# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
#
# 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.
import cgi
import logging
import random
import sys
import urllib

from six import string_types
from six.moves.urllib import parse as urlparse

from canonicaljson import encode_canonical_json, json
from prometheus_client import Counter
from signedjson.sign import sign_json

from twisted.internet import defer, protocol, reactor
from twisted.internet.error import DNSLookupError
from twisted.web._newclient import ResponseDone
from twisted.web.client import Agent, HTTPConnectionPool, readBody
from twisted.web.http_headers import Headers

import synapse.metrics
import synapse.util.retryutils
from synapse.api.errors import (
    Codes,
    FederationDeniedError,
    HttpResponseException,
    SynapseError,
)
from synapse.http import cancelled_to_request_timed_out_error
from synapse.http.endpoint import matrix_federation_endpoint
from synapse.util import logcontext
from synapse.util.async import add_timeout_to_deferred
from synapse.util.logcontext import make_deferred_yieldable

logger = logging.getLogger(__name__)
outbound_logger = logging.getLogger("synapse.http.outbound")

outgoing_requests_counter = Counter("synapse_http_matrixfederationclient_requests",
                                    "", ["method"])
incoming_responses_counter = Counter("synapse_http_matrixfederationclient_responses",
                                     "", ["method", "code"])


MAX_LONG_RETRIES = 10
MAX_SHORT_RETRIES = 3


class MatrixFederationEndpointFactory(object):
    def __init__(self, hs):
        self.tls_server_context_factory = hs.tls_server_context_factory

    def endpointForURI(self, uri):
        destination = uri.netloc

        return matrix_federation_endpoint(
            reactor, destination, timeout=10,
            ssl_context_factory=self.tls_server_context_factory
        )


class MatrixFederationHttpClient(object):
    """HTTP client used to talk to other homeservers over the federation
    protocol. Send client certificates and signs requests.

    Attributes:
        agent (twisted.web.client.Agent): The twisted Agent used to send the
            requests.
    """

    def __init__(self, hs):
        self.hs = hs
        self.signing_key = hs.config.signing_key[0]
        self.server_name = hs.hostname
        pool = HTTPConnectionPool(reactor)
        pool.maxPersistentPerHost = 5
        pool.cachedConnectionTimeout = 2 * 60
        self.agent = Agent.usingEndpointFactory(
            reactor, MatrixFederationEndpointFactory(hs), pool=pool
        )
        self.clock = hs.get_clock()
        self._store = hs.get_datastore()
        self.version_string = hs.version_string
        self._next_id = 1

    def _create_url(self, destination, path_bytes, param_bytes, query_bytes):
        return urlparse.urlunparse(
            ("matrix", destination, path_bytes, param_bytes, query_bytes, "")
        )

    @defer.inlineCallbacks
    def _request(self, destination, method, path,
                 body_callback, headers_dict={}, param_bytes=b"",
                 query_bytes=b"", retry_on_dns_fail=True,
                 timeout=None, long_retries=False,
                 ignore_backoff=False,
                 backoff_on_404=False):
        """ Creates and sends a request to the given server
        Args:
            destination (str): The remote server to send the HTTP request to.
            method (str): HTTP method
            path (str): The HTTP path
            ignore_backoff (bool): true to ignore the historical backoff data
                and try the request anyway.
            backoff_on_404 (bool): Back off if we get a 404

        Returns:
            Deferred: resolves with the http response object on success.

            Fails with ``HTTPRequestException``: if we get an HTTP response
                code >= 300.

            Fails with ``NotRetryingDestination`` if we are not yet ready
                to retry this server.

            Fails with ``FederationDeniedError`` if this destination
                is not on our federation whitelist

            (May also fail with plenty of other Exceptions for things like DNS
                failures, connection failures, SSL failures.)
        """
        if (
            self.hs.config.federation_domain_whitelist and
            destination not in self.hs.config.federation_domain_whitelist
        ):
            raise FederationDeniedError(destination)

        limiter = yield synapse.util.retryutils.get_retry_limiter(
            destination,
            self.clock,
            self._store,
            backoff_on_404=backoff_on_404,
            ignore_backoff=ignore_backoff,
        )

        destination = destination.encode("ascii")
        path_bytes = path.encode("ascii")
        with limiter:
            headers_dict[b"User-Agent"] = [self.version_string]
            headers_dict[b"Host"] = [destination]

            url_bytes = self._create_url(
                destination, path_bytes, param_bytes, query_bytes
            )

            txn_id = "%s-O-%s" % (method, self._next_id)
            self._next_id = (self._next_id + 1) % (sys.maxint - 1)

            outbound_logger.info(
                "{%s} [%s] Sending request: %s %s",
                txn_id, destination, method, url_bytes
            )

            # XXX: Would be much nicer to retry only at the transaction-layer
            # (once we have reliable transactions in place)
            if long_retries:
                retries_left = MAX_LONG_RETRIES
            else:
                retries_left = MAX_SHORT_RETRIES

            http_url_bytes = urlparse.urlunparse(
                ("", "", path_bytes, param_bytes, query_bytes, "")
            )

            log_result = None
            try:
                while True:
                    producer = None
                    if body_callback:
                        producer = body_callback(method, http_url_bytes, headers_dict)

                    try:
                        request_deferred = self.agent.request(
                            method,
                            url_bytes,
                            Headers(headers_dict),
                            producer
                        )
                        add_timeout_to_deferred(
                            request_deferred,
                            timeout / 1000. if timeout else 60,
                            self.hs.get_reactor(),
                            cancelled_to_request_timed_out_error,
                        )
                        response = yield make_deferred_yieldable(
                            request_deferred,
                        )

                        log_result = "%d %s" % (response.code, response.phrase,)
                        break
                    except Exception as e:
                        if not retry_on_dns_fail and isinstance(e, DNSLookupError):
                            logger.warn(
                                "DNS Lookup failed to %s with %s",
                                destination,
                                e
                            )
                            log_result = "DNS Lookup failed to %s with %s" % (
                                destination, e
                            )
                            raise

                        logger.warn(
                            "{%s} Sending request failed to %s: %s %s: %s",
                            txn_id,
                            destination,
                            method,
                            url_bytes,
                            _flatten_response_never_received(e),
                        )

                        log_result = _flatten_response_never_received(e)

                        if retries_left and not timeout:
                            if long_retries:
                                delay = 4 ** (MAX_LONG_RETRIES + 1 - retries_left)
                                delay = min(delay, 60)
                                delay *= random.uniform(0.8, 1.4)
                            else:
                                delay = 0.5 * 2 ** (MAX_SHORT_RETRIES - retries_left)
                                delay = min(delay, 2)
                                delay *= random.uniform(0.8, 1.4)

                            yield self.clock.sleep(delay)
                            retries_left -= 1
                        else:
                            raise
            finally:
                outbound_logger.info(
                    "{%s} [%s] Result: %s",
                    txn_id,
                    destination,
                    log_result,
                )

            if 200 <= response.code < 300:
                pass
            else:
                # :'(
                # Update transactions table?
                with logcontext.PreserveLoggingContext():
                    body = yield readBody(response)
                raise HttpResponseException(
                    response.code, response.phrase, body
                )

            defer.returnValue(response)

    def sign_request(self, destination, method, url_bytes, headers_dict,
                     content=None, destination_is=None):
        """
        Signs a request by adding an Authorization header to headers_dict
        Args:
            destination (bytes|None): The desination home server of the request.
                May be None if the destination is an identity server, in which case
                destination_is must be non-None.
            method (bytes): The HTTP method of the request
            url_bytes (bytes): The URI path of the request
            headers_dict (dict): Dictionary of request headers to append to
            content (bytes): The body of the request
            destination_is (bytes): As 'destination', but if the destination is an
                identity server

        Returns:
            None
        """
        request = {
            "method": method,
            "uri": url_bytes,
            "origin": self.server_name,
        }

        if destination is not None:
            request["destination"] = destination

        if destination_is is not None:
            request["destination_is"] = destination_is

        if content is not None:
            request["content"] = content

        request = sign_json(request, self.server_name, self.signing_key)

        auth_headers = []

        for key, sig in request["signatures"][self.server_name].items():
            auth_headers.append(bytes(
                "X-Matrix origin=%s,key=\"%s\",sig=\"%s\"" % (
                    self.server_name, key, sig,
                )
            ))

        headers_dict[b"Authorization"] = auth_headers

    @defer.inlineCallbacks
    def put_json(self, destination, path, args={}, data={},
                 json_data_callback=None,
                 long_retries=False, timeout=None,
                 ignore_backoff=False,
                 backoff_on_404=False):
        """ Sends the specifed json data using PUT

        Args:
            destination (str): The remote server to send the HTTP request
                to.
            path (str): The HTTP path.
            args (dict): query params
            data (dict): A dict containing the data that will be used as
                the request body. This will be encoded as JSON.
            json_data_callback (callable): A callable returning the dict to
                use as the request body.
            long_retries (bool): A boolean that indicates whether we should
                retry for a short or long time.
            timeout(int): How long to try (in ms) the destination for before
                giving up. None indicates no timeout.
            ignore_backoff (bool): true to ignore the historical backoff data
                and try the request anyway.
            backoff_on_404 (bool): True if we should count a 404 response as
                a failure of the server (and should therefore back off future
                requests)

        Returns:
            Deferred: Succeeds when we get a 2xx HTTP response. The result
            will be the decoded JSON body.

            Fails with ``HTTPRequestException`` if we get an HTTP response
            code >= 300.

            Fails with ``NotRetryingDestination`` if we are not yet ready
            to retry this server.

            Fails with ``FederationDeniedError`` if this destination
            is not on our federation whitelist
        """

        if not json_data_callback:
            def json_data_callback():
                return data

        def body_callback(method, url_bytes, headers_dict):
            json_data = json_data_callback()
            self.sign_request(
                destination, method, url_bytes, headers_dict, json_data
            )
            producer = _JsonProducer(json_data)
            return producer

        response = yield self._request(
            destination,
            "PUT",
            path,
            body_callback=body_callback,
            headers_dict={"Content-Type": ["application/json"]},
            query_bytes=encode_query_args(args),
            long_retries=long_retries,
            timeout=timeout,
            ignore_backoff=ignore_backoff,
            backoff_on_404=backoff_on_404,
        )

        if 200 <= response.code < 300:
            # We need to update the transactions table to say it was sent?
            check_content_type_is_json(response.headers)

        with logcontext.PreserveLoggingContext():
            body = yield readBody(response)
        defer.returnValue(json.loads(body))

    @defer.inlineCallbacks
    def post_json(self, destination, path, data={}, long_retries=False,
                  timeout=None, ignore_backoff=False, args={}):
        """ Sends the specifed json data using POST

        Args:
            destination (str): The remote server to send the HTTP request
                to.
            path (str): The HTTP path.
            data (dict): A dict containing the data that will be used as
                the request body. This will be encoded as JSON.
            long_retries (bool): A boolean that indicates whether we should
                retry for a short or long time.
            timeout(int): How long to try (in ms) the destination for before
                giving up. None indicates no timeout.
            ignore_backoff (bool): true to ignore the historical backoff data and
                try the request anyway.
            args (dict): query params
        Returns:
            Deferred: Succeeds when we get a 2xx HTTP response. The result
            will be the decoded JSON body.

            Fails with ``HTTPRequestException`` if we get an HTTP response
            code >= 300.

            Fails with ``NotRetryingDestination`` if we are not yet ready
            to retry this server.

            Fails with ``FederationDeniedError`` if this destination
            is not on our federation whitelist
        """

        def body_callback(method, url_bytes, headers_dict):
            self.sign_request(
                destination, method, url_bytes, headers_dict, data
            )
            return _JsonProducer(data)

        response = yield self._request(
            destination,
            "POST",
            path,
            query_bytes=encode_query_args(args),
            body_callback=body_callback,
            headers_dict={"Content-Type": ["application/json"]},
            long_retries=long_retries,
            timeout=timeout,
            ignore_backoff=ignore_backoff,
        )

        if 200 <= response.code < 300:
            # We need to update the transactions table to say it was sent?
            check_content_type_is_json(response.headers)

        with logcontext.PreserveLoggingContext():
            body = yield readBody(response)

        defer.returnValue(json.loads(body))

    @defer.inlineCallbacks
    def get_json(self, destination, path, args={}, retry_on_dns_fail=True,
                 timeout=None, ignore_backoff=False):
        """ GETs some json from the given host homeserver and path

        Args:
            destination (str): The remote server to send the HTTP request
                to.
            path (str): The HTTP path.
            args (dict): A dictionary used to create query strings, defaults to
                None.
            timeout (int): How long to try (in ms) the destination for before
                giving up. None indicates no timeout and that the request will
                be retried.
            ignore_backoff (bool): true to ignore the historical backoff data
                and try the request anyway.
        Returns:
            Deferred: Succeeds when we get a 2xx HTTP response. The result
            will be the decoded JSON body.

            Fails with ``HTTPRequestException`` if we get an HTTP response
            code >= 300.

            Fails with ``NotRetryingDestination`` if we are not yet ready
            to retry this server.

            Fails with ``FederationDeniedError`` if this destination
            is not on our federation whitelist
        """
        logger.debug("get_json args: %s", args)

        logger.debug("Query bytes: %s Retry DNS: %s", args, retry_on_dns_fail)

        def body_callback(method, url_bytes, headers_dict):
            self.sign_request(destination, method, url_bytes, headers_dict)
            return None

        response = yield self._request(
            destination,
            "GET",
            path,
            query_bytes=encode_query_args(args),
            body_callback=body_callback,
            retry_on_dns_fail=retry_on_dns_fail,
            timeout=timeout,
            ignore_backoff=ignore_backoff,
        )

        if 200 <= response.code < 300:
            # We need to update the transactions table to say it was sent?
            check_content_type_is_json(response.headers)

        with logcontext.PreserveLoggingContext():
            body = yield readBody(response)

        defer.returnValue(json.loads(body))

    @defer.inlineCallbacks
    def delete_json(self, destination, path, long_retries=False,
                    timeout=None, ignore_backoff=False, args={}):
        """Send a DELETE request to the remote expecting some json response

        Args:
            destination (str): The remote server to send the HTTP request
                to.
            path (str): The HTTP path.
            long_retries (bool): A boolean that indicates whether we should
                retry for a short or long time.
            timeout(int): How long to try (in ms) the destination for before
                giving up. None indicates no timeout.
            ignore_backoff (bool): true to ignore the historical backoff data and
                try the request anyway.
        Returns:
            Deferred: Succeeds when we get a 2xx HTTP response. The result
            will be the decoded JSON body.

            Fails with ``HTTPRequestException`` if we get an HTTP response
            code >= 300.

            Fails with ``NotRetryingDestination`` if we are not yet ready
            to retry this server.

            Fails with ``FederationDeniedError`` if this destination
            is not on our federation whitelist
        """

        response = yield self._request(
            destination,
            "DELETE",
            path,
            query_bytes=encode_query_args(args),
            headers_dict={"Content-Type": ["application/json"]},
            long_retries=long_retries,
            timeout=timeout,
            ignore_backoff=ignore_backoff,
        )

        if 200 <= response.code < 300:
            # We need to update the transactions table to say it was sent?
            check_content_type_is_json(response.headers)

        with logcontext.PreserveLoggingContext():
            body = yield readBody(response)

        defer.returnValue(json.loads(body))

    @defer.inlineCallbacks
    def get_file(self, destination, path, output_stream, args={},
                 retry_on_dns_fail=True, max_size=None,
                 ignore_backoff=False):
        """GETs a file from a given homeserver
        Args:
            destination (str): The remote server to send the HTTP request to.
            path (str): The HTTP path to GET.
            output_stream (file): File to write the response body to.
            args (dict): Optional dictionary used to create the query string.
            ignore_backoff (bool): true to ignore the historical backoff data
                and try the request anyway.
        Returns:
            Deferred: resolves with an (int,dict) tuple of the file length and
            a dict of the response headers.

            Fails with ``HTTPRequestException`` if we get an HTTP response code
            >= 300

            Fails with ``NotRetryingDestination`` if we are not yet ready
            to retry this server.

            Fails with ``FederationDeniedError`` if this destination
            is not on our federation whitelist
        """

        encoded_args = {}
        for k, vs in args.items():
            if isinstance(vs, string_types):
                vs = [vs]
            encoded_args[k] = [v.encode("UTF-8") for v in vs]

        query_bytes = urllib.urlencode(encoded_args, True)
        logger.debug("Query bytes: %s Retry DNS: %s", query_bytes, retry_on_dns_fail)

        def body_callback(method, url_bytes, headers_dict):
            self.sign_request(destination, method, url_bytes, headers_dict)
            return None

        response = yield self._request(
            destination,
            "GET",
            path,
            query_bytes=query_bytes,
            body_callback=body_callback,
            retry_on_dns_fail=retry_on_dns_fail,
            ignore_backoff=ignore_backoff,
        )

        headers = dict(response.headers.getAllRawHeaders())

        try:
            with logcontext.PreserveLoggingContext():
                length = yield _readBodyToFile(
                    response, output_stream, max_size
                )
        except Exception:
            logger.exception("Failed to download body")
            raise

        defer.returnValue((length, headers))


class _ReadBodyToFileProtocol(protocol.Protocol):
    def __init__(self, stream, deferred, max_size):
        self.stream = stream
        self.deferred = deferred
        self.length = 0
        self.max_size = max_size

    def dataReceived(self, data):
        self.stream.write(data)
        self.length += len(data)
        if self.max_size is not None and self.length >= self.max_size:
            self.deferred.errback(SynapseError(
                502,
                "Requested file is too large > %r bytes" % (self.max_size,),
                Codes.TOO_LARGE,
            ))
            self.deferred = defer.Deferred()
            self.transport.loseConnection()

    def connectionLost(self, reason):
        if reason.check(ResponseDone):
            self.deferred.callback(self.length)
        else:
            self.deferred.errback(reason)


def _readBodyToFile(response, stream, max_size):
    d = defer.Deferred()
    response.deliverBody(_ReadBodyToFileProtocol(stream, d, max_size))
    return d


class _JsonProducer(object):
    """ Used by the twisted http client to create the HTTP body from json
    """
    def __init__(self, jsn):
        self.reset(jsn)

    def reset(self, jsn):
        self.body = encode_canonical_json(jsn)
        self.length = len(self.body)

    def startProducing(self, consumer):
        consumer.write(self.body)
        return defer.succeed(None)

    def pauseProducing(self):
        pass

    def stopProducing(self):
        pass

    def resumeProducing(self):
        pass


def _flatten_response_never_received(e):
    if hasattr(e, "reasons"):
        reasons = ", ".join(
            _flatten_response_never_received(f.value)
            for f in e.reasons
        )

        return "%s:[%s]" % (type(e).__name__, reasons)
    else:
        return repr(e)


def check_content_type_is_json(headers):
    """
    Check that a set of HTTP headers have a Content-Type header, and that it
    is application/json.

    Args:
        headers (twisted.web.http_headers.Headers): headers to check

    Raises:
        RuntimeError if the

    """
    c_type = headers.getRawHeaders(b"Content-Type")
    if c_type is None:
        raise RuntimeError(
            "No Content-Type header"
        )

    c_type = c_type[0]  # only the first header
    val, options = cgi.parse_header(c_type)
    if val != "application/json":
        raise RuntimeError(
            "Content-Type not application/json: was '%s'" % c_type
        )


def encode_query_args(args):
    encoded_args = {}
    for k, vs in args.items():
        if isinstance(vs, string_types):
            vs = [vs]
        encoded_args[k] = [v.encode("UTF-8") for v in vs]

    query_bytes = urllib.urlencode(encoded_args, True)

    return query_bytes
