/*
 * Copyright (C) 2012 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.tradefed.device;

import com.android.tradefed.command.remote.DeviceDescriptor;

import java.util.List;

/**
 * Interface for monitoring state of devices.  Intended to be passed to an {@link IDeviceManager}
 * instance, at which point the {@link IDeviceManager} will invoke callbacks as the related events
 * are triggered.  Any caching or batching needs to be performed within the {@link IDeviceMonitor}
 * instance.
 */
public interface IDeviceMonitor {
    /**
     * A method that will be called after all of the Monitor's @Option fields have been set.
     */
    public void run();

    /** A method that will be called when the Monitor need to be stopped. */
    public void stop();

    /**
     * A {@link Runnable}-like class that should return the known devices and their states. This
     * class allows the {@link IDeviceMonitor} to fetch device info from its own thread, which
     * should avoid deadlocks that may occur while listing devices.
     */
    public abstract static class DeviceLister {
        public abstract List<DeviceDescriptor> listDevices();

        public abstract DeviceDescriptor getDeviceDescriptor(String serial);
    }

    /**
     * Allows the {@link DeviceLister} to be set.  After a successful attempt to set the Lister,
     * implementations may discard all subsequent attempts.
     */
    public void setDeviceLister(DeviceLister lister);

    /**
     * Signals the {@link IDeviceMonitor} that a device state has been changed.
     * Monitor implementations should limit the amount of processing and
     * IDeviceManager/DeviceLister interaction they do in this method.
     */
    public void notifyDeviceStateChange(String serial, DeviceAllocationState oldState,
            DeviceAllocationState newState);

}