/*
 * Copyright (C) 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.
 */

package com.android.server.wm.utils;

import android.util.Log;

import org.mockito.Mockito;
import org.mockito.MockitoFramework;
import org.mockito.internal.creation.settings.CreationSettings;
import org.mockito.internal.util.MockUtil;
import org.mockito.listeners.MockCreationListener;
import org.mockito.mock.MockCreationSettings;

import java.lang.reflect.Field;
import java.util.IdentityHashMap;

/**
 * An util class used to track mock creation, and reset them when closing. Note only one instance is
 * allowed at anytime, as Mockito framework throws exception if there is already a listener of the
 * same type registered.
 */
public class MockTracker implements MockCreationListener, AutoCloseable {
    private static final String TAG = MockTracker.class.getSimpleName();

    private static final Field SPIED_INSTANCE_FIELD;

    static {
        try {
            SPIED_INSTANCE_FIELD = CreationSettings.class.getDeclaredField("spiedInstance");
            SPIED_INSTANCE_FIELD.setAccessible(true);
        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        }
    }

    private final MockitoFramework mMockitoFramework = Mockito.framework();

    private final IdentityHashMap<Object, Void> mMocks = new IdentityHashMap<>();

    public MockTracker() {
        mMockitoFramework.addListener(this);
    }

    public void stopTracking() {
        mMockitoFramework.removeListener(this);
    }

    @Override
    public void onMockCreated(Object mock, MockCreationSettings settings) {
        mMocks.put(mock, null);
        clearSpiedInstanceIfNeeded(mock, settings);
    }

    // HACK: Changing Mockito core implementation details.
    // TODO(b/123984854): Remove this once there is a real fix.
    private void clearSpiedInstanceIfNeeded(Object mock, MockCreationSettings settings) {
        if (mock != settings.getSpiedInstance()) {
            // Not a spyOn instance.
            return;
        }
        if (!(settings instanceof CreationSettings)) {
            throw new IllegalStateException("Unexpected type of settings: " + settings.getClass());
        }
        try {
            SPIED_INSTANCE_FIELD.set(settings, null);
            Log.d(TAG, "Setting spiedInstance for " + mock + " to null.");
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void close() {
        mMockitoFramework.removeListener(this);

        for (final Object mock : mMocks.keySet()) {
            if (MockUtil.isMock(mock)) {
                mMockitoFramework.clearInlineMock(mock);
            }
        }
        mMocks.clear();
    }
}