/*
 * Copyright (C) 2011 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 static android.content.pm.PackageManager.GET_SIGNATURES;
import static android.net.NetworkPolicy.CYCLE_NONE;
import static android.text.format.Time.MONTH_DAY;

import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.Signature;
import android.os.RemoteException;
import android.os.UserHandle;
import android.text.format.Time;
import android.util.DebugUtils;

import com.google.android.collect.Sets;

import java.util.HashSet;

/**
 * Manager for creating and modifying network policy rules.
 *
 * {@hide}
 */
public class NetworkPolicyManager {

    /* POLICY_* are masks and can be ORed */
    /** No specific network policy, use system default. */
    public static final int POLICY_NONE = 0x0;
    /** Reject network usage on metered networks when application in background. */
    public static final int POLICY_REJECT_METERED_BACKGROUND = 0x1;
    /** Allow network use (metered or not) in the background in battery save mode. */
    public static final int POLICY_ALLOW_BACKGROUND_BATTERY_SAVE = 0x2;

    /*
     * Rules defining whether an uid has access to a network given its type (metered / non-metered).
     *
     * These rules are bits and can be used in bitmask operations; in particular:
     * - rule & RULE_MASK_METERED: returns the metered-networks status.
     * - rule & RULE_MASK_ALL: returns the all-networks status.
     *
     * The RULE_xxx_ALL rules applies to all networks (metered or non-metered), but on
     * metered networks, the RULE_xxx_METERED rules should be checked first. For example,
     * if the device is on Battery Saver Mode and Data Saver Mode simulatenously, and a uid
     * is whitelisted for the former but not the latter, its status would be
     * RULE_REJECT_METERED | RULE_ALLOW_ALL, meaning it could have access to non-metered
     * networks but not to metered networks.
     *
     * See network-policy-restrictions.md for more info.
     */
    /** No specific rule was set */
    public static final int RULE_NONE = 0;
    /** Allow traffic on metered networks. */
    public static final int RULE_ALLOW_METERED = 1 << 0;
    /** Temporarily allow traffic on metered networks because app is on foreground. */
    public static final int RULE_TEMPORARY_ALLOW_METERED = 1 << 1;
    /** Reject traffic on metered networks. */
    public static final int RULE_REJECT_METERED = 1 << 2;
    /** Network traffic should be allowed on all networks (metered or non-metered), although
     * metered-network restrictions could still apply. */
    public static final int RULE_ALLOW_ALL = 1 << 5;
    /** Reject traffic on all networks. */
    public static final int RULE_REJECT_ALL = 1 << 6;
    /** Mask used to get the {@code RULE_xxx_METERED} rules */
    public static final int MASK_METERED_NETWORKS = 0b00001111;
    /** Mask used to get the {@code RULE_xxx_ALL} rules */
    public static final int MASK_ALL_NETWORKS     = 0b11110000;

    public static final int FIREWALL_RULE_DEFAULT = 0;
    public static final int FIREWALL_RULE_ALLOW = 1;
    public static final int FIREWALL_RULE_DENY = 2;

    public static final int FIREWALL_TYPE_WHITELIST = 0;
    public static final int FIREWALL_TYPE_BLACKLIST = 1;

    public static final int FIREWALL_CHAIN_NONE = 0;
    public static final int FIREWALL_CHAIN_DOZABLE = 1;
    public static final int FIREWALL_CHAIN_STANDBY = 2;
    public static final int FIREWALL_CHAIN_POWERSAVE = 3;

    public static final String FIREWALL_CHAIN_NAME_NONE = "none";
    public static final String FIREWALL_CHAIN_NAME_DOZABLE = "dozable";
    public static final String FIREWALL_CHAIN_NAME_STANDBY = "standby";
    public static final String FIREWALL_CHAIN_NAME_POWERSAVE = "powersave";

    private static final boolean ALLOW_PLATFORM_APP_POLICY = true;

    /**
     * {@link Intent} extra that indicates which {@link NetworkTemplate} rule it
     * applies to.
     */
    public static final String EXTRA_NETWORK_TEMPLATE = "android.net.NETWORK_TEMPLATE";

    private final Context mContext;
    private INetworkPolicyManager mService;

    public NetworkPolicyManager(Context context, INetworkPolicyManager service) {
        if (service == null) {
            throw new IllegalArgumentException("missing INetworkPolicyManager");
        }
        mContext = context;
        mService = service;
    }

    public static NetworkPolicyManager from(Context context) {
        return (NetworkPolicyManager) context.getSystemService(Context.NETWORK_POLICY_SERVICE);
    }

    /**
     * Set policy flags for specific UID.
     *
     * @param policy {@link #POLICY_NONE} or combination of flags like
     * {@link #POLICY_REJECT_METERED_BACKGROUND} or {@link #POLICY_ALLOW_BACKGROUND_BATTERY_SAVE}.
     */
    public void setUidPolicy(int uid, int policy) {
        try {
            mService.setUidPolicy(uid, policy);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Add policy flags for specific UID.  The given policy bits will be set for
     * the uid.  Policy flags may be either
     * {@link #POLICY_REJECT_METERED_BACKGROUND} or {@link #POLICY_ALLOW_BACKGROUND_BATTERY_SAVE}.
     */
    public void addUidPolicy(int uid, int policy) {
        try {
            mService.addUidPolicy(uid, policy);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Clear/remove policy flags for specific UID.  The given policy bits will be set for
     * the uid.  Policy flags may be either
     * {@link #POLICY_REJECT_METERED_BACKGROUND} or {@link #POLICY_ALLOW_BACKGROUND_BATTERY_SAVE}.
     */
    public void removeUidPolicy(int uid, int policy) {
        try {
            mService.removeUidPolicy(uid, policy);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public int getUidPolicy(int uid) {
        try {
            return mService.getUidPolicy(uid);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public int[] getUidsWithPolicy(int policy) {
        try {
            return mService.getUidsWithPolicy(policy);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public void registerListener(INetworkPolicyListener listener) {
        try {
            mService.registerListener(listener);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public void unregisterListener(INetworkPolicyListener listener) {
        try {
            mService.unregisterListener(listener);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public void setNetworkPolicies(NetworkPolicy[] policies) {
        try {
            mService.setNetworkPolicies(policies);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public NetworkPolicy[] getNetworkPolicies() {
        try {
            return mService.getNetworkPolicies(mContext.getOpPackageName());
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public void setRestrictBackground(boolean restrictBackground) {
        try {
            mService.setRestrictBackground(restrictBackground);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    public boolean getRestrictBackground() {
        try {
            return mService.getRestrictBackground();
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Resets network policy settings back to factory defaults.
     *
     * @hide
     */
    public void factoryReset(String subscriber) {
        try {
            mService.factoryReset(subscriber);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    /**
     * Compute the last cycle boundary for the given {@link NetworkPolicy}. For
     * example, if cycle day is 20th, and today is June 15th, it will return May
     * 20th. When cycle day doesn't exist in current month, it snaps to the 1st
     * of following month.
     *
     * @hide
     */
    public static long computeLastCycleBoundary(long currentTime, NetworkPolicy policy) {
        if (policy.cycleDay == CYCLE_NONE) {
            throw new IllegalArgumentException("Unable to compute boundary without cycleDay");
        }

        final Time now = new Time(policy.cycleTimezone);
        now.set(currentTime);

        // first, find cycle boundary for current month
        final Time cycle = new Time(now);
        cycle.hour = cycle.minute = cycle.second = 0;
        snapToCycleDay(cycle, policy.cycleDay);

        if (Time.compare(cycle, now) >= 0) {
            // cycle boundary is beyond now, use last cycle boundary; start by
            // pushing ourselves squarely into last month.
            final Time lastMonth = new Time(now);
            lastMonth.hour = lastMonth.minute = lastMonth.second = 0;
            lastMonth.monthDay = 1;
            lastMonth.month -= 1;
            lastMonth.normalize(true);

            cycle.set(lastMonth);
            snapToCycleDay(cycle, policy.cycleDay);
        }

        return cycle.toMillis(true);
    }

    /** {@hide} */
    public static long computeNextCycleBoundary(long currentTime, NetworkPolicy policy) {
        if (policy.cycleDay == CYCLE_NONE) {
            throw new IllegalArgumentException("Unable to compute boundary without cycleDay");
        }

        final Time now = new Time(policy.cycleTimezone);
        now.set(currentTime);

        // first, find cycle boundary for current month
        final Time cycle = new Time(now);
        cycle.hour = cycle.minute = cycle.second = 0;
        snapToCycleDay(cycle, policy.cycleDay);

        if (Time.compare(cycle, now) <= 0) {
            // cycle boundary is before now, use next cycle boundary; start by
            // pushing ourselves squarely into next month.
            final Time nextMonth = new Time(now);
            nextMonth.hour = nextMonth.minute = nextMonth.second = 0;
            nextMonth.monthDay = 1;
            nextMonth.month += 1;
            nextMonth.normalize(true);

            cycle.set(nextMonth);
            snapToCycleDay(cycle, policy.cycleDay);
        }

        return cycle.toMillis(true);
    }

    /**
     * Snap to the cycle day for the current month given; when cycle day doesn't
     * exist, it snaps to last second of current month.
     *
     * @hide
     */
    public static void snapToCycleDay(Time time, int cycleDay) {
        if (cycleDay > time.getActualMaximum(MONTH_DAY)) {
            // cycle day isn't valid this month; snap to last second of month
            time.month += 1;
            time.monthDay = 1;
            time.second = -1;
        } else {
            time.monthDay = cycleDay;
        }
        time.normalize(true);
    }

    /**
     * Check if given UID can have a {@link #setUidPolicy(int, int)} defined,
     * usually to protect critical system services.
     */
    @Deprecated
    public static boolean isUidValidForPolicy(Context context, int uid) {
        // first, quick-reject non-applications
        if (!UserHandle.isApp(uid)) {
            return false;
        }

        if (!ALLOW_PLATFORM_APP_POLICY) {
            final PackageManager pm = context.getPackageManager();
            final HashSet<Signature> systemSignature;
            try {
                systemSignature = Sets.newHashSet(
                        pm.getPackageInfo("android", GET_SIGNATURES).signatures);
            } catch (NameNotFoundException e) {
                throw new RuntimeException("problem finding system signature", e);
            }

            try {
                // reject apps signed with platform cert
                for (String packageName : pm.getPackagesForUid(uid)) {
                    final HashSet<Signature> packageSignature = Sets.newHashSet(
                            pm.getPackageInfo(packageName, GET_SIGNATURES).signatures);
                    if (packageSignature.containsAll(systemSignature)) {
                        return false;
                    }
                }
            } catch (NameNotFoundException e) {
            }
        }

        // nothing found above; we can apply policy to UID
        return true;
    }

    /*
     * @hide
     */
    public static String uidRulesToString(int uidRules) {
        final StringBuilder string = new StringBuilder().append(uidRules).append(" (");
        if (uidRules == RULE_NONE) {
            string.append("NONE");
        } else {
            string.append(DebugUtils.flagsToString(NetworkPolicyManager.class, "RULE_", uidRules));
        }
        string.append(")");
        return string.toString();
    }
}