"""Support gathering system information of hosts which are running netdata."""
from datetime import timedelta
import logging

from netdata import Netdata
from netdata.exceptions import NetdataError
import voluptuous as vol

from homeassistant.components.sensor import PLATFORM_SCHEMA
from homeassistant.const import (
    CONF_HOST,
    CONF_ICON,
    CONF_NAME,
    CONF_PORT,
    CONF_RESOURCES,
    UNIT_PERCENTAGE,
)
from homeassistant.exceptions import PlatformNotReady
from homeassistant.helpers.aiohttp_client import async_get_clientsession
import homeassistant.helpers.config_validation as cv
from homeassistant.helpers.entity import Entity
from homeassistant.util import Throttle

_LOGGER = logging.getLogger(__name__)

MIN_TIME_BETWEEN_UPDATES = timedelta(minutes=1)

CONF_DATA_GROUP = "data_group"
CONF_ELEMENT = "element"
CONF_INVERT = "invert"

DEFAULT_HOST = "localhost"
DEFAULT_NAME = "Netdata"
DEFAULT_PORT = 19999

DEFAULT_ICON = "mdi:desktop-classic"

RESOURCE_SCHEMA = vol.Any(
    {
        vol.Required(CONF_DATA_GROUP): cv.string,
        vol.Required(CONF_ELEMENT): cv.string,
        vol.Optional(CONF_ICON, default=DEFAULT_ICON): cv.icon,
        vol.Optional(CONF_INVERT, default=False): cv.boolean,
    }
)

PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
    {
        vol.Optional(CONF_HOST, default=DEFAULT_HOST): cv.string,
        vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
        vol.Optional(CONF_PORT, default=DEFAULT_PORT): cv.port,
        vol.Required(CONF_RESOURCES): vol.Schema({cv.string: RESOURCE_SCHEMA}),
    }
)


async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
    """Set up the Netdata sensor."""

    name = config.get(CONF_NAME)
    host = config.get(CONF_HOST)
    port = config.get(CONF_PORT)
    resources = config.get(CONF_RESOURCES)

    session = async_get_clientsession(hass)
    netdata = NetdataData(Netdata(host, hass.loop, session, port=port))
    await netdata.async_update()

    if netdata.api.metrics is None:
        raise PlatformNotReady

    dev = []
    for entry, data in resources.items():
        icon = data[CONF_ICON]
        sensor = data[CONF_DATA_GROUP]
        element = data[CONF_ELEMENT]
        invert = data[CONF_INVERT]
        sensor_name = entry
        try:
            resource_data = netdata.api.metrics[sensor]
            unit = (
                UNIT_PERCENTAGE
                if resource_data["units"] == "percentage"
                else resource_data["units"]
            )
        except KeyError:
            _LOGGER.error("Sensor is not available: %s", sensor)
            continue

        dev.append(
            NetdataSensor(
                netdata, name, sensor, sensor_name, element, icon, unit, invert
            )
        )

    async_add_entities(dev, True)


class NetdataSensor(Entity):
    """Implementation of a Netdata sensor."""

    def __init__(self, netdata, name, sensor, sensor_name, element, icon, unit, invert):
        """Initialize the Netdata sensor."""
        self.netdata = netdata
        self._state = None
        self._sensor = sensor
        self._element = element
        self._sensor_name = self._sensor if sensor_name is None else sensor_name
        self._name = name
        self._icon = icon
        self._unit_of_measurement = unit
        self._invert = invert

    @property
    def name(self):
        """Return the name of the sensor."""
        return f"{self._name} {self._sensor_name}"

    @property
    def unit_of_measurement(self):
        """Return the unit the value is expressed in."""
        return self._unit_of_measurement

    @property
    def icon(self):
        """Return the icon to use in the frontend, if any."""
        return self._icon

    @property
    def state(self):
        """Return the state of the resources."""
        return self._state

    @property
    def available(self):
        """Could the resource be accessed during the last update call."""
        return self.netdata.available

    async def async_update(self):
        """Get the latest data from Netdata REST API."""
        await self.netdata.async_update()
        resource_data = self.netdata.api.metrics.get(self._sensor)
        self._state = round(resource_data["dimensions"][self._element]["value"], 2) * (
            -1 if self._invert else 1
        )


class NetdataData:
    """The class for handling the data retrieval."""

    def __init__(self, api):
        """Initialize the data object."""
        self.api = api
        self.available = True

    @Throttle(MIN_TIME_BETWEEN_UPDATES)
    async def async_update(self):
        """Get the latest data from the Netdata REST API."""

        try:
            await self.api.get_allmetrics()
            self.available = True
        except NetdataError:
            _LOGGER.error("Unable to retrieve data from Netdata")
            self.available = False