import logging
import os
import os.path
import socket
import sys
from base64 import b64encode

from urllib3 import PoolManager, Timeout, proxy_from_url
from urllib3.exceptions import (
    ConnectTimeoutError as URLLib3ConnectTimeoutError,
)
from urllib3.exceptions import (
    LocationParseError,
    NewConnectionError,
    ProtocolError,
    ProxyError,
)
from urllib3.exceptions import ReadTimeoutError as URLLib3ReadTimeoutError
from urllib3.exceptions import SSLError as URLLib3SSLError
from urllib3.util.retry import Retry
from urllib3.util.ssl_ import (
    OP_NO_COMPRESSION,
    PROTOCOL_TLS,
    OP_NO_SSLv2,
    OP_NO_SSLv3,
    is_ipaddress,
    ssl,
)
from urllib3.util.url import parse_url

from concurrent.futures import CancelledError

try:
    from urllib3.util.ssl_ import OP_NO_TICKET, PROTOCOL_TLS_CLIENT
except ImportError:
    # Fallback directly to ssl for version of urllib3 before 1.26.
    # They are available in the standard library starting in Python 3.6.
    from ssl import OP_NO_TICKET, PROTOCOL_TLS_CLIENT

try:
    # Always import the original SSLContext, even if it has been patched
    from urllib3.contrib.pyopenssl import orig_util_SSLContext as SSLContext
except ImportError:
    from urllib3.util.ssl_ import SSLContext

try:
    from urllib3.util.ssl_ import DEFAULT_CIPHERS
except ImportError:
    # Defer to system configuration starting with
    # urllib3 2.0. This will choose the ciphers provided by
    # Openssl 1.1.1+ or secure system defaults.
    DEFAULT_CIPHERS = None

import botocore.awsrequest
from botocore.compat import (
    IPV6_ADDRZ_RE,
    ensure_bytes,
    filter_ssl_warnings,
    unquote,
    urlparse,
)
from botocore.exceptions import (
    ConnectionClosedError,
    ConnectTimeoutError,
    EndpointConnectionError,
    HTTPClientError,
    InvalidProxiesConfigError,
    ProxyConnectionError,
    ReadTimeoutError,
    SSLError,
)

filter_ssl_warnings()
logger = logging.getLogger(__name__)
DEFAULT_TIMEOUT = 60
MAX_POOL_CONNECTIONS = 10
DEFAULT_CA_BUNDLE = os.path.join(os.path.dirname(__file__), 'cacert.pem')

try:
    from certifi import where
except ImportError:

    def where():
        return DEFAULT_CA_BUNDLE


def get_cert_path(verify):
    if verify is not True:
        return verify

    cert_path = where()
    logger.debug(f"Certificate path: {cert_path}")

    return cert_path


def create_urllib3_context(
    ssl_version=None, cert_reqs=None, options=None, ciphers=None
):
    """This function is a vendored version of the same function in urllib3

    We vendor this function to ensure that the SSL contexts we construct
    always use the std lib SSLContext instead of pyopenssl.
    """
    # PROTOCOL_TLS is deprecated in Python 3.10
    if not ssl_version or ssl_version == PROTOCOL_TLS:
        ssl_version = PROTOCOL_TLS_CLIENT

    context = SSLContext(ssl_version)

    if ciphers:
        context.set_ciphers(ciphers)
    elif DEFAULT_CIPHERS:
        context.set_ciphers(DEFAULT_CIPHERS)

    # Setting the default here, as we may have no ssl module on import
    cert_reqs = ssl.CERT_REQUIRED if cert_reqs is None else cert_reqs

    if options is None:
        options = 0
        # SSLv2 is easily broken and is considered harmful and dangerous
        options |= OP_NO_SSLv2
        # SSLv3 has several problems and is now dangerous
        options |= OP_NO_SSLv3
        # Disable compression to prevent CRIME attacks for OpenSSL 1.0+
        # (issue urllib3#309)
        options |= OP_NO_COMPRESSION
        # TLSv1.2 only. Unless set explicitly, do not request tickets.
        # This may save some bandwidth on wire, and although the ticket is encrypted,
        # there is a risk associated with it being on wire,
        # if the server is not rotating its ticketing keys properly.
        options |= OP_NO_TICKET

    context.options |= options

    # Enable post-handshake authentication for TLS 1.3, see GH #1634. PHA is
    # necessary for conditional client cert authentication with TLS 1.3.
    # The attribute is None for OpenSSL <= 1.1.0 or does not exist in older
    # versions of Python.  We only enable on Python 3.7.4+ or if certificate
    # verification is enabled to work around Python issue #37428
    # See: https://bugs.python.org/issue37428
    if (
        cert_reqs == ssl.CERT_REQUIRED or sys.version_info >= (3, 7, 4)
    ) and getattr(context, "post_handshake_auth", None) is not None:
        context.post_handshake_auth = True

    def disable_check_hostname():
        if (
            getattr(context, "check_hostname", None) is not None
        ):  # Platform-specific: Python 3.2
            # We do our own verification, including fingerprints and alternative
            # hostnames. So disable it here
            context.check_hostname = False

    # The order of the below lines setting verify_mode and check_hostname
    # matter due to safe-guards SSLContext has to prevent an SSLContext with
    # check_hostname=True, verify_mode=NONE/OPTIONAL. This is made even more
    # complex because we don't know whether PROTOCOL_TLS_CLIENT will be used
    # or not so we don't know the initial state of the freshly created SSLContext.
    if cert_reqs == ssl.CERT_REQUIRED:
        context.verify_mode = cert_reqs
        disable_check_hostname()
    else:
        disable_check_hostname()
        context.verify_mode = cert_reqs

    # Enable logging of TLS session keys via defacto standard environment variable
    # 'SSLKEYLOGFILE', if the feature is available (Python 3.8+). Skip empty values.
    if hasattr(context, "keylog_filename"):
        sslkeylogfile = os.environ.get("SSLKEYLOGFILE")
        if sslkeylogfile and not sys.flags.ignore_environment:
            context.keylog_filename = sslkeylogfile

    return context


def ensure_boolean(val):
    """Ensures a boolean value if a string or boolean is provided

    For strings, the value for True/False is case insensitive
    """
    if isinstance(val, bool):
        return val
    else:
        return val.lower() == 'true'


def mask_proxy_url(proxy_url):
    """
    Mask proxy url credentials.

    :type proxy_url: str
    :param proxy_url: The proxy url, i.e. https://username:password@proxy.com

    :return: Masked proxy url, i.e. https://***:***@proxy.com
    """
    mask = '*' * 3
    parsed_url = urlparse(proxy_url)
    if parsed_url.username:
        proxy_url = proxy_url.replace(parsed_url.username, mask, 1)
    if parsed_url.password:
        proxy_url = proxy_url.replace(parsed_url.password, mask, 1)
    return proxy_url


def _is_ipaddress(host):
    """Wrap urllib3's is_ipaddress to support bracketed IPv6 addresses."""
    return is_ipaddress(host) or bool(IPV6_ADDRZ_RE.match(host))


class ProxyConfiguration:
    """Represents a proxy configuration dictionary and additional settings.

    This class represents a proxy configuration dictionary and provides utility
    functions to retreive well structured proxy urls and proxy headers from the
    proxy configuration dictionary.
    """

    def __init__(self, proxies=None, proxies_settings=None):
        if proxies is None:
            proxies = {}
        if proxies_settings is None:
            proxies_settings = {}

        self._proxies = proxies
        self._proxies_settings = proxies_settings

    def proxy_url_for(self, url):
        """Retrieves the corresponding proxy url for a given url."""
        parsed_url = urlparse(url)
        proxy = self._proxies.get(parsed_url.scheme)
        if proxy:
            proxy = self._fix_proxy_url(proxy)
        return proxy

    def proxy_headers_for(self, proxy_url):
        """Retrieves the corresponding proxy headers for a given proxy url."""
        headers = {}
        username, password = self._get_auth_from_url(proxy_url)
        if username and password:
            basic_auth = self._construct_basic_auth(username, password)
            headers['Proxy-Authorization'] = basic_auth
        return headers

    @property
    def settings(self):
        return self._proxies_settings

    def _fix_proxy_url(self, proxy_url):
        if proxy_url.startswith('http:') or proxy_url.startswith('https:'):
            return proxy_url
        elif proxy_url.startswith('//'):
            return 'http:' + proxy_url
        else:
            return 'http://' + proxy_url

    def _construct_basic_auth(self, username, password):
        auth_str = f'{username}:{password}'
        encoded_str = b64encode(auth_str.encode('ascii')).strip().decode()
        return f'Basic {encoded_str}'

    def _get_auth_from_url(self, url):
        parsed_url = urlparse(url)
        try:
            return unquote(parsed_url.username), unquote(parsed_url.password)
        except (AttributeError, TypeError):
            return None, None


class URLLib3Session:
    """A basic HTTP client that supports connection pooling and proxies.

    This class is inspired by requests.adapters.HTTPAdapter, but has been
    boiled down to meet the use cases needed by botocore. For the most part
    this classes matches the functionality of HTTPAdapter in requests v2.7.0
    (the same as our vendored version). The only major difference of note is
    that we currently do not support sending chunked requests. While requests
    v2.7.0 implemented this themselves, later version urllib3 support this
    directly via a flag to urlopen so enabling it if needed should be trivial.
    """

    def __init__(
        self,
        verify=True,
        proxies=None,
        timeout=None,
        max_pool_connections=MAX_POOL_CONNECTIONS,
        socket_options=None,
        client_cert=None,
        proxies_config=None,
    ):
        self._verify = verify
        self._proxy_config = ProxyConfiguration(
            proxies=proxies, proxies_settings=proxies_config
        )
        self._pool_classes_by_scheme = {
            'http': botocore.awsrequest.AWSHTTPConnectionPool,
            'https': botocore.awsrequest.AWSHTTPSConnectionPool,
        }
        if timeout is None:
            timeout = DEFAULT_TIMEOUT
        if not isinstance(timeout, (int, float)):
            timeout = Timeout(connect=timeout[0], read=timeout[1])

        self._cert_file = None
        self._key_file = None
        if isinstance(client_cert, str):
            self._cert_file = client_cert
        elif isinstance(client_cert, tuple):
            self._cert_file, self._key_file = client_cert

        self._timeout = timeout
        self._max_pool_connections = max_pool_connections
        self._socket_options = socket_options
        if socket_options is None:
            self._socket_options = []
        self._proxy_managers = {}
        self._manager = PoolManager(**self._get_pool_manager_kwargs())
        self._manager.pool_classes_by_scheme = self._pool_classes_by_scheme

    def _proxies_kwargs(self, **kwargs):
        proxies_settings = self._proxy_config.settings
        proxies_kwargs = {
            'use_forwarding_for_https': proxies_settings.get(
                'proxy_use_forwarding_for_https'
            ),
            **kwargs,
        }
        return {k: v for k, v in proxies_kwargs.items() if v is not None}

    def _get_pool_manager_kwargs(self, **extra_kwargs):
        pool_manager_kwargs = {
            'timeout': self._timeout,
            'maxsize': self._max_pool_connections,
            'ssl_context': self._get_ssl_context(),
            'socket_options': self._socket_options,
            'cert_file': self._cert_file,
            'key_file': self._key_file,
        }
        pool_manager_kwargs.update(**extra_kwargs)
        return pool_manager_kwargs

    def _get_ssl_context(self):
        return create_urllib3_context()

    def _get_proxy_manager(self, proxy_url):
        if proxy_url not in self._proxy_managers:
            proxy_headers = self._proxy_config.proxy_headers_for(proxy_url)
            proxy_ssl_context = self._setup_proxy_ssl_context(proxy_url)
            proxy_manager_kwargs = self._get_pool_manager_kwargs(
                proxy_headers=proxy_headers
            )
            proxy_manager_kwargs.update(
                self._proxies_kwargs(proxy_ssl_context=proxy_ssl_context)
            )
            proxy_manager = proxy_from_url(proxy_url, **proxy_manager_kwargs)
            proxy_manager.pool_classes_by_scheme = self._pool_classes_by_scheme
            self._proxy_managers[proxy_url] = proxy_manager

        return self._proxy_managers[proxy_url]

    def _path_url(self, url):
        parsed_url = urlparse(url)
        path = parsed_url.path
        if not path:
            path = '/'
        if parsed_url.query:
            path = path + '?' + parsed_url.query
        return path

    def _setup_ssl_cert(self, conn, url, verify):
        if url.lower().startswith('https') and verify:
            conn.cert_reqs = 'CERT_REQUIRED'
            conn.ca_certs = get_cert_path(verify)
        else:
            conn.cert_reqs = 'CERT_NONE'
            conn.ca_certs = None

    def _setup_proxy_ssl_context(self, proxy_url):
        proxies_settings = self._proxy_config.settings
        proxy_ca_bundle = proxies_settings.get('proxy_ca_bundle')
        proxy_cert = proxies_settings.get('proxy_client_cert')
        if proxy_ca_bundle is None and proxy_cert is None:
            return None

        context = self._get_ssl_context()
        try:
            url = parse_url(proxy_url)
            # urllib3 disables this by default but we need it for proper
            # proxy tls negotiation when proxy_url is not an IP Address
            if not _is_ipaddress(url.host):
                context.check_hostname = True
            if proxy_ca_bundle is not None:
                context.load_verify_locations(cafile=proxy_ca_bundle)

            if isinstance(proxy_cert, tuple):
                context.load_cert_chain(proxy_cert[0], keyfile=proxy_cert[1])
            elif isinstance(proxy_cert, str):
                context.load_cert_chain(proxy_cert)

            return context
        except (OSError, URLLib3SSLError, LocationParseError) as e:
            raise InvalidProxiesConfigError(error=e)

    def _get_connection_manager(self, url, proxy_url=None):
        if proxy_url:
            manager = self._get_proxy_manager(proxy_url)
        else:
            manager = self._manager
        return manager

    def _get_request_target(self, url, proxy_url):
        has_proxy = proxy_url is not None

        if not has_proxy:
            return self._path_url(url)

        # HTTP proxies expect the request_target to be the absolute url to know
        # which host to establish a connection to. urllib3 also supports
        # forwarding for HTTPS through the 'use_forwarding_for_https' parameter.
        proxy_scheme = urlparse(proxy_url).scheme
        using_https_forwarding_proxy = (
            proxy_scheme == 'https'
            and self._proxies_kwargs().get('use_forwarding_for_https', False)
        )

        if using_https_forwarding_proxy or url.startswith('http:'):
            return url
        else:
            return self._path_url(url)

    def _chunked(self, headers):
        transfer_encoding = headers.get('Transfer-Encoding', b'')
        transfer_encoding = ensure_bytes(transfer_encoding)
        return transfer_encoding.lower() == b'chunked'

    def close(self):
        self._manager.clear()
        for manager in self._proxy_managers.values():
            manager.clear()

    def send(self, request):
        try:
            proxy_url = self._proxy_config.proxy_url_for(request.url)
            manager = self._get_connection_manager(request.url, proxy_url)
            conn = manager.connection_from_url(request.url)
            self._setup_ssl_cert(conn, request.url, self._verify)
            if ensure_boolean(
                os.environ.get('BOTO_EXPERIMENTAL__ADD_PROXY_HOST_HEADER', '')
            ):
                # This is currently an "experimental" feature which provides
                # no guarantees of backwards compatibility. It may be subject
                # to change or removal in any patch version. Anyone opting in
                # to this feature should strictly pin botocore.
                host = urlparse(request.url).hostname
                conn.proxy_headers['host'] = host

            request_target = self._get_request_target(request.url, proxy_url)
            urllib_response = conn.urlopen(
                method=request.method,
                url=request_target,
                body=request.body,
                headers=request.headers,
                retries=Retry(False),
                assert_same_host=False,
                preload_content=False,
                decode_content=False,
                chunked=self._chunked(request.headers),
            )

            http_response = botocore.awsrequest.AWSResponse(
                request.url,
                urllib_response.status,
                urllib_response.headers,
                urllib_response,
            )

            if not request.stream_output:
                # Cause the raw stream to be exhausted immediately. We do it
                # this way instead of using preload_content because
                # preload_content will never buffer chunked responses
                http_response.content

            return http_response
        except URLLib3SSLError as e:
            raise SSLError(endpoint_url=request.url, error=e)
        except (NewConnectionError, socket.gaierror) as e:
            raise EndpointConnectionError(endpoint_url=request.url, error=e)
        except ProxyError as e:
            raise ProxyConnectionError(
                proxy_url=mask_proxy_url(proxy_url), error=e
            )
        except URLLib3ConnectTimeoutError as e:
            raise ConnectTimeoutError(endpoint_url=request.url, error=e)
        except URLLib3ReadTimeoutError as e:
            raise ReadTimeoutError(endpoint_url=request.url, error=e)
        except ProtocolError as e:
            raise ConnectionClosedError(
                error=e, request=request, endpoint_url=request.url
            )
        except CancelledError:
            raise
        except Exception as e:
            message = 'Exception received when sending urllib3 HTTP request'
            logger.debug(message, exc_info=True)
            raise HTTPClientError(error=e)
