/*
 * 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 android.net;

import android.annotation.SystemApi;
import android.app.PendingIntent;
import android.os.Bundle;
import android.os.Parcelable;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.util.Log;

import com.android.internal.annotations.VisibleForTesting;

/** {@hide} */
@SystemApi
public class ConnectivityMetricsLogger {
    private static String TAG = "ConnectivityMetricsLogger";
    private static final boolean DBG = true;

    public static final String CONNECTIVITY_METRICS_LOGGER_SERVICE = "connectivity_metrics_logger";

    // Component Tags
    public static final int COMPONENT_TAG_CONNECTIVITY = 0;
    public static final int COMPONENT_TAG_BLUETOOTH    = 1;
    public static final int COMPONENT_TAG_WIFI         = 2;
    public static final int COMPONENT_TAG_TELECOM      = 3;
    public static final int COMPONENT_TAG_TELEPHONY    = 4;
    public static final int NUMBER_OF_COMPONENTS       = 5;

    // Event Tag
    public static final int TAG_SKIPPED_EVENTS = -1;

    public static final String DATA_KEY_EVENTS_COUNT = "count";

    /** {@hide} */ protected IConnectivityMetricsLogger mService;
    /** {@hide} */ protected volatile long mServiceUnblockedTimestampMillis;
    private int mNumSkippedEvents;

    public ConnectivityMetricsLogger() {
        // TODO: consider not initializing mService in constructor
        this(IConnectivityMetricsLogger.Stub.asInterface(
                ServiceManager.getService(CONNECTIVITY_METRICS_LOGGER_SERVICE)));
    }

    /** {@hide} */
    @VisibleForTesting
    public ConnectivityMetricsLogger(IConnectivityMetricsLogger service) {
        mService = service;
    }

    /** {@hide} */
    protected boolean checkLoggerService() {
        if (mService != null) {
            return true;
        }
        // Two threads racing here will write the same pointer because getService
        // is idempotent once MetricsLoggerService is initialized.
        mService = IConnectivityMetricsLogger.Stub.asInterface(
                ServiceManager.getService(CONNECTIVITY_METRICS_LOGGER_SERVICE));
        return mService != null;
    }

    /**
     * Log a ConnectivityMetricsEvent.
     *
     * This method keeps track of skipped events when MetricsLoggerService throttles input events.
     * It skips logging when MetricsLoggerService is active. When throttling ends, it logs a
     * meta-event containing the number of events dropped. It is not safe to call this method
     * concurrently from different threads.
     *
     * @param timestamp is the epoch timestamp of the event in ms.
     * @param componentTag is the COMPONENT_* constant the event belongs to.
     * @param eventTag is an event type constant whose meaning is specific to the component tag.
     * @param data is a Parcelable instance representing the event.
     */
    public void logEvent(long timestamp, int componentTag, int eventTag, Parcelable data) {
        if (mService == null) {
            if (DBG) {
                Log.d(TAG, "logEvent(" + componentTag + "," + eventTag + ") Service not ready");
            }
            return;
        }

        if (mServiceUnblockedTimestampMillis > 0) {
            if (System.currentTimeMillis() < mServiceUnblockedTimestampMillis) {
                // Service is throttling events.
                // Don't send new events because they will be dropped.
                mNumSkippedEvents++;
                return;
            }
        }

        ConnectivityMetricsEvent skippedEventsEvent = null;
        if (mNumSkippedEvents > 0) {
            // Log number of skipped events
            Bundle b = new Bundle();
            b.putInt(DATA_KEY_EVENTS_COUNT, mNumSkippedEvents);

            // Log the skipped event.
            // TODO: Note that some of the clients push all states events into the server,
            // If we lose some states logged here, we might mess up the statistics happened at the
            // backend. One of the options is to introduce a non-skippable flag for important events
            // that are logged.
            skippedEventsEvent = new ConnectivityMetricsEvent(mServiceUnblockedTimestampMillis,
                    componentTag, TAG_SKIPPED_EVENTS, b);

            mServiceUnblockedTimestampMillis = 0;
        }

        ConnectivityMetricsEvent event = new ConnectivityMetricsEvent(timestamp, componentTag,
                eventTag, data);

        try {
            long result;
            if (skippedEventsEvent == null) {
                result = mService.logEvent(event);
            } else {
                result = mService.logEvents(new ConnectivityMetricsEvent[]
                        {skippedEventsEvent, event});
            }

            if (result == 0) {
                mNumSkippedEvents = 0;
            } else {
                mNumSkippedEvents++;
                if (result > 0) { // events are throttled
                    mServiceUnblockedTimestampMillis = result;
                }
            }
        } catch (RemoteException e) {
            Log.e(TAG, "Error logging event", e);
        }
    }

    /**
     * Retrieve events
     *
     * @param reference of the last event previously returned. The function will return
     *                  events following it.
     *                  If 0 then all events will be returned.
     *                  After the function call it will contain reference of the
     *                  last returned event.
     * @return events
     */
    public ConnectivityMetricsEvent[] getEvents(ConnectivityMetricsEvent.Reference reference) {
        try {
            return mService.getEvents(reference);
        } catch (RemoteException e) {
            Log.e(TAG, "IConnectivityMetricsLogger.getEvents", e);
            return null;
        }
    }

    /**
     * Register PendingIntent which will be sent when new events are ready to be retrieved.
     */
    public boolean register(PendingIntent newEventsIntent) {
        try {
            return mService.register(newEventsIntent);
        } catch (RemoteException e) {
            Log.e(TAG, "IConnectivityMetricsLogger.register", e);
            return false;
        }
    }

    public boolean unregister(PendingIntent newEventsIntent) {
        try {
            mService.unregister(newEventsIntent);
            return true;
        } catch (RemoteException e) {
            Log.e(TAG, "IConnectivityMetricsLogger.unregister", e);
            return false;
        }
    }
}