# Copyright 2015-present MongoDB, Inc.
#
# 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.

"""Utilities for testing Server Selection and Max Staleness."""

import datetime
import os
import sys

sys.path[0:0] = [""]

from bson import json_util
from pymongo.common import clean_node, HEARTBEAT_FREQUENCY
from pymongo.errors import AutoReconnect, ConfigurationError
from pymongo.hello import Hello
from pymongo.hello_compat import HelloCompat
from pymongo.server_description import ServerDescription
from pymongo.settings import TopologySettings
from pymongo.server_selectors import writable_server_selector
from pymongo.topology import Topology
from test import unittest
from test.utils import MockPool, parse_read_preference


class MockMonitor(object):
    def __init__(self, server_description, topology, pool, topology_settings):
        pass

    def cancel_check(self):
        pass

    def open(self):
        pass

    def request_check(self):
        pass

    def close(self):
        pass


def get_addresses(server_list):
    seeds = []
    hosts = []
    for server in server_list:
        seeds.append(clean_node(server['address']))
        hosts.append(server['address'])
    return seeds, hosts


def make_last_write_date(server):
    epoch = datetime.datetime.utcfromtimestamp(0)
    millis = server.get('lastWrite', {}).get('lastWriteDate')
    if millis:
        diff = ((millis % 1000) + 1000) % 1000
        seconds = (millis - diff) / 1000
        micros = diff * 1000
        return epoch + datetime.timedelta(
            seconds=seconds, microseconds=micros)
    else:
        # "Unknown" server.
        return epoch


def make_server_description(server, hosts):
    """Make a ServerDescription from server info in a JSON test."""
    server_type = server['type']
    if server_type in ("Unknown", "PossiblePrimary"):
        return ServerDescription(clean_node(server['address']), Hello({}))

    hello_response = {'ok': True, 'hosts': hosts}
    if server_type != "Standalone" and server_type != "Mongos":
        hello_response['setName'] = "rs"

    if server_type == "RSPrimary":
        hello_response[HelloCompat.LEGACY_PRIMARY] = True
    elif server_type == "RSSecondary":
        hello_response['secondary'] = True
    elif server_type == "Mongos":
        hello_response['msg'] = 'isdbgrid'

    hello_response['lastWrite'] = {
        'lastWriteDate': make_last_write_date(server)
    }

    for field in 'maxWireVersion', 'tags', 'idleWritePeriodMillis':
        if field in server:
            hello_response[field] = server[field]

    hello_response.setdefault('maxWireVersion', 6)

    # Sets _last_update_time to now.
    sd = ServerDescription(clean_node(server['address']),
                           Hello(hello_response),
                           round_trip_time=server['avg_rtt_ms'] / 1000.0)

    if 'lastUpdateTime' in server:
        sd._last_update_time = server['lastUpdateTime'] / 1000.0  # ms to sec.

    return sd


def get_topology_type_name(scenario_def):
    td = scenario_def['topology_description']
    name = td['type']
    if name == 'Unknown':
        # PyMongo never starts a topology in type Unknown.
        return 'Sharded' if len(td['servers']) > 1 else 'Single'
    else:
        return name


def get_topology_settings_dict(**kwargs):
    settings = dict(
        monitor_class=MockMonitor,
        heartbeat_frequency=HEARTBEAT_FREQUENCY,
        pool_class=MockPool
    )
    settings.update(kwargs)
    return settings


def create_topology(scenario_def, **kwargs):
    # Initialize topologies.
    if 'heartbeatFrequencyMS' in scenario_def:
        frequency = int(scenario_def['heartbeatFrequencyMS']) / 1000.0
    else:
        frequency = HEARTBEAT_FREQUENCY

    seeds, hosts = get_addresses(
        scenario_def['topology_description']['servers'])

    topology_type = get_topology_type_name(scenario_def)
    if topology_type == 'LoadBalanced':
        kwargs.setdefault('load_balanced', True)

    settings = get_topology_settings_dict(
        heartbeat_frequency=frequency,
        seeds=seeds,
        **kwargs
    )

    # "Eligible servers" is defined in the server selection spec as
    # the set of servers matching both the ReadPreference's mode
    # and tag sets.
    topology = Topology(TopologySettings(**settings))
    topology.open()

    # Update topologies with server descriptions.
    for server in scenario_def['topology_description']['servers']:
        server_description = make_server_description(server, hosts)
        topology.on_change(server_description)

    if topology_type == 'LoadBalanced':
        assert topology.description.topology_type_name == 'LoadBalanced'

    return topology


def create_test(scenario_def):
    def run_scenario(self):
        _, hosts = get_addresses(
            scenario_def['topology_description']['servers'])
        # "Eligible servers" is defined in the server selection spec as
        # the set of servers matching both the ReadPreference's mode
        # and tag sets.
        top_latency = create_topology(scenario_def)

        # "In latency window" is defined in the server selection
        # spec as the subset of suitable_servers that falls within the
        # allowable latency window.
        top_suitable = create_topology(
            scenario_def, local_threshold_ms=1000000)

        # Create server selector.
        if scenario_def.get("operation") == "write":
            pref = writable_server_selector
        else:
            # Make first letter lowercase to match read_pref's modes.
            pref_def = scenario_def['read_preference']
            if scenario_def.get('error'):
                with self.assertRaises((ConfigurationError, ValueError)):
                    # Error can be raised when making Read Pref or selecting.
                    pref = parse_read_preference(pref_def)
                    top_latency.select_server(pref)
                return

            pref = parse_read_preference(pref_def)

        # Select servers.
        if not scenario_def.get('suitable_servers'):
            with self.assertRaises(AutoReconnect):
                top_suitable.select_server(pref, server_selection_timeout=0)

            return

        if not scenario_def['in_latency_window']:
            with self.assertRaises(AutoReconnect):
                top_latency.select_server(pref, server_selection_timeout=0)

            return

        actual_suitable_s = top_suitable.select_servers(
            pref, server_selection_timeout=0)
        actual_latency_s = top_latency.select_servers(
            pref, server_selection_timeout=0)

        expected_suitable_servers = {}
        for server in scenario_def['suitable_servers']:
            server_description = make_server_description(server, hosts)
            expected_suitable_servers[server['address']] = server_description

        actual_suitable_servers = {}
        for s in actual_suitable_s:
            actual_suitable_servers["%s:%d" % (s.description.address[0],
                                    s.description.address[1])] = s.description

        self.assertEqual(len(actual_suitable_servers),
                         len(expected_suitable_servers))
        for k, actual in actual_suitable_servers.items():
            expected = expected_suitable_servers[k]
            self.assertEqual(expected.address, actual.address)
            self.assertEqual(expected.server_type, actual.server_type)
            self.assertEqual(expected.round_trip_time, actual.round_trip_time)
            self.assertEqual(expected.tags, actual.tags)
            self.assertEqual(expected.all_hosts, actual.all_hosts)

        expected_latency_servers = {}
        for server in scenario_def['in_latency_window']:
            server_description = make_server_description(server, hosts)
            expected_latency_servers[server['address']] = server_description

        actual_latency_servers = {}
        for s in actual_latency_s:
            actual_latency_servers["%s:%d" %
                                   (s.description.address[0],
                                    s.description.address[1])] = s.description

        self.assertEqual(len(actual_latency_servers),
                         len(expected_latency_servers))
        for k, actual in actual_latency_servers.items():
            expected = expected_latency_servers[k]
            self.assertEqual(expected.address, actual.address)
            self.assertEqual(expected.server_type, actual.server_type)
            self.assertEqual(expected.round_trip_time, actual.round_trip_time)
            self.assertEqual(expected.tags, actual.tags)
            self.assertEqual(expected.all_hosts, actual.all_hosts)

    return run_scenario


def create_selection_tests(test_dir):
    class TestAllScenarios(unittest.TestCase):
        pass

    for dirpath, _, filenames in os.walk(test_dir):
        dirname = os.path.split(dirpath)
        dirname = os.path.split(dirname[-2])[-1] + '_' + dirname[-1]

        for filename in filenames:
            with open(os.path.join(dirpath, filename)) as scenario_stream:
                scenario_def = json_util.loads(scenario_stream.read())

            # Construct test from scenario.
            new_test = create_test(scenario_def)
            test_name = 'test_%s_%s' % (
                dirname, os.path.splitext(filename)[0])

            new_test.__name__ = test_name
            setattr(TestAllScenarios, new_test.__name__, new_test)

    return TestAllScenarios