import logging
import os
import subprocess
import warnings


logger = logging.getLogger()


class RADVDSvc(object):
    svc_name = 'radvd'

    def __init__(self):
        self.name = self.svc_name
        self.is_systemd = False
        self._get_manager()

    def _get_manager(self):
        chkpaths = ('/run/systemd/system',
                    '/dev/.run/systemd',
                    '/dev/.systemd')
        for _ in chkpaths:
            if os.path.exists(_):
                self.is_systemd = True
                break
        return(None)

    def restart(self):
        if self.is_systemd:
            cmd = ['systemd', 'restart', self.name]
        else:
            # Systemd haters, if you don't understand the benefits of unified service management across all linux
            # distros, you've obviously never done wide-platform management or scripting.
            # Let this else block be a learning experience for you.
            cmd = None
            has_pkill = False
            for p in os.environ.get('PATH', '/usr/bin').split(':'):
                fpath = os.path.abspath(os.path.expanduser(p))
                bins = os.listdir(fpath)
                if 'pkill' in bins:
                    has_pkill = True
                if 'service' in bins:  # CentOS/RHEL pre-7.x
                    cmd = ['service', self.name, 'restart']
                    break
                elif 'initctl' in bins:  # older Ubuntu and other Upstart distros
                    cmd = ['initctl', 'restart', self.name]
                    break
                elif 'rc-service' in bins:  # OpenRC
                    cmd = ['rc-service', self.name, 'restart']
                    break
                # That wasn't even all of them.
            if not cmd and has_pkill:  # last-ditch effort.
                cmd = ['pkill', '-HUP', self.name]
            if not cmd:
                logger.error('Could not find which service manager this system is using.')
                raise RuntimeError('Could not determine service manager')
            cmd_exec = subprocess.run(cmd, stdin = subprocess.PIPE, stdout = subprocess.PIPE)
            if cmd_exec.returncode != 0:
                logger.warning('Could not successfully restart {0}; returned status {1}'.format(self.name,
                                                                                                cmd_exec.returncode))
                for i in ('stdout', 'stderr'):
                    s = getattr(cmd_exec, i).decode('utf-8')
                    if s.strip() != '':
                        logger.warning('{0}: {1}'.format(i.upper(), s))
                warnings.warn('Service did not restart successfully')
        return(None)


class RADVDConf(object):
    path = '/etc/radvd.conf'
    tpl = ('interface {iface} {{\n'
           '\tAdvSendAdvert on;\n'
           # '\tAdvLinkMTU 1280;\n'  # Is it 1480 or 1280? Arch wiki says 1480, but everything else (older) says 1280.
           '\tAdvLinkMTU 1480;\n'
           '\tMinRtrAdvInterval 60;\n'
           '\tMaxRtrAdvInterval 600;\n'
           '\tAdvDefaultLifetime 9000;\n'
           '{prefix}'
           'route ::/0 {{\n'
           '\t\tAdvRouteLifetime infinity;'
           '}};\n'
           '{rdnss}'
           '}};\n\n')
    tpl_prefix = ('\tprefix {subnet} {{\n'
                  '\t\tAdvOnLink on;'
                  '\t\tAdvAutonomous on;'
                  '\t\tAdvRouterAddr off;\n'
                  '}};\n')
    tpl_rdnss = ('\tRDNSS {client_ip} {{\n'
                 '\t\tAdvRDNSSOpen on;\n'
                 '\t\tAdvRDNSSPreference 2;\n'
                 '}};\n')

    def __init__(self, cfg = None):
        if not cfg:
            self.cfg = self.path
        else:
            self.cfg = os.path.abspath(os.path.expanduser(cfg))
        self.cfgStr = None

    def generate(self, assign_objs):
        self.cfgStr = ''
        for assign_obj in assign_objs:
            prefix = self.tpl_prefix.format(subnet = str(assign_obj.net))
            if assign_obj.dns:
                dns = self.tpl_rdnss.format(client_ip = assign_obj.iface_ip.str)
            else:
                dns = ''
            self.cfgStr += self.tpl.format(prefix = prefix, rdnss = dns)


class RADVD(object):
    def __init__(self):
        self.svc = RADVDSvc()
        self.conf = RADVDConf(cfg = '/etc/radvd.conf')