# -*- coding: utf-8 -*-
# Copyright 2014, 2015 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.


from twisted.internet import defer

from .persistence import TransactionActions
from .units import Transaction

from synapse.api.errors import HttpResponseException
from synapse.util.logutils import log_function
from synapse.util.logcontext import PreserveLoggingContext

import logging


logger = logging.getLogger(__name__)


class TransactionQueue(object):
    """This class makes sure we only have one transaction in flight at
    a time for a given destination.

    It batches pending PDUs into single transactions.
    """

    def __init__(self, hs, transport_layer):
        self.server_name = hs.hostname

        self.store = hs.get_datastore()
        self.transaction_actions = TransactionActions(self.store)

        self.transport_layer = transport_layer

        self._clock = hs.get_clock()

        # Is a mapping from destinations -> deferreds. Used to keep track
        # of which destinations have transactions in flight and when they are
        # done
        self.pending_transactions = {}

        # Is a mapping from destination -> list of
        # tuple(pending pdus, deferred, order)
        self.pending_pdus_by_dest = {}
        # destination -> list of tuple(edu, deferred)
        self.pending_edus_by_dest = {}

        # destination -> list of tuple(failure, deferred)
        self.pending_failures_by_dest = {}

        # HACK to get unique tx id
        self._next_txn_id = int(self._clock.time_msec())

    @defer.inlineCallbacks
    @log_function
    def enqueue_pdu(self, pdu, destinations, order):
        # We loop through all destinations to see whether we already have
        # a transaction in progress. If we do, stick it in the pending_pdus
        # table and we'll get back to it later.

        destinations = set(destinations)
        destinations.discard(self.server_name)
        destinations.discard("localhost")

        logger.debug("Sending to: %s", str(destinations))

        if not destinations:
            return

        deferreds = []

        for destination in destinations:
            deferred = defer.Deferred()
            self.pending_pdus_by_dest.setdefault(destination, []).append(
                (pdu, deferred, order)
            )

            def eb(failure):
                if not deferred.called:
                    deferred.errback(failure)
                else:
                    logger.warn("Failed to send pdu", failure)

            with PreserveLoggingContext():
                self._attempt_new_transaction(destination).addErrback(eb)

            deferreds.append(deferred)

        yield defer.DeferredList(deferreds)

    # NO inlineCallbacks
    def enqueue_edu(self, edu):
        destination = edu.destination

        if destination == self.server_name:
            return

        deferred = defer.Deferred()
        self.pending_edus_by_dest.setdefault(destination, []).append(
            (edu, deferred)
        )

        def eb(failure):
            if not deferred.called:
                deferred.errback(failure)
            else:
                logger.warn("Failed to send edu", failure)

        with PreserveLoggingContext():
            self._attempt_new_transaction(destination).addErrback(eb)

        return deferred

    @defer.inlineCallbacks
    def enqueue_failure(self, failure, destination):
        deferred = defer.Deferred()

        self.pending_failures_by_dest.setdefault(
            destination, []
        ).append(
            (failure, deferred)
        )

        yield deferred

    @defer.inlineCallbacks
    @log_function
    def _attempt_new_transaction(self, destination):

        (retry_last_ts, retry_interval) = (0, 0)
        retry_timings = yield self.store.get_destination_retry_timings(
            destination
        )
        if retry_timings:
            (retry_last_ts, retry_interval) = (
                retry_timings.retry_last_ts, retry_timings.retry_interval
            )
            if retry_last_ts + retry_interval > int(self._clock.time_msec()):
                logger.info(
                    "TX [%s] not ready for retry yet - "
                    "dropping transaction for now",
                    destination,
                )
                return
            else:
                logger.info("TX [%s] is ready for retry", destination)

        logger.info("TX [%s] _attempt_new_transaction", destination)

        if destination in self.pending_transactions:
            # XXX: pending_transactions can get stuck on by a never-ending
            # request at which point pending_pdus_by_dest just keeps growing.
            # we need application-layer timeouts of some flavour of these
            # requests
            return

        # list of (pending_pdu, deferred, order)
        pending_pdus = self.pending_pdus_by_dest.pop(destination, [])
        pending_edus = self.pending_edus_by_dest.pop(destination, [])
        pending_failures = self.pending_failures_by_dest.pop(destination, [])

        if pending_pdus:
            logger.info("TX [%s] len(pending_pdus_by_dest[dest]) = %d",
                        destination, len(pending_pdus))

        if not pending_pdus and not pending_edus and not pending_failures:
            return

        logger.debug(
            "TX [%s] Attempting new transaction"
            " (pdus: %d, edus: %d, failures: %d)",
            destination,
            len(pending_pdus),
            len(pending_edus),
            len(pending_failures)
        )

        # Sort based on the order field
        pending_pdus.sort(key=lambda t: t[2])

        pdus = [x[0] for x in pending_pdus]
        edus = [x[0] for x in pending_edus]
        failures = [x[0].get_dict() for x in pending_failures]
        deferreds = [
            x[1]
            for x in pending_pdus + pending_edus + pending_failures
        ]

        try:
            self.pending_transactions[destination] = 1

            logger.debug("TX [%s] Persisting transaction...", destination)

            transaction = Transaction.create_new(
                origin_server_ts=int(self._clock.time_msec()),
                transaction_id=str(self._next_txn_id),
                origin=self.server_name,
                destination=destination,
                pdus=pdus,
                edus=edus,
                pdu_failures=failures,
            )

            self._next_txn_id += 1

            yield self.transaction_actions.prepare_to_send(transaction)

            logger.debug("TX [%s] Persisted transaction", destination)
            logger.info(
                "TX [%s] Sending transaction [%s]",
                destination,
                transaction.transaction_id,
            )

            # Actually send the transaction

            # FIXME (erikj): This is a bit of a hack to make the Pdu age
            # keys work
            def json_data_cb():
                data = transaction.get_dict()
                now = int(self._clock.time_msec())
                if "pdus" in data:
                    for p in data["pdus"]:
                        if "age_ts" in p:
                            unsigned = p.setdefault("unsigned", {})
                            unsigned["age"] = now - int(p["age_ts"])
                            del p["age_ts"]
                return data

            try:
                response = yield self.transport_layer.send_transaction(
                    transaction, json_data_cb
                )
                code = 200
            except HttpResponseException as e:
                code = e.code
                response = e.response

            logger.info("TX [%s] got %d response", destination, code)

            logger.debug("TX [%s] Sent transaction", destination)
            logger.debug("TX [%s] Marking as delivered...", destination)

            yield self.transaction_actions.delivered(
                transaction, code, response
            )

            logger.debug("TX [%s] Marked as delivered", destination)
            logger.debug("TX [%s] Yielding to callbacks...", destination)

            for deferred in deferreds:
                if code == 200:
                    if retry_last_ts:
                        # this host is alive! reset retry schedule
                        yield self.store.set_destination_retry_timings(
                            destination, 0, 0
                        )
                    deferred.callback(None)
                else:
                    self.set_retrying(destination, retry_interval)
                    deferred.errback(RuntimeError("Got status %d" % code))

                # Ensures we don't continue until all callbacks on that
                # deferred have fired
                try:
                    yield deferred
                except:
                    pass

            logger.debug("TX [%s] Yielded to callbacks", destination)
        except RuntimeError as e:
            # We capture this here as there as nothing actually listens
            # for this finishing functions deferred.
            logger.warn(
                "TX [%s] Problem in _attempt_transaction: %s",
                destination,
                e,
            )
        except Exception as e:
            # We capture this here as there as nothing actually listens
            # for this finishing functions deferred.
            logger.exception(
                "TX [%s] Problem in _attempt_transaction: %s",
                destination,
                e,
            )

            self.set_retrying(destination, retry_interval)

            for deferred in deferreds:
                if not deferred.called:
                    deferred.errback(e)

        finally:
            # We want to be *very* sure we delete this after we stop processing
            self.pending_transactions.pop(destination, None)

            # Check to see if there is anything else to send.
            self._attempt_new_transaction(destination)

    @defer.inlineCallbacks
    def set_retrying(self, destination, retry_interval):
        # track that this destination is having problems and we should
        # give it a chance to recover before trying it again

        if retry_interval:
            retry_interval *= 2
            # plateau at hourly retries for now
            if retry_interval >= 60 * 60 * 1000:
                retry_interval = 60 * 60 * 1000
        else:
            retry_interval = 2000  # try again at first after 2 seconds

        yield self.store.set_destination_retry_timings(
            destination,
            int(self._clock.time_msec()),
            retry_interval
        )