/*
 * Copyright (C) 2018 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.settings.network.telephony;

import android.annotation.IntDef;
import android.telephony.AccessNetworkConstants.AccessNetworkType;
import android.telephony.CellInfo;
import android.telephony.NetworkScan;
import android.telephony.NetworkScanRequest;
import android.telephony.RadioAccessSpecifier;
import android.telephony.TelephonyManager;
import android.telephony.TelephonyScanManager;
import android.util.Log;

import com.android.internal.telephony.CellNetworkScanResult;

import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;
import java.util.concurrent.Executor;
import java.util.stream.Collectors;

/**
 * A helper class that builds the common interface and performs the network scan for two different
 * network scan APIs.
 */
public class NetworkScanHelper {
    public static final String TAG = "NetworkScanHelper";
    private static final boolean DBG = true;

    /**
     * Callbacks interface to inform the network scan results.
     */
    public interface NetworkScanCallback {
        /**
         * Called when the results is returned from {@link TelephonyManager}. This method will be
         * called at least one time if there is no error occurred during the network scan.
         *
         * <p> This method can be called multiple times in one network scan, until
         * {@link #onComplete()} or {@link #onError(int)} is called.
         *
         * @param results
         */
        void onResults(List<CellInfo> results);

        /**
         * Called when the current network scan process is finished. No more
         * {@link #onResults(List)} will be called for the current network scan after this method is
         * called.
         */
        void onComplete();

        /**
         * Called when an error occurred during the network scan process.
         *
         * <p> There is no more result returned from {@link TelephonyManager} if an error occurred.
         *
         * <p> {@link #onComplete()} will not be called if an error occurred.
         *
         * @see {@link NetworkScan.ScanErrorCode}
         */
        void onError(int errorCode);
    }

    @Retention(RetentionPolicy.SOURCE)
    @IntDef({NETWORK_SCAN_TYPE_WAIT_FOR_ALL_RESULTS, NETWORK_SCAN_TYPE_INCREMENTAL_RESULTS})
    public @interface NetworkQueryType {}

    /**
     * Performs the network scan using {@link TelephonyManager#getAvailableNetworks()}. The network
     * scan results won't be returned to the caller until the network scan is completed.
     *
     * <p> This is typically used when the modem doesn't support the new network scan api
     * {@link TelephonyManager#requestNetworkScan(
     * NetworkScanRequest, Executor, TelephonyScanManager.NetworkScanCallback)}.
     */
    public static final int NETWORK_SCAN_TYPE_WAIT_FOR_ALL_RESULTS = 1;

    /**
     * Performs the network scan using {@link TelephonyManager#requestNetworkScan(
     * NetworkScanRequest, Executor, TelephonyScanManager.NetworkScanCallback)} The network scan
     * results will be returned to the caller periodically in a small time window until the network
     * scan is completed. The complete results should be returned in the last called of
     * {@link NetworkScanCallback#onResults(List)}.
     *
     * <p> This is recommended to be used if modem supports the new network scan api
     * {@link TelephonyManager#requestNetworkScan(
     * NetworkScanRequest, Executor, TelephonyScanManager.NetworkScanCallback)}
     */
    public static final int NETWORK_SCAN_TYPE_INCREMENTAL_RESULTS = 2;

    /** The constants below are used in the async network scan. */
    private static final boolean INCREMENTAL_RESULTS = true;
    private static final int SEARCH_PERIODICITY_SEC = 5;
    private static final int MAX_SEARCH_TIME_SEC = 300;
    private static final int INCREMENTAL_RESULTS_PERIODICITY_SEC = 3;

    private static final NetworkScanRequest NETWORK_SCAN_REQUEST =
            new NetworkScanRequest(
                    NetworkScanRequest.SCAN_TYPE_ONE_SHOT,
                    new RadioAccessSpecifier[]{
                            // GSM
                            new RadioAccessSpecifier(
                                    AccessNetworkType.GERAN,
                                    null /* bands */,
                                    null /* channels */),
                            // LTE
                            new RadioAccessSpecifier(
                                    AccessNetworkType.EUTRAN,
                                    null /* bands */,
                                    null /* channels */),
                            // WCDMA
                            new RadioAccessSpecifier(
                                    AccessNetworkType.UTRAN,
                                    null /* bands */,
                                    null /* channels */)
                    },
                    SEARCH_PERIODICITY_SEC,
                    MAX_SEARCH_TIME_SEC,
                    INCREMENTAL_RESULTS,
                    INCREMENTAL_RESULTS_PERIODICITY_SEC,
                    null /* List of PLMN ids (MCC-MNC) */);

    private final NetworkScanCallback mNetworkScanCallback;
    private final TelephonyManager mTelephonyManager;
    private final TelephonyScanManager.NetworkScanCallback mInternalNetworkScanCallback;
    private final Executor mExecutor;

    private NetworkScan mNetworkScanRequester;

    /** Callbacks for sync network scan */
    private ListenableFuture<List<CellInfo>> mNetworkScanFuture;

    public NetworkScanHelper(TelephonyManager tm, NetworkScanCallback callback, Executor executor) {
        mTelephonyManager = tm;
        mNetworkScanCallback = callback;
        mInternalNetworkScanCallback = new NetworkScanCallbackImpl();
        mExecutor = executor;
    }

    /**
     * Performs a network scan for the given type {@code type}.
     * {@link #NETWORK_SCAN_TYPE_INCREMENTAL_RESULTS} is recommended if modem supports
     * {@link TelephonyManager#requestNetworkScan(
     * NetworkScanRequest, Executor, TelephonyScanManager.NetworkScanCallback)}.
     *
     * @param type used to tell which network scan API should be used.
     */
    public void startNetworkScan(@NetworkQueryType int type) {
        if (type == NETWORK_SCAN_TYPE_WAIT_FOR_ALL_RESULTS) {
            mNetworkScanFuture = SettableFuture.create();
            Futures.addCallback(mNetworkScanFuture, new FutureCallback<List<CellInfo>>() {
                @Override
                public void onSuccess(List<CellInfo> result) {
                    onResults(result);
                    onComplete();
                }

                @Override
                public void onFailure(Throwable t) {
                    int errCode = Integer.parseInt(t.getMessage());
                    onError(errCode);
                }
            });
            mExecutor.execute(new NetworkScanSyncTask(
                    mTelephonyManager, (SettableFuture) mNetworkScanFuture));
        } else if (type == NETWORK_SCAN_TYPE_INCREMENTAL_RESULTS) {
            if (DBG) Log.d(TAG, "start network scan async");
            mNetworkScanRequester = mTelephonyManager.requestNetworkScan(
                    NETWORK_SCAN_REQUEST,
                    mExecutor,
                    mInternalNetworkScanCallback);
        }
    }

    /**
     * The network scan of type {@link #NETWORK_SCAN_TYPE_WAIT_FOR_ALL_RESULTS} can't be stopped,
     * however, the result of the current network scan won't be returned to the callback after
     * calling this method.
     */
    public void stopNetworkQuery() {
        if (mNetworkScanRequester != null) {
            mNetworkScanRequester.stopScan();
            mNetworkScanFuture = null;
        }

        if (mNetworkScanFuture != null) {
            mNetworkScanFuture.cancel(true /* mayInterruptIfRunning */);
            mNetworkScanFuture = null;
        }
    }

    private void onResults(List<CellInfo> cellInfos) {
        mNetworkScanCallback.onResults(cellInfos);
    }

    private void onComplete() {
        mNetworkScanCallback.onComplete();
    }

    private void onError(int errCode) {
        mNetworkScanCallback.onError(errCode);
    }

    /**
     * Converts the status code of {@link CellNetworkScanResult} to one of the
     * {@link NetworkScan.ScanErrorCode}.
     * @param errCode status code from {@link CellNetworkScanResult}.
     *
     * @return one of the scan error code from {@link NetworkScan.ScanErrorCode}.
     */
    private static int convertToScanErrorCode(int errCode) {
        switch (errCode) {
            case CellNetworkScanResult.STATUS_RADIO_NOT_AVAILABLE:
                return NetworkScan.ERROR_RADIO_INTERFACE_ERROR;
            case CellNetworkScanResult.STATUS_RADIO_GENERIC_FAILURE:
            default:
                return NetworkScan.ERROR_MODEM_ERROR;
        }
    }

    private final class NetworkScanCallbackImpl extends TelephonyScanManager.NetworkScanCallback {
        public void onResults(List<CellInfo> results) {
            if (DBG) Log.d(TAG, "async scan onResults() results = " + results);
            NetworkScanHelper.this.onResults(results);
        }

        public void onComplete() {
            if (DBG) Log.d(TAG, "async scan onComplete()");
            NetworkScanHelper.this.onComplete();
        }

        public void onError(@NetworkScan.ScanErrorCode int errCode) {
            if (DBG) Log.d(TAG, "async scan onError() errorCode = " + errCode);
            NetworkScanHelper.this.onError(errCode);
        }
    }

    private static final class NetworkScanSyncTask implements Runnable {
        private final SettableFuture<List<CellInfo>> mCallback;
        private final TelephonyManager mTelephonyManager;

        NetworkScanSyncTask(
                TelephonyManager telephonyManager, SettableFuture<List<CellInfo>> callback) {
            mTelephonyManager = telephonyManager;
            mCallback = callback;
        }

        @Override
        public void run() {
            if (DBG) Log.d(TAG, "sync scan start");
            CellNetworkScanResult result = mTelephonyManager.getAvailableNetworks();
            if (result.getStatus() == CellNetworkScanResult.STATUS_SUCCESS) {
                List<CellInfo> cellInfos = result.getOperators()
                        .stream()
                        .map(operatorInfo
                                -> CellInfoUtil.convertOperatorInfoToCellInfo(operatorInfo))
                        .collect(Collectors.toList());
                if (DBG) Log.d(TAG, "sync scan complete");
                mCallback.set(cellInfos);
            } else {
                mCallback.setException(new Throwable(
                        Integer.toString(convertToScanErrorCode(result.getStatus()))));
            }
        }
    }
}