/*
 * Copyright (C) 2017 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 android.service.resolver;

import android.annotation.SdkConstant;
import android.annotation.SystemApi;
import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.os.IBinder;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.RemoteException;
import android.service.resolver.ResolverTarget;
import android.util.Log;

import java.util.List;
import java.util.Map;

A service to rank apps according to usage stats of apps, when the system is resolving targets for
an Intent.
To extend this class, you must declare the service in your manifest file with the BIND_RESOLVER_RANKER_SERVICE.BIND_RESOLVER_RANKER_SERVICE permission, and include an intent filter with the SERVICE_INTERFACE action. For example:
    <service android:name=".MyResolverRankerService"
            android:exported="true"
            android:priority="100"
            android:permission="android.permission.BIND_RESOLVER_RANKER_SERVICE">
        <intent-filter>
            <action android:name="android.service.resolver.ResolverRankerService" />
        </intent-filter>
    </service>

@hide
/**
 * A service to rank apps according to usage stats of apps, when the system is resolving targets for
 * an Intent.
 *
 * <p>To extend this class, you must declare the service in your manifest file with the
 * {@link android.Manifest.permission#BIND_RESOLVER_RANKER_SERVICE} permission, and include an
 * intent filter with the {@link #SERVICE_INTERFACE} action. For example:</p>
 * <pre>
 *     &lt;service android:name=".MyResolverRankerService"
 *             android:exported="true"
 *             android:priority="100"
 *             android:permission="android.permission.BIND_RESOLVER_RANKER_SERVICE"&gt;
 *         &lt;intent-filter&gt;
 *             &lt;action android:name="android.service.resolver.ResolverRankerService" /&gt;
 *         &lt;/intent-filter&gt;
 *     &lt;/service&gt;
 * </pre>
 * @hide
 */
@SystemApi
public abstract class ResolverRankerService extends Service {

    private static final String TAG = "ResolverRankerService";

    private static final boolean DEBUG = false;

    
The Intent action that a service must respond to. Add it to the intent filter of the service
in its manifest.
/**
     * The Intent action that a service must respond to. Add it to the intent filter of the service
     * in its manifest.
     */
    @SdkConstant(SdkConstant.SdkConstantType.SERVICE_ACTION)
    public static final String SERVICE_INTERFACE = "android.service.resolver.ResolverRankerService";

    
The permission that a service must hold. If the service does not hold the permission, the
system will skip that service.
/**
     * The permission that a service must hold. If the service does not hold the permission, the
     * system will skip that service.
     */
    public static final String HOLD_PERMISSION = "android.permission.PROVIDE_RESOLVER_RANKER_SERVICE";

    
The permission that a service must require to ensure that only Android system can bind to it.
If this permission is not enforced in the AndroidManifest of the service, the system will
skip that service.
/**
     * The permission that a service must require to ensure that only Android system can bind to it.
     * If this permission is not enforced in the AndroidManifest of the service, the system will
     * skip that service.
     */
    public static final String BIND_PERMISSION = "android.permission.BIND_RESOLVER_RANKER_SERVICE";

    private ResolverRankerServiceWrapper mWrapper = null;

    
Called by the system to retrieve a list of probabilities to rank apps/options. To implement it, set selectProbability of each input ResolverTarget. The higher the selectProbability is, the more likely the ResolverTarget will be selected by the user. Override this function to provide prediction results. 
Params:
targets – a list of ResolverTarget, for the list of apps to be ranked.
Throws:
Exception – when the prediction task fails./**
     * Called by the system to retrieve a list of probabilities to rank apps/options. To implement
     * it, set selectProbability of each input {@link ResolverTarget}. The higher the
     * selectProbability is, the more likely the {@link ResolverTarget} will be selected by the
     * user. Override this function to provide prediction results.
     *
     * @param targets a list of {@link ResolverTarget}, for the list of apps to be ranked.
     *
     * @throws Exception when the prediction task fails.
     */
    public void onPredictSharingProbabilities(final List<ResolverTarget> targets) {}

    
Called by the system to train/update a ranking service, after the user makes a selection from
the ranked list of apps. Override this function to enable model updates.
Params:
targets – a list of ResolverTarget, for the list of apps to be ranked.
selectedPosition – the position of the selected app in the list.
Throws:
Exception – when the training task fails./**
     * Called by the system to train/update a ranking service, after the user makes a selection from
     * the ranked list of apps. Override this function to enable model updates.
     *
     * @param targets a list of {@link ResolverTarget}, for the list of apps to be ranked.
     * @param selectedPosition the position of the selected app in the list.
     *
     * @throws Exception when the training task fails.
     */
    public void onTrainRankingModel(
            final List<ResolverTarget> targets, final int selectedPosition) {}

    private static final String HANDLER_THREAD_NAME = "RESOLVER_RANKER_SERVICE";
    private volatile Handler mHandler;
    private HandlerThread mHandlerThread;

    @Override
    public IBinder onBind(Intent intent) {
        if (DEBUG) Log.d(TAG, "onBind " + intent);
        if (!SERVICE_INTERFACE.equals(intent.getAction())) {
            if (DEBUG) Log.d(TAG, "bad intent action " + intent.getAction() + "; returning null");
            return null;
        }
        if (mHandlerThread == null) {
            mHandlerThread = new HandlerThread(HANDLER_THREAD_NAME);
            mHandlerThread.start();
            mHandler = new Handler(mHandlerThread.getLooper());
        }
        if (mWrapper == null) {
            mWrapper = new ResolverRankerServiceWrapper();
        }
        return mWrapper;
    }

    @Override
    public void onDestroy() {
        mHandler = null;
        if (mHandlerThread != null) {
            mHandlerThread.quitSafely();
        }
        super.onDestroy();
    }

    private static void sendResult(List<ResolverTarget> targets, IResolverRankerResult result) {
        try {
            result.sendResult(targets);
        } catch (Exception e) {
            Log.e(TAG, "failed to send results: " + e);
        }
    }

    private class ResolverRankerServiceWrapper extends IResolverRankerService.Stub {

        @Override
        public void predict(final List<ResolverTarget> targets, final IResolverRankerResult result)
                throws RemoteException {
            Runnable predictRunnable = new Runnable() {
                @Override
                public void run() {
                    try {
                        if (DEBUG) {
                            Log.d(TAG, "predict calls onPredictSharingProbabilities.");
                        }
                        onPredictSharingProbabilities(targets);
                        sendResult(targets, result);
                    } catch (Exception e) {
                        Log.e(TAG, "onPredictSharingProbabilities failed; send null results: " + e);
                        sendResult(null, result);
                    }
                }
            };
            final Handler h = mHandler;
            if (h != null) {
                h.post(predictRunnable);
            }
        }

        @Override
        public void train(final List<ResolverTarget> targets, final int selectedPosition)
                throws RemoteException {
            Runnable trainRunnable = new Runnable() {
                @Override
                public void run() {
                    try {
                        if (DEBUG) {
                            Log.d(TAG, "train calls onTranRankingModel");
                        }
                        onTrainRankingModel(targets, selectedPosition);
                    } catch (Exception e) {
                        Log.e(TAG, "onTrainRankingModel failed; skip train: " + e);
                    }
                }
            };
            final Handler h = mHandler;
            if (h != null) {
                h.post(trainRunnable);
            }
        }
    }
}