#!/usr/bin/env python3
"""SNMP defaults linux python check"""
"""dependencys:
- pip3 install nagiosplugin
- pip3 install argparse
- pip3 install easysnmp
    - https://easysnmp.readthedocs.io/en/latest/index.html
    - https://easysnmp.readthedocs.io/en/latest/session_api.html
"""

__version__     = '0.1.2'
__author__      = 'anima'

# imports
import logging
import argparse
import nagiosplugin
from easysnmp import Session

# log settings
logging.basicConfig(format='[%(asctime)s] %(levelname)s %(message)s', level=logging.INFO)

def init_snmp_session(hostname: str = 'localhost', snmp_version: str | int = '2', snmp_community: str = 'public',
    snmp_security_level: str = 'auth_with_privacy', snmp_security_username: str = 'monitoring',
    snmp_auth_protocol: str = 'SHA256', snmp_auth_password: str | None = None,
    snmp_privacy_protocol: str = 'AES', snmp_privacy_password: str | None = None
    ) -> Session:
    """init a easysnmp session

    Args:
        hostname (str, optional): hostname or ip of host. Defaults to 'localhost'.
        snmp_version (str, optional): version of snmp (1, 2, 3). Defaults to 2.
        snmp_community (str, only need for v1 & v2): snmp community if snmp v1 or v2 used (any). Defaults to 'public'.
        snmp_security_level (str, only need for v3): security level (no_auth_or_privacy, auth_without_privacy or auth_with_privacy). Defaults to 'auth_with_privacy'.
        snmp_security_username (str, only need for v3): security name (any). Defaults to 'monitoring'.
        snmp_auth_protocol (str, only need for v3): authentication protocol (MD5, SHA256, SHA512). Defaults to 'SHA256'.
        snmp_auth_password (str, only need for v3): authentication passphrase (any). Defaults to None.
        snmp_privacy_protocol (str, only need for v3): privacy protocol (AES, DES). Defaults to 'AES'.
        snmp_privacy_password (str, only need for v3): privacy passphrase (any). Defaults to None.
    
    Return:
        easysnmp.Session: session for get or walk actions
    """
    # check if snmp version an valid str or int and saves as int
    valid_versions: list[str, int] = ['1','2','3', 1, 2, 3]
    if snmp_version not in valid_versions:
        raise ValueError(f'{snmp_version=} non of {valid_versions=}')
    else:
        snmp_version = int(snmp_version)

    if snmp_version == '3':
        # check if snmp security level valid
        valid_security_levels: list[str] = ['no_auth_or_privacy', 'auth_without_privacy', 'auth_with_privacy']
        if snmp_security_level not in valid_security_levels:
            raise ValueError(f'{snmp_security_level=} is non of {valid_security_levels=}')

        # check if auth protocol valid
        if snmp_security_level.startswith('auth'):
            valid_auth_protocols: list[str] = ['MD5', 'SHA', 'SHA256', 'SHA512']
            if snmp_auth_protocol not in valid_auth_protocols:
                raise ValueError(f'{snmp_auth_protocol=} is non of {valid_auth_protocols=}')

            if snmp_auth_password is None:
                raise ValueError(f'{snmp_auth_password=} is not set')

        # check if privacy protocol valid
        if not snmp_security_level.startswith('no'):
            valid_privacy_protocols: list[str] = ['AES', 'DES']
            if snmp_privacy_protocol not in valid_privacy_protocols:
                raise ValueError(f'{snmp_privacy_protocol=} is non of {valid_privacy_protocols=}')

            if snmp_privacy_password is None:
                raise ValueError(f'{snmp_privacy_password=} is not set')


    if snmp_version == 3: # 2025-01-02: only 'auth_with_privacy' is tested
        session = Session(hostname=hostname, version=snmp_version, 
            security_level=snmp_security_level, security_username=snmp_security_username,
            privacy_protocol=snmp_privacy_protocol, privacy_password=snmp_privacy_password,
            auth_protocol=snmp_auth_protocol, auth_password=snmp_auth_password)
    else:
        session = Session(hostname=hostname, version=snmp_version, community=snmp_community)
    return session


#
# General Summary
#
class SNMPSummary(nagiosplugin.Summary):
    """default summary for own results"""
    def verbose(self, results):
        """creates a multiline response"""
        result_str = ''
        for result in results:
            result_str += f'{str(result)}\n'
        return result_str

    def ok(self, results):
        return

    def problem(self, results):
        return


#
# Disk
#
class SNMPDiskResource(nagiosplugin.Resource):
    def __init__(self, session, exclude_tmpfs:bool = True):
        """disk check via snmp

        Args:
            session (easysnmp.Session): Easysnmp Session object
            exclude_tmpfs (bool, optional): ignore disks from dev type tmpfs. Defaults to True.
        """
        self.session = session
        self.exclude_tmpfs = exclude_tmpfs

    def probe(self) -> list:
        """check disk size of all disks
        
        Returns:
            list[nagisplugin.Metric]: multiple metric elements (yield)
        """
        baseoid = '.1.3.6.1.4.1.2021.9.1'
        oids = dict()
        oids['dskIndex']        = '.1'
        oids['dskPath']         = '.2'
        oids['dskDevice']       = '.3'
        oids['dskTotal']        = '.6'
        oids['dskAvail']        = '.7'
        oids['dskUsed']         = '.8'
        oids['dskPercent']      = '.9'
        oids['dskPercentNode']  = '.10'
        results = dict()
        disks = dict()
        for key,value in oids.items():
            results[key] = self.session.walk(baseoid + value)
            if len(results[key]) <= 0:
                raise ValueError('no values from snmp')
        for key, value in results.items():
            for item in value:
                if item.oid_index == '':
                    if key == 'dskIndex':

                        disks[item.value] = dict()
                    else:
                        disks[item.oid.split('.')[-1]][key] = item.value
                else:
                    if key == 'dskIndex':
                        disks[item.value] = dict()
                    else:
                        disks[item.oid_index][key] = item.value

        for disk in disks.values():
            if not (self.exclude_tmpfs and disk['dskDevice'] == 'tmpfs'):
                yield nagiosplugin.Metric(name=disk['dskPath'], value=int(disk['dskPercent']), uom='%', context='scalar_context')
                yield nagiosplugin.Metric(name=disk['dskPath'], value=disk, context='disk_info')


class SNMPDiskResult(nagiosplugin.Result):
    def human_size(self, value: int | float, source_unit: str = 'b', target_unit: str = 'gb') -> list[float, str]:
        """convert a byte int to a higher unit

        stop convert if value < 1024
        supported units: ['b', 'kb', 'mb', 'gb', 'tb']

        Args:
            value (int | float): original value
            source_unit (str, optional): unit of original unit. Defaults to 'b'.
            target_unit (str, optional): target unit. Defaults to 'gb'.

        Returns:
            list[float, str]: [new_value, unit]
        """
        units = ['b', 'kb', 'mb', 'gb', 'tb']
        if value < 1024 or source_unit == target_unit:
            return [value, source_unit]
        return self.human_size(value / 1024, units[units.index(source_unit) + 1], target_unit=target_unit)

    def __str__(self):
        free_size, free_unit = self.human_size(int(self.metric.value["dskAvail"]), 'kb')
        return f'{self.metric.value["dskPath"]} has {round(free_size, 2)} {free_unit} free'


def parse_args() -> argparse.Namespace:
    """evaluates given arguments

    Returns:
        argsparse.Namespace: Namespace Object with all arguments insert (use: args.long_name_of_argument)
    """
    argp = argparse.ArgumentParser(description=__doc__)
    # Default args
    argp.add_argument('-v', '--verbose', action='count', default=0,
        help='increase output verbosity (use up to 3 times)')
    argp.add_argument('-H', '--hostname', default='localhost',
        help='IP address or hostname of device to query')
    argp.add_argument('-t', '--timeout', default=30,
        help='abort execution after TIMEOUT seconds')
    argp.add_argument('-m', '--check_mode',
        choices=[
            'disk',
            'cpu',
            'load?',
            'memory',
        ],
        help='check mode to run')

    # Nagios args / see https://nagios-plugins.org/doc/guidelines.html#THRESHOLDFORMAT
    argp.add_argument('-w', '--warning', default=':80',
        help='warning threshold')
    argp.add_argument('-c', '--critical', default=':90',
        help='critical threshold')

    # SNMP args (same -* as snmpwalk / snmpget linux command; exept -C/-c & -V /-v because already used (see above))
    argp.add_argument('-V', '--snmp-version', default='2',
        help='Used SNMP Version. (1, 2, 3)')
    argp.add_argument('-C', '--snmp_community', default='public',
        help='SNMP community if snmp v1 or v2 used (any).')
    argp.add_argument('-l', '--snmp-security-level', default='auth_with_privacy',
        help='Security level (no_auth_or_privacy, auth_without_privacy or auth_with_privacy)')
    argp.add_argument('-u', '--snmp-security-username', default='monitoring',
        help='Security name (any)')
    argp.add_argument('-a', '--snmp-auth-protocol', default='SHA256',
        help='Authentication protocol (MD5, SHA256, SHA512)')
    argp.add_argument('-A', '--snmp-auth-pass', default=None,
        help='Authentication passphrase (any)')
    argp.add_argument('-x', '--snmp-privacy-protocol', default='AES',
        help='Privacy protocol (AES, DES)')
    argp.add_argument('-X', '--snmp-privacy-pass', default=None,
        help='Privacy passphrase (any)')

    args = argp.parse_args()
    return args


def main():
    args = parse_args()
    if args.verbose >= 3:
        logging.getLogger().setLevel(logging.DEBUG)

    session = init_snmp_session(hostname=args.hostname, snmp_version=args.snmp_version, snmp_community=args.snmp_community,
        snmp_security_level=args.snmp_security_level, snmp_security_username=args.snmp_security_username,
        snmp_auth_protocol=args.snmp_auth_protocol, snmp_auth_password=args.snmp_auth_pass,
        snmp_privacy_protocol=args.snmp_privacy_protocol, snmp_privacy_password=args.snmp_privacy_pass)

    # dice which check will be run bases on check_mode
    match args.check_mode:
        case 'disk':
            check = nagiosplugin.Check(
                SNMPDiskResource(session=session),
                nagiosplugin.Context(name='disk_info', result_cls=SNMPDiskResult),
                nagiosplugin.ScalarContext(name='scalar_context', fmt_metric='{name} is {value}{uom} used', warning=args.warning, critical=args.critical),
                SNMPSummary())
            check.name = "Disk usage"
        case _:
            raise nagiosplugin.CheckError(f'Unknown check mode: {args.check_mode}')

    check.main(args.verbose, args.timeout)

if __name__ == '__main__':
    main()