from __future__ import annotations

import sys

from bayes_opt.bayesian_optimization import Observable
from bayes_opt.event import Events
from bayes_opt.observer import _Tracker

EVENTS = ["a", "b", "c"]


class SimpleObserver:
    def __init__(self):
        self.counter = 0

    def update(self, event, instance):
        self.counter += 1


def test_get_subscribers():
    observer = SimpleObserver()
    observable = Observable(events=EVENTS)
    observable.subscribe("a", observer)

    assert observer in observable.get_subscribers("a")
    assert observer not in observable.get_subscribers("b")
    assert observer not in observable.get_subscribers("c")

    assert len(observable.get_subscribers("a")) == 1
    assert len(observable.get_subscribers("b")) == 0
    assert len(observable.get_subscribers("c")) == 0


def test_unsubscribe():
    observer = SimpleObserver()
    observable = Observable(events=EVENTS)

    observable.subscribe("a", observer)
    observable.unsubscribe("a", observer)

    assert observer not in observable.get_subscribers("a")
    assert len(observable.get_subscribers("a")) == 0


def test_dispatch():
    observer_a = SimpleObserver()
    observer_b = SimpleObserver()
    observable = Observable(events=EVENTS)

    observable.subscribe("a", observer_a)
    observable.subscribe("b", observer_b)

    assert observer_a.counter == 0
    assert observer_b.counter == 0

    observable.dispatch("b")
    assert observer_a.counter == 0
    assert observer_b.counter == 1

    observable.dispatch("a")
    observable.dispatch("b")
    assert observer_a.counter == 1
    assert observer_b.counter == 2

    observable.dispatch("a")
    observable.dispatch("c")
    assert observer_a.counter == 2
    assert observer_a.counter == 2


def test_tracker():
    class MockInstance:
        def __init__(self, max_target=1, max_params=None):
            self._max_target = max_target
            self._max_params = max_params or [1, 1]

        @property
        def max(self):
            return {"target": self._max_target, "params": self._max_params}

    tracker = _Tracker()
    assert tracker._iterations == 0
    assert tracker._previous_max is None
    assert tracker._previous_max_params is None

    test_instance = MockInstance()
    tracker._update_tracker("other_event", test_instance)
    assert tracker._iterations == 0
    assert tracker._previous_max is None
    assert tracker._previous_max_params is None

    tracker._update_tracker(Events.OPTIMIZATION_STEP, test_instance)
    assert tracker._iterations == 1
    assert tracker._previous_max == 1
    assert tracker._previous_max_params == [1, 1]

    new_instance = MockInstance(max_target=7, max_params=[7, 7])
    tracker._update_tracker(Events.OPTIMIZATION_STEP, new_instance)
    assert tracker._iterations == 2
    assert tracker._previous_max == 7
    assert tracker._previous_max_params == [7, 7]

    other_instance = MockInstance(max_target=2, max_params=[2, 2])
    tracker._update_tracker(Events.OPTIMIZATION_STEP, other_instance)
    assert tracker._iterations == 3
    assert tracker._previous_max == 7
    assert tracker._previous_max_params == [7, 7]

    tracker._time_metrics()
    start_time = tracker._start_time
    previous_time = tracker._previous_time

    tracker._time_metrics()
    assert start_time == tracker._start_time
    if "win" not in sys.platform:
        assert previous_time < tracker._previous_time


if __name__ == "__main__":
    r"""
    CommandLine:
        python tests/test_observer.py
    """
    import pytest

    pytest.main([__file__])