# Licensed to Elasticsearch B.V under one or more agreements.
# Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
# See the LICENSE file in the project root for more information

import time
import ssl
import urllib3
from urllib3.exceptions import ReadTimeoutError, SSLError as UrllibSSLError
from urllib3.util.retry import Retry
import warnings

from .base import Connection
from ..exceptions import (
    ConnectionError,
    ImproperlyConfigured,
    ConnectionTimeout,
    SSLError,
)
from ..compat import urlencode

# sentinel value for `verify_certs` and `ssl_show_warn`.
# This is used to detect if a user is passing in a value
# for SSL kwargs if also using an SSLContext.
VERIFY_CERTS_DEFAULT = object()
SSL_SHOW_WARN_DEFAULT = object()

CA_CERTS = "/etc/ssl/certs/ca-certificates.crt"

try:
    import certifi

    CA_CERTS = certifi.where()
except ImportError:
    pass


def create_ssl_context(**kwargs):
    """
    A helper function around creating an SSL context

    https://docs.python.org/3/library/ssl.html#context-creation

    Accepts kwargs in the same manner as `create_default_context`.
    """
    ctx = ssl.create_default_context(**kwargs)
    return ctx


class Urllib3HttpConnection(Connection):
    """
    Default connection class using the `urllib3` library and the http protocol.

    :arg host: hostname of the node (default: localhost)
    :arg port: port to use (integer, default: 9200)
    :arg url_prefix: optional url prefix for elasticsearch
    :arg timeout: default timeout in seconds (float, default: 10)
    :arg http_auth: optional http auth information as either ':' separated
        string or a tuple
    :arg use_ssl: use ssl for the connection if `True`
    :arg verify_certs: whether to verify SSL certificates
    :arg ssl_show_warn: show warning when verify certs is disabled
    :arg ca_certs: optional path to CA bundle.
        See https://urllib3.readthedocs.io/en/latest/security.html#using-certifi-with-urllib3
        for instructions how to get default set
    :arg client_cert: path to the file containing the private key and the
        certificate, or cert only if using client_key
    :arg client_key: path to the file containing the private key if using
        separate cert and key files (client_cert will contain only the cert)
    :arg ssl_version: version of the SSL protocol to use. Choices are:
        SSLv23 (default) SSLv2 SSLv3 TLSv1 (see ``PROTOCOL_*`` constants in the
        ``ssl`` module for exact options for your environment).
    :arg ssl_assert_hostname: use hostname verification if not `False`
    :arg ssl_assert_fingerprint: verify the supplied certificate fingerprint if not `None`
    :arg maxsize: the number of connections which will be kept open to this
        host. See https://urllib3.readthedocs.io/en/1.4/pools.html#api for more
        information.
    :arg headers: any custom http headers to be add to requests
    :arg http_compress: Use gzip compression
    :arg cloud_id: The Cloud ID from ElasticCloud. Convenient way to connect to cloud instances.
        Other host connection params will be ignored.
    :arg api_key: optional API Key authentication as either base64 encoded string or a tuple.
    :arg opaque_id: Send this value in the 'X-Opaque-Id' HTTP header
        For tracing all requests made by this transport.
    """

    def __init__(
        self,
        host="localhost",
        port=None,
        http_auth=None,
        use_ssl=False,
        verify_certs=VERIFY_CERTS_DEFAULT,
        ssl_show_warn=SSL_SHOW_WARN_DEFAULT,
        ca_certs=None,
        client_cert=None,
        client_key=None,
        ssl_version=None,
        ssl_assert_hostname=None,
        ssl_assert_fingerprint=None,
        maxsize=10,
        headers=None,
        ssl_context=None,
        http_compress=None,
        cloud_id=None,
        api_key=None,
        opaque_id=None,
        **kwargs
    ):
        # Initialize headers before calling super().__init__().
        self.headers = urllib3.make_headers(keep_alive=True)

        super(Urllib3HttpConnection, self).__init__(
            host=host,
            port=port,
            use_ssl=use_ssl,
            headers=headers,
            http_compress=http_compress,
            cloud_id=cloud_id,
            api_key=api_key,
            opaque_id=opaque_id,
            **kwargs
        )
        if http_auth is not None:
            if isinstance(http_auth, (tuple, list)):
                http_auth = ":".join(http_auth)
            self.headers.update(urllib3.make_headers(basic_auth=http_auth))

        pool_class = urllib3.HTTPConnectionPool
        kw = {}

        # if providing an SSL context, raise error if any other SSL related flag is used
        if ssl_context and (
            (verify_certs is not VERIFY_CERTS_DEFAULT)
            or (ssl_show_warn is not SSL_SHOW_WARN_DEFAULT)
            or ca_certs
            or client_cert
            or client_key
            or ssl_version
        ):
            warnings.warn(
                "When using `ssl_context`, all other SSL related kwargs are ignored"
            )

        # if ssl_context provided use SSL by default
        if ssl_context and self.use_ssl:
            pool_class = urllib3.HTTPSConnectionPool
            kw.update(
                {
                    "assert_fingerprint": ssl_assert_fingerprint,
                    "ssl_context": ssl_context,
                }
            )

        elif self.use_ssl:
            pool_class = urllib3.HTTPSConnectionPool
            kw.update(
                {
                    "ssl_version": ssl_version,
                    "assert_hostname": ssl_assert_hostname,
                    "assert_fingerprint": ssl_assert_fingerprint,
                }
            )

            # Convert all sentinel values to their actual default
            # values if not using an SSLContext.
            if verify_certs is VERIFY_CERTS_DEFAULT:
                verify_certs = True
            if ssl_show_warn is SSL_SHOW_WARN_DEFAULT:
                ssl_show_warn = True

            ca_certs = CA_CERTS if ca_certs is None else ca_certs
            if verify_certs:
                if not ca_certs:
                    raise ImproperlyConfigured(
                        "Root certificates are missing for certificate "
                        "validation. Either pass them in using the ca_certs parameter or "
                        "install certifi to use it automatically."
                    )

                kw.update(
                    {
                        "cert_reqs": "CERT_REQUIRED",
                        "ca_certs": ca_certs,
                        "cert_file": client_cert,
                        "key_file": client_key,
                    }
                )
            else:
                kw["cert_reqs"] = "CERT_NONE"
                if ssl_show_warn:
                    warnings.warn(
                        "Connecting to %s using SSL with verify_certs=False is insecure."
                        % self.host
                    )
                if not ssl_show_warn:
                    urllib3.disable_warnings()

        self.pool = pool_class(
            self.hostname, port=self.port, timeout=self.timeout, maxsize=maxsize, **kw
        )

    def perform_request(
        self, method, url, params=None, body=None, timeout=None, ignore=(), headers=None
    ):
        url = self.url_prefix + url
        if params:
            url = "%s?%s" % (url, urlencode(params))
        full_url = self.host + url

        start = time.time()
        orig_body = body
        try:
            kw = {}
            if timeout:
                kw["timeout"] = timeout

            # in python2 we need to make sure the url and method are not
            # unicode. Otherwise the body will be decoded into unicode too and
            # that will fail (#133, #201).
            if not isinstance(url, str):
                url = url.encode("utf-8")
            if not isinstance(method, str):
                method = method.encode("utf-8")

            request_headers = self.headers.copy()
            request_headers.update(headers or ())

            if self.http_compress and body:
                body = self._gzip_compress(body)
                request_headers["content-encoding"] = "gzip"

            response = self.pool.urlopen(
                method, url, body, retries=Retry(False), headers=request_headers, **kw
            )
            duration = time.time() - start
            raw_data = response.data.decode("utf-8", "surrogatepass")
        except Exception as e:
            self.log_request_fail(
                method, full_url, url, orig_body, time.time() - start, exception=e
            )
            if isinstance(e, UrllibSSLError):
                raise SSLError("N/A", str(e), e)
            if isinstance(e, ReadTimeoutError):
                raise ConnectionTimeout("TIMEOUT", str(e), e)
            raise ConnectionError("N/A", str(e), e)

        # raise warnings if any from the 'Warnings' header.
        warning_headers = response.headers.get_all("warning", ())
        self._raise_warnings(warning_headers)

        # raise errors based on http status codes, let the client handle those if needed
        if not (200 <= response.status < 300) and response.status not in ignore:
            self.log_request_fail(
                method, full_url, url, orig_body, duration, response.status, raw_data
            )
            self._raise_error(response.status, raw_data)

        self.log_request_success(
            method, full_url, url, orig_body, response.status, raw_data, duration
        )

        return response.status, response.getheaders(), raw_data

    def close(self):
        """
        Explicitly closes connection
        """
        self.pool.close()
