"""
Support for THOMSON routers.

For more details about this platform, please refer to the documentation at
https://home-assistant.io/components/device_tracker.thomson/
"""
import logging
import re
import telnetlib
import threading
from datetime import timedelta

from homeassistant.components.device_tracker import DOMAIN
from homeassistant.const import CONF_HOST, CONF_PASSWORD, CONF_USERNAME
from homeassistant.helpers import validate_config
from homeassistant.util import Throttle

# Return cached results if last scan was less then this time ago.
MIN_TIME_BETWEEN_SCANS = timedelta(seconds=10)

_LOGGER = logging.getLogger(__name__)

_DEVICES_REGEX = re.compile(
    r'(?P<mac>(([0-9a-f]{2}[:-]){5}([0-9a-f]{2})))\s' +
    r'(?P<ip>([0-9]{1,3}[\.]){3}[0-9]{1,3})\s+' +
    r'(?P<status>([^\s]+))\s+' +
    r'(?P<type>([^\s]+))\s+' +
    r'(?P<intf>([^\s]+))\s+' +
    r'(?P<hwintf>([^\s]+))\s+' +
    r'(?P<host>([^\s]+))')


# pylint: disable=unused-argument
def get_scanner(hass, config):
    """Validate the configuration and return a THOMSON scanner."""
    if not validate_config(config,
                           {DOMAIN: [CONF_HOST, CONF_USERNAME, CONF_PASSWORD]},
                           _LOGGER):
        return None

    scanner = ThomsonDeviceScanner(config[DOMAIN])

    return scanner if scanner.success_init else None


class ThomsonDeviceScanner(object):
    """This class queries a router running THOMSON firmware."""

    def __init__(self, config):
        """Initialize the scanner."""
        self.host = config[CONF_HOST]
        self.username = config[CONF_USERNAME]
        self.password = config[CONF_PASSWORD]

        self.lock = threading.Lock()

        self.last_results = {}

        # Test the router is accessible.
        data = self.get_thomson_data()
        self.success_init = data is not None

    def scan_devices(self):
        """Scan for new devices and return a list with found device IDs."""
        self._update_info()
        return [client['mac'] for client in self.last_results]

    def get_device_name(self, device):
        """Return the name of the given device or None if we don't know."""
        if not self.last_results:
            return None
        for client in self.last_results:
            if client['mac'] == device:
                return client['host']
        return None

    @Throttle(MIN_TIME_BETWEEN_SCANS)
    def _update_info(self):
        """Ensure the information from the THOMSON router is up to date.

        Return boolean if scanning successful.
        """
        if not self.success_init:
            return False

        with self.lock:
            _LOGGER.info("Checking ARP")
            data = self.get_thomson_data()
            if not data:
                return False

            # Flag C stands for CONNECTED
            active_clients = [client for client in data.values() if
                              client['status'].find('C') != -1]
            self.last_results = active_clients
            return True

    def get_thomson_data(self):
        """Retrieve data from THOMSON and return parsed result."""
        try:
            telnet = telnetlib.Telnet(self.host)
            telnet.read_until(b'Username : ')
            telnet.write((self.username + '\r\n').encode('ascii'))
            telnet.read_until(b'Password : ')
            telnet.write((self.password + '\r\n').encode('ascii'))
            telnet.read_until(b'=>')
            telnet.write(('hostmgr list\r\n').encode('ascii'))
            devices_result = telnet.read_until(b'=>').split(b'\r\n')
            telnet.write('exit\r\n'.encode('ascii'))
        except EOFError:
            _LOGGER.exception("Unexpected response from router")
            return
        except ConnectionRefusedError:
            _LOGGER.exception("Connection refused by router," +
                              " is telnet enabled?")
            return

        devices = {}
        for device in devices_result:
            match = _DEVICES_REGEX.search(device.decode('utf-8'))
            if match:
                devices[match.group('ip')] = {
                    'ip': match.group('ip'),
                    'mac': match.group('mac').upper(),
                    'host': match.group('host'),
                    'status': match.group('status')
                    }
        return devices
