/*
 * Copyright (C) 2015 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.car;

import android.car.IPerUserCarService;
import android.car.user.CarUserManager;
import android.car.user.CarUserManager.UserLifecycleListener;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.os.UserHandle;
import android.util.IndentingPrintWriter;
import android.util.Slog;

import com.android.car.user.CarUserService;
import com.android.internal.annotations.GuardedBy;

import java.util.ArrayList;
import java.util.List;

/**
 * A Helper class that helps with the following:
 * 1. Provide methods to Bind/Unbind to the {@link PerUserCarService} as the current User
 * 2. Set up a listener to UserSwitch Broadcasts and call clients that have registered callbacks.
 *
 */
public class PerUserCarServiceHelper implements CarServiceBase {

    private static final String TAG = CarLog.tagFor(PerUserCarServiceHelper.class);
    private static boolean DBG = false;

    private final Context mContext;
    private final CarUserService mUserService;
    private IPerUserCarService mPerUserCarService;
    // listener to call on a ServiceConnection to PerUserCarService
    private List<ServiceCallback> mServiceCallbacks;
    private final Object mServiceBindLock = new Object();
    @GuardedBy("mServiceBindLock")
    private boolean mBound;

    public PerUserCarServiceHelper(Context context, CarUserService userService) {
        mContext = context;
        mServiceCallbacks = new ArrayList<>();
        mUserService = userService;
        mUserService.addUserLifecycleListener(mUserLifecycleListener);
    }

    @Override
    public void init() {
        synchronized (mServiceBindLock) {
            bindToPerUserCarService();
        }
    }

    @Override
    public void release() {
        synchronized (mServiceBindLock) {
            unbindFromPerUserCarService();
            mUserService.removeUserLifecycleListener(mUserLifecycleListener);
        }
    }

    private final UserLifecycleListener mUserLifecycleListener = event -> {
        if (DBG) {
            Slog.d(TAG, "onEvent(" + event + ")");
        }
        if (CarUserManager.USER_LIFECYCLE_EVENT_TYPE_SWITCHING == event.getEventType()) {
            List<ServiceCallback> callbacks;
            int userId = event.getUserId();
            if (DBG) {
                Slog.d(TAG, "User Switch Happened. New User" + userId);
            }

            // Before unbinding, notify the callbacks about unbinding from the service
            // so the callbacks can clean up their state through the binder before the service is
            // killed.
            synchronized (mServiceBindLock) {
                // copy the callbacks
                callbacks = new ArrayList<>(mServiceCallbacks);
            }
            // call them
            for (ServiceCallback callback : callbacks) {
                callback.onPreUnbind();
            }
            // unbind from the service running as the previous user.
            unbindFromPerUserCarService();
            // bind to the service running as the new user
            bindToPerUserCarService();
        }
    };

    /**
     * ServiceConnection to detect connecting/disconnecting to {@link PerUserCarService}
     */
    private final ServiceConnection mUserServiceConnection = new ServiceConnection() {
        // On connecting to the service, get the binder object to the CarBluetoothService
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder service) {
            List<ServiceCallback> callbacks;
            if (DBG) {
                Slog.d(TAG, "Connected to User Service");
            }
            mPerUserCarService = IPerUserCarService.Stub.asInterface(service);
            if (mPerUserCarService != null) {
                synchronized (mServiceBindLock) {
                    // copy the callbacks
                    callbacks = new ArrayList<>(mServiceCallbacks);
                }
                // call them
                for (ServiceCallback callback : callbacks) {
                    callback.onServiceConnected(mPerUserCarService);
                }
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {
            List<ServiceCallback> callbacks;
            if (DBG) {
                Slog.d(TAG, "Disconnected from User Service");
            }
            synchronized (mServiceBindLock) {
                // copy the callbacks
                callbacks = new ArrayList<>(mServiceCallbacks);
            }
            // call them
            for (ServiceCallback callback : callbacks) {
                callback.onServiceDisconnected();
            }
        }
    };

    /**
     * Bind to the PerUserCarService {@link PerUserCarService} which is created to run as the
     * Current User.
     */
    private void bindToPerUserCarService() {
        if (DBG) {
            Slog.d(TAG, "Binding to User service");
        }
        Intent startIntent = new Intent(mContext, PerUserCarService.class);
        synchronized (mServiceBindLock) {
            mBound = true;
            boolean bindSuccess = mContext.bindServiceAsUser(startIntent, mUserServiceConnection,
                    mContext.BIND_AUTO_CREATE, UserHandle.CURRENT);
            // If valid connection not obtained, unbind
            if (!bindSuccess) {
                Slog.e(TAG, "bindToPerUserCarService() failed to get valid connection");
                unbindFromPerUserCarService();
            }
        }
    }

    /**
     * Unbind from the {@link PerUserCarService} running as the Current user.
     */
    private void unbindFromPerUserCarService() {
        synchronized (mServiceBindLock) {
            // mBound flag makes sure we are unbinding only when the service is bound.
            if (mBound) {
                if (DBG) {
                    Slog.d(TAG, "Unbinding from User Service");
                }
                mContext.unbindService(mUserServiceConnection);
                mBound = false;
            }
        }
    }

    /**
     * Register a listener that gets called on Connection state changes to the
     * {@link PerUserCarService}
     * @param listener - Callback to invoke on user switch event.
     */
    public void registerServiceCallback(ServiceCallback listener) {
        if (listener != null) {
            if (DBG) {
                Slog.d(TAG, "Registering PerUserCarService Listener");
            }
            synchronized (mServiceBindLock) {
                mServiceCallbacks.add(listener);
            }
        }
    }

    /**
     * Unregister the Service Listener
     * @param listener - Callback method to unregister
     */
    public void unregisterServiceCallback(ServiceCallback listener) {
        if (DBG) {
            Slog.d(TAG, "Unregistering PerUserCarService Listener");
        }
        if (listener != null) {
            synchronized (mServiceBindLock) {
                mServiceCallbacks.remove(listener);
            }
        }
    }

    /**
     * Listener to the PerUserCarService connection status that clients need to implement.
     */
    public interface ServiceCallback {
        /**
         * Invoked when a service connects.
         *
         * @param perUserCarService the instance of IPerUserCarService.
         */
        void onServiceConnected(IPerUserCarService perUserCarService);

        /**
         * Invoked before an unbind call is going to be made.
         */
        void onPreUnbind();

        /**
         * Invoked when a service is crashed or disconnected.
         */
        void onServiceDisconnected();
    }

    @Override
    public final void dump(IndentingPrintWriter pw) {
        pw.println("PerUserCarServiceHelper");
        pw.increaseIndent();
        synchronized (mServiceBindLock) {
            pw.printf("bound: %b\n", mBound);
            if (mServiceCallbacks == null) {
                pw.println("no callbacks");
            } else {
                int size = mServiceCallbacks.size();
                pw.printf("%d callback%s\n", size, (size > 1 ? "s" : ""));
            }
        }
        pw.decreaseIndent();
    }
}