# -*- coding: utf-8 -*-
# Copyright 2014 OpenMarket 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.

"""The transport layer is responsible for both sending transactions to remote
home servers and receiving a variety of requests from other home servers.

Typically, this is done over HTTP (and all home servers are required to
support HTTP), however individual pairings of servers may decide to communicate
over a different (albeit still reliable) protocol.
"""

from twisted.internet import defer

from synapse.api.urls import FEDERATION_PREFIX as PREFIX
from synapse.api.errors import Codes, SynapseError
from synapse.util.logutils import log_function

import logging
import json
import re


logger = logging.getLogger(__name__)


class TransportLayer(object):
    """This is a basic implementation of the transport layer that translates
    transactions and other requests to/from HTTP.

    Attributes:
        server_name (str): Local home server host

        server (synapse.http.server.HttpServer): the http server to
                register listeners on

        client (synapse.http.client.HttpClient): the http client used to
                send requests

        request_handler (TransportRequestHandler): The handler to fire when we
            receive requests for data.

        received_handler (TransportReceivedHandler): The handler to fire when
            we receive data.
    """

    def __init__(self, homeserver, server_name, server, client):
        """
        Args:
            server_name (str): Local home server host
            server (synapse.protocol.http.HttpServer): the http server to
                register listeners on
            client (synapse.protocol.http.HttpClient): the http client used to
                send requests
        """
        self.keyring = homeserver.get_keyring()
        self.server_name = server_name
        self.server = server
        self.client = client
        self.request_handler = None
        self.received_handler = None

    @log_function
    def get_context_state(self, destination, context, event_id=None):
        """ Requests all state for a given context (i.e. room) from the
        given server.

        Args:
            destination (str): The host name of the remote home server we want
                to get the state from.
            context (str): The name of the context we want the state of

        Returns:
            Deferred: Results in a dict received from the remote homeserver.
        """
        logger.debug("get_context_state dest=%s, context=%s",
                     destination, context)

        subpath = "/state/%s/" % context

        args = {}
        if event_id:
            args["event_id"] = event_id

        return self._do_request_for_transaction(
            destination, subpath, args=args
        )

    @log_function
    def get_event(self, destination, event_id):
        """ Requests the pdu with give id and origin from the given server.

        Args:
            destination (str): The host name of the remote home server we want
                to get the state from.
            event_id (str): The id of the event being requested.

        Returns:
            Deferred: Results in a dict received from the remote homeserver.
        """
        logger.debug("get_pdu dest=%s, event_id=%s",
                     destination, event_id)

        subpath = "/event/%s/" % (event_id, )

        return self._do_request_for_transaction(destination, subpath)

    @log_function
    def backfill(self, dest, context, event_tuples, limit):
        """ Requests `limit` previous PDUs in a given context before list of
        PDUs.

        Args:
            dest (str)
            context (str)
            event_tuples (list)
            limt (int)

        Returns:
            Deferred: Results in a dict received from the remote homeserver.
        """
        logger.debug(
            "backfill dest=%s, context=%s, event_tuples=%s, limit=%s",
            dest, context, repr(event_tuples), str(limit)
        )

        if not event_tuples:
            # TODO: raise?
            return

        subpath = "/backfill/%s/" % (context,)

        args = {
            "v": event_tuples,
            "limit": [str(limit)],
        }

        return self._do_request_for_transaction(
            dest,
            subpath,
            args=args,
        )

    @defer.inlineCallbacks
    @log_function
    def send_transaction(self, transaction, json_data_callback=None):
        """ Sends the given Transaction to it's destination

        Args:
            transaction (Transaction)

        Returns:
            Deferred: Results of the deferred is a tuple in the form of
            (response_code, response_body) where the response_body is a
            python dict decoded from json
        """
        logger.debug(
            "send_data dest=%s, txid=%s",
            transaction.destination, transaction.transaction_id
        )

        if transaction.destination == self.server_name:
            raise RuntimeError("Transport layer cannot send to itself!")

        # FIXME: This is only used by the tests. The actual json sent is
        # generated by the json_data_callback.
        json_data = transaction.get_dict()

        code, response = yield self.client.put_json(
            transaction.destination,
            path=PREFIX + "/send/%s/" % transaction.transaction_id,
            data=json_data,
            json_data_callback=json_data_callback,
        )

        logger.debug(
            "send_data dest=%s, txid=%s, got response: %d",
            transaction.destination, transaction.transaction_id, code
        )

        defer.returnValue((code, response))

    @defer.inlineCallbacks
    @log_function
    def make_query(self, destination, query_type, args, retry_on_dns_fail):
        path = PREFIX + "/query/%s" % query_type

        response = yield self.client.get_json(
            destination=destination,
            path=path,
            args=args,
            retry_on_dns_fail=retry_on_dns_fail,
        )

        defer.returnValue(response)

    @defer.inlineCallbacks
    @log_function
    def make_join(self, destination, context, user_id, retry_on_dns_fail=True):
        path = PREFIX + "/make_join/%s/%s" % (context, user_id,)

        response = yield self.client.get_json(
            destination=destination,
            path=path,
            retry_on_dns_fail=retry_on_dns_fail,
        )

        defer.returnValue(response)

    @defer.inlineCallbacks
    @log_function
    def send_join(self, destination, context, event_id, content):
        path = PREFIX + "/send_join/%s/%s" % (
            context,
            event_id,
        )

        code, content = yield self.client.put_json(
            destination=destination,
            path=path,
            data=content,
        )

        if not 200 <= code < 300:
            raise RuntimeError("Got %d from send_join", code)

        defer.returnValue(json.loads(content))

    @defer.inlineCallbacks
    @log_function
    def send_invite(self, destination, context, event_id, content):
        path = PREFIX + "/invite/%s/%s" % (
            context,
            event_id,
        )

        code, content = yield self.client.put_json(
            destination=destination,
            path=path,
            data=content,
        )

        if not 200 <= code < 300:
            raise RuntimeError("Got %d from send_invite", code)

        defer.returnValue(json.loads(content))

    @defer.inlineCallbacks
    @log_function
    def get_event_auth(self, destination, context, event_id):
        path = PREFIX + "/event_auth/%s/%s" % (
            context,
            event_id,
        )

        response = yield self.client.get_json(
            destination=destination,
            path=path,
        )

        defer.returnValue(response)

    @defer.inlineCallbacks
    def _authenticate_request(self, request):
        json_request = {
            "method": request.method,
            "uri": request.uri,
            "destination": self.server_name,
            "signatures": {},
        }

        content = None
        origin = None

        if request.method == "PUT":
            # TODO: Handle other method types? other content types?
            try:
                content_bytes = request.content.read()
                content = json.loads(content_bytes)
                json_request["content"] = content
            except:
                raise SynapseError(400, "Unable to parse JSON", Codes.BAD_JSON)

        def parse_auth_header(header_str):
            try:
                params = auth.split(" ")[1].split(",")
                param_dict = dict(kv.split("=") for kv in params)

                def strip_quotes(value):
                    if value.startswith("\""):
                        return value[1:-1]
                    else:
                        return value

                origin = strip_quotes(param_dict["origin"])
                key = strip_quotes(param_dict["key"])
                sig = strip_quotes(param_dict["sig"])
                return (origin, key, sig)
            except:
                raise SynapseError(
                    400, "Malformed Authorization header", Codes.UNAUTHORIZED
                )

        auth_headers = request.requestHeaders.getRawHeaders(b"Authorization")

        if not auth_headers:
            raise SynapseError(
                401, "Missing Authorization headers", Codes.UNAUTHORIZED,
            )

        for auth in auth_headers:
            if auth.startswith("X-Matrix"):
                (origin, key, sig) = parse_auth_header(auth)
                json_request["origin"] = origin
                json_request["signatures"].setdefault(origin, {})[key] = sig

        if not json_request["signatures"]:
            raise SynapseError(
                401, "Missing Authorization headers", Codes.UNAUTHORIZED,
            )

        yield self.keyring.verify_json_for_server(origin, json_request)

        defer.returnValue((origin, content))

    def _with_authentication(self, handler):
        @defer.inlineCallbacks
        def new_handler(request, *args, **kwargs):
            try:
                (origin, content) = yield self._authenticate_request(request)
                response = yield handler(
                    origin, content, request.args, *args, **kwargs
                )
            except:
                logger.exception("_authenticate_request failed")
                raise
            defer.returnValue(response)
        return new_handler

    @log_function
    def register_received_handler(self, handler):
        """ Register a handler that will be fired when we receive data.

        Args:
            handler (TransportReceivedHandler)
        """
        self.received_handler = handler

        # This is when someone is trying to send us a bunch of data.
        self.server.register_path(
            "PUT",
            re.compile("^" + PREFIX + "/send/([^/]*)/$"),
            self._with_authentication(self._on_send_request)
        )

    @log_function
    def register_request_handler(self, handler):
        """ Register a handler that will be fired when we get asked for data.

        Args:
            handler (TransportRequestHandler)
        """
        self.request_handler = handler

        # TODO(markjh): Namespace the federation URI paths

        # This is for when someone asks us for everything since version X
        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/pull/$"),
            self._with_authentication(
                lambda origin, content, query:
                handler.on_pull_request(query["origin"][0], query["v"])
            )
        )

        # This is when someone asks for a data item for a given server
        # data_id pair.
        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/event/([^/]*)/$"),
            self._with_authentication(
                lambda origin, content, query, event_id:
                handler.on_pdu_request(origin, event_id)
            )
        )

        # This is when someone asks for all data for a given context.
        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/state/([^/]*)/$"),
            self._with_authentication(
                lambda origin, content, query, context:
                handler.on_context_state_request(
                    origin,
                    context,
                    query.get("event_id", [None])[0],
                )
            )
        )

        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/backfill/([^/]*)/$"),
            self._with_authentication(
                lambda origin, content, query, context:
                self._on_backfill_request(
                    origin, context, query["v"], query["limit"]
                )
            )
        )

        # This is when we receive a server-server Query
        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/query/([^/]*)$"),
            self._with_authentication(
                lambda origin, content, query, query_type:
                handler.on_query_request(
                    query_type,
                    {k: v[0].decode("utf-8") for k, v in query.items()}
                )
            )
        )

        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/make_join/([^/]*)/([^/]*)$"),
            self._with_authentication(
                lambda origin, content, query, context, user_id:
                self._on_make_join_request(
                    origin, content, query, context, user_id
                )
            )
        )

        self.server.register_path(
            "GET",
            re.compile("^" + PREFIX + "/event_auth/([^/]*)/([^/]*)$"),
            self._with_authentication(
                lambda origin, content, query, context, event_id:
                handler.on_event_auth(
                    origin, context, event_id,
                )
            )
        )

        self.server.register_path(
            "PUT",
            re.compile("^" + PREFIX + "/send_join/([^/]*)/([^/]*)$"),
            self._with_authentication(
                lambda origin, content, query, context, event_id:
                self._on_send_join_request(
                    origin, content, query,
                )
            )
        )

        self.server.register_path(
            "PUT",
            re.compile("^" + PREFIX + "/invite/([^/]*)/([^/]*)$"),
            self._with_authentication(
                lambda origin, content, query, context, event_id:
                self._on_invite_request(
                    origin, content, query,
                )
            )
        )

    @defer.inlineCallbacks
    @log_function
    def _on_send_request(self, origin, content, query, transaction_id):
        """ Called on PUT /send/<transaction_id>/

        Args:
            request (twisted.web.http.Request): The HTTP request.
            transaction_id (str): The transaction_id associated with this
                request. This is *not* None.

        Returns:
            Deferred: Results in a tuple of `(code, response)`, where
            `response` is a python dict to be converted into JSON that is
            used as the response body.
        """
        # Parse the request
        try:
            transaction_data = content

            logger.debug(
                "Decoded %s: %s",
                transaction_id, str(transaction_data)
            )

            # We should ideally be getting this from the security layer.
            # origin = body["origin"]

            # Add some extra data to the transaction dict that isn't included
            # in the request body.
            transaction_data.update(
                transaction_id=transaction_id,
                destination=self.server_name
            )

        except Exception as e:
            logger.exception(e)
            defer.returnValue((400, {"error": "Invalid transaction"}))
            return

        try:
            handler = self.received_handler
            code, response = yield handler.on_incoming_transaction(
                transaction_data
            )
        except:
            logger.exception("on_incoming_transaction failed")
            raise

        defer.returnValue((code, response))

    @defer.inlineCallbacks
    @log_function
    def _do_request_for_transaction(self, destination, subpath, args={}):
        """
        Args:
            destination (str)
            path (str)
            args (dict): This is parsed directly to the HttpClient.

        Returns:
            Deferred: Results in a dict.
        """

        data = yield self.client.get_json(
            destination,
            path=PREFIX + subpath,
            args=args,
        )

        # Add certain keys to the JSON, ready for decoding as a Transaction
        data.update(
            origin=destination,
            destination=self.server_name,
            transaction_id=None
        )

        defer.returnValue(data)

    @log_function
    def _on_backfill_request(self, origin, context, v_list, limits):
        if not limits:
            return defer.succeed(
                (400, {"error": "Did not include limit param"})
            )

        limit = int(limits[-1])

        versions = v_list

        return self.request_handler.on_backfill_request(
            origin, context, versions, limit
        )

    @defer.inlineCallbacks
    @log_function
    def _on_make_join_request(self, origin, content, query, context, user_id):
        content = yield self.request_handler.on_make_join_request(
            context, user_id,
        )
        defer.returnValue((200, content))

    @defer.inlineCallbacks
    @log_function
    def _on_send_join_request(self, origin, content, query):
        content = yield self.request_handler.on_send_join_request(
            origin, content,
        )

        defer.returnValue((200, content))

    @defer.inlineCallbacks
    @log_function
    def _on_invite_request(self, origin, content, query):
        content = yield self.request_handler.on_invite_request(
            origin, content,
        )

        defer.returnValue((200, content))