/*
 * Copyright (C) 2019 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.util;

import android.content.Context;
import android.content.pm.PackageManager.NameNotFoundException;
import android.provider.DeviceConfig;
import android.util.Log;
import android.util.SparseArray;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import java.io.FileDescriptor;
import java.io.IOException;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.List;
import java.util.function.Predicate;

/**
 * Collection of utilities for the network stack.
 */
public class NetworkStackUtils {
    private static final String TAG = "NetworkStackUtils";

    /**
     * A list of captive portal detection specifications used in addition to the fallback URLs.
     * Each spec has the format url@@/@@statusCodeRegex@@/@@contentRegex. Specs are separated
     * by "@@,@@".
     */
    public static final String CAPTIVE_PORTAL_FALLBACK_PROBE_SPECS =
            "captive_portal_fallback_probe_specs";

    /**
     * A comma separated list of URLs used for captive portal detection in addition to the
     * fallback HTTP url associated with the CAPTIVE_PORTAL_FALLBACK_URL settings.
     */
    public static final String CAPTIVE_PORTAL_OTHER_FALLBACK_URLS =
            "captive_portal_other_fallback_urls";

    /**
     * A comma separated list of URLs used for captive portal detection in addition to the HTTP url
     * associated with the CAPTIVE_PORTAL_HTTP_URL settings.
     */
    public static final String CAPTIVE_PORTAL_OTHER_HTTP_URLS = "captive_portal_other_http_urls";

    /**
     * A comma separated list of URLs used for network validation. in addition to the HTTPS url
     * associated with the CAPTIVE_PORTAL_HTTPS_URL settings.
     */
    public static final String CAPTIVE_PORTAL_OTHER_HTTPS_URLS = "captive_portal_other_https_urls";

    /**
     * Which User-Agent string to use in the header of the captive portal detection probes.
     * The User-Agent field is unset when this setting has no value (HttpUrlConnection default).
     */
    public static final String CAPTIVE_PORTAL_USER_AGENT = "captive_portal_user_agent";

    /**
     * Whether to use HTTPS for network validation. This is enabled by default and the setting
     * needs to be set to 0 to disable it. This setting is a misnomer because captive portals
     * don't actually use HTTPS, but it's consistent with the other settings.
     */
    public static final String CAPTIVE_PORTAL_USE_HTTPS = "captive_portal_use_https";

    /**
     * The URL used for HTTPS captive portal detection upon a new connection.
     * A 204 response code from the server is used for validation.
     */
    public static final String CAPTIVE_PORTAL_HTTPS_URL = "captive_portal_https_url";

    /**
     * The URL used for HTTP captive portal detection upon a new connection.
     * A 204 response code from the server is used for validation.
     */
    public static final String CAPTIVE_PORTAL_HTTP_URL = "captive_portal_http_url";

    /**
     * A test URL used to override configuration settings and overlays for the network validation
     * HTTPS URL, when set in {@link android.provider.DeviceConfig} configuration.
     *
     * <p>This URL will be ignored if the host is not "localhost" (it can only be used to test with
     * a local test server), and must not be set in production scenarios (as enforced by CTS tests).
     *
     * <p>{@link #TEST_URL_EXPIRATION_TIME} must also be set to use this setting.
     */
    public static final String TEST_CAPTIVE_PORTAL_HTTPS_URL = "test_captive_portal_https_url";

    /**
     * A test URL used to override configuration settings and overlays for the network validation
     * HTTP URL, when set in {@link android.provider.DeviceConfig} configuration.
     *
     * <p>This URL will be ignored if the host is not "localhost" (it can only be used to test with
     * a local test server), and must not be set in production scenarios (as enforced by CTS tests).
     *
     * <p>{@link #TEST_URL_EXPIRATION_TIME} must also be set to use this setting.
     */
    public static final String TEST_CAPTIVE_PORTAL_HTTP_URL = "test_captive_portal_http_url";

    /**
     * Expiration time of the test URL, in ms, relative to {@link System#currentTimeMillis()}.
     *
     * <p>After this expiration time, test URLs will be ignored. They will also be ignored if
     * the expiration time is more than 10 minutes in the future, to avoid misconfiguration
     * following test runs.
     */
    public static final String TEST_URL_EXPIRATION_TIME = "test_url_expiration_time";

    /**
     * The URL used for fallback HTTP captive portal detection when previous HTTP
     * and HTTPS captive portal detection attemps did not return a conclusive answer.
     */
    public static final String CAPTIVE_PORTAL_FALLBACK_URL = "captive_portal_fallback_url";

    /**
     * What to do when connecting a network that presents a captive portal.
     * Must be one of the CAPTIVE_PORTAL_MODE_* constants above.
     *
     * The default for this setting is CAPTIVE_PORTAL_MODE_PROMPT.
     */
    public static final String CAPTIVE_PORTAL_MODE = "captive_portal_mode";

    /**
     * Don't attempt to detect captive portals.
     */
    public static final int CAPTIVE_PORTAL_MODE_IGNORE = 0;

    /**
     * When detecting a captive portal, display a notification that
     * prompts the user to sign in.
     */
    public static final int CAPTIVE_PORTAL_MODE_PROMPT = 1;

    /**
     * When detecting a captive portal, immediately disconnect from the
     * network and do not reconnect to that network in the future.
     */
    public static final int CAPTIVE_PORTAL_MODE_AVOID = 2;

    /**
     * DNS probe timeout for network validation. Enough for 3 DNS queries 5 seconds apart.
     */
    public static final int DEFAULT_CAPTIVE_PORTAL_DNS_PROBE_TIMEOUT = 12500;

    /**
     * List of fallback probe specs to use for detecting captive portals. This is an alternative to
     * fallback URLs that provides more flexibility on detection rules. Empty, so unused by default.
     */
    public static final String[] DEFAULT_CAPTIVE_PORTAL_FALLBACK_PROBE_SPECS =
            new String[] {};

    /**
     * The default list of HTTP URLs to use for detecting captive portals.
     */
    public static final String[] DEFAULT_CAPTIVE_PORTAL_HTTP_URLS =
            new String [] {"http://connectivitycheck.gstatic.com/generate_204"};

    /**
     * The default list of HTTPS URLs for network validation, to use for confirming internet
     * connectivity.
     */
    public static final String[] DEFAULT_CAPTIVE_PORTAL_HTTPS_URLS =
            new String [] {"https://www.google.com/generate_204"};

    /**
     * @deprecated Considering boolean experiment flag is likely to cause misconfiguration
     *             particularly when NetworkStack module rolls back to previous version. It's
     *             much safer to determine whether or not to enable one specific experimental
     *             feature by comparing flag version with module version.
     */
    @Deprecated
    public static final String DHCP_INIT_REBOOT_ENABLED = "dhcp_init_reboot_enabled";

    /**
     * @deprecated See above explanation.
     */
    @Deprecated
    public static final String DHCP_RAPID_COMMIT_ENABLED = "dhcp_rapid_commit_enabled";

    /**
     * Minimum module version at which to enable the DHCP INIT-REBOOT state.
     */
    public static final String DHCP_INIT_REBOOT_VERSION = "dhcp_init_reboot_version";

    /**
     * Minimum module version at which to enable the DHCP Rapid Commit option.
     */
    public static final String DHCP_RAPID_COMMIT_VERSION = "dhcp_rapid_commit_version";

    /**
     * Minimum module version at which to enable the IP address conflict detection feature.
     */
    public static final String DHCP_IP_CONFLICT_DETECT_VERSION = "dhcp_ip_conflict_detect_version";

    /**
     * Minimum module version at which to enable dismissal CaptivePortalLogin app in validated
     * network feature. CaptivePortalLogin app will also use validation facilities in
     * {@link NetworkMonitor} to perform portal validation if feature is enabled.
     */
    public static final String DISMISS_PORTAL_IN_VALIDATED_NETWORK =
            "dismiss_portal_in_validated_network";

    /**
     * Experiment flag to enable considering DNS probes returning private IP addresses as failed
     * when attempting to detect captive portals.
     *
     * This flag is enabled if !=0 and less than the module APK version.
     */
    public static final String DNS_PROBE_PRIVATE_IP_NO_INTERNET_VERSION =
            "dns_probe_private_ip_no_internet";

    /**
     * Experiment flag to enable validation metrics sent by NetworkMonitor.
     *
     * Metrics are sent by default. They can be disabled by setting the flag to a number greater
     * than the APK version (for example 999999999).
     * @see #isFeatureEnabled(Context, String, String, boolean)
     */
    public static final String VALIDATION_METRICS_VERSION = "validation_metrics_version";

    static {
        System.loadLibrary("networkstackutilsjni");
    }

    /**
     * @return True if the array is null or 0-length.
     */
    public static <T> boolean isEmpty(T[] array) {
        return array == null || array.length == 0;
    }

    /**
     * Close a socket, ignoring any exception while closing.
     */
    public static void closeSocketQuietly(FileDescriptor fd) {
        try {
            SocketUtils.closeSocket(fd);
        } catch (IOException ignored) {
        }
    }

    /**
     * Returns an int array from the given Integer list.
     */
    public static int[] convertToIntArray(@NonNull List<Integer> list) {
        int[] array = new int[list.size()];
        for (int i = 0; i < list.size(); i++) {
            array[i] = list.get(i);
        }
        return array;
    }

    /**
     * Returns a long array from the given long list.
     */
    public static long[] convertToLongArray(@NonNull List<Long> list) {
        long[] array = new long[list.size()];
        for (int i = 0; i < list.size(); i++) {
            array[i] = list.get(i);
        }
        return array;
    }

    /**
     * @return True if there exists at least one element in the sparse array for which
     * condition {@code predicate}
     */
    public static <T> boolean any(SparseArray<T> array, Predicate<T> predicate) {
        for (int i = 0; i < array.size(); ++i) {
            if (predicate.test(array.valueAt(i))) {
                return true;
            }
        }
        return false;
    }

    /**
     * Look up the value of a property for a particular namespace from {@link DeviceConfig}.
     * @param namespace The namespace containing the property to look up.
     * @param name The name of the property to look up.
     * @param defaultValue The value to return if the property does not exist or has no valid value.
     * @return the corresponding value, or defaultValue if none exists.
     */
    @Nullable
    public static String getDeviceConfigProperty(@NonNull String namespace, @NonNull String name,
            @Nullable String defaultValue) {
        String value = DeviceConfig.getProperty(namespace, name);
        return value != null ? value : defaultValue;
    }

    /**
     * Look up the value of a property for a particular namespace from {@link DeviceConfig}.
     * @param namespace The namespace containing the property to look up.
     * @param name The name of the property to look up.
     * @param defaultValue The value to return if the property does not exist or its value is null.
     * @return the corresponding value, or defaultValue if none exists.
     */
    public static int getDeviceConfigPropertyInt(@NonNull String namespace, @NonNull String name,
            int defaultValue) {
        String value = getDeviceConfigProperty(namespace, name, null /* defaultValue */);
        try {
            return (value != null) ? Integer.parseInt(value) : defaultValue;
        } catch (NumberFormatException e) {
            return defaultValue;
        }
    }

    /**
     * Look up the value of a property for a particular namespace from {@link DeviceConfig}.
     * @param namespace The namespace containing the property to look up.
     * @param name The name of the property to look up.
     * @param minimumValue The minimum value of a property.
     * @param maximumValue The maximum value of a property.
     * @param defaultValue The value to return if the property does not exist or its value is null.
     * @return the corresponding value, or defaultValue if none exists or the fetched value is
     *         greater than maximumValue.
     */
    public static int getDeviceConfigPropertyInt(@NonNull String namespace, @NonNull String name,
            int minimumValue, int maximumValue, int defaultValue) {
        int value = getDeviceConfigPropertyInt(namespace, name, defaultValue);
        if (value < minimumValue || value > maximumValue) return defaultValue;
        return value;
    }

    /**
     * Look up the value of a property for a particular namespace from {@link DeviceConfig}.
     * @param namespace The namespace containing the property to look up.
     * @param name The name of the property to look up.
     * @param defaultValue The value to return if the property does not exist or its value is null.
     * @return the corresponding value, or defaultValue if none exists.
     */
    public static boolean getDeviceConfigPropertyBoolean(@NonNull String namespace,
            @NonNull String name, boolean defaultValue) {
        String value = getDeviceConfigProperty(namespace, name, null /* defaultValue */);
        return (value != null) ? Boolean.parseBoolean(value) : defaultValue;
    }

    /**
     * Check whether or not one specific experimental feature for a particular namespace from
     * {@link DeviceConfig} is enabled by comparing NetworkStack module version {@link NetworkStack}
     * with current version of property. If this property version is valid, the corresponding
     * experimental feature would be enabled, otherwise disabled.
     *
     * This is useful to ensure that if a module install is rolled back, flags are not left fully
     * rolled out on a version where they have not been well tested.
     * @param context The global context information about an app environment.
     * @param namespace The namespace containing the property to look up.
     * @param name The name of the property to look up.
     * @return true if this feature is enabled, or false if disabled.
     */
    public static boolean isFeatureEnabled(@NonNull Context context, @NonNull String namespace,
            @NonNull String name) {
        return isFeatureEnabled(context, namespace, name, false /* defaultEnabled */);
    }

    /**
     * Check whether or not one specific experimental feature for a particular namespace from
     * {@link DeviceConfig} is enabled by comparing NetworkStack module version {@link NetworkStack}
     * with current version of property. If this property version is valid, the corresponding
     * experimental feature would be enabled, otherwise disabled.
     *
     * This is useful to ensure that if a module install is rolled back, flags are not left fully
     * rolled out on a version where they have not been well tested.
     * @param context The global context information about an app environment.
     * @param namespace The namespace containing the property to look up.
     * @param name The name of the property to look up.
     * @param defaultEnabled The value to return if the property does not exist or its value is
     *                       null.
     * @return true if this feature is enabled, or false if disabled.
     */
    public static boolean isFeatureEnabled(@NonNull Context context, @NonNull String namespace,
            @NonNull String name, boolean defaultEnabled) {
        try {
            final int propertyVersion = getDeviceConfigPropertyInt(namespace, name,
                    0 /* default value */);
            final long packageVersion = context.getPackageManager().getPackageInfo(
                    context.getPackageName(), 0).getLongVersionCode();
            return (propertyVersion == 0 && defaultEnabled)
                    || (propertyVersion != 0 && packageVersion >= (long) propertyVersion);
        } catch (NameNotFoundException e) {
            Log.e(TAG, "Could not find the package name", e);
            return false;
        }
    }

    /**
     * Attaches a socket filter that accepts DHCP packets to the given socket.
     */
    public static native void attachDhcpFilter(FileDescriptor fd) throws SocketException;

    /**
     * Attaches a socket filter that accepts ICMPv6 router advertisements to the given socket.
     * @param fd the socket's {@link FileDescriptor}.
     * @param packetType the hardware address type, one of ARPHRD_*.
     */
    public static native void attachRaFilter(FileDescriptor fd, int packetType)
            throws SocketException;

    /**
     * Attaches a socket filter that accepts L2-L4 signaling traffic required for IP connectivity.
     *
     * This includes: all ARP, ICMPv6 RS/RA/NS/NA messages, and DHCPv4 exchanges.
     *
     * @param fd the socket's {@link FileDescriptor}.
     * @param packetType the hardware address type, one of ARPHRD_*.
     */
    public static native void attachControlPacketFilter(FileDescriptor fd, int packetType)
            throws SocketException;

    /**
     * Add an entry into the ARP cache.
     */
    public static void addArpEntry(Inet4Address ipv4Addr, android.net.MacAddress ethAddr,
            String ifname, FileDescriptor fd) throws IOException {
        addArpEntry(ethAddr.toByteArray(), ipv4Addr.getAddress(), ifname, fd);
    }

    private static native void addArpEntry(byte[] ethAddr, byte[] netAddr, String ifname,
            FileDescriptor fd) throws IOException;

    /**
     * Return IP address and port in a string format.
     */
    public static String addressAndPortToString(InetAddress address, int port) {
        return String.format(
                (address instanceof Inet6Address) ? "[%s]:%d" : "%s:%d",
                        address.getHostAddress(), port);
    }

    /**
     * Return true if the provided address is non-null and an IPv6 Unique Local Address (RFC4193).
     */
    public static boolean isIPv6ULA(@Nullable InetAddress addr) {
        return addr instanceof Inet6Address
                && ((addr.getAddress()[0] & 0xfe) == 0xfc);
    }

    /**
     * Returns the {@code int} nearest in value to {@code value}.
     *
     * @param value any {@code long} value
     * @return the same value cast to {@code int} if it is in the range of the {@code int}
     * type, {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if
     * it is too small
     */
    public static int saturatedCast(long value) {
        if (value > Integer.MAX_VALUE) {
            return Integer.MAX_VALUE;
        }
        if (value < Integer.MIN_VALUE) {
            return Integer.MIN_VALUE;
        }
        return (int) value;
    }
}