#!/usr/bin/env python2
#
# 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.

"""Non-blocking HTTP client implementation using pycurl."""

from __future__ import absolute_import, division, print_function, with_statement

import collections
import functools
import logging
import pycurl
import threading
import time
from io import BytesIO

from tornado import httputil
from tornado import ioloop
from tornado import stack_context

from tornado.escape import utf8, native_str
from tornado.httpclient import HTTPResponse, HTTPError, AsyncHTTPClient, main

curl_log = logging.getLogger('tornado.curl_httpclient')


class CurlAsyncHTTPClient(AsyncHTTPClient):
    def initialize(self, io_loop, max_clients=10, defaults=None):
        super(CurlAsyncHTTPClient, self).initialize(io_loop, defaults=defaults)
        self._multi = pycurl.CurlMulti()
        self._multi.setopt(pycurl.M_TIMERFUNCTION, self._set_timeout)
        self._multi.setopt(pycurl.M_SOCKETFUNCTION, self._handle_socket)
        self._curls = [self._curl_create() for i in range(max_clients)]
        self._free_list = self._curls[:]
        self._requests = collections.deque()
        self._fds = {}
        self._timeout = None

        # libcurl has bugs that sometimes cause it to not report all
        # relevant file descriptors and timeouts to TIMERFUNCTION/
        # SOCKETFUNCTION.  Mitigate the effects of such bugs by
        # forcing a periodic scan of all active requests.
        self._force_timeout_callback = ioloop.PeriodicCallback(
            self._handle_force_timeout, 1000, io_loop=io_loop)
        self._force_timeout_callback.start()

        # Work around a bug in libcurl 7.29.0: Some fields in the curl
        # multi object are initialized lazily, and its destructor will
        # segfault if it is destroyed without having been used.  Add
        # and remove a dummy handle to make sure everything is
        # initialized.
        dummy_curl_handle = pycurl.Curl()
        self._multi.add_handle(dummy_curl_handle)
        self._multi.remove_handle(dummy_curl_handle)

    def close(self):
        self._force_timeout_callback.stop()
        if self._timeout is not None:
            self.io_loop.remove_timeout(self._timeout)
        for curl in self._curls:
            curl.close()
        self._multi.close()
        super(CurlAsyncHTTPClient, self).close()

    def fetch_impl(self, request, callback):
        self._requests.append((request, callback))
        self._process_queue()
        self._set_timeout(0)

    def _handle_socket(self, event, fd, multi, data):
        """Called by libcurl when it wants to change the file descriptors
        it cares about.
        """
        event_map = {
            pycurl.POLL_NONE: ioloop.IOLoop.NONE,
            pycurl.POLL_IN: ioloop.IOLoop.READ,
            pycurl.POLL_OUT: ioloop.IOLoop.WRITE,
            pycurl.POLL_INOUT: ioloop.IOLoop.READ | ioloop.IOLoop.WRITE
        }
        if event == pycurl.POLL_REMOVE:
            if fd in self._fds:
                self.io_loop.remove_handler(fd)
                del self._fds[fd]
        else:
            ioloop_event = event_map[event]
            # libcurl sometimes closes a socket and then opens a new
            # one using the same FD without giving us a POLL_NONE in
            # between.  This is a problem with the epoll IOLoop,
            # because the kernel can tell when a socket is closed and
            # removes it from the epoll automatically, causing future
            # update_handler calls to fail.  Since we can't tell when
            # this has happened, always use remove and re-add
            # instead of update.
            if fd in self._fds:
                self.io_loop.remove_handler(fd)
            self.io_loop.add_handler(fd, self._handle_events,
                                     ioloop_event)
            self._fds[fd] = ioloop_event

    def _set_timeout(self, msecs):
        """Called by libcurl to schedule a timeout."""
        if self._timeout is not None:
            self.io_loop.remove_timeout(self._timeout)
        self._timeout = self.io_loop.add_timeout(
            self.io_loop.time() + msecs / 1000.0, self._handle_timeout)

    def _handle_events(self, fd, events):
        """Called by IOLoop when there is activity on one of our
        file descriptors.
        """
        action = 0
        if events & ioloop.IOLoop.READ:
            action |= pycurl.CSELECT_IN
        if events & ioloop.IOLoop.WRITE:
            action |= pycurl.CSELECT_OUT
        while True:
            try:
                ret, num_handles = self._multi.socket_action(fd, action)
            except pycurl.error as e:
                ret = e.args[0]
            if ret != pycurl.E_CALL_MULTI_PERFORM:
                break
        self._finish_pending_requests()

    def _handle_timeout(self):
        """Called by IOLoop when the requested timeout has passed."""
        with stack_context.NullContext():
            self._timeout = None
            while True:
                try:
                    ret, num_handles = self._multi.socket_action(
                        pycurl.SOCKET_TIMEOUT, 0)
                except pycurl.error as e:
                    ret = e.args[0]
                if ret != pycurl.E_CALL_MULTI_PERFORM:
                    break
            self._finish_pending_requests()

        # In theory, we shouldn't have to do this because curl will
        # call _set_timeout whenever the timeout changes.  However,
        # sometimes after _handle_timeout we will need to reschedule
        # immediately even though nothing has changed from curl's
        # perspective.  This is because when socket_action is
        # called with SOCKET_TIMEOUT, libcurl decides internally which
        # timeouts need to be processed by using a monotonic clock
        # (where available) while tornado uses python's time.time()
        # to decide when timeouts have occurred.  When those clocks
        # disagree on elapsed time (as they will whenever there is an
        # NTP adjustment), tornado might call _handle_timeout before
        # libcurl is ready.  After each timeout, resync the scheduled
        # timeout with libcurl's current state.
        new_timeout = self._multi.timeout()
        if new_timeout >= 0:
            self._set_timeout(new_timeout)

    def _handle_force_timeout(self):
        """Called by IOLoop periodically to ask libcurl to process any
        events it may have forgotten about.
        """
        with stack_context.NullContext():
            while True:
                try:
                    ret, num_handles = self._multi.socket_all()
                except pycurl.error as e:
                    ret = e.args[0]
                if ret != pycurl.E_CALL_MULTI_PERFORM:
                    break
            self._finish_pending_requests()

    def _finish_pending_requests(self):
        """Process any requests that were completed by the last
        call to multi.socket_action.
        """
        while True:
            num_q, ok_list, err_list = self._multi.info_read()
            for curl in ok_list:
                self._finish(curl)
            for curl, errnum, errmsg in err_list:
                self._finish(curl, errnum, errmsg)
            if num_q == 0:
                break
        self._process_queue()

    def _process_queue(self):
        with stack_context.NullContext():
            while True:
                started = 0
                while self._free_list and self._requests:
                    started += 1
                    curl = self._free_list.pop()
                    (request, callback) = self._requests.popleft()
                    curl.info = {
                        "headers": httputil.HTTPHeaders(),
                        "buffer": BytesIO(),
                        "request": request,
                        "callback": callback,
                        "curl_start_time": time.time(),
                    }
                    try:
                        self._curl_setup_request(
                            curl, request, curl.info["buffer"],
                            curl.info["headers"])
                    except Exception as e:
                        # If there was an error in setup, pass it on
                        # to the callback. Note that allowing the
                        # error to escape here will appear to work
                        # most of the time since we are still in the
                        # caller's original stack frame, but when
                        # _process_queue() is called from
                        # _finish_pending_requests the exceptions have
                        # nowhere to go.
                        callback(HTTPResponse(
                            request=request,
                            code=599,
                            error=e))
                    else:
                        self._multi.add_handle(curl)

                if not started:
                    break

    def _finish(self, curl, curl_error=None, curl_message=None):
        info = curl.info
        curl.info = None
        self._multi.remove_handle(curl)
        self._free_list.append(curl)
        buffer = info["buffer"]
        if curl_error:
            error = CurlError(curl_error, curl_message)
            code = error.code
            effective_url = None
            buffer.close()
            buffer = None
        else:
            error = None
            code = curl.getinfo(pycurl.HTTP_CODE)
            effective_url = curl.getinfo(pycurl.EFFECTIVE_URL)
            buffer.seek(0)
        # the various curl timings are documented at
        # http://curl.haxx.se/libcurl/c/curl_easy_getinfo.html
        time_info = dict(
            queue=info["curl_start_time"] - info["request"].start_time,
            namelookup=curl.getinfo(pycurl.NAMELOOKUP_TIME),
            connect=curl.getinfo(pycurl.CONNECT_TIME),
            pretransfer=curl.getinfo(pycurl.PRETRANSFER_TIME),
            starttransfer=curl.getinfo(pycurl.STARTTRANSFER_TIME),
            total=curl.getinfo(pycurl.TOTAL_TIME),
            redirect=curl.getinfo(pycurl.REDIRECT_TIME),
        )
        try:
            info["callback"](HTTPResponse(
                request=info["request"], code=code, headers=info["headers"],
                buffer=buffer, effective_url=effective_url, error=error,
                reason=info['headers'].get("X-Http-Reason", None),
                request_time=time.time() - info["curl_start_time"],
                time_info=time_info))
        except Exception:
            self.handle_callback_exception(info["callback"])

    def handle_callback_exception(self, callback):
        self.io_loop.handle_callback_exception(callback)

    def _curl_create(self):
        curl = pycurl.Curl()
        if curl_log.isEnabledFor(logging.DEBUG):
            curl.setopt(pycurl.VERBOSE, 1)
            curl.setopt(pycurl.DEBUGFUNCTION, self._curl_debug)
        return curl

    def _curl_setup_request(self, curl, request, buffer, headers):
        curl.setopt(pycurl.URL, native_str(request.url))

        # libcurl's magic "Expect: 100-continue" behavior causes delays
        # with servers that don't support it (which include, among others,
        # Google's OpenID endpoint).  Additionally, this behavior has
        # a bug in conjunction with the curl_multi_socket_action API
        # (https://sourceforge.net/tracker/?func=detail&atid=100976&aid=3039744&group_id=976),
        # which increases the delays.  It's more trouble than it's worth,
        # so just turn off the feature (yes, setting Expect: to an empty
        # value is the official way to disable this)
        if "Expect" not in request.headers:
            request.headers["Expect"] = ""

        # libcurl adds Pragma: no-cache by default; disable that too
        if "Pragma" not in request.headers:
            request.headers["Pragma"] = ""

        curl.setopt(pycurl.HTTPHEADER,
                    ["%s: %s" % (native_str(k), native_str(v))
                     for k, v in request.headers.get_all()])

        curl.setopt(pycurl.HEADERFUNCTION,
                    functools.partial(self._curl_header_callback,
                                      headers, request.header_callback))
        if request.streaming_callback:
            def write_function(chunk):
                self.io_loop.add_callback(request.streaming_callback, chunk)
        else:
            write_function = buffer.write
        if bytes is str:  # py2
            curl.setopt(pycurl.WRITEFUNCTION, write_function)
        else:  # py3
            # Upstream pycurl doesn't support py3, but ubuntu 12.10 includes
            # a fork/port.  That version has a bug in which it passes unicode
            # strings instead of bytes to the WRITEFUNCTION.  This means that
            # if you use a WRITEFUNCTION (which tornado always does), you cannot
            # download arbitrary binary data.  This needs to be fixed in the
            # ported pycurl package, but in the meantime this lambda will
            # make it work for downloading (utf8) text.
            curl.setopt(pycurl.WRITEFUNCTION, lambda s: write_function(utf8(s)))
        curl.setopt(pycurl.FOLLOWLOCATION, request.follow_redirects)
        curl.setopt(pycurl.MAXREDIRS, request.max_redirects)
        curl.setopt(pycurl.CONNECTTIMEOUT_MS, int(1000 * request.connect_timeout))
        curl.setopt(pycurl.TIMEOUT_MS, int(1000 * request.request_timeout))
        if request.user_agent:
            curl.setopt(pycurl.USERAGENT, native_str(request.user_agent))
        else:
            curl.setopt(pycurl.USERAGENT, "Mozilla/5.0 (compatible; pycurl)")
        if request.network_interface:
            curl.setopt(pycurl.INTERFACE, request.network_interface)
        if request.decompress_response:
            curl.setopt(pycurl.ENCODING, "gzip,deflate")
        else:
            curl.setopt(pycurl.ENCODING, "none")
        if request.proxy_host and request.proxy_port:
            curl.setopt(pycurl.PROXY, request.proxy_host)
            curl.setopt(pycurl.PROXYPORT, request.proxy_port)
            if request.proxy_username:
                credentials = '%s:%s' % (request.proxy_username,
                                         request.proxy_password)
                curl.setopt(pycurl.PROXYUSERPWD, credentials)
        else:
            curl.setopt(pycurl.PROXY, '')
            curl.unsetopt(pycurl.PROXYUSERPWD)
        if request.validate_cert:
            curl.setopt(pycurl.SSL_VERIFYPEER, 1)
            curl.setopt(pycurl.SSL_VERIFYHOST, 2)
        else:
            curl.setopt(pycurl.SSL_VERIFYPEER, 0)
            curl.setopt(pycurl.SSL_VERIFYHOST, 0)
        if request.ca_certs is not None:
            curl.setopt(pycurl.CAINFO, request.ca_certs)
        else:
            # There is no way to restore pycurl.CAINFO to its default value
            # (Using unsetopt makes it reject all certificates).
            # I don't see any way to read the default value from python so it
            # can be restored later.  We'll have to just leave CAINFO untouched
            # if no ca_certs file was specified, and require that if any
            # request uses a custom ca_certs file, they all must.
            pass

        if request.allow_ipv6 is False:
            # Curl behaves reasonably when DNS resolution gives an ipv6 address
            # that we can't reach, so allow ipv6 unless the user asks to disable.
            curl.setopt(pycurl.IPRESOLVE, pycurl.IPRESOLVE_V4)
        else:
            curl.setopt(pycurl.IPRESOLVE, pycurl.IPRESOLVE_WHATEVER)

        # Set the request method through curl's irritating interface which makes
        # up names for almost every single method
        curl_options = {
            "GET": pycurl.HTTPGET,
            "POST": pycurl.POST,
            "PUT": pycurl.UPLOAD,
            "HEAD": pycurl.NOBODY,
        }
        custom_methods = set(["DELETE", "OPTIONS", "PATCH"])
        for o in curl_options.values():
            curl.setopt(o, False)
        if request.method in curl_options:
            curl.unsetopt(pycurl.CUSTOMREQUEST)
            curl.setopt(curl_options[request.method], True)
        elif request.allow_nonstandard_methods or request.method in custom_methods:
            curl.setopt(pycurl.CUSTOMREQUEST, request.method)
        else:
            raise KeyError('unknown method ' + request.method)

        # Handle curl's cryptic options for every individual HTTP method
        if request.method == "GET":
            if request.body is not None:
                raise ValueError('Body must be None for GET request')
        elif request.method in ("POST", "PUT") or request.body:
            if request.body is None:
                raise ValueError(
                    'Body must not be None for "%s" request'
                    % request.method)

            request_buffer = BytesIO(utf8(request.body))

            def ioctl(cmd):
                if cmd == curl.IOCMD_RESTARTREAD:
                    request_buffer.seek(0)
            curl.setopt(pycurl.READFUNCTION, request_buffer.read)
            curl.setopt(pycurl.IOCTLFUNCTION, ioctl)
            if request.method == "POST":
                curl.setopt(pycurl.POSTFIELDSIZE, len(request.body))
            else:
                curl.setopt(pycurl.UPLOAD, True)
                curl.setopt(pycurl.INFILESIZE, len(request.body))

        if request.auth_username is not None:
            userpwd = "%s:%s" % (request.auth_username, request.auth_password or '')

            if request.auth_mode is None or request.auth_mode == "basic":
                curl.setopt(pycurl.HTTPAUTH, pycurl.HTTPAUTH_BASIC)
            elif request.auth_mode == "digest":
                curl.setopt(pycurl.HTTPAUTH, pycurl.HTTPAUTH_DIGEST)
            else:
                raise ValueError("Unsupported auth_mode %s" % request.auth_mode)

            curl.setopt(pycurl.USERPWD, native_str(userpwd))
            curl_log.debug("%s %s (username: %r)", request.method, request.url,
                           request.auth_username)
        else:
            curl.unsetopt(pycurl.USERPWD)
            curl_log.debug("%s %s", request.method, request.url)

        if request.client_cert is not None:
            curl.setopt(pycurl.SSLCERT, request.client_cert)

        if request.client_key is not None:
            curl.setopt(pycurl.SSLKEY, request.client_key)

        if request.ssl_options is not None:
            raise ValueError("ssl_options not supported in curl_httpclient")

        if threading.activeCount() > 1:
            # libcurl/pycurl is not thread-safe by default.  When multiple threads
            # are used, signals should be disabled.  This has the side effect
            # of disabling DNS timeouts in some environments (when libcurl is
            # not linked against ares), so we don't do it when there is only one
            # thread.  Applications that use many short-lived threads may need
            # to set NOSIGNAL manually in a prepare_curl_callback since
            # there may not be any other threads running at the time we call
            # threading.activeCount.
            curl.setopt(pycurl.NOSIGNAL, 1)
        if request.prepare_curl_callback is not None:
            request.prepare_curl_callback(curl)

    def _curl_header_callback(self, headers, header_callback, header_line):
        header_line = native_str(header_line)
        if header_callback is not None:
            self.io_loop.add_callback(header_callback, header_line)
        # header_line as returned by curl includes the end-of-line characters.
        header_line = header_line.strip()
        if header_line.startswith("HTTP/"):
            headers.clear()
            try:
                (__, __, reason) = httputil.parse_response_start_line(header_line)
                header_line = "X-Http-Reason: %s" % reason
            except httputil.HTTPInputError:
                return
        if not header_line:
            return
        headers.parse_line(header_line)

    def _curl_debug(self, debug_type, debug_msg):
        debug_types = ('I', '<', '>', '<', '>')
        if debug_type == 0:
            curl_log.debug('%s', debug_msg.strip())
        elif debug_type in (1, 2):
            for line in debug_msg.splitlines():
                curl_log.debug('%s %s', debug_types[debug_type], line)
        elif debug_type == 4:
            curl_log.debug('%s %r', debug_types[debug_type], debug_msg)


class CurlError(HTTPError):
    def __init__(self, errno, message):
        HTTPError.__init__(self, 599, message)
        self.errno = errno


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