/*
 * Copyright (C) 2016 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.connectivity;

import static android.util.TimeUtils.NANOS_PER_MS;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.INetdEventCallback;
import android.net.Network;
import android.net.NetworkCapabilities;
import android.net.metrics.ConnectStats;
import android.net.metrics.DnsEvent;
import android.net.metrics.INetdEventListener;
import android.net.metrics.IpConnectivityLog;
import android.net.metrics.WakeupEvent;
import android.net.metrics.WakeupStats;
import android.os.RemoteException;
import android.text.format.DateUtils;
import android.util.Log;
import android.util.ArrayMap;
import android.util.SparseArray;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.util.BitUtils;
import com.android.internal.util.IndentingPrintWriter;
import com.android.internal.util.TokenBucket;
import com.android.server.connectivity.metrics.nano.IpConnectivityLogClass.IpConnectivityEvent;
import java.io.PrintWriter;
import java.util.List;
import java.util.function.Function;
import java.util.function.IntFunction;

/**
 * Implementation of the INetdEventListener interface.
 */
public class NetdEventListenerService extends INetdEventListener.Stub {

    public static final String SERVICE_NAME = "netd_listener";

    private static final String TAG = NetdEventListenerService.class.getSimpleName();
    private static final boolean DBG = false;
    private static final boolean VDBG = false;

    private static final int INITIAL_DNS_BATCH_SIZE = 100;

    // Rate limit connect latency logging to 1 measurement per 15 seconds (5760 / day) with maximum
    // bursts of 5000 measurements.
    private static final int CONNECT_LATENCY_BURST_LIMIT  = 5000;
    private static final int CONNECT_LATENCY_FILL_RATE    = 15 * (int) DateUtils.SECOND_IN_MILLIS;
    private static final int CONNECT_LATENCY_MAXIMUM_RECORDS = 20000;

    @VisibleForTesting
    static final int WAKEUP_EVENT_BUFFER_LENGTH = 1024;
    // TODO: dedup this String constant with the one used in
    // ConnectivityService#wakeupModifyInterface().
    @VisibleForTesting
    static final String WAKEUP_EVENT_IFACE_PREFIX = "iface:";

    // Sparse arrays of DNS and connect events, grouped by net id.
    @GuardedBy("this")
    private final SparseArray<DnsEvent> mDnsEvents = new SparseArray<>();
    @GuardedBy("this")
    private final SparseArray<ConnectStats> mConnectEvents = new SparseArray<>();

    // Array of aggregated wakeup event stats, grouped by interface name.
    @GuardedBy("this")
    private final ArrayMap<String, WakeupStats> mWakeupStats = new ArrayMap<>();
    // Ring buffer array for storing packet wake up events sent by Netd.
    @GuardedBy("this")
    private final WakeupEvent[] mWakeupEvents = new WakeupEvent[WAKEUP_EVENT_BUFFER_LENGTH];
    @GuardedBy("this")
    private long mWakeupEventCursor = 0;

    private final ConnectivityManager mCm;

    @GuardedBy("this")
    private final TokenBucket mConnectTb =
            new TokenBucket(CONNECT_LATENCY_FILL_RATE, CONNECT_LATENCY_BURST_LIMIT);
    // Callback should only be registered/unregistered when logging is being enabled/disabled in DPM
    // by the device owner. It's DevicePolicyManager's responsibility to ensure that.
    @GuardedBy("this")
    private INetdEventCallback mNetdEventCallback;

    public synchronized boolean registerNetdEventCallback(INetdEventCallback callback) {
        mNetdEventCallback = callback;
        return true;
    }

    public synchronized boolean unregisterNetdEventCallback() {
        mNetdEventCallback = null;
        return true;
    }

    public NetdEventListenerService(Context context) {
        this(context.getSystemService(ConnectivityManager.class));
    }

    @VisibleForTesting
    public NetdEventListenerService(ConnectivityManager cm) {
        // We are started when boot is complete, so ConnectivityService should already be running.
        mCm = cm;
    }

    @Override
    // Called concurrently by multiple binder threads.
    // This method must not block or perform long-running operations.
    public synchronized void onDnsEvent(int netId, int eventType, int returnCode, int latencyMs,
            String hostname, String[] ipAddresses, int ipAddressesCount, int uid)
            throws RemoteException {
        maybeVerboseLog("onDnsEvent(%d, %d, %d, %dms)", netId, eventType, returnCode, latencyMs);

        DnsEvent dnsEvent = mDnsEvents.get(netId);
        if (dnsEvent == null) {
            dnsEvent = makeDnsEvent(netId);
            mDnsEvents.put(netId, dnsEvent);
        }
        dnsEvent.addResult((byte) eventType, (byte) returnCode, latencyMs);

        if (mNetdEventCallback != null) {
            long timestamp = System.currentTimeMillis();
            mNetdEventCallback.onDnsEvent(hostname, ipAddresses, ipAddressesCount, timestamp, uid);
        }
    }

    @Override
    // Called concurrently by multiple binder threads.
    // This method must not block or perform long-running operations.
    public synchronized void onConnectEvent(int netId, int error, int latencyMs, String ipAddr,
            int port, int uid) throws RemoteException {
        maybeVerboseLog("onConnectEvent(%d, %d, %dms)", netId, error, latencyMs);

        ConnectStats connectStats = mConnectEvents.get(netId);
        if (connectStats == null) {
            connectStats = makeConnectStats(netId);
            mConnectEvents.put(netId, connectStats);
        }
        connectStats.addEvent(error, latencyMs, ipAddr);

        if (mNetdEventCallback != null) {
            mNetdEventCallback.onConnectEvent(ipAddr, port, System.currentTimeMillis(), uid);
        }
    }

    @Override
    public synchronized void onWakeupEvent(String prefix, int uid, int gid, long timestampNs) {
        maybeVerboseLog("onWakeupEvent(%s, %d, %d, %sns)", prefix, uid, gid, timestampNs);

        // TODO: add ip protocol and port

        String iface = prefix.replaceFirst(WAKEUP_EVENT_IFACE_PREFIX, "");
        final long timestampMs;
        if (timestampNs > 0) {
            timestampMs = timestampNs / NANOS_PER_MS;
        } else {
            timestampMs = System.currentTimeMillis();
        }

        addWakeupEvent(iface, timestampMs, uid);
    }

    @GuardedBy("this")
    private void addWakeupEvent(String iface, long timestampMs, int uid) {
        int index = wakeupEventIndex(mWakeupEventCursor);
        mWakeupEventCursor++;
        WakeupEvent event = new WakeupEvent();
        event.iface = iface;
        event.timestampMs = timestampMs;
        event.uid = uid;
        mWakeupEvents[index] = event;
        WakeupStats stats = mWakeupStats.get(iface);
        if (stats == null) {
            stats = new WakeupStats(iface);
            mWakeupStats.put(iface, stats);
        }
        stats.countEvent(event);
    }

    @GuardedBy("this")
    private WakeupEvent[] getWakeupEvents() {
        int length = (int) Math.min(mWakeupEventCursor, (long) mWakeupEvents.length);
        WakeupEvent[] out = new WakeupEvent[length];
        // Reverse iteration from youngest event to oldest event.
        long inCursor = mWakeupEventCursor - 1;
        int outIdx = out.length - 1;
        while (outIdx >= 0) {
            out[outIdx--] = mWakeupEvents[wakeupEventIndex(inCursor--)];
        }
        return out;
    }

    private static int wakeupEventIndex(long cursor) {
        return (int) Math.abs(cursor % WAKEUP_EVENT_BUFFER_LENGTH);
    }

    public synchronized void flushStatistics(List<IpConnectivityEvent> events) {
        flushProtos(events, mConnectEvents, IpConnectivityEventBuilder::toProto);
        flushProtos(events, mDnsEvents, IpConnectivityEventBuilder::toProto);
        for (int i = 0; i < mWakeupStats.size(); i++) {
            events.add(IpConnectivityEventBuilder.toProto(mWakeupStats.valueAt(i)));
        }
        mWakeupStats.clear();
    }

    public synchronized void dump(PrintWriter writer) {
        IndentingPrintWriter pw = new IndentingPrintWriter(writer, "  ");
        pw.println(TAG + ":");
        pw.increaseIndent();
        list(pw);
        pw.decreaseIndent();
    }

    public synchronized void list(PrintWriter pw) {
        listEvents(pw, mConnectEvents, (x) -> x, "\n");
        listEvents(pw, mDnsEvents, (x) -> x, "\n");
        for (int i = 0; i < mWakeupStats.size(); i++) {
            pw.println(mWakeupStats.valueAt(i));
        }
        for (WakeupEvent wakeup : getWakeupEvents()) {
            pw.println(wakeup);
        }
    }

    public synchronized void listAsProtos(PrintWriter pw) {
        listEvents(pw, mConnectEvents, IpConnectivityEventBuilder::toProto, "");
        listEvents(pw, mDnsEvents, IpConnectivityEventBuilder::toProto, "");
        for (int i = 0; i < mWakeupStats.size(); i++) {
            pw.print(IpConnectivityEventBuilder.toProto(mWakeupStats.valueAt(i)));
        }
    }

    private static <T> void flushProtos(List<IpConnectivityEvent> out, SparseArray<T> in,
            Function<T, IpConnectivityEvent> mapper) {
        for (int i = 0; i < in.size(); i++) {
            out.add(mapper.apply(in.valueAt(i)));
        }
        in.clear();
    }

    private static <T> void listEvents(
            PrintWriter pw, SparseArray<T> events, Function<T, Object> mapper, String separator) {
        // Proto derived Classes have toString method that adds a \n at the end.
        // Let the caller control that by passing in the line separator explicitly.
        for (int i = 0; i < events.size(); i++) {
            pw.print(mapper.apply(events.valueAt(i)));
            pw.print(separator);
        }
    }

    private ConnectStats makeConnectStats(int netId) {
        long transports = getTransports(netId);
        return new ConnectStats(netId, transports, mConnectTb, CONNECT_LATENCY_MAXIMUM_RECORDS);
    }

    private DnsEvent makeDnsEvent(int netId) {
        long transports = getTransports(netId);
        return new DnsEvent(netId, transports, INITIAL_DNS_BATCH_SIZE);
    }

    private long getTransports(int netId) {
        // TODO: directly query ConnectivityService instead of going through Binder interface.
        NetworkCapabilities nc = mCm.getNetworkCapabilities(new Network(netId));
        if (nc == null) {
            return 0;
        }
        return BitUtils.packBits(nc.getTransportTypes());
    }

    private static void maybeLog(String s, Object... args) {
        if (DBG) Log.d(TAG, String.format(s, args));
    }

    private static void maybeVerboseLog(String s, Object... args) {
        if (VDBG) Log.d(TAG, String.format(s, args));
    }
}