"""The dhcp integration."""

from __future__ import annotations

import asyncio
from collections.abc import Callable
from dataclasses import dataclass
from datetime import timedelta
from fnmatch import translate
from functools import lru_cache
import itertools
import logging
import re
from typing import Any, Final

import aiodhcpwatcher
from aiodiscover import DiscoverHosts
from aiodiscover.discovery import (
    HOSTNAME as DISCOVERY_HOSTNAME,
    IP_ADDRESS as DISCOVERY_IP_ADDRESS,
    MAC_ADDRESS as DISCOVERY_MAC_ADDRESS,
)
from cached_ipaddress import cached_ip_addresses

from homeassistant import config_entries
from homeassistant.components.device_tracker import (
    ATTR_HOST_NAME,
    ATTR_IP,
    ATTR_MAC,
    ATTR_SOURCE_TYPE,
    CONNECTED_DEVICE_REGISTERED,
    DOMAIN as DEVICE_TRACKER_DOMAIN,
    SourceType,
)
from homeassistant.const import (
    EVENT_HOMEASSISTANT_STARTED,
    EVENT_HOMEASSISTANT_STOP,
    STATE_HOME,
)
from homeassistant.core import (
    Event,
    EventStateChangedData,
    HomeAssistant,
    State,
    callback,
)
from homeassistant.data_entry_flow import BaseServiceInfo
from homeassistant.helpers import (
    config_validation as cv,
    device_registry as dr,
    discovery_flow,
)
from homeassistant.helpers.device_registry import CONNECTION_NETWORK_MAC, format_mac
from homeassistant.helpers.dispatcher import async_dispatcher_connect
from homeassistant.helpers.event import (
    async_track_state_added_domain,
    async_track_time_interval,
)
from homeassistant.helpers.typing import ConfigType
from homeassistant.loader import DHCPMatcher, async_get_dhcp

from .const import DOMAIN

CONFIG_SCHEMA = cv.empty_config_schema(DOMAIN)

HOSTNAME: Final = "hostname"
MAC_ADDRESS: Final = "macaddress"
IP_ADDRESS: Final = "ip"
REGISTERED_DEVICES: Final = "registered_devices"
SCAN_INTERVAL = timedelta(minutes=60)


_LOGGER = logging.getLogger(__name__)


@dataclass(slots=True)
class DhcpServiceInfo(BaseServiceInfo):
    """Prepared info from dhcp entries."""

    ip: str
    hostname: str
    macaddress: str


@dataclass(slots=True)
class DhcpMatchers:
    """Prepared info from dhcp entries."""

    registered_devices_domains: set[str]
    no_oui_matchers: dict[str, list[DHCPMatcher]]
    oui_matchers: dict[str, list[DHCPMatcher]]


def async_index_integration_matchers(
    integration_matchers: list[DHCPMatcher],
) -> DhcpMatchers:
    """Index the integration matchers.

    We have three types of matchers:

    1. Registered devices
    2. Devices with no OUI - index by first char of lower() hostname
    3. Devices with OUI - index by OUI
    """
    registered_devices_domains: set[str] = set()
    no_oui_matchers: dict[str, list[DHCPMatcher]] = {}
    oui_matchers: dict[str, list[DHCPMatcher]] = {}
    for matcher in integration_matchers:
        domain = matcher["domain"]
        if REGISTERED_DEVICES in matcher:
            registered_devices_domains.add(domain)
            continue

        if mac_address := matcher.get(MAC_ADDRESS):
            oui_matchers.setdefault(mac_address[:6], []).append(matcher)
            continue

        if hostname := matcher.get(HOSTNAME):
            first_char = hostname[0].lower()
            no_oui_matchers.setdefault(first_char, []).append(matcher)

    return DhcpMatchers(
        registered_devices_domains=registered_devices_domains,
        no_oui_matchers=no_oui_matchers,
        oui_matchers=oui_matchers,
    )


async def async_setup(hass: HomeAssistant, config: ConfigType) -> bool:
    """Set up the dhcp component."""
    watchers: list[WatcherBase] = []
    address_data: dict[str, dict[str, str]] = {}
    integration_matchers = async_index_integration_matchers(await async_get_dhcp(hass))
    # For the passive classes we need to start listening
    # for state changes and connect the dispatchers before
    # everything else starts up or we will miss events
    device_watcher = DeviceTrackerWatcher(hass, address_data, integration_matchers)
    device_watcher.async_start()
    watchers.append(device_watcher)

    device_tracker_registered_watcher = DeviceTrackerRegisteredWatcher(
        hass, address_data, integration_matchers
    )
    device_tracker_registered_watcher.async_start()
    watchers.append(device_tracker_registered_watcher)

    async def _async_initialize(event: Event) -> None:
        await aiodhcpwatcher.async_init()

        network_watcher = NetworkWatcher(hass, address_data, integration_matchers)
        network_watcher.async_start()
        watchers.append(network_watcher)

        dhcp_watcher = DHCPWatcher(hass, address_data, integration_matchers)
        await dhcp_watcher.async_start()
        watchers.append(dhcp_watcher)

        @callback
        def _async_stop(event: Event) -> None:
            for watcher in watchers:
                watcher.async_stop()

        hass.bus.async_listen_once(EVENT_HOMEASSISTANT_STOP, _async_stop)

    hass.bus.async_listen_once(EVENT_HOMEASSISTANT_STARTED, _async_initialize)
    return True


class WatcherBase:
    """Base class for dhcp and device tracker watching."""

    def __init__(
        self,
        hass: HomeAssistant,
        address_data: dict[str, dict[str, str]],
        integration_matchers: DhcpMatchers,
    ) -> None:
        """Initialize class."""
        super().__init__()

        self.hass = hass
        self._integration_matchers = integration_matchers
        self._address_data = address_data
        self._unsub: Callable[[], None] | None = None

    @callback
    def async_stop(self) -> None:
        """Stop scanning for new devices on the network."""
        if self._unsub:
            self._unsub()
            self._unsub = None

    @callback
    def async_process_client(
        self, ip_address: str, hostname: str, unformatted_mac_address: str
    ) -> None:
        """Process a client."""
        if (made_ip_address := cached_ip_addresses(ip_address)) is None:
            # Ignore invalid addresses
            _LOGGER.debug("Ignoring invalid IP Address: %s", ip_address)
            return

        if (
            made_ip_address.is_link_local
            or made_ip_address.is_loopback
            or made_ip_address.is_unspecified
        ):
            # Ignore self assigned addresses, loopback, invalid
            return

        formatted_mac = format_mac(unformatted_mac_address)
        # Historically, the MAC address was formatted without colons
        # and since all consumers of this data are expecting it to be
        # formatted without colons we will continue to do so
        mac_address = formatted_mac.replace(":", "")

        data = self._address_data.get(ip_address)
        if (
            data
            and data[MAC_ADDRESS] == mac_address
            and data[HOSTNAME].startswith(hostname)
        ):
            # If the address data is the same no need
            # to process it
            return

        data = {MAC_ADDRESS: mac_address, HOSTNAME: hostname}
        self._address_data[ip_address] = data

        lowercase_hostname = hostname.lower()
        uppercase_mac = mac_address.upper()

        _LOGGER.debug(
            "Processing updated address data for %s: mac=%s hostname=%s",
            ip_address,
            uppercase_mac,
            lowercase_hostname,
        )

        matched_domains: set[str] = set()
        matchers = self._integration_matchers
        registered_devices_domains = matchers.registered_devices_domains

        dev_reg = dr.async_get(self.hass)
        if device := dev_reg.async_get_device(
            connections={(CONNECTION_NETWORK_MAC, formatted_mac)}
        ):
            for entry_id in device.config_entries:
                if (
                    entry := self.hass.config_entries.async_get_entry(entry_id)
                ) and entry.domain in registered_devices_domains:
                    matched_domains.add(entry.domain)

        oui = uppercase_mac[:6]
        lowercase_hostname_first_char = (
            lowercase_hostname[0] if len(lowercase_hostname) else ""
        )
        for matcher in itertools.chain(
            matchers.no_oui_matchers.get(lowercase_hostname_first_char, ()),
            matchers.oui_matchers.get(oui, ()),
        ):
            domain = matcher["domain"]
            if (
                matcher_hostname := matcher.get(HOSTNAME)
            ) is not None and not _memorized_fnmatch(
                lowercase_hostname, matcher_hostname
            ):
                continue

            _LOGGER.debug("Matched %s against %s", data, matcher)
            matched_domains.add(domain)

        for domain in matched_domains:
            discovery_flow.async_create_flow(
                self.hass,
                domain,
                {"source": config_entries.SOURCE_DHCP},
                DhcpServiceInfo(
                    ip=ip_address,
                    hostname=lowercase_hostname,
                    macaddress=mac_address,
                ),
            )


class NetworkWatcher(WatcherBase):
    """Class to query ptr records routers."""

    def __init__(
        self,
        hass: HomeAssistant,
        address_data: dict[str, dict[str, str]],
        integration_matchers: DhcpMatchers,
    ) -> None:
        """Initialize class."""
        super().__init__(hass, address_data, integration_matchers)
        self._discover_hosts: DiscoverHosts | None = None
        self._discover_task: asyncio.Task | None = None

    @callback
    def async_stop(self) -> None:
        """Stop scanning for new devices on the network."""
        super().async_stop()
        if self._discover_task:
            self._discover_task.cancel()
            self._discover_task = None

    @callback
    def async_start(self) -> None:
        """Start scanning for new devices on the network."""
        self._discover_hosts = DiscoverHosts()
        self._unsub = async_track_time_interval(
            self.hass,
            self.async_start_discover,
            SCAN_INTERVAL,
            name="DHCP network watcher",
        )
        self.async_start_discover()

    @callback
    def async_start_discover(self, *_: Any) -> None:
        """Start a new discovery task if one is not running."""
        if self._discover_task and not self._discover_task.done():
            return
        self._discover_task = self.hass.async_create_background_task(
            self.async_discover(), name="dhcp discovery", eager_start=True
        )

    async def async_discover(self) -> None:
        """Process discovery."""
        assert self._discover_hosts is not None
        for host in await self._discover_hosts.async_discover():
            self.async_process_client(
                host[DISCOVERY_IP_ADDRESS],
                host[DISCOVERY_HOSTNAME],
                host[DISCOVERY_MAC_ADDRESS],
            )


class DeviceTrackerWatcher(WatcherBase):
    """Class to watch dhcp data from routers."""

    @callback
    def async_start(self) -> None:
        """Stop watching for new device trackers."""
        self._unsub = async_track_state_added_domain(
            self.hass, [DEVICE_TRACKER_DOMAIN], self._async_process_device_event
        )
        for state in self.hass.states.async_all(DEVICE_TRACKER_DOMAIN):
            self._async_process_device_state(state)

    @callback
    def _async_process_device_event(self, event: Event[EventStateChangedData]) -> None:
        """Process a device tracker state change event."""
        self._async_process_device_state(event.data["new_state"])

    @callback
    def _async_process_device_state(self, state: State | None) -> None:
        """Process a device tracker state."""
        if state is None or state.state != STATE_HOME:
            return

        attributes = state.attributes

        if attributes.get(ATTR_SOURCE_TYPE) != SourceType.ROUTER:
            return

        ip_address = attributes.get(ATTR_IP)
        hostname = attributes.get(ATTR_HOST_NAME, "")
        mac_address = attributes.get(ATTR_MAC)

        if ip_address is None or mac_address is None:
            return

        self.async_process_client(ip_address, hostname, mac_address)


class DeviceTrackerRegisteredWatcher(WatcherBase):
    """Class to watch data from device tracker registrations."""

    @callback
    def async_start(self) -> None:
        """Stop watching for device tracker registrations."""
        self._unsub = async_dispatcher_connect(
            self.hass, CONNECTED_DEVICE_REGISTERED, self._async_process_device_data
        )

    @callback
    def _async_process_device_data(self, data: dict[str, str | None]) -> None:
        """Process a device tracker state."""
        ip_address = data[ATTR_IP]
        hostname = data[ATTR_HOST_NAME] or ""
        mac_address = data[ATTR_MAC]

        if ip_address is None or mac_address is None:
            return

        self.async_process_client(ip_address, hostname, mac_address)


class DHCPWatcher(WatcherBase):
    """Class to watch dhcp requests."""

    @callback
    def _async_process_dhcp_request(self, response: aiodhcpwatcher.DHCPRequest) -> None:
        """Process a dhcp request."""
        self.async_process_client(
            response.ip_address, response.hostname, response.mac_address
        )

    async def async_start(self) -> None:
        """Start watching for dhcp packets."""
        self._unsub = await aiodhcpwatcher.async_start(self._async_process_dhcp_request)


@lru_cache(maxsize=4096, typed=True)
def _compile_fnmatch(pattern: str) -> re.Pattern:
    """Compile a fnmatch pattern."""
    return re.compile(translate(pattern))


@lru_cache(maxsize=1024, typed=True)
def _memorized_fnmatch(name: str, pattern: str) -> bool:
    """Memorized version of fnmatch that has a larger lru_cache.

    The default version of fnmatch only has a lru_cache of 256 entries.
    With many devices we quickly reach that limit and end up compiling
    the same pattern over and over again.

    DHCP has its own memorized fnmatch with its own lru_cache
    since the data is going to be relatively the same
    since the devices will not change frequently
    """
    return bool(_compile_fnmatch(pattern).match(name))
