#!/usr/bin/env python3

import urllib.request, urllib.error, urllib.parse
import base64
import json
import argparse
import sys
import ssl
from pprint import pprint
from urllib.error import HTTPError
from urllib.error import URLError

plugin_description = \
"""
Check HTTP JSON Nagios Plugin

Generic Nagios plugin which checks json values from a given endpoint against
argument specified rules and determines the status and performance data for
that service.
"""

OK_CODE = 0
WARNING_CODE = 1
CRITICAL_CODE = 2
UNKNOWN_CODE = 3

__version__ = '2.1.2'
__version_date__ = '2022-09-15'

class NagiosHelper:
    """
    Help with Nagios specific status string formatting.
    """

    message_prefixes = {OK_CODE: 'OK',
                        WARNING_CODE: 'WARNING',
                        CRITICAL_CODE: 'CRITICAL',
                        UNKNOWN_CODE: 'UNKNOWN'}
    performance_data = ''
    warning_message = ''
    critical_message = ''
    unknown_message = ''

    def getMessage(self, message=''):
        """
        Build a status-prefixed message with optional performance data
        generated externally
        """

        message += self.warning_message
        message += self.critical_message
        message += self.unknown_message
        code = self.message_prefixes[self.getCode()]
        output = "{code}: Status {code}. {message}".format(code=code, message=message.strip())
        if self.performance_data:
            output = "{code}: {perf_data} Status {code}. {message}|{perf_data}".format(
                code=code,
                message=message.strip(),
                perf_data=self.performance_data)
        return output.strip()

    def getCode(self):
        code = OK_CODE
        if (self.warning_message != ''):
            code = WARNING_CODE
        if (self.critical_message != ''):
            code = CRITICAL_CODE
        if (self.unknown_message != ''):
            code = UNKNOWN_CODE
        return code

    def append_warning(self, warning_message):
        self.warning_message += warning_message

    def append_critical(self, critical_message):
        self.critical_message += critical_message

    def append_unknown(self, unknown_message):
        self.unknown_message += unknown_message

    def append_metrics(self, metrics):
        (performance_data, warning_message, critical_message) = metrics
        self.performance_data += performance_data
        self.append_warning(warning_message)
        self.append_critical(critical_message)


class JsonHelper:
    """
    Perform simple comparison operations against values in a given
    JSON dict
    """

    def __init__(self, json_data, separator, value_separator):
        self.data = json_data
        self.separator = separator
        self.value_separator = value_separator
        self.arrayOpener = '('
        self.arrayCloser = ')'

    def getSubElement(self, key, data):
        separatorIndex = key.find(self.separator)
        partialKey = key[:separatorIndex]
        remainingKey = key[separatorIndex + 1:]
        if partialKey in data:
            return self.get(remainingKey, data[partialKey])
        return (None, 'not_found')

    def getSubArrayElement(self, key, data):
        subElemKey = key[:key.find(self.arrayOpener)]
        index = int(key[key.find(self.arrayOpener) +
                        1:key.find(self.arrayCloser)])
        remainingKey = key[key.find(self.arrayCloser + self.separator) + 2:]

        if key.find(self.arrayCloser + self.separator) == -1:
            remainingKey = key[key.find(self.arrayCloser) + 1:]
        if subElemKey in data:
            if index < len(data[subElemKey]):
                return self.get(remainingKey, data[subElemKey][index])
            else:
                return (None, 'not_found')
        if index >= len(data):
            return (None, 'not_found')
        else:
            if not subElemKey:
                return self.get(remainingKey, data[index])
            else:
                return (None, 'not_found')

    def equals(self, key, value):
        return self.exists(key) and \
            str(self.get(key)) in value.split(self.value_separator)

    def lte(self, key, value):
        return self.exists(key) and float(self.get(key)) <= float(value)

    def lt(self, key, value):
        return self.exists(key) and float(self.get(key)) < float(value)

    def gte(self, key, value):
        return self.exists(key) and float(self.get(key)) >= float(value)

    def gt(self, key, value):
        return self.exists(key) and float(self.get(key)) > float(value)

    def exists(self, key):
        return (self.get(key) != (None, 'not_found'))

    def get(self, key, temp_data=''):
        """
        Can navigate nested json keys with a dot format
        (Element.Key.NestedKey). Returns (None, 'not_found') if not found
        """

        if temp_data != '':
            data = temp_data
        else:
            data = self.data
        if len(key) <= 0:
            return data
        if key.find(self.separator) != -1 and \
           key.find(self.arrayOpener) != -1:
            if key.find(self.separator) < key.find(self.arrayOpener):
                return self.getSubElement(key, data)
            else:
                return self.getSubArrayElement(key, data)
        else:
            if key.find(self.separator) != -1:
                return self.getSubElement(key, data)
            else:
                if key.find(self.arrayOpener) != -1:
                    return self.getSubArrayElement(key, data)
                else:
                    if isinstance(data, dict) and key in data:
                        return data[key]
                    else:
                        return (None, 'not_found')

    def expandKey(self, key, keys):
        if '(*)' not in key:
            keys.append(key)
            return keys
        subElemKey = ''
        if key.find('(*)') > 0:
            subElemKey = key[:key.find('(*)')-1]
        remainingKey = key[key.find('(*)')+3:]
        elemData = self.get(subElemKey)
        if elemData == (None, 'not_found'):
            keys.append(key)
            return keys
        if subElemKey != '':
            subElemKey = subElemKey + '.'
        for i in range(len(elemData)):
            newKey = subElemKey + '(' + str(i) + ')' + remainingKey
            newKeys = self.expandKey(newKey, [])
            for j in newKeys:
                keys.append(j)

        return keys


def _getKeyAlias(original_key):
    key = original_key
    alias = original_key
    if '>' in original_key:
        keys = original_key.split('>')
        if len(keys) == 2:
            key, alias = keys
    return key, alias


class JsonRuleProcessor:
    """
    Perform checks and gather values from a JSON dict given rules
    and metrics definitions
    """

    def __init__(self, json_data, rules_args):
        self.data = json_data
        self.rules = rules_args
        separator = '.'
        value_separator = ':'
        if self.rules.separator:
            separator = self.rules.separator
        if self.rules.value_separator:
            value_separator = self.rules.value_separator
        self.helper = JsonHelper(self.data, separator, value_separator)
        debugPrint(rules_args.debug, "rules: %s" % rules_args)
        debugPrint(rules_args.debug, "separator: %s" % separator)
        debugPrint(rules_args.debug, "value_separator: %s" % value_separator)
        self.metric_list = self.expandKeys(self.rules.metric_list)
        self.key_threshold_warning = self.expandKeys(
            self.rules.key_threshold_warning)
        self.key_threshold_critical = self.expandKeys(
            self.rules.key_threshold_critical)
        self.key_value_list = self.expandKeys(self.rules.key_value_list)
        self.key_value_list_not = self.expandKeys(
            self.rules.key_value_list_not)
        self.key_list = self.expandKeys(self.rules.key_list)
        self.key_value_list_critical = self.expandKeys(
            self.rules.key_value_list_critical)
        self.key_value_list_not_critical = self.expandKeys(
            self.rules.key_value_list_not_critical)
        self.key_list_critical = self.expandKeys(self.rules.key_list_critical)
        self.key_value_list_unknown = self.expandKeys(
            self.rules.key_value_list_unknown)

    def expandKeys(self, src):
        if src is None:
            return []
        dest = []
        for key in src:
            newKeys = self.helper.expandKey(key, [])
            for k in newKeys:
                dest.append(k)
        return dest

    def checkExists(self, exists_list):
        failure = ''
        for k in exists_list:
            key, alias = _getKeyAlias(k)
            if (self.helper.exists(key) is False):
                failure += " Key %s did not exist." % alias
        return failure

    def checkEquality(self, equality_list):
        failure = ''
        for kv in equality_list:
            k, v = kv.split(',')
            key, alias = _getKeyAlias(k)
            if not self.helper.equals(key, v):
                failure += " Key %s mismatch. %s != %s" % (alias, v,
                                                           self.helper.get(key))
        return failure

    def checkNonEquality(self, equality_list):
        failure = ''
        for kv in equality_list:
            k, v = kv.split(',')
            key, alias = _getKeyAlias(k)
            if self.helper.equals(key, v):
                failure += " Key %s match found. %s == %s" % (alias, v,
                                                              self.helper.get(key))
        return failure

    def checkThreshold(self, key, alias, r):
        failure = ''
        invert = False
        start = 0
        end = 'infinity'
        if r.startswith('@'):
            invert = True
            r = r[1:]
        vals = r.split(':')
        if len(vals) == 1:
            end = vals[0]
        if len(vals) == 2:
            start = vals[0]
            if vals[1] != '':
                end = vals[1]
        if(start == '~'):
            if (invert and self.helper.lte(key, end)):
                failure += " Value (%s) for key %s was less than or equal to %s." % \
                           (self.helper.get(key), alias, end)
            elif (not invert and self.helper.gt(key, end)):
                failure += " Value (%s) for key %s was greater than %s." % \
                           (self.helper.get(key), alias, end)
        elif(end == 'infinity'):
            if (invert and self.helper.gte(key, start)):
                failure += " Value (%s) for key %s was greater than or equal to %s." % \
                           (self.helper.get(key), alias, start)
            elif (not invert and self.helper.lt(key, start)):
                failure += " Value (%s) for key %s was less than %s." % \
                           (self.helper.get(key), alias, start)
        else:
            if (invert and self.helper.gte(key, start) and
                    self.helper.lte(key, end)):
                failure += " Value (%s) for key %s was inside the range %s:%s." % \
                           (self.helper.get(key), alias, start, end)
            elif (not invert and (self.helper.lt(key, start) or
                                  self.helper.gt(key, end))):
                failure += " Value (%s) for key %s was outside the range %s:%s." % \
                           (self.helper.get(key), alias, start, end)

        return failure

    def checkThresholds(self, threshold_list):
        failure = ''
        for threshold in threshold_list:
            k, r = threshold.split(',')
            key, alias = _getKeyAlias(k)
            failure += self.checkThreshold(key, alias, r)
        return failure

    def checkWarning(self):
        failure = ''
        if self.key_threshold_warning is not None:
            failure += self.checkThresholds(self.key_threshold_warning)
        if self.key_value_list is not None:
            failure += self.checkEquality(self.key_value_list)
        if self.key_value_list_not is not None:
            failure += self.checkNonEquality(self.key_value_list_not)
        if self.key_list is not None:
            failure += self.checkExists(self.key_list)
        return failure

    def checkCritical(self):
        failure = ''
        if not self.data:
            failure = " Empty JSON data."
        if self.key_threshold_critical is not None:
            failure += self.checkThresholds(self.key_threshold_critical)
        if self.key_value_list_critical is not None:
            failure += self.checkEquality(self.key_value_list_critical)
        if self.key_value_list_not_critical is not None:
            failure += self.checkNonEquality(self.key_value_list_not_critical)
        if self.key_list_critical is not None:
            failure += self.checkExists(self.key_list_critical)
        return failure

    def checkUnknown(self):
        unknown = ''
        if self.key_value_list_unknown is not None:
            unknown += self.checkEquality(self.key_value_list_unknown)
        return unknown

    def checkMetrics(self):
        """
        Return a Nagios specific performance metrics string given keys
        and parameter definitions
        """

        metrics = ''
        warning = ''
        critical = ''
        if self.metric_list is not None:
            for metric in self.metric_list:
                key = metric
                minimum = maximum = warn_range = crit_range = None
                uom = ''
                if ',' in metric:
                    vals = metric.split(',')
                    if len(vals) == 2:
                        key, uom = vals
                    if len(vals) == 4:
                        key, uom, warn_range, crit_range = vals
                    if len(vals) == 6:
                        key, uom, warn_range, crit_range, \
                            minimum, maximum = vals
                key, alias = _getKeyAlias(key)
                if self.helper.exists(key):
                    metrics += "'%s'=%s" % (alias, self.helper.get(key))
                    if uom:
                        metrics += uom
                    if warn_range is not None:
                        warning += self.checkThreshold(key, alias, warn_range)
                        metrics += ";%s" % warn_range
                    if crit_range is not None:
                        critical += self.checkThreshold(key, alias, crit_range)
                        metrics += ";%s" % crit_range
                    if minimum is not None:
                        critical += self.checkThreshold(key, alias, minimum +
                                                        ':')
                        metrics += ";%s" % minimum
                    if maximum is not None:
                        critical += self.checkThreshold(key, alias, '~:' +
                                                        maximum)
                        metrics += ";%s" % maximum
                metrics += ' '
        return ("%s" % metrics, warning, critical)


def parseArgs(args):
    """
    CLI argument definitions and parsing
    """

    parser = argparse.ArgumentParser(
        description=plugin_description + '\n\nVersion: %s (%s)'
        %(__version__, __version_date__),
        formatter_class=argparse.RawDescriptionHelpFormatter
    )

    parser.add_argument('-d', '--debug', action='store_true',
                        help='debug mode')
    parser.add_argument('-s', '--ssl', action='store_true',
                        help='use TLS to connect to remote host')
    parser.add_argument('-H', '--host', dest='host',
                        required=not ('-V' in args or '--version' in args),
                        help='remote host to query')
    parser.add_argument('-k', '--insecure', action='store_true',
                        help='do not check server SSL certificate')
    parser.add_argument('-X', '--request', dest='method', default='GET', choices=['GET', 'POST'],
                        help='Specifies a custom request method to use when communicating  with  the HTTP server')
    parser.add_argument('-V', '--version', action='store_true',
                        help='print version of this plugin')
    parser.add_argument('--cacert',
                        dest='cacert', help='SSL CA certificate')
    parser.add_argument('--cert',
                        dest='cert', help='SSL client certificate')
    parser.add_argument('--key', dest='key',
                        help='SSL client key ( if not bundled into the cert )')
    parser.add_argument('-P', '--port', dest='port', help='TCP port')
    parser.add_argument('-p', '--path', dest='path', help='Path')
    parser.add_argument('-t', '--timeout', type=int,
                        help='Connection timeout (seconds)')
    parser.add_argument('-B', '--basic-auth', dest='auth',
                        help='Basic auth string "username:password"')
    parser.add_argument('-D', '--data', dest='data',
                        help='The http payload to send as a POST')
    parser.add_argument('-A', '--headers', dest='headers',
                        help='The http headers in JSON format.')
    parser.add_argument('-f', '--field_separator', dest='separator',
                        help='''JSON Field separator, defaults to ".";
                        Select element in an array with "(" ")"''')
    parser.add_argument('-F', '--value_separator', dest='value_separator',
                        help='''JSON Value separator, defaults to ":"''')
    parser.add_argument('-w', '--warning', dest='key_threshold_warning',
                        nargs='*',
                        help='''Warning threshold for these values
                        (key1[>alias],WarnRange key2[>alias],WarnRange).
                        WarnRange is in the format [@]start:end, more
                        information at
                        nagios-plugins.org/doc/guidelines.html.''')
    parser.add_argument('-c', '--critical', dest='key_threshold_critical',
                        nargs='*',
                        help='''Critical threshold for these values
                        (key1[>alias],CriticalRange key2[>alias],CriticalRange.
                        CriticalRange is in the format [@]start:end, more
                        information at
                        nagios-plugins.org/doc/guidelines.html.''')
    parser.add_argument('-e', '--key_exists', dest='key_list', nargs='*',
                        help='''Checks existence of these keys to determine
                        status. Return warning if key is not present.''')
    parser.add_argument('-E', '--key_exists_critical',
                        dest='key_list_critical',
                        nargs='*',
                        help='''Same as -e but return critical if key is
                        not present.''')
    parser.add_argument('-q', '--key_equals', dest='key_value_list', nargs='*',
                        help='''Checks equality of these keys and values
                        (key[>alias],value key2,value2) to determine status.
                        Multiple key values can be delimited with colon
                        (key,value1:value2). Return warning if equality
                        check fails''')
    parser.add_argument('-Q', '--key_equals_critical',
                        dest='key_value_list_critical', nargs='*',
                        help='''Same as -q but return critical if
                        equality check fails.''')
    parser.add_argument('-u', '--key_equals_unknown',
                        dest='key_value_list_unknown', nargs='*',
                        help='''Same as -q but return unknown if
                        equality check fails.''')
    parser.add_argument('-y', '--key_not_equals',
                        dest='key_value_list_not', nargs='*',
                        help='''Checks equality of these keys and values
                        (key[>alias],value key2,value2) to determine status.
                        Multiple key values can be delimited with colon
                        (key,value1:value2). Return warning if equality
                        check succeeds''')
    parser.add_argument('-Y', '--key_not_equals_critical',
                        dest='key_value_list_not_critical', nargs='*',
                        help='''Same as -q but return critical if equality
                        check succeeds.''')
    parser.add_argument('-m', '--key_metric', dest='metric_list', nargs='*',
                        help='''Gathers the values of these keys (key[>alias],
                        UnitOfMeasure,WarnRange,CriticalRange,Min,Max) for
                        Nagios performance data. More information about Range
                        format and units of measure for nagios can be found at
                        nagios-plugins.org/doc/guidelines.html
                        Additional formats for this parameter are:
                        (key[>alias]), (key[>alias],UnitOfMeasure),
                        (key[>alias],UnitOfMeasure,WarnRange,
                        CriticalRange).''')

    return parser.parse_args(args)


def debugPrint(debug_flag, message, pretty_flag=False):
    """
    Print debug messages if -d (debug_flat ) is set.
    """

    if debug_flag:
        if pretty_flag:
            pprint(message)
        else:
            print(message)


def main(cliargs):
    """
    Main entrypoint for CLI
    """

    args = parseArgs(cliargs)
    nagios = NagiosHelper()
    context = None

    if args.version:
        print('Version: %s - Date: %s' % (__version__, __version_date__))
        sys.exit(0)

    if args.ssl:
        url = "https://%s" % args.host

        context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
        context.options |= ssl.OP_NO_SSLv2
        context.options |= ssl.OP_NO_SSLv3

        if args.insecure:
            context.check_hostname = False
            context.verify_mode = ssl.CERT_NONE
        else:
            context.verify_mode = ssl.CERT_OPTIONAL
            context.load_default_certs()
            if args.cacert:
                try:
                    context.load_verify_locations(args.cacert)
                except ssl.SSLError:
                    nagios.append_unknown(
                        'Error loading SSL CA cert "%s"!'
                        % args.cacert)

            if args.cert:
                try:
                    context.load_cert_chain(args.cert, keyfile=args.key)
                except ssl.SSLError:
                    if args.key:
                        nagios.append_unknown(
                            'Error loading SSL cert. Make sure key "%s" belongs to cert "%s"!'
                            % (args.key, args.cert))
                    else:
                        nagios.append_unknown(
                            'Error loading SSL cert. Make sure "%s" contains the key as well!'
                            % (args.cert))

        if nagios.getCode() != OK_CODE:
            print(nagios.getMessage())
            sys.exit(nagios.getCode())

    else:
        url = "http://%s" % args.host
    if args.port:
        url += ":%s" % args.port
    if args.path:
        url += "/%s" % args.path

    debugPrint(args.debug, "url:%s" % url)
    json_data = ''

    try:
        req = urllib.request.Request(url, method=args.method)
        req.add_header("User-Agent", "check_http_json")
        if args.auth:
            authbytes = str(args.auth).encode()
            base64str = base64.encodebytes(authbytes).decode().replace('\n', '')
            req.add_header('Authorization', 'Basic %s' % base64str)
        if args.headers:
            headers = json.loads(args.headers)
            debugPrint(args.debug, "Headers:\n %s" % headers)
            for header in headers:
                req.add_header(header, headers[header])
        if args.timeout and args.data:
            databytes = str(args.data).encode()
            response = urllib.request.urlopen(req, timeout=args.timeout,
                                              data=databytes, context=context)
        elif args.timeout:
            response = urllib.request.urlopen(req, timeout=args.timeout,
                                              context=context)
        elif args.data:
            databytes = str(args.data).encode()
            response = urllib.request.urlopen(req, data=databytes, context=context)
        else:
            # pylint: disable=consider-using-with
            response = urllib.request.urlopen(req, context=context)

        json_data = response.read()

    except HTTPError as e:
        # Try to recover from HTTP Error, if there is JSON in the response
        if "json" in e.info().get_content_subtype():
            json_data = e.read()
        else:
            nagios.append_unknown(" HTTPError[%s], url:%s" % (str(e.code), url))
    except URLError as e:
        nagios.append_critical(" URLError[%s], url:%s" % (str(e.reason), url))

    try:
        data = json.loads(json_data)
    except ValueError as e:
        nagios.append_unknown(" Parser error: %s" % str(e))

    else:
        debugPrint(args.debug, 'json:')
        debugPrint(args.debug, data, True)
        # Apply rules to returned JSON data
        processor = JsonRuleProcessor(data, args)
        nagios.append_warning(processor.checkWarning())
        nagios.append_critical(processor.checkCritical())
        nagios.append_metrics(processor.checkMetrics())
        nagios.append_unknown(processor.checkUnknown())

    # Print Nagios specific string and exit appropriately
    print(nagios.getMessage())
    sys.exit(nagios.getCode())


if __name__ == "__main__":
    # Program entry point
    main(sys.argv[1:])

#EOF