Add a TelephonySubscriptionTracker to track subId/subGrp changes

/*

 * Copyright (C) 2020 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.vcn;

import static android.telephony.CarrierConfigManager.ACTION_CARRIER_CONFIG_CHANGED;

import static android.telephony.CarrierConfigManager.EXTRA_SLOT_INDEX;

import static android.telephony.CarrierConfigManager.EXTRA_SUBSCRIPTION_INDEX;

import static android.telephony.SubscriptionManager.INVALID_SIM_SLOT_INDEX;

import static android.telephony.SubscriptionManager.INVALID_SUBSCRIPTION_ID;

import android.annotation.NonNull;

import android.annotation.Nullable;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.content.IntentFilter;

import android.os.Handler;

import android.os.HandlerExecutor;

import android.os.ParcelUuid;

import android.os.PersistableBundle;

import android.telephony.CarrierConfigManager;

import android.telephony.SubscriptionInfo;

import android.telephony.SubscriptionManager;

import android.telephony.SubscriptionManager.OnSubscriptionsChangedListener;

import android.util.ArraySet;

import android.util.Slog;

import com.android.internal.annotations.VisibleForTesting;

import com.android.internal.annotations.VisibleForTesting.Visibility;

import java.util.Collections;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Objects;

import java.util.Set;

/**

 * TelephonySubscriptionTracker provides a caching layer for tracking active subscription groups.

 *

 * <p>This class performs two roles:

 *

 * <ol>

 *   <li>De-noises subscription changes by ensuring that only changes in active and ready

 *       subscription groups are acted upon

 *   <li>Caches mapping between subIds and subscription groups

 * </ol>

 *

 * <p>An subscription group is active and ready if any of its contained subIds has had BOTH the

 * {@link CarrierConfigManager#isConfigForIdentifiedCarrier()} return true, AND the subscription is

 * listed as active per SubscriptionManager#getAllSubscriptionInfoList().

 *

 * <p>Note that due to the asynchronous nature of callbacks and broadcasts, the output of this class

 * is (only) eventually consistent.

 *

 * @hide

 */

public class TelephonySubscriptionTracker extends BroadcastReceiver {

    @NonNull private static final String TAG = TelephonySubscriptionTracker.class.getSimpleName();

    private static final boolean LOG_DBG = false; // STOPSHIP if true

    @NonNull private final Context mContext;

    @NonNull private final Handler mHandler;

    @NonNull private final TelephonySubscriptionTrackerCallback mCallback;

    @NonNull private final Dependencies mDeps;

    @NonNull private final SubscriptionManager mSubscriptionManager;

    @NonNull private final CarrierConfigManager mCarrierConfigManager;

    // TODO (Android T+): Add ability to handle multiple subIds per slot.

    @NonNull private final Map<Integer, Integer> mReadySubIdsBySlotId = new HashMap<>();

    @NonNull private final OnSubscriptionsChangedListener mSubscriptionChangedListener;

    @NonNull private TelephonySubscriptionSnapshot mCurrentSnapshot;

    public TelephonySubscriptionTracker(

            @NonNull Context context,

            @NonNull Handler handler,

            @NonNull TelephonySubscriptionTrackerCallback callback) {

        this(context, handler, callback, new Dependencies());

    }

    @VisibleForTesting(visibility = Visibility.PRIVATE)

    TelephonySubscriptionTracker(

            @NonNull Context context,

            @NonNull Handler handler,

            @NonNull TelephonySubscriptionTrackerCallback callback,

            @NonNull Dependencies deps) {

        mContext = Objects.requireNonNull(context, "Missing context");

        mHandler = Objects.requireNonNull(handler, "Missing handler");

        mCallback = Objects.requireNonNull(callback, "Missing callback");

        mDeps = Objects.requireNonNull(deps, "Missing deps");

        mSubscriptionManager = mContext.getSystemService(SubscriptionManager.class);

        mCarrierConfigManager = mContext.getSystemService(CarrierConfigManager.class);

        mSubscriptionChangedListener =

                new OnSubscriptionsChangedListener() {

                    @Override

                    public void onSubscriptionsChanged() {

                        handleSubscriptionsChanged();

                    }

                };

    }

    /** Registers the receivers, and starts tracking subscriptions. */

    public void register() {

        mContext.registerReceiver(

                this, new IntentFilter(ACTION_CARRIER_CONFIG_CHANGED), null, mHandler);

        mSubscriptionManager.addOnSubscriptionsChangedListener(

                new HandlerExecutor(mHandler), mSubscriptionChangedListener);

    }

    /** Unregisters the receivers, and stops tracking subscriptions. */

    public void unregister() {

        mContext.unregisterReceiver(this);

        mSubscriptionManager.removeOnSubscriptionsChangedListener(mSubscriptionChangedListener);

    }

    /**

     * Handles subscription changes, correlating available subscriptions and loaded carrier configs

     *

     * <p>The subscription change listener is registered with a HandlerExecutor backed by mHandler,

     * so callbacks & broadcasts are all serialized on mHandler, avoiding the need for locking.

     */

    public void handleSubscriptionsChanged() {

        final Set<ParcelUuid> activeSubGroups = new ArraySet<>();

        final Map<Integer, ParcelUuid> newSubIdToGroupMap = new HashMap<>();

        final List<SubscriptionInfo> allSubs = mSubscriptionManager.getAllSubscriptionInfoList();

        if (allSubs == null) {

            return; // Telephony crashed; no way to verify subscriptions.

        }

        // If allSubs is empty, no subscriptions exist. Cache will be cleared by virtue of no active

        // subscriptions

        for (SubscriptionInfo subInfo : allSubs) {

            if (subInfo.getGroupUuid() == null) {

                continue;

            }

            // Build subId -> subGrp cache

            newSubIdToGroupMap.put(subInfo.getSubscriptionId(), subInfo.getGroupUuid());

            // Update subscription groups that are both ready, and active. For a group to be

            // considered active, both of the following must be true:

            //

            // 1. A final CARRIER_CONFIG_CHANGED (where config is for an identified carrier)

            // broadcast must have been received for the subId

            // 2. A active subscription (is loaded into a SIM slot) must be part of the subscription

            // group.

            if (subInfo.getSimSlotIndex() != INVALID_SIM_SLOT_INDEX

                    && mReadySubIdsBySlotId.values().contains(subInfo.getSubscriptionId())) {

                activeSubGroups.add(subInfo.getGroupUuid());

            }

        }

        final TelephonySubscriptionSnapshot newSnapshot =

                new TelephonySubscriptionSnapshot(newSubIdToGroupMap, activeSubGroups);

        // If snapshot was meaningfully updated, fire the callback

        if (!newSnapshot.equals(mCurrentSnapshot)) {

            mCurrentSnapshot = newSnapshot;

            mHandler.post(

                    () -> {

                        mCallback.onNewSnapshot(newSnapshot);

                    });

        }

    }

    /**

     * Broadcast receiver for ACTION_CARRIER_CONFIG_CHANGED

     *

     * <p>The broadcast receiver is registered with mHandler, so callbacks & broadcasts are all

     * serialized on mHandler, avoiding the need for locking.

     */

    @Override

    public void onReceive(Context context, Intent intent) {

        // Accept sticky broadcasts; if CARRIER_CONFIG_CHANGED was previously broadcast and it

        // already was for an identified carrier, we can stop waiting for initial load to complete

        if (!ACTION_CARRIER_CONFIG_CHANGED.equals(intent.getAction())) {

            return;

        }

        final int subId = intent.getIntExtra(EXTRA_SUBSCRIPTION_INDEX, INVALID_SUBSCRIPTION_ID);

        final int slotId = intent.getIntExtra(EXTRA_SLOT_INDEX, INVALID_SIM_SLOT_INDEX);

        if (slotId == INVALID_SIM_SLOT_INDEX) {

            return;

        }

        if (SubscriptionManager.isValidSubscriptionId(subId)) {

            final PersistableBundle carrierConfigs = mCarrierConfigManager.getConfigForSubId(subId);

            if (mDeps.isConfigForIdentifiedCarrier(carrierConfigs)) {

                Slog.v(TAG, String.format("SubId %s ready for SlotId %s", subId, slotId));

                mReadySubIdsBySlotId.put(slotId, subId);

                handleSubscriptionsChanged();

            }

        } else {

            Slog.v(TAG, "Slot unloaded: " + slotId);

            mReadySubIdsBySlotId.remove(slotId);

            handleSubscriptionsChanged();

        }

    }

    @VisibleForTesting(visibility = Visibility.PRIVATE)

    void setReadySubIdsBySlotId(Map<Integer, Integer> readySubIdsBySlotId) {

        mReadySubIdsBySlotId.putAll(readySubIdsBySlotId);

    }

    @VisibleForTesting(visibility = Visibility.PRIVATE)

    Map<Integer, Integer> getReadySubIdsBySlotId() {

        return Collections.unmodifiableMap(mReadySubIdsBySlotId);

    }

    /** TelephonySubscriptionSnapshot is a class containing info about active subscriptions */

    public static class TelephonySubscriptionSnapshot {

        private final Map<Integer, ParcelUuid> mSubIdToGroupMap;

        private final Set<ParcelUuid> mActiveGroups;

        @VisibleForTesting(visibility = Visibility.PRIVATE)

        TelephonySubscriptionSnapshot(

                @NonNull Map<Integer, ParcelUuid> subIdToGroupMap,

                @NonNull Set<ParcelUuid> activeGroups) {

            mSubIdToGroupMap = Collections.unmodifiableMap(

                    Objects.requireNonNull(subIdToGroupMap, "subIdToGroupMap was null"));

            mActiveGroups = Collections.unmodifiableSet(

                    Objects.requireNonNull(activeGroups, "activeGroups was null"));

        }

        /** Returns the active subscription groups */

        @NonNull

        public Set<ParcelUuid> getActiveSubscriptionGroups() {

            return mActiveGroups;

        }

        /** Returns the Subscription Group for a given subId. */

        @Nullable

        public ParcelUuid getGroupForSubId(int subId) {

            return mSubIdToGroupMap.get(subId);

        }

        /**

         * Returns all the subIds in a given group, including available, but inactive subscriptions.

         */

        @NonNull

        public Set<Integer> getAllSubIdsInGroup(ParcelUuid subGrp) {

            final Set<Integer> subIds = new ArraySet<>();

            for (Entry<Integer, ParcelUuid> entry : mSubIdToGroupMap.entrySet()) {

                if (subGrp.equals(entry.getValue())) {

                    subIds.add(entry.getKey());

                }

            }

            return subIds;

        }

        @Override

        public int hashCode() {

            return Objects.hash(mSubIdToGroupMap, mActiveGroups);

        }

        @Override

        public boolean equals(Object obj) {

            if (!(obj instanceof TelephonySubscriptionSnapshot)) {

                return false;

            }

            final TelephonySubscriptionSnapshot other = (TelephonySubscriptionSnapshot) obj;

            return mSubIdToGroupMap.equals(other.mSubIdToGroupMap)

                    && mActiveGroups.equals(other.mActiveGroups);

        }

    }

    /**

     * Interface for listening to changes in subscriptions

     *

     * @see TelephonySubscriptionTracker

     */

    public interface TelephonySubscriptionTrackerCallback {

        /**

         * Called when subscription information changes, and a new subscription snapshot was taken

         *

         * @param snapshot the snapshot of subscription information.

         */

        void onNewSnapshot(@NonNull TelephonySubscriptionSnapshot snapshot);

    }

    /** External static dependencies for test injection */

    @VisibleForTesting(visibility = Visibility.PRIVATE)

    public static class Dependencies {

        /** Checks if the given bundle is for an identified carrier */

        public boolean isConfigForIdentifiedCarrier(PersistableBundle bundle) {

            return CarrierConfigManager.isConfigForIdentifiedCarrier(bundle);

        }

    }

}