giveup,
                    to_addr,
                    inject_sql_smtp_and_subj,
                    inject_sql_giveup
                )
                cursor.execute(sql,{'subj':subj,'subj':subj})
                msg_id,sent = cursor.fetchone()

            # Let's determine the delay, as calculated by the receive-script (if the
            # receive script has been executed, at all)
            sql = """
                SELECT * FROM
                (
                    SELECT first_received_header_ts - sent AS delay
                    FROM %s.%s
                    WHERE first_received_header_ts IS NOT NULL
                      AND to_addr='%s'
                        %s
                    ORDER BY sent DESC FETCH FIRST 1 ROWS ONLY
                ) AS delay,
                (
                    SELECT CURRENT_TIMESTAMP-receive_execution_ts AS interval_since_last_receive_execution
                    FROM %s.%s
                    WHERE to_addr='%s'
                        %s
                ) AS interval_since_last_receive_execution
            """ % (
                db_schema,db_message_table,to_addr,inject_sql_smtp_and_subj,
                db_schema,db_receive_execution_table,to_addr,inject_sql_smtp_and_subj
            )
            cursor.execute(sql,{'subj':subj,'subj':subj})
            receive_row = cursor.fetchone()
            interval_since_last_receive_execution_minutes = None
            delay_seconds = None
            if receive_row:
                delay,interval_since_last_receive_execution = receive_row
                if delay:
                    delay_seconds = (
                        delay.days*(24*60*60) + 
                        delay.seconds + delay.microseconds/1000000.0
                    )
                interval_since_last_receive_execution_minutes = (
                    interval_since_last_receive_execution.days*(24*60*60) +
                    interval_since_last_receive_execution.seconds/60
                )

        cursor.close()

    except StandardError, msg:
        print("Error working with the message database")
        sys.stderr.write('Database error: %s' % msg)
        sys.exit(3)

    # return with relevant exit code and message

    if interval_since_last_send_minutes is None:
        print "MAILFLOW UNKNOWN: No probe mail has successfully been sent yet"
        sys.exit(3)

    if interval_since_last_send_minutes > unknown_minutes:
        print "MAILFLOW UNKNOWN: No probe mail has successfully been sent for %d minutes" % \
            interval_since_last_send_minutes
        sys.exit(3)

    if interval_since_last_receive_execution_minutes is None:
        print "MAILFLOW UNKNOWN: The receive script has never been successfully run after a probe mail"
        sys.exit(3)

    if interval_since_last_receive_execution_minutes > unknown_minutes:
        print "MAILFLOW UNKNOWN: The receive script has not been successfully run for %d minutes" % \
            interval_since_last_receive_execution_minutes
        sys.exit(3)

    # Prepare performance data
    perf_intrans = 'num_in_transit=%d' % num_intransit
    perf_delay = ''
    if delay_seconds is not None:
        perf_delay = ' delay_of_last_delivery=%.3fs' % delay_seconds
    perf_str = '%s%s' % (perf_intrans, perf_delay)

    if num_crit==0 and num_warn==0:
        print "MAILFLOW OK: Probe mails in transit: %d; none older than %d minutes|%s" % (num_intransit,warning_minutes,perf_str)
        sys.exit(0)
    else:
        output_trailer = \
            "%d in-transit probe mail(s) older than %d minutes; msg_id of oldest missing message: '%s', sent to '%s' at time %s|%s" % \
            (output_num,lookfor_age,msg_id,to_addr,sent,perf_str)
        if num_crit != 0:
            print "MAILFLOW CRITICAL: %s" % output_trailer
            sys.exit(2)
        if num_warn != 0:
            print "MAILFLOW WARNING: %s" % output_trailer
            sys.exit(1)

except SystemExit, e:
    sys.exit(int(str(e)))
except:
    print "MAILFLOW UNKNOWN: An unhandled error occurred"
    sys.stderr.write('Unhandled error: %s' % sys.exc_info()[1])
    sys.exit(3)