#
#   utilities.py
#
#   Commonly used general functions
#

import re
import os
import socket
import inspect
from systemd import journal
from datetime import datetime, timedelta

import logging
logger = logging.getLogger(__name__)

from pkg_resources import Requirement, resource_filename

from . import config

def hostname(path): # get the hostname of current server
    hnfile = open(path, 'r')
    hn = re.search('^(\w*)\n*', hnfile.read()).group(1)
    return hn

def getlocaldomain(): # get the parent fqdn of current server
    domain = socket.getfqdn().split('.', 1) # Note: if socket.fetfqdn() returns localhost, make sure the first entry in /etc/hosts contains the fqdn
    if len(domain) != 2:
        logger.warning('Could not get domain of this server, only hostname. Please consider updating /etc/hosts')
        return 'localdomain'
    else:
        return domain[-1]

def resolve(ip, fqdn=None):        # try to resolve an ip to hostname
    # Possible values for fqdn:
    #   fqdn            show full hostname and domain
    #   fqdn-implicit   show hostname and domain unless local
    #   host-only       only show hostname
    #   ip              never resolve anything
    # resolve-domains defined in individual sections of the config take priority over global config
    
    if not fqdn:
        fqdn = config.prefs['resolve-domains']

    if fqdn == 'ip':
        return(ip)

    try:
        socket.inet_aton(ip)  # succeeds if text contains ip
        hn = socket.gethostbyaddr(ip)[0] # resolve ip to hostname
        if fqdn == 'fqdn-implicit' and hn.split('.', 1)[1] == getlocaldomain():
            return(hn.split('.')[0])
        elif fqdn == 'fqdn' or fqdn == 'fqdn-implicit':
            return(hn)
        elif fqdn == 'host-only':
            return(hn.split('.')[0])
        else:
            logger.warning("invalid value for fqdn config")
            return(hn)
    except socket.herror:
        # cannot resolve ip
        logger.debug(ip + " cannot be found, might not exist anymore")
        return(ip)
    except (OSError, socket.error): # socket.error for Python 2 compatibility
        # already a hostname
        logger.debug(ip + " is already a hostname")
        return(ip)
    except Exception as err:
        logger.warning("failed to resolve hostname for " + ip + ": " + str(err))
        return(ip)  # return ip if no hostname exists

def readlog(path = None, mode = 'r'):   # read file
    if (path == None):
        logger.error("no path provided")
        return
    else:
        if (os.path.isfile(path) is False):
            logger.error("Log at {0} was requested but does not exist".format(path))
            return ''
        else:
            try:
                return open(path, mode).read()
            except IOError or OSError as e:
                logger.warning("Error reading log at {0}: {1}".format(path, e.strerror))
                return 1