/*
 * 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.networkrecommendation;

import android.content.Context;
import android.net.NetworkKey;
import android.net.NetworkRecommendationProvider;
import android.net.NetworkScoreManager;
import android.net.RecommendationRequest;
import android.net.RecommendationResult;
import android.net.RssiCurve;
import android.net.ScoredNetwork;
import android.net.WifiKey;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiConfiguration;
import android.os.Bundle;
import android.support.annotation.VisibleForTesting;
import android.text.TextUtils;
import android.util.ArrayMap;

import com.android.networkrecommendation.util.Blog;
import com.android.networkrecommendation.util.SsidUtil;

import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executor;

import javax.annotation.concurrent.GuardedBy;

/**
 * In memory, debuggable network recommendation provider.
 *
 * <p>This example evaluates networks in a scan and picks the "least bad" network, returning a
 * result to the RecommendedNetworkEvaluator, regardless of configuration point.
 *
 * <p>This recommender is not yet recommended for non-development devices.
 *
 * <p>To debug:
 * $ adb shell dumpsys activity service NetworkRecommendationService
 *
 * <p>Clear stored scores:
 * $ adb shell dumpsys activity service NetworkRecommendationService clear
 *
 * <p>Score a network:
 * $ adb shell dumpsys activity service NetworkRecommendationService addScore $SCORE
 *
 * <p>SCORE: "Quoted SSID",bssid|$RSSI_CURVE|metered|captivePortal|BADGE
 *
 * <p>RSSI_CURVE: bucketWidth,score,score,score,score,...
 *
 * <p>curve, metered and captive portal are optional, as expressed by an empty value.
 *
 * <p>BADGE: NONE, SD, HD, 4K
 *
 * <p>All commands should be executed on one line, no spaces between each line of the command..
 * <p>Eg, A high quality, paid network with captive portal:
 * $ adb shell dumpsys activity service NetworkRecommendationService addScore \
 * '\"Metered\",aa:bb:cc:dd:ee:ff\|
 * 10,-128,-128,-128,-128,-128,-128,-128,-128,27,27,27,27,27,-128\|1\|1'
 *
 * <p>Eg, A high quality, unmetered network with captive portal:
 * $ adb shell dumpsys activity service NetworkRecommendationService addScore \
 * '\"Captive\",aa:bb:cc:dd:ee:ff\|
 * 10,-128,-128,-128,-128,-128,-128,-128,-128,28,28,28,28,28,-128\|0\|1'
 *
 * <p>Eg, A high quality, unmetered network with any bssid:
 * $ adb shell dumpsys activity service NetworkRecommendationService addScore \
 * '\"AnySsid\",00:00:00:00:00:00\|
 * 10,-128,-128,-128,-128,-128,-128,-128,-128,29,29,29,29,29,-128\|0\|0'
 */
@VisibleForTesting
public class DefaultNetworkRecommendationProvider
        extends NetworkRecommendationProvider implements SynchronousNetworkRecommendationProvider {
    static final String TAG = "DefaultNetRecProvider";

    private static final String WILDCARD_MAC = "00:00:00:00:00:00";

    /**
     * The lowest RSSI value at which a fixed score should apply.
     * Only used for development / testing purpose.
     */
    @VisibleForTesting
    static final int CONSTANT_CURVE_START = -150;

    @VisibleForTesting
    static final RssiCurve BADGE_CURVE_SD =
            new RssiCurve(
                    CONSTANT_CURVE_START,
                    10 /* bucketWidth */,
                    new byte[] {0, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
                    0 /* defaultActiveNetworkBoost */);

    @VisibleForTesting
    static final RssiCurve BADGE_CURVE_HD =
            new RssiCurve(
                    CONSTANT_CURVE_START,
                    10 /* bucketWidth */,
                    new byte[] {0, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20},
                    0 /* defaultActiveNetworkBoost */);

    @VisibleForTesting
    static final RssiCurve BADGE_CURVE_4K =
            new RssiCurve(
                    CONSTANT_CURVE_START,
                    10 /* bucketWidth */,
                    new byte[] {0, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30},
                    0 /* defaultActiveNetworkBoost */);

    private final NetworkScoreManager mScoreManager;
    private final ScoreStorage mStorage;

    private final Object mStatsLock = new Object();
    @GuardedBy("mStatsLock")
    private int mRecommendationCounter = 0;
    @GuardedBy("mStatsLock")
    private WifiConfiguration mLastRecommended = null;
    @GuardedBy("mStatsLock")
    private int mScoreCounter = 0;


    public DefaultNetworkRecommendationProvider(Context context, Executor executor,
            NetworkScoreManager scoreManager, ScoreStorage storage) {
        super(context, executor);
        mScoreManager = scoreManager;
        mStorage = storage;
    }

    /**
     * Recommend the wireless network with the highest RSSI and run
     * {@link ResultCallback#onResult(RecommendationResult)}.
     */
    @Override
    public void onRequestRecommendation(RecommendationRequest request,
            ResultCallback callback) {
        callback.onResult(requestRecommendation(request));
    }

    @Override
    /** Recommend the wireless network with the highest RSSI. */
    public RecommendationResult requestRecommendation(RecommendationRequest request) {
        ScanResult recommendedScanResult = null;
        int recommendedScore = Integer.MIN_VALUE;

        ScanResult[] results = request.getScanResults();
        if (results != null) {
            for (int i = 0; i < results.length; i++) {
                final ScanResult scanResult = results[i];
                Blog.v(TAG, "Scan: " + scanResult + " " + i);

                // We only want to recommend open networks. This check is taken from
                // places like WifiNotificationController and will be extracted to ScanResult in
                // a future CL.
                if (!"[ESS]".equals(scanResult.capabilities)) {
                    Blog.v(TAG, "Discarding closed network: " + scanResult);
                    continue;
                }

                final NetworkKey networkKey = new NetworkKey(
                        new WifiKey(SsidUtil.quoteSsid(scanResult.SSID),
                                scanResult.BSSID));
                Blog.v(TAG, "Evaluating network: " + networkKey);

                // We will only score networks we know about.
                final ScoredNetwork network = mStorage.get(networkKey);
                if (network == null) {
                    Blog.v(TAG, "Discarding unscored network: " + scanResult);
                    continue;
                }

                final int score = network.rssiCurve.lookupScore(scanResult.level);
                Blog.v(TAG, "Scored " + scanResult + ": " + score);
                if (score > recommendedScore) {
                    recommendedScanResult = scanResult;
                    recommendedScore = score;
                    Blog.v(TAG, "New recommended network: " + scanResult);
                    continue;
                }
            }
        } else {
            Blog.w(TAG, "Received null scan results in request.");
        }

        // If we ended up without a recommendation, recommend the provided configuration
        // instead. If we wanted the platform to avoid this network, too, we could send back an
        // empty recommendation.
        RecommendationResult recommendationResult;
        if (recommendedScanResult == null) {
            if (request.getDefaultWifiConfig() != null) {
                recommendationResult = RecommendationResult
                        .createConnectRecommendation(request.getDefaultWifiConfig());
            } else {
                recommendationResult = RecommendationResult.createDoNotConnectRecommendation();
            }
        } else {
            // Build a configuration based on the scan.
            WifiConfiguration recommendedConfig = new WifiConfiguration();
            recommendedConfig.SSID = SsidUtil.quoteSsid(recommendedScanResult.SSID);
            recommendedConfig.BSSID = recommendedScanResult.BSSID;
            recommendedConfig.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.NONE);
            recommendationResult = RecommendationResult
                    .createConnectRecommendation(recommendedConfig);
        }
        synchronized (mStatsLock) {
            mLastRecommended = recommendationResult.getWifiConfiguration();
            mRecommendationCounter++;
            Blog.d(TAG, "Recommending network: " + configToString(mLastRecommended));
        }
        return recommendationResult;
    }

    /** Score networks based on a few properties ... */
    @Override
    public void onRequestScores(NetworkKey[] networks) {
        synchronized (mStatsLock) {
            mScoreCounter++;
        }
        List<ScoredNetwork> scoredNetworks = new ArrayList<>();
        for (int i = 0; i < networks.length; i++) {
            NetworkKey key = networks[i];

            // Score a network if we know about it.
            ScoredNetwork scoredNetwork = mStorage.get(key);
            if (scoredNetwork != null) {
                scoredNetworks.add(scoredNetwork);
                continue;
            }

            // We only want to score wifi networks at the moment.
            if (key.type != NetworkKey.TYPE_WIFI) {
                scoredNetworks.add(new ScoredNetwork(key, null, false /* meteredHint */));
                continue;
            }

            // We don't know about this network, even though its a wifi network. Inject
            // an empty score to satisfy the cache.
            scoredNetworks.add(new ScoredNetwork(key, null, false /* meteredHint */));
            continue;
        }
        if (scoredNetworks.isEmpty()) {
            return;
        }

        Blog.d(TAG, "Scored networks: " + scoredNetworks);
        safelyUpdateScores(scoredNetworks.toArray(new ScoredNetwork[scoredNetworks.size()]));
    }

    void dump(FileDescriptor fd, PrintWriter writer, String[] args) {
        for (int i = 0; i < args.length; i++) {
            if ("clear".equals(args[i])) {
                i++;
                clearScoresForTest();
                writer.println("Clearing store");
                return;
            } else if ("addScore".equals(args[i])) {
                i++;
                ScoredNetwork scoredNetwork = parseScore(args[i]);
                addScoreForTest(scoredNetwork);
                writer.println("Added: " + scoredNetwork);
                return;
            } else {
                writer.println("Unrecognized command: " + args[i]);
            }
        }
        mStorage.dump(fd, writer, args);
        synchronized (mStatsLock) {
            writer.println("Recommendation requests: " + mRecommendationCounter);
            writer.println("Last Recommended: " + configToString(mLastRecommended));
            writer.println("Score requests: " + mScoreCounter);
        }
    }

    @VisibleForTesting
    void addScoreForTest(ScoredNetwork scoredNetwork) {
        mStorage.addScore(scoredNetwork);
        if (!WILDCARD_MAC.equals(scoredNetwork.networkKey.wifiKey.bssid)) {
            safelyUpdateScores(new ScoredNetwork[]{scoredNetwork});
        }
    }

    @VisibleForTesting
    void clearScoresForTest() {
        mStorage.clear();
        safelyClearScores();
    }

    private void safelyUpdateScores(ScoredNetwork[] networkScores) {
        // Depending on races, etc, we might be alive when not the active scorer. Safely catch
        // and ignore security exceptions
        try {
            mScoreManager.updateScores(networkScores);
        } catch (SecurityException e) {
            Blog.w(TAG, "Tried to update scores when not the active scorer.");
        }
    }

    private void safelyClearScores() {
        // Depending on races, etc, we might be alive when not the active scorer. Safely catch
        // and ignore security exceptions
        try {
            mScoreManager.clearScores();
        } catch (SecurityException e) {
            Blog.w(TAG, "Tried to update scores when not the active scorer.");
        }
    }

    private static ScoredNetwork parseScore(String score) {
        String[] splitScore = score.split("\\|");
        String[] splitWifiKey = splitScore[0].split(",");
        NetworkKey networkKey = new NetworkKey(new WifiKey(splitWifiKey[0], splitWifiKey[1]));

        String[] splitRssiCurve = splitScore[1].split(",");
        int bucketWidth = Integer.parseInt(splitRssiCurve[0]);
        byte[] rssiBuckets = new byte[splitRssiCurve.length - 1];
        for (int i = 1; i < splitRssiCurve.length; i++) {
            rssiBuckets[i - 1] = Integer.valueOf(splitRssiCurve[i]).byteValue();
        }

        boolean meteredHint = "1".equals(splitScore[2]);
        Bundle attributes = new Bundle();
        if (!TextUtils.isEmpty(splitScore[3])) {
            attributes.putBoolean(
                    ScoredNetwork.ATTRIBUTES_KEY_HAS_CAPTIVE_PORTAL, "1".equals(splitScore[3]));
        }
        if (splitScore.length > 4) {
            String badge = splitScore[4].toUpperCase();
            if ("SD".equals(badge)) {
                attributes.putParcelable(
                        ScoredNetwork.ATTRIBUTES_KEY_BADGING_CURVE, BADGE_CURVE_SD);
            } else if ("HD".equals(badge)) {
                attributes.putParcelable(
                        ScoredNetwork.ATTRIBUTES_KEY_BADGING_CURVE, BADGE_CURVE_HD);
            } else if ("4K".equals(badge)) {
                attributes.putParcelable(
                        ScoredNetwork.ATTRIBUTES_KEY_BADGING_CURVE, BADGE_CURVE_4K);
            }
        }
        RssiCurve rssiCurve = new RssiCurve(CONSTANT_CURVE_START, bucketWidth, rssiBuckets, 0);
        return new ScoredNetwork(networkKey, rssiCurve, meteredHint, attributes);
    }

    /** Print a shorter config string, for dumpsys. */
    private static String configToString(WifiConfiguration config) {
        if (config == null) {
            return null;
        }
        StringBuilder sb = new StringBuilder()
                .append("ID=").append(config.networkId)
                .append(",SSID=").append(config.SSID)
                .append(",useExternalScores=").append(config.useExternalScores)
                .append(",meteredHint=").append(config.meteredHint);
        return sb.toString();
    }

    /** Stores scores about networks. Initial implementation is in-memory-only. */
    @VisibleForTesting
    static class ScoreStorage {

        @GuardedBy("mScores")
        private final ArrayMap<NetworkKey, ScoredNetwork> mScores = new ArrayMap<>();

        /**
         * Store a score in storage.
         *
         * @param scoredNetwork the network to score.
         *     If {@code scoredNetwork.networkKey.wifiKey.bssid} is "00:00:00:00:00:00", treat this
         *     score as applying to any bssid with the provided ssid.
         */
        public void addScore(ScoredNetwork scoredNetwork) {
            Blog.d(TAG, "addScore: " + scoredNetwork);
            synchronized (mScores) {
                mScores.put(scoredNetwork.networkKey, scoredNetwork);
            }
        }

        public ScoredNetwork get(NetworkKey key) {
            synchronized (mScores) {
                // Try to find a score for the requested bssid.
                ScoredNetwork scoredNetwork = mScores.get(key);
                if (scoredNetwork != null) {
                    return scoredNetwork;
                }
                // Try to find a score for a wildcard ssid.
                NetworkKey wildcardKey = new NetworkKey(
                        new WifiKey(key.wifiKey.ssid, WILDCARD_MAC));
                scoredNetwork = mScores.get(wildcardKey);
                if (scoredNetwork != null) {
                    // If the fetched score was a wildcard score, construct a synthetic score
                    // for the requested bssid and return it.
                    return new ScoredNetwork(
                            key, scoredNetwork.rssiCurve, scoredNetwork.meteredHint,
                            scoredNetwork.attributes);
                }
                return null;
            }
        }

        public void clear() {
            synchronized (mScores) {
                mScores.clear();
            }
        }

        public void dump(FileDescriptor fd, PrintWriter writer, String[] args) {
            synchronized (mScores) {
                for (ScoredNetwork score : mScores.values()) {
                    writer.println(score);
                }
            }
        }
    }

    @Override
    public ScoredNetwork getCachedScoredNetwork(NetworkKey networkKey) {
        return mStorage.get(networkKey);
    }
}