# SPDX-License-Identifier: AGPL-3.0-or-later

import atexit
import asyncio
import ipaddress
from itertools import cycle

import httpx

from .client import new_client, get_loop, AsyncHTTPTransportNoHttp


DEFAULT_NAME = '__DEFAULT__'
NETWORKS = {}
# requests compatibility when reading proxy settings from settings.yml
PROXY_PATTERN_MAPPING = {
    'http': 'http://',
    'https': 'https://',
    'socks4': 'socks4://',
    'socks5': 'socks5://',
    'socks5h': 'socks5h://',
    'http:': 'http://',
    'https:': 'https://',
    'socks4:': 'socks4://',
    'socks5:': 'socks5://',
    'socks5h:': 'socks5h://',
}

ADDRESS_MAPPING = {
    'ipv4': '0.0.0.0',
    'ipv6': '::'
}


class Network:

    __slots__ = ('enable_http', 'verify', 'enable_http2',
                 'max_connections', 'max_keepalive_connections', 'keepalive_expiry',
                 'local_addresses', 'proxies', 'using_tor_proxy', 'max_redirects', 'retries', 'retry_on_http_error',
                 '_local_addresses_cycle', '_proxies_cycle', '_clients')

    _TOR_CHECK_RESULT = {}

    def __init__(self,
                 enable_http=True,
                 verify=True,
                 enable_http2=False,
                 max_connections=None,
                 max_keepalive_connections=None,
                 keepalive_expiry=None,
                 proxies=None,
                 using_tor_proxy=False,
                 local_addresses=None,
                 retries=0,
                 retry_on_http_error=None,
                 max_redirects=30):
        self.enable_http = enable_http
        self.verify = verify
        self.enable_http2 = enable_http2
        self.max_connections = max_connections
        self.max_keepalive_connections = max_keepalive_connections
        self.keepalive_expiry = keepalive_expiry
        self.proxies = proxies
        self.using_tor_proxy = using_tor_proxy
        self.local_addresses = local_addresses
        self.retries = retries
        self.retry_on_http_error = retry_on_http_error
        self.max_redirects = max_redirects
        self._local_addresses_cycle = self.get_ipaddress_cycle()
        self._proxies_cycle = self.get_proxy_cycles()
        self._clients = {}
        self.check_parameters()

    def check_parameters(self):
        for address in self.iter_ipaddresses():
            if '/' in address:
                ipaddress.ip_network(address, False)
            else:
                ipaddress.ip_address(address)

        if self.proxies is not None and not isinstance(self.proxies, (str, dict)):
            raise ValueError('proxies type has to be str, dict or None')

    def iter_ipaddresses(self):
        local_addresses = self.local_addresses
        if not local_addresses:
            return
        elif isinstance(local_addresses, str):
            local_addresses = [local_addresses]
        for address in local_addresses:
            yield address

    def get_ipaddress_cycle(self):
        while True:
            count = 0
            for address in self.iter_ipaddresses():
                if '/' in address:
                    for a in ipaddress.ip_network(address, False).hosts():
                        yield str(a)
                        count += 1
                else:
                    a = ipaddress.ip_address(address)
                    yield str(a)
                    count += 1
            if count == 0:
                yield None

    def iter_proxies(self):
        if not self.proxies:
            return
        # https://www.python-httpx.org/compatibility/#proxy-keys
        if isinstance(self.proxies, str):
            yield 'all://', [self.proxies]
        else:
            for pattern, proxy_url in self.proxies.items():
                pattern = PROXY_PATTERN_MAPPING.get(pattern, pattern)
                if isinstance(proxy_url, str):
                    proxy_url = [proxy_url]
                yield pattern, proxy_url

    def get_proxy_cycles(self):
        proxy_settings = {}
        for pattern, proxy_urls in self.iter_proxies():
            proxy_settings[pattern] = cycle(proxy_urls)
        while True:
            yield tuple((pattern, next(proxy_url_cycle)) for pattern, proxy_url_cycle in proxy_settings.items())

    @staticmethod
    async def check_tor_proxy(client: httpx.AsyncClient, proxies) -> bool:
        if proxies in Network._TOR_CHECK_RESULT:
            return Network._TOR_CHECK_RESULT[proxies]

        result = True
        # ignore client._transport because it is not used with all://
        for transport in client._mounts.values():  # pylint: disable=protected-access
            if isinstance(transport, AsyncHTTPTransportNoHttp):
                continue
            if not getattr(transport, '_rdns', False):
                result = False
                break
        else:
            response = await client.get('https://check.torproject.org/api/ip')
            if not response.json()['IsTor']:
                result = False
        Network._TOR_CHECK_RESULT[proxies] = result
        return result

    async def get_client(self, verify=None, max_redirects=None):
        verify = self.verify if verify is None else verify
        max_redirects = self.max_redirects if max_redirects is None else max_redirects
        local_address = next(self._local_addresses_cycle)
        proxies = next(self._proxies_cycle)  # is a tuple so it can be part of the key
        key = (verify, max_redirects, local_address, proxies)
        if key not in self._clients or self._clients[key].is_closed:
            client = new_client(
                self.enable_http,
                verify,
                self.enable_http2,
                self.max_connections,
                self.max_keepalive_connections,
                self.keepalive_expiry,
                dict(proxies),
                local_address,
                0,
                max_redirects
            )
            if self.using_tor_proxy and not await self.check_tor_proxy(client, proxies):
                await client.aclose()
                raise httpx.ProxyError('Network configuration problem: not using Tor')
            self._clients[key] = client
        return self._clients[key]

    async def aclose(self):
        async def close_client(client):
            try:
                await client.aclose()
            except httpx.HTTPError:
                pass
        await asyncio.gather(*[close_client(client) for client in self._clients.values()], return_exceptions=False)

    @staticmethod
    def get_kwargs_clients(kwargs):
        kwargs_clients = {}
        if 'verify' in kwargs:
            kwargs_clients['verify'] = kwargs.pop('verify')
        if 'max_redirects' in kwargs:
            kwargs_clients['max_redirects'] = kwargs.pop('max_redirects')
        return kwargs_clients

    def is_valid_respones(self, response):
        if (self.retry_on_http_error is True and 400 <= response.status_code <= 599) \
           or (isinstance(self.retry_on_http_error, list) and response.status_code in self.retry_on_http_error) \
           or (isinstance(self.retry_on_http_error, int) and response.status_code == self.retry_on_http_error):
            return False
        return True

    async def request(self, method, url, **kwargs):
        retries = self.retries
        while retries >= 0:  # pragma: no cover
            kwargs_clients = Network.get_kwargs_clients(kwargs)
            client = await self.get_client(**kwargs_clients)
            try:
                response = await client.request(method, url, **kwargs)
                if self.is_valid_respones(response) or retries <= 0:
                    return response
            except (httpx.RequestError, httpx.HTTPStatusError) as e:
                if retries <= 0:
                    raise e
            retries -= 1

    async def stream(self, method, url, **kwargs):
        retries = self.retries
        while retries >= 0:  # pragma: no cover
            kwargs_clients = Network.get_kwargs_clients(kwargs)
            client = await self.get_client(**kwargs_clients)
            try:
                response = client.stream(method, url, **kwargs)
                if self.is_valid_respones(response) or retries <= 0:
                    return response
            except (httpx.RequestError, httpx.HTTPStatusError) as e:
                if retries <= 0:
                    raise e
            retries -= 1

    @classmethod
    async def aclose_all(cls):
        await asyncio.gather(*[network.aclose() for network in NETWORKS.values()], return_exceptions=False)


def get_network(name=None):
    global NETWORKS
    return NETWORKS[name or DEFAULT_NAME]


def check_network_configuration():
    async def check():
        exception_count = 0
        for network in NETWORKS.values():
            if network.using_tor_proxy:
                try:
                    await network.get_client()
                except Exception:  # pylint: disable=broad-except
                    exception_count += 1
        return exception_count
    future = asyncio.run_coroutine_threadsafe(check(), get_loop())
    exception_count = future.result()
    if exception_count > 0:
        raise RuntimeError("Invalid network configuration")


def initialize(settings_engines=None, settings_outgoing=None):
    from searx.engines import engines
    from searx import settings

    global NETWORKS

    settings_engines = settings_engines or settings.get('engines')
    settings_outgoing = settings_outgoing or settings.get('outgoing')

    # default parameters for AsyncHTTPTransport
    # see https://github.com/encode/httpx/blob/e05a5372eb6172287458b37447c30f650047e1b8/httpx/_transports/default.py#L108-L121  # noqa
    default_params = {
        'enable_http': False,
        'verify': True,
        'enable_http2': settings_outgoing.get('enable_http2', True),
        # Magic number kept from previous code
        'max_connections': settings_outgoing.get('pool_connections', 100),
        # Picked from constructor
        'max_keepalive_connections': settings_outgoing.get('pool_maxsize', 10),
        #
        'keepalive_expiry': settings_outgoing.get('keepalive_expiry', 5.0),
        'local_addresses': settings_outgoing.get('source_ips'),
        'proxies': settings_outgoing.get('proxies'),
        'using_tor_proxy': settings_outgoing.get('using_tor_proxy'),
        # default maximum redirect
        # from https://github.com/psf/requests/blob/8c211a96cdbe9fe320d63d9e1ae15c5c07e179f8/requests/models.py#L55
        'max_redirects': settings_outgoing.get('max_redirects', 30),
        #
        'retries': settings_outgoing.get('retries', 0),
        'retry_on_http_error': None,
    }

    def new_network(params):
        nonlocal default_params
        result = {}
        result.update(default_params)
        result.update(params)
        return Network(**result)

    def iter_networks():
        nonlocal settings_engines
        for engine_spec in settings_engines:
            engine_name = engine_spec['name']
            engine = engines.get(engine_name)
            if engine is None:
                continue
            network = getattr(engine, 'network', None)
            yield engine_name, engine, network

    if NETWORKS:
        done()
    NETWORKS.clear()
    NETWORKS[DEFAULT_NAME] = new_network({})
    NETWORKS['ipv4'] = new_network({'local_addresses': '0.0.0.0'})
    NETWORKS['ipv6'] = new_network({'local_addresses': '::'})

    # define networks from outgoing.networks
    for network_name, network in settings_outgoing.get('networks', {}).items():
        NETWORKS[network_name] = new_network(network)

    # define networks from engines.[i].network (except references)
    for engine_name, engine, network in iter_networks():
        if network is None:
            network = {}
            for attribute_name, attribute_value in default_params.items():
                if hasattr(engine, attribute_name):
                    network[attribute_name] = getattr(engine, attribute_name)
                else:
                    network[attribute_name] = attribute_value
            NETWORKS[engine_name] = new_network(network)
        elif isinstance(network, dict):
            NETWORKS[engine_name] = new_network(network)

    # define networks from engines.[i].network (references)
    for engine_name, engine, network in iter_networks():
        if isinstance(network, str):
            NETWORKS[engine_name] = NETWORKS[network]

    # the /image_proxy endpoint has a dedicated network.
    # same parameters than the default network, but HTTP/2 is disabled.
    # It decreases the CPU load average, and the total time is more or less the same
    if 'image_proxy' not in NETWORKS:
        image_proxy_params = default_params.copy()
        image_proxy_params['enable_http2'] = False
        NETWORKS['image_proxy'] = new_network(image_proxy_params)


@atexit.register
def done():
    """Close all HTTP client

    Avoid a warning at exit
    see https://github.com/encode/httpx/blob/1a6e254f72d9fd5694a1c10a28927e193ab4f76b/httpx/_client.py#L1785

    Note: since Network.aclose has to be async, it is not possible to call this method on Network.__del__
    So Network.aclose is called here using atexit.register
    """
    try:
        loop = get_loop()
        if loop:
            future = asyncio.run_coroutine_threadsafe(Network.aclose_all(), loop)
            # wait 3 seconds to close the HTTP clients
            future.result(3)
    finally:
        NETWORKS.clear()


NETWORKS[DEFAULT_NAME] = Network()