from tornado.escape import _unicode
from tornado import gen, version
from tornado.httpclient import (
    HTTPResponse,
    HTTPError,
    AsyncHTTPClient,
    main,
    _RequestProxy,
    HTTPRequest,
)
from tornado import httputil
from tornado.http1connection import HTTP1Connection, HTTP1ConnectionParameters
from tornado.ioloop import IOLoop
from tornado.iostream import StreamClosedError, IOStream
from tornado.netutil import (
    Resolver,
    OverrideResolver,
    _client_ssl_defaults,
    is_valid_ip,
)
from tornado.log import gen_log
from tornado.tcpclient import TCPClient

import base64
import collections
import copy
import functools
import re
import socket
import ssl
import sys
import time
from io import BytesIO
import urllib.parse

from typing import Dict, Any, Callable, Optional, Type, Union
from types import TracebackType
import typing

if typing.TYPE_CHECKING:
    from typing import Deque, Tuple, List  # noqa: F401


class HTTPTimeoutError(HTTPError):
    """Error raised by SimpleAsyncHTTPClient on timeout.

    For historical reasons, this is a subclass of `.HTTPClientError`
    which simulates a response code of 599.

    .. versionadded:: 5.1
    """

    def __init__(self, message: str) -> None:
        super().__init__(599, message=message)

    def __str__(self) -> str:
        return self.message or "Timeout"


class HTTPStreamClosedError(HTTPError):
    """Error raised by SimpleAsyncHTTPClient when the underlying stream is closed.

    When a more specific exception is available (such as `ConnectionResetError`),
    it may be raised instead of this one.

    For historical reasons, this is a subclass of `.HTTPClientError`
    which simulates a response code of 599.

    .. versionadded:: 5.1
    """

    def __init__(self, message: str) -> None:
        super().__init__(599, message=message)

    def __str__(self) -> str:
        return self.message or "Stream closed"


class SimpleAsyncHTTPClient(AsyncHTTPClient):
    """Non-blocking HTTP client with no external dependencies.

    This class implements an HTTP 1.1 client on top of Tornado's IOStreams.
    Some features found in the curl-based AsyncHTTPClient are not yet
    supported.  In particular, proxies are not supported, connections
    are not reused, and callers cannot select the network interface to be
    used.
    """

    def initialize(  # type: ignore
        self,
        max_clients: int = 10,
        hostname_mapping: Optional[Dict[str, str]] = None,
        max_buffer_size: int = 104857600,
        resolver: Optional[Resolver] = None,
        defaults: Optional[Dict[str, Any]] = None,
        max_header_size: Optional[int] = None,
        max_body_size: Optional[int] = None,
    ) -> None:
        """Creates a AsyncHTTPClient.

        Only a single AsyncHTTPClient instance exists per IOLoop
        in order to provide limitations on the number of pending connections.
        ``force_instance=True`` may be used to suppress this behavior.

        Note that because of this implicit reuse, unless ``force_instance``
        is used, only the first call to the constructor actually uses
        its arguments. It is recommended to use the ``configure`` method
        instead of the constructor to ensure that arguments take effect.

        ``max_clients`` is the number of concurrent requests that can be
        in progress; when this limit is reached additional requests will be
        queued. Note that time spent waiting in this queue still counts
        against the ``request_timeout``.

        ``hostname_mapping`` is a dictionary mapping hostnames to IP addresses.
        It can be used to make local DNS changes when modifying system-wide
        settings like ``/etc/hosts`` is not possible or desirable (e.g. in
        unittests).

        ``max_buffer_size`` (default 100MB) is the number of bytes
        that can be read into memory at once. ``max_body_size``
        (defaults to ``max_buffer_size``) is the largest response body
        that the client will accept.  Without a
        ``streaming_callback``, the smaller of these two limits
        applies; with a ``streaming_callback`` only ``max_body_size``
        does.

        .. versionchanged:: 4.2
           Added the ``max_body_size`` argument.
        """
        super().initialize(defaults=defaults)
        self.max_clients = max_clients
        self.queue = (
            collections.deque()
        )  # type: Deque[Tuple[object, HTTPRequest, Callable[[HTTPResponse], None]]]
        self.active = (
            {}
        )  # type: Dict[object, Tuple[HTTPRequest, Callable[[HTTPResponse], None]]]
        self.waiting = (
            {}
        )  # type: Dict[object, Tuple[HTTPRequest, Callable[[HTTPResponse], None], object]]
        self.max_buffer_size = max_buffer_size
        self.max_header_size = max_header_size
        self.max_body_size = max_body_size
        # TCPClient could create a Resolver for us, but we have to do it
        # ourselves to support hostname_mapping.
        if resolver:
            self.resolver = resolver
            self.own_resolver = False
        else:
            self.resolver = Resolver()
            self.own_resolver = True
        if hostname_mapping is not None:
            self.resolver = OverrideResolver(
                resolver=self.resolver, mapping=hostname_mapping
            )
        self.tcp_client = TCPClient(resolver=self.resolver)

    def close(self) -> None:
        super().close()
        if self.own_resolver:
            self.resolver.close()
        self.tcp_client.close()

    def fetch_impl(
        self, request: HTTPRequest, callback: Callable[[HTTPResponse], None]
    ) -> None:
        key = object()
        self.queue.append((key, request, callback))
        assert request.connect_timeout is not None
        assert request.request_timeout is not None
        timeout_handle = None
        if len(self.active) >= self.max_clients:
            timeout = (
                min(request.connect_timeout, request.request_timeout)
                or request.connect_timeout
                or request.request_timeout
            )  # min but skip zero
            if timeout:
                timeout_handle = self.io_loop.add_timeout(
                    self.io_loop.time() + timeout,
                    functools.partial(self._on_timeout, key, "in request queue"),
                )
        self.waiting[key] = (request, callback, timeout_handle)
        self._process_queue()
        if self.queue:
            gen_log.debug(
                "max_clients limit reached, request queued. "
                "%d active, %d queued requests." % (len(self.active), len(self.queue))
            )

    def _process_queue(self) -> None:
        while self.queue and len(self.active) < self.max_clients:
            key, request, callback = self.queue.popleft()
            if key not in self.waiting:
                continue
            self._remove_timeout(key)
            self.active[key] = (request, callback)
            release_callback = functools.partial(self._release_fetch, key)
            self._handle_request(request, release_callback, callback)

    def _connection_class(self) -> type:
        return _HTTPConnection

    def _handle_request(
        self,
        request: HTTPRequest,
        release_callback: Callable[[], None],
        final_callback: Callable[[HTTPResponse], None],
    ) -> None:
        self._connection_class()(
            self,
            request,
            release_callback,
            final_callback,
            self.max_buffer_size,
            self.tcp_client,
            self.max_header_size,
            self.max_body_size,
        )

    def _release_fetch(self, key: object) -> None:
        del self.active[key]
        self._process_queue()

    def _remove_timeout(self, key: object) -> None:
        if key in self.waiting:
            request, callback, timeout_handle = self.waiting[key]
            if timeout_handle is not None:
                self.io_loop.remove_timeout(timeout_handle)
            del self.waiting[key]

    def _on_timeout(self, key: object, info: Optional[str] = None) -> None:
        """Timeout callback of request.

        Construct a timeout HTTPResponse when a timeout occurs.

        :arg object key: A simple object to mark the request.
        :info string key: More detailed timeout information.
        """
        request, callback, timeout_handle = self.waiting[key]
        self.queue.remove((key, request, callback))

        error_message = "Timeout {0}".format(info) if info else "Timeout"
        timeout_response = HTTPResponse(
            request,
            599,
            error=HTTPTimeoutError(error_message),
            request_time=self.io_loop.time() - request.start_time,
        )
        self.io_loop.add_callback(callback, timeout_response)
        del self.waiting[key]


class _HTTPConnection(httputil.HTTPMessageDelegate):
    _SUPPORTED_METHODS = set(
        ["GET", "HEAD", "POST", "PUT", "DELETE", "PATCH", "OPTIONS"]
    )

    def __init__(
        self,
        client: Optional[SimpleAsyncHTTPClient],
        request: HTTPRequest,
        release_callback: Callable[[], None],
        final_callback: Callable[[HTTPResponse], None],
        max_buffer_size: int,
        tcp_client: TCPClient,
        max_header_size: int,
        max_body_size: int,
    ) -> None:
        self.io_loop = IOLoop.current()
        self.start_time = self.io_loop.time()
        self.start_wall_time = time.time()
        self.client = client
        self.request = request
        self.release_callback = release_callback
        self.final_callback = final_callback
        self.max_buffer_size = max_buffer_size
        self.tcp_client = tcp_client
        self.max_header_size = max_header_size
        self.max_body_size = max_body_size
        self.code = None  # type: Optional[int]
        self.headers = None  # type: Optional[httputil.HTTPHeaders]
        self.chunks = []  # type: List[bytes]
        self._decompressor = None
        # Timeout handle returned by IOLoop.add_timeout
        self._timeout = None  # type: object
        self._sockaddr = None
        IOLoop.current().add_future(
            gen.convert_yielded(self.run()), lambda f: f.result()
        )

    async def run(self) -> None:
        try:
            self.parsed = urllib.parse.urlsplit(_unicode(self.request.url))
            if self.parsed.scheme not in ("http", "https"):
                raise ValueError("Unsupported url scheme: %s" % self.request.url)
            # urlsplit results have hostname and port results, but they
            # didn't support ipv6 literals until python 2.7.
            netloc = self.parsed.netloc
            if "@" in netloc:
                userpass, _, netloc = netloc.rpartition("@")
            host, port = httputil.split_host_and_port(netloc)
            if port is None:
                port = 443 if self.parsed.scheme == "https" else 80
            if re.match(r"^\[.*\]$", host):
                # raw ipv6 addresses in urls are enclosed in brackets
                host = host[1:-1]
            self.parsed_hostname = host  # save final host for _on_connect

            if self.request.allow_ipv6 is False:
                af = socket.AF_INET
            else:
                af = socket.AF_UNSPEC

            ssl_options = self._get_ssl_options(self.parsed.scheme)

            source_ip = None
            if self.request.network_interface:
                if is_valid_ip(self.request.network_interface):
                    source_ip = self.request.network_interface
                else:
                    raise ValueError(
                        "Unrecognized IPv4 or IPv6 address for network_interface, got %r"
                        % (self.request.network_interface,)
                    )

            timeout = (
                min(self.request.connect_timeout, self.request.request_timeout)
                or self.request.connect_timeout
                or self.request.request_timeout
            )  # min but skip zero
            if timeout:
                self._timeout = self.io_loop.add_timeout(
                    self.start_time + timeout,
                    functools.partial(self._on_timeout, "while connecting"),
                )
            stream = await self.tcp_client.connect(
                host,
                port,
                af=af,
                ssl_options=ssl_options,
                max_buffer_size=self.max_buffer_size,
                source_ip=source_ip,
            )

            if self.final_callback is None:
                # final_callback is cleared if we've hit our timeout.
                stream.close()
                return
            self.stream = stream
            self.stream.set_close_callback(self.on_connection_close)
            self._remove_timeout()
            if self.final_callback is None:
                return
            if self.request.request_timeout:
                self._timeout = self.io_loop.add_timeout(
                    self.start_time + self.request.request_timeout,
                    functools.partial(self._on_timeout, "during request"),
                )
            if (
                self.request.method not in self._SUPPORTED_METHODS
                and not self.request.allow_nonstandard_methods
            ):
                raise KeyError("unknown method %s" % self.request.method)
            for key in (
                "proxy_host",
                "proxy_port",
                "proxy_username",
                "proxy_password",
                "proxy_auth_mode",
            ):
                if getattr(self.request, key, None):
                    raise NotImplementedError("%s not supported" % key)
            if "Connection" not in self.request.headers:
                self.request.headers["Connection"] = "close"
            if "Host" not in self.request.headers:
                if "@" in self.parsed.netloc:
                    self.request.headers["Host"] = self.parsed.netloc.rpartition("@")[
                        -1
                    ]
                else:
                    self.request.headers["Host"] = self.parsed.netloc
            username, password = None, None
            if self.parsed.username is not None:
                username, password = self.parsed.username, self.parsed.password
            elif self.request.auth_username is not None:
                username = self.request.auth_username
                password = self.request.auth_password or ""
            if username is not None:
                assert password is not None
                if self.request.auth_mode not in (None, "basic"):
                    raise ValueError("unsupported auth_mode %s", self.request.auth_mode)
                self.request.headers["Authorization"] = "Basic " + _unicode(
                    base64.b64encode(
                        httputil.encode_username_password(username, password)
                    )
                )
            if self.request.user_agent:
                self.request.headers["User-Agent"] = self.request.user_agent
            elif self.request.headers.get("User-Agent") is None:
                self.request.headers["User-Agent"] = "Tornado/{}".format(version)
            if not self.request.allow_nonstandard_methods:
                # Some HTTP methods nearly always have bodies while others
                # almost never do. Fail in this case unless the user has
                # opted out of sanity checks with allow_nonstandard_methods.
                body_expected = self.request.method in ("POST", "PATCH", "PUT")
                body_present = (
                    self.request.body is not None
                    or self.request.body_producer is not None
                )
                if (body_expected and not body_present) or (
                    body_present and not body_expected
                ):
                    raise ValueError(
                        "Body must %sbe None for method %s (unless "
                        "allow_nonstandard_methods is true)"
                        % ("not " if body_expected else "", self.request.method)
                    )
            if self.request.expect_100_continue:
                self.request.headers["Expect"] = "100-continue"
            if self.request.body is not None:
                # When body_producer is used the caller is responsible for
                # setting Content-Length (or else chunked encoding will be used).
                self.request.headers["Content-Length"] = str(len(self.request.body))
            if (
                self.request.method == "POST"
                and "Content-Type" not in self.request.headers
            ):
                self.request.headers[
                    "Content-Type"
                ] = "application/x-www-form-urlencoded"
            if self.request.decompress_response:
                self.request.headers["Accept-Encoding"] = "gzip"
            req_path = (self.parsed.path or "/") + (
                ("?" + self.parsed.query) if self.parsed.query else ""
            )
            self.connection = self._create_connection(stream)
            start_line = httputil.RequestStartLine(self.request.method, req_path, "")
            self.connection.write_headers(start_line, self.request.headers)
            if self.request.expect_100_continue:
                await self.connection.read_response(self)
            else:
                await self._write_body(True)
        except Exception:
            if not self._handle_exception(*sys.exc_info()):
                raise

    def _get_ssl_options(
        self, scheme: str
    ) -> Union[None, Dict[str, Any], ssl.SSLContext]:
        if scheme == "https":
            if self.request.ssl_options is not None:
                return self.request.ssl_options
            # If we are using the defaults, don't construct a
            # new SSLContext.
            if (
                self.request.validate_cert
                and self.request.ca_certs is None
                and self.request.client_cert is None
                and self.request.client_key is None
            ):
                return _client_ssl_defaults
            ssl_ctx = ssl.create_default_context(
                ssl.Purpose.SERVER_AUTH, cafile=self.request.ca_certs
            )
            if not self.request.validate_cert:
                ssl_ctx.check_hostname = False
                ssl_ctx.verify_mode = ssl.CERT_NONE
            if self.request.client_cert is not None:
                ssl_ctx.load_cert_chain(
                    self.request.client_cert, self.request.client_key
                )
            if hasattr(ssl, "OP_NO_COMPRESSION"):
                # See netutil.ssl_options_to_context
                ssl_ctx.options |= ssl.OP_NO_COMPRESSION
            return ssl_ctx
        return None

    def _on_timeout(self, info: Optional[str] = None) -> None:
        """Timeout callback of _HTTPConnection instance.

        Raise a `HTTPTimeoutError` when a timeout occurs.

        :info string key: More detailed timeout information.
        """
        self._timeout = None
        error_message = "Timeout {0}".format(info) if info else "Timeout"
        if self.final_callback is not None:
            self._handle_exception(
                HTTPTimeoutError, HTTPTimeoutError(error_message), None
            )

    def _remove_timeout(self) -> None:
        if self._timeout is not None:
            self.io_loop.remove_timeout(self._timeout)
            self._timeout = None

    def _create_connection(self, stream: IOStream) -> HTTP1Connection:
        stream.set_nodelay(True)
        connection = HTTP1Connection(
            stream,
            True,
            HTTP1ConnectionParameters(
                no_keep_alive=True,
                max_header_size=self.max_header_size,
                max_body_size=self.max_body_size,
                decompress=bool(self.request.decompress_response),
            ),
            self._sockaddr,
        )
        return connection

    async def _write_body(self, start_read: bool) -> None:
        if self.request.body is not None:
            self.connection.write(self.request.body)
        elif self.request.body_producer is not None:
            fut = self.request.body_producer(self.connection.write)
            if fut is not None:
                await fut
        self.connection.finish()
        if start_read:
            try:
                await self.connection.read_response(self)
            except StreamClosedError:
                if not self._handle_exception(*sys.exc_info()):
                    raise

    def _release(self) -> None:
        if self.release_callback is not None:
            release_callback = self.release_callback
            self.release_callback = None  # type: ignore
            release_callback()

    def _run_callback(self, response: HTTPResponse) -> None:
        self._release()
        if self.final_callback is not None:
            final_callback = self.final_callback
            self.final_callback = None  # type: ignore
            self.io_loop.add_callback(final_callback, response)

    def _handle_exception(
        self,
        typ: "Optional[Type[BaseException]]",
        value: Optional[BaseException],
        tb: Optional[TracebackType],
    ) -> bool:
        if self.final_callback:
            self._remove_timeout()
            if isinstance(value, StreamClosedError):
                if value.real_error is None:
                    value = HTTPStreamClosedError("Stream closed")
                else:
                    value = value.real_error
            self._run_callback(
                HTTPResponse(
                    self.request,
                    599,
                    error=value,
                    request_time=self.io_loop.time() - self.start_time,
                    start_time=self.start_wall_time,
                )
            )

            if hasattr(self, "stream"):
                # TODO: this may cause a StreamClosedError to be raised
                # by the connection's Future.  Should we cancel the
                # connection more gracefully?
                self.stream.close()
            return True
        else:
            # If our callback has already been called, we are probably
            # catching an exception that is not caused by us but rather
            # some child of our callback. Rather than drop it on the floor,
            # pass it along, unless it's just the stream being closed.
            return isinstance(value, StreamClosedError)

    def on_connection_close(self) -> None:
        if self.final_callback is not None:
            message = "Connection closed"
            if self.stream.error:
                raise self.stream.error
            try:
                raise HTTPStreamClosedError(message)
            except HTTPStreamClosedError:
                self._handle_exception(*sys.exc_info())

    async def headers_received(
        self,
        first_line: Union[httputil.ResponseStartLine, httputil.RequestStartLine],
        headers: httputil.HTTPHeaders,
    ) -> None:
        assert isinstance(first_line, httputil.ResponseStartLine)
        if self.request.expect_100_continue and first_line.code == 100:
            await self._write_body(False)
            return
        self.code = first_line.code
        self.reason = first_line.reason
        self.headers = headers

        if self._should_follow_redirect():
            return

        if self.request.header_callback is not None:
            # Reassemble the start line.
            self.request.header_callback("%s %s %s\r\n" % first_line)
            for k, v in self.headers.get_all():
                self.request.header_callback("%s: %s\r\n" % (k, v))
            self.request.header_callback("\r\n")

    def _should_follow_redirect(self) -> bool:
        if self.request.follow_redirects:
            assert self.request.max_redirects is not None
            return (
                self.code in (301, 302, 303, 307, 308)
                and self.request.max_redirects > 0
                and self.headers is not None
                and self.headers.get("Location") is not None
            )
        return False

    def finish(self) -> None:
        assert self.code is not None
        data = b"".join(self.chunks)
        self._remove_timeout()
        original_request = getattr(self.request, "original_request", self.request)
        if self._should_follow_redirect():
            assert isinstance(self.request, _RequestProxy)
            new_request = copy.copy(self.request.request)
            new_request.url = urllib.parse.urljoin(
                self.request.url, self.headers["Location"]
            )
            new_request.max_redirects = self.request.max_redirects - 1
            del new_request.headers["Host"]
            # https://tools.ietf.org/html/rfc7231#section-6.4
            #
            # The original HTTP spec said that after a 301 or 302
            # redirect, the request method should be preserved.
            # However, browsers implemented this by changing the
            # method to GET, and the behavior stuck. 303 redirects
            # always specified this POST-to-GET behavior, arguably
            # for *all* methods, but libcurl < 7.70 only does this
            # for POST, while libcurl >= 7.70 does it for other methods.
            if (self.code == 303 and self.request.method != "HEAD") or (
                self.code in (301, 302) and self.request.method == "POST"
            ):
                new_request.method = "GET"
                new_request.body = None
                for h in [
                    "Content-Length",
                    "Content-Type",
                    "Content-Encoding",
                    "Transfer-Encoding",
                ]:
                    try:
                        del self.request.headers[h]
                    except KeyError:
                        pass
            new_request.original_request = original_request
            final_callback = self.final_callback
            self.final_callback = None
            self._release()
            fut = self.client.fetch(new_request, raise_error=False)
            fut.add_done_callback(lambda f: final_callback(f.result()))
            self._on_end_request()
            return
        if self.request.streaming_callback:
            buffer = BytesIO()
        else:
            buffer = BytesIO(data)  # TODO: don't require one big string?
        response = HTTPResponse(
            original_request,
            self.code,
            reason=getattr(self, "reason", None),
            headers=self.headers,
            request_time=self.io_loop.time() - self.start_time,
            start_time=self.start_wall_time,
            buffer=buffer,
            effective_url=self.request.url,
        )
        self._run_callback(response)
        self._on_end_request()

    def _on_end_request(self) -> None:
        self.stream.close()

    def data_received(self, chunk: bytes) -> None:
        if self._should_follow_redirect():
            # We're going to follow a redirect so just discard the body.
            return
        if self.request.streaming_callback is not None:
            self.request.streaming_callback(chunk)
        else:
            self.chunks.append(chunk)


if __name__ == "__main__":
    AsyncHTTPClient.configure(SimpleAsyncHTTPClient)
    main()
