#!/usr/bin/env python
#
# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

"""A non-blocking, single-threaded HTTP server.

Typical applications have little direct interaction with the `HTTPServer`
class except to start a server at the beginning of the process
(and even that is often done indirectly via `tornado.web.Application.listen`).

This module also defines the `HTTPRequest` class which is exposed via
`tornado.web.RequestHandler.request`.
"""

from __future__ import absolute_import, division, print_function, with_statement

import socket
import ssl
import time

from tornado.escape import native_str, parse_qs_bytes
from tornado import httputil
from tornado import iostream
from tornado.log import gen_log
from tornado import netutil
from tornado.tcpserver import TCPServer
from tornado import stack_context
from tornado.util import bytes_type

try:
    import Cookie # py2
except ImportError:
    import http.cookies as Cookie # py3


class HTTPServer(TCPServer):
    r"""A non-blocking, single-threaded HTTP server.

    A server is defined by a request callback that takes an HTTPRequest
    instance as an argument and writes a valid HTTP response with
    `HTTPRequest.write`. `HTTPRequest.finish` finishes the request (but does
    not necessarily close the connection in the case of HTTP/1.1 keep-alive
    requests). A simple example server that echoes back the URI you
    requested::

        import tornado.httpserver
        import tornado.ioloop

        def handle_request(request):
           message = "You requested %s\n" % request.uri
           request.write("HTTP/1.1 200 OK\r\nContent-Length: %d\r\n\r\n%s" % (
                         len(message), message))
           request.finish()

        http_server = tornado.httpserver.HTTPServer(handle_request)
        http_server.listen(8888)
        tornado.ioloop.IOLoop.instance().start()

    `HTTPServer` is a very basic connection handler.  It parses the request
    headers and body, but the request callback is responsible for producing
    the response exactly as it will appear on the wire.  This affords
    maximum flexibility for applications to implement whatever parts
    of HTTP responses are required.

    `HTTPServer` supports keep-alive connections by default
    (automatically for HTTP/1.1, or for HTTP/1.0 when the client
    requests ``Connection: keep-alive``).  This means that the request
    callback must generate a properly-framed response, using either
    the ``Content-Length`` header or ``Transfer-Encoding: chunked``.
    Applications that are unable to frame their responses properly
    should instead return a ``Connection: close`` header in each
    response and pass ``no_keep_alive=True`` to the `HTTPServer`
    constructor.

    If ``xheaders`` is ``True``, we support the
    ``X-Real-Ip``/``X-Forwarded-For`` and
    ``X-Scheme``/``X-Forwarded-Proto`` headers, which override the
    remote IP and URI scheme/protocol for all requests.  These headers
    are useful when running Tornado behind a reverse proxy or load
    balancer.  The ``protocol`` argument can also be set to ``https``
    if Tornado is run behind an SSL-decoding proxy that does not set one of
    the supported ``xheaders``.

    To make this server serve SSL traffic, send the ``ssl_options`` dictionary
    argument with the arguments required for the `ssl.wrap_socket` method,
    including ``certfile`` and ``keyfile``.  (In Python 3.2+ you can pass
    an `ssl.SSLContext` object instead of a dict)::

       HTTPServer(applicaton, ssl_options={
           "certfile": os.path.join(data_dir, "mydomain.crt"),
           "keyfile": os.path.join(data_dir, "mydomain.key"),
       })

    `HTTPServer` initialization follows one of three patterns (the
    initialization methods are defined on `tornado.tcpserver.TCPServer`):

    1. `~tornado.tcpserver.TCPServer.listen`: simple single-process::

            server = HTTPServer(app)
            server.listen(8888)
            IOLoop.instance().start()

       In many cases, `tornado.web.Application.listen` can be used to avoid
       the need to explicitly create the `HTTPServer`.

    2. `~tornado.tcpserver.TCPServer.bind`/`~tornado.tcpserver.TCPServer.start`:
       simple multi-process::

            server = HTTPServer(app)
            server.bind(8888)
            server.start(0)  # Forks multiple sub-processes
            IOLoop.instance().start()

       When using this interface, an `.IOLoop` must *not* be passed
       to the `HTTPServer` constructor.  `~.TCPServer.start` will always start
       the server on the default singleton `.IOLoop`.

    3. `~tornado.tcpserver.TCPServer.add_sockets`: advanced multi-process::

            sockets = tornado.netutil.bind_sockets(8888)
            tornado.process.fork_processes(0)
            server = HTTPServer(app)
            server.add_sockets(sockets)
            IOLoop.instance().start()

       The `~.TCPServer.add_sockets` interface is more complicated,
       but it can be used with `tornado.process.fork_processes` to
       give you more flexibility in when the fork happens.
       `~.TCPServer.add_sockets` can also be used in single-process
       servers if you want to create your listening sockets in some
       way other than `tornado.netutil.bind_sockets`.

    """
    def __init__(self, request_callback, no_keep_alive = False, io_loop = None,
                 xheaders = False, ssl_options = None, protocol = None, **kwargs):
        self.request_callback = request_callback
        self.no_keep_alive = no_keep_alive
        self.xheaders = xheaders
        self.protocol = protocol
        TCPServer.__init__(self, io_loop = io_loop, ssl_options = ssl_options,
                           **kwargs)

    def handle_stream(self, stream, address):
        HTTPConnection(stream, address, self.request_callback,
                       self.no_keep_alive, self.xheaders, self.protocol)


class _BadRequestException(Exception):
    """Exception class for malformed HTTP requests."""
    pass


class HTTPConnection(object):
    """Handles a connection to an HTTP client, executing HTTP requests.

    We parse HTTP headers and bodies, and execute the request callback
    until the HTTP conection is closed.
    """
    def __init__(self, stream, address, request_callback, no_keep_alive = False,
                 xheaders = False, protocol = None):
        self.stream = stream
        self.address = address
        # Save the socket's address family now so we know how to
        # interpret self.address even after the stream is closed
        # and its socket attribute replaced with None.
        self.address_family = stream.socket.family
        self.request_callback = request_callback
        self.no_keep_alive = no_keep_alive
        self.xheaders = xheaders
        self.protocol = protocol
        self._request = None
        self._request_finished = False
        self._write_callback = None
        self._close_callback = None
        # Save stack context here, outside of any request.  This keeps
        # contexts from one request from leaking into the next.
        self._header_callback = stack_context.wrap(self._on_headers)
        self.stream.read_until(b"\r\n\r\n", self._header_callback)

    def _clear_callbacks(self):
        """Clears the per-request callbacks.

        This is run in between requests to allow the previous handler
        to be garbage collected (and prevent spurious close callbacks),
        and when the connection is closed (to break up cycles and
        facilitate garbage collection in cpython).
        """
        self._write_callback = None
        self._close_callback = None

    def set_close_callback(self, callback):
        """Sets a callback that will be run when the connection is closed.

        Use this instead of accessing
        `HTTPConnection.stream.set_close_callback
        <.BaseIOStream.set_close_callback>` directly (which was the
        recommended approach prior to Tornado 3.0).
        """
        self._close_callback = stack_context.wrap(callback)
        self.stream.set_close_callback(self._on_connection_close)

    def _on_connection_close(self):
        callback = self._close_callback
        self._close_callback = None
        if callback: callback()
        # Delete any unfinished callbacks to break up reference cycles.
        self._header_callback = None
        self._clear_callbacks()

    def close(self):
        self.stream.close()
        # Remove this reference to self, which would otherwise cause a
        # cycle and delay garbage collection of this connection.
        self._header_callback = None
        self._clear_callbacks()

    def write(self, chunk, callback = None):
        """Writes a chunk of output to the stream."""
        assert self._request, "Request closed"
        if not self.stream.closed():
            self._write_callback = stack_context.wrap(callback)
            self.stream.write(chunk, self._on_write_complete)

    def finish(self):
        """Finishes the request."""
        assert self._request, "Request closed"
        self._request_finished = True
        if not self.stream.writing():
            self._finish_request()

    def _on_write_complete(self):
        if self._write_callback is not None:
            callback = self._write_callback
            self._write_callback = None
            callback()
        # _on_write_complete is enqueued on the IOLoop whenever the
        # IOStream's write buffer becomes empty, but it's possible for
        # another callback that runs on the IOLoop before it to
        # simultaneously write more data and finish the request.  If
        # there is still data in the IOStream, a future
        # _on_write_complete will be responsible for calling
        # _finish_request.
        if self._request_finished and not self.stream.writing():
            self._finish_request()

    def _finish_request(self):
        if self.no_keep_alive:
            disconnect = True
        else:
            connection_header = self._request.headers.get("Connection")
            if connection_header is not None:
                connection_header = connection_header.lower()
            if self._request.supports_http_1_1():
                disconnect = connection_header == "close"
            elif ("Content-Length" in self._request.headers
                    or self._request.method in ("HEAD", "GET")):
                disconnect = connection_header != "keep-alive"
            else:
                disconnect = True
        self._request = None
        self._request_finished = False
        self._clear_callbacks()
        if disconnect:
            self.close()
            return
        try:
            # Use a try/except instead of checking stream.closed()
            # directly, because in some cases the stream doesn't discover
            # that it's closed until you try to read from it.
            self.stream.read_until(b"\r\n\r\n", self._header_callback)
        except iostream.StreamClosedError:
            self.close()

    def _on_headers(self, data):
        try:
            data = native_str(data.decode('latin1'))
            eol = data.find("\r\n")
            start_line = data[:eol]
            try:
                method, uri, version = start_line.split(" ")
            except ValueError:
                raise _BadRequestException("Malformed HTTP request line")
            if not version.startswith("HTTP/"):
                raise _BadRequestException("Malformed HTTP version in HTTP Request-Line")
            try:
                headers = httputil.HTTPHeaders.parse(data[eol:])
            except ValueError:
                # Probably from split() if there was no ':' in the line
                raise _BadRequestException("Malformed HTTP headers")

            # HTTPRequest wants an IP, not a full socket address
            if self.address_family in (socket.AF_INET, socket.AF_INET6):
                remote_ip = self.address[0]
            else:
                # Unix (or other) socket; fake the remote address
                remote_ip = '0.0.0.0'

            self._request = HTTPRequest(
                connection = self, method = method, uri = uri, version = version,
                headers = headers, remote_ip = remote_ip, protocol = self.protocol)

            content_length = headers.get("Content-Length")
            if content_length:
                content_length = int(content_length)
                if content_length > self.stream.max_buffer_size:
                    raise _BadRequestException("Content-Length too long")
                if headers.get("Expect") == "100-continue":
                    self.stream.write(b"HTTP/1.1 100 (Continue)\r\n\r\n")
                self.stream.read_bytes(content_length, self._on_request_body)
                return

            self.request_callback(self._request)
        except _BadRequestException as e:
            gen_log.info("Malformed HTTP request from %s: %s",
                         self.address[0], e)
            self.close()
            return

    def _on_request_body(self, data):
        self._request.body = data
        if self._request.method in ("POST", "PATCH", "PUT"):
            httputil.parse_body_arguments(
                self._request.headers.get("Content-Type", ""), data,
                self._request.arguments, self._request.files)
        self.request_callback(self._request)


class HTTPRequest(object):
    """A single HTTP request.

    All attributes are type `str` unless otherwise noted.

    .. attribute:: method

       HTTP request method, e.g. "GET" or "POST"

    .. attribute:: uri

       The requested uri.

    .. attribute:: path

       The path portion of `uri`

    .. attribute:: query

       The query portion of `uri`

    .. attribute:: version

       HTTP version specified in request, e.g. "HTTP/1.1"

    .. attribute:: headers

       `.HTTPHeaders` dictionary-like object for request headers.  Acts like
       a case-insensitive dictionary with additional methods for repeated
       headers.

    .. attribute:: body

       Request body, if present, as a byte string.

    .. attribute:: remote_ip

       Client's IP address as a string.  If ``HTTPServer.xheaders`` is set,
       will pass along the real IP address provided by a load balancer
       in the ``X-Real-Ip`` header

    .. attribute:: protocol

       The protocol used, either "http" or "https".  If ``HTTPServer.xheaders``
       is set, will pass along the protocol used by a load balancer if
       reported via an ``X-Scheme`` header.

    .. attribute:: host

       The requested hostname, usually taken from the ``Host`` header.

    .. attribute:: arguments

       GET/POST arguments are available in the arguments property, which
       maps arguments names to lists of values (to support multiple values
       for individual names). Names are of type `str`, while arguments
       are byte strings.  Note that this is different from
       `.RequestHandler.get_argument`, which returns argument values as
       unicode strings.

    .. attribute:: files

       File uploads are available in the files property, which maps file
       names to lists of `.HTTPFile`.

    .. attribute:: connection

       An HTTP request is attached to a single HTTP connection, which can
       be accessed through the "connection" attribute. Since connections
       are typically kept open in HTTP/1.1, multiple requests can be handled
       sequentially on a single connection.
    """
    def __init__(self, method, uri, version = "HTTP/1.0", headers = None,
                 body = None, remote_ip = None, protocol = None, host = None,
                 files = None, connection = None):
        self.method = method
        self.uri = uri
        self.version = version
        self.headers = headers or httputil.HTTPHeaders()
        self.body = body or ""

        # set remote IP and protocol
        self.remote_ip = remote_ip
        if protocol:
            self.protocol = protocol
        elif connection and isinstance(connection.stream,
                                       iostream.SSLIOStream):
            self.protocol = "https"
        else:
            self.protocol = "http"

        # xheaders can override the defaults
        if connection and connection.xheaders:
            # Squid uses X-Forwarded-For, others use X-Real-Ip
            ip = self.headers.get(
                "X-Real-Ip", self.headers.get("X-Forwarded-For", self.remote_ip))
            if netutil.is_valid_ip(ip):
                self.remote_ip = ip
            # AWS uses X-Forwarded-Proto
            proto = self.headers.get(
                "X-Scheme", self.headers.get("X-Forwarded-Proto", self.protocol))
            if proto in ("http", "https"):
                self.protocol = proto


        self.host = host or self.headers.get("Host") or "127.0.0.1"
        self.files = files or {}
        self.connection = connection
        self._start_time = time.time()
        self._finish_time = None

        self.path, sep, self.query = uri.partition('?')
        self.arguments = parse_qs_bytes(self.query, keep_blank_values = True)

    def supports_http_1_1(self):
        """Returns True if this request supports HTTP/1.1 semantics"""
        return self.version == "HTTP/1.1"

    @property
    def cookies(self):
        """A dictionary of Cookie.Morsel objects."""
        if not hasattr(self, "_cookies"):
            self._cookies = Cookie.SimpleCookie()
            if "Cookie" in self.headers:
                try:
                    self._cookies.load(
                        native_str(self.headers["Cookie"]))
                except Exception:
                    self._cookies = {}
        return self._cookies

    def write(self, chunk, callback = None):
        """Writes the given chunk to the response stream."""
        assert isinstance(chunk, bytes_type)
        self.connection.write(chunk, callback = callback)

    def finish(self):
        """Finishes this HTTP request on the open connection."""
        self.connection.finish()
        self._finish_time = time.time()

    def full_url(self):
        """Reconstructs the full URL for this request."""
        return self.protocol + "://" + self.host + self.uri

    def request_time(self):
        """Returns the amount of time it took for this request to execute."""
        if self._finish_time is None:
            return time.time() - self._start_time
        else:
            return self._finish_time - self._start_time

    def get_ssl_certificate(self, binary_form = False):
        """Returns the client's SSL certificate, if any.

        To use client certificates, the HTTPServer must have been constructed
        with cert_reqs set in ssl_options, e.g.::

            server = HTTPServer(app,
                ssl_options=dict(
                    certfile="foo.crt",
                    keyfile="foo.key",
                    cert_reqs=ssl.CERT_REQUIRED,
                    ca_certs="cacert.crt"))

        By default, the return value is a dictionary (or None, if no
        client certificate is present).  If ``binary_form`` is true, a
        DER-encoded form of the certificate is returned instead.  See
        SSLSocket.getpeercert() in the standard library for more
        details.
        http://docs.python.org/library/ssl.html#sslsocket-objects
        """
        try:
            return self.connection.stream.socket.getpeercert(
                binary_form = binary_form)
        except ssl.SSLError:
            return None

    def __repr__(self):
        attrs = ("protocol", "host", "method", "uri", "version", "remote_ip",
                 "body")
        args = ", ".join(["%s=%r" % (n, getattr(self, n)) for n in attrs])
        return "%s(%s, headers=%s)" % (
            self.__class__.__name__, args, dict(self.headers))
