#!/usr/bin/env python3
#
#   Copyright 2019 - The Android Open Source Project
#
#   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 datetime import datetime, timedelta
import logging
from queue import SimpleQueue, Empty

from acts import asserts

from google.protobuf import text_format

from cert.event_callback_stream import EventCallbackStream


class EventAsserts(object):
    """
    A class that handles various asserts with respect to a gRPC unary stream

    This class must be created before an event happens as events in a
    EventCallbackStream is not sticky and will be lost if you don't subscribe
    to them before generating those events.

    When asserting on sequential events, a single EventAsserts object is enough

    When asserting on simultaneous events, you would need multiple EventAsserts
    objects as each EventAsserts object owns a separate queue that is actively
    being popped as asserted events happen
    """
    DEFAULT_TIMEOUT_SECONDS = 3

    def __init__(self, event_callback_stream):
        if event_callback_stream is None:
            raise ValueError("event_callback_stream cannot be None")
        self.event_callback_stream = event_callback_stream
        self.event_queue = SimpleQueue()
        self.callback = lambda event: self.event_queue.put(event)
        self.event_callback_stream.register_callback(self.callback)

    def __del__(self):
        self.event_callback_stream.unregister_callback(self.callback)

    def remaining_time_delta(self, end_time):
        remaining = end_time - datetime.now()
        if remaining < timedelta(milliseconds=0):
            remaining = timedelta(milliseconds=0)
        return remaining

    def assert_none(self, timeout=timedelta(seconds=DEFAULT_TIMEOUT_SECONDS)):
        """
        Assert no event happens within timeout period

        :param timeout: a timedelta object
        :return:
        """
        logging.debug("assert_none %fs" % (timeout.total_seconds()))
        try:
            event = self.event_queue.get(timeout=timeout.total_seconds())
            asserts.assert_true(
                event is None,
                msg=("Expected None, but got %s" % text_format.MessageToString(
                    event, as_one_line=True)))
        except Empty:
            return

    def assert_none_matching(
            self, match_fn, timeout=timedelta(seconds=DEFAULT_TIMEOUT_SECONDS)):
        """
        Assert no events where match_fn(event) is True happen within timeout
        period

        :param match_fn: return True/False on match_fn(event)
        :param timeout: a timedelta object
        :return:
        """
        logging.debug("assert_none_matching %fs" % (timeout.total_seconds()))
        event = None
        end_time = datetime.now() + timeout
        while event is None and datetime.now() < end_time:
            remaining = self.remaining_time_delta(end_time)
            logging.debug("Waiting for event (%fs remaining)" %
                          (remaining.total_seconds()))
            try:
                current_event = self.event_queue.get(
                    timeout=remaining.total_seconds())
                if match_fn(current_event):
                    event = current_event
            except Empty:
                continue
        logging.debug("Done waiting for an event")
        if event is None:
            return  # Avoid an assert in MessageToString(None, ...)
        asserts.assert_true(
            event is None,
            msg=("Expected None matching, but got %s" %
                 text_format.MessageToString(event, as_one_line=True)))

    def assert_event_occurs(self,
                            match_fn,
                            at_least_times=1,
                            timeout=timedelta(seconds=DEFAULT_TIMEOUT_SECONDS)):
        """
        Assert at least |at_least_times| instances of events happen where
        match_fn(event) returns True within timeout period

        :param match_fn: returns True/False on match_fn(event)
        :param timeout: a timedelta object
        :param at_least_times: how many times at least a matching event should
                               happen
        :return:
        """
        logging.debug("assert_event_occurs %d %fs" % (at_least_times,
                                                      timeout.total_seconds()))
        event_list = []
        end_time = datetime.now() + timeout
        while len(event_list) < at_least_times and datetime.now() < end_time:
            remaining = self.remaining_time_delta(end_time)
            logging.debug("Waiting for event (%fs remaining)" %
                          (remaining.total_seconds()))
            try:
                current_event = self.event_queue.get(
                    timeout=remaining.total_seconds())
                if match_fn(current_event):
                    event_list.append(current_event)
            except Empty:
                continue
        logging.debug("Done waiting for event")
        asserts.assert_true(
            len(event_list) >= at_least_times,
            msg=("Expected at least %d events, but got %d" % (at_least_times,
                                                              len(event_list))))

    def assert_event_occurs_at_most(
            self,
            match_fn,
            at_most_times,
            timeout=timedelta(seconds=DEFAULT_TIMEOUT_SECONDS)):
        """
        Assert at most |at_most_times| instances of events happen where
        match_fn(event) returns True within timeout period

        :param match_fn: returns True/False on match_fn(event)
        :param at_most_times: how many times at most a matching event should
                               happen
        :param timeout:a timedelta object
        :return:
        """
        logging.debug("assert_event_occurs_at_most")
        event_list = []
        end_time = datetime.now() + timeout
        while len(event_list) <= at_most_times and datetime.now() < end_time:
            remaining = self.remaining_time_delta(end_time)
            logging.debug("Waiting for event iteration (%fs remaining)" %
                          (remaining.total_seconds()))
            try:
                current_event = self.event_queue.get(
                    timeout=remaining.total_seconds())
                if match_fn(current_event):
                    event_list.append(current_event)
            except Empty:
                continue
        logging.debug("Done waiting, got %d events" % len(event_list))
        asserts.assert_true(
            len(event_list) <= at_most_times,
            msg=("Expected at most %d events, but got %d" % (at_most_times,
                                                             len(event_list))))