/*
 * Copyright 2014 Open Networking Laboratory
 *
 * 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 org.onlab.packet;

import java.net.InetAddress;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Objects;

import com.google.common.net.InetAddresses;
import com.google.common.primitives.UnsignedBytes;

import static com.google.common.base.Preconditions.checkState;

/**
 * A class representing an IP address.
 * TODO: Add support for IPv6 as well.
 */
public final class IpAddress implements Comparable<IpAddress> {
    // IP Versions
    public enum Version { INET, INET6 };

    // lengths of address, in bytes
    public static final int INET_BYTE_LENGTH = 4;
    public static final int INET_BIT_LENGTH = INET_BYTE_LENGTH * Byte.SIZE;
    public static final int INET6_BYTE_LENGTH = 16;
    public static final int INET6_BIT_LENGTH = INET6_BYTE_LENGTH * Byte.SIZE;

    private final Version version;
    private final byte[] octets;

    /**
     * Constructor for given IP address version and address octets.
     *
     * @param version the IP address version
     * @param value the IP address value stored in network byte order
     * (i.e., the most significant byte first)
     * @throws IllegalArgumentException if the arguments are invalid
     */
    private IpAddress(Version version, byte[] value) {
        checkArguments(version, value, 0);
        this.version = version;
        switch (version) {
        case INET:
            this.octets = Arrays.copyOf(value, INET_BYTE_LENGTH);
            break;
        case INET6:
            this.octets = Arrays.copyOf(value, INET6_BYTE_LENGTH);
            break;
        default:
            // Should not be reached
            this.octets = null;
            break;
        }
    }

    /**
     * Returns the IP version of this address.
     *
     * @return the version
     */
    public Version version() {
        return this.version;
    }

    /**
     * Returns the IP address as a byte array.
     *
     * @return a byte array
     */
    public byte[] toOctets() {
        return Arrays.copyOf(octets, octets.length);
    }

    /**
     * Returns the integral value of this IP address.
     * TODO: This method should be moved to Ip4Address.
     *
     * @return the IP address's value as an integer
     */
    public int toInt() {
        ByteBuffer bb = ByteBuffer.wrap(octets);
        return bb.getInt();
    }

    /**
     * Computes the IP address byte length for a given IP version.
     *
     * @param version the IP version
     * @return the IP address byte length for the IP version
     * @throws IllegalArgumentException if the IP version is invalid
     */
    public static int byteLength(Version version) {
        switch (version) {
        case INET:
            return INET_BYTE_LENGTH;
        case INET6:
            return INET6_BYTE_LENGTH;
        default:
            String msg = "Invalid IP version " + version;
            throw new IllegalArgumentException(msg);
        }
    }

    /**
     * Converts an integer into an IPv4 address.
     *
     * @param value an integer representing an IPv4 address value
     * @return an IP address
     */
    public static IpAddress valueOf(int value) {
        byte[] bytes =
            ByteBuffer.allocate(INET_BYTE_LENGTH).putInt(value).array();
        return new IpAddress(Version.INET, bytes);
    }

    /**
     * Converts a byte array into an IP address.
     *
     * @param version the IP address version
     * @param value the IP address value stored in network byte order
     * (i.e., the most significant byte first)
     * @return an IP address
     * @throws IllegalArgumentException if the arguments are invalid
     */
    public static IpAddress valueOf(Version version, byte[] value) {
        return new IpAddress(version, value);
    }

    /**
     * Converts a byte array and a given offset from the beginning of the
     * array into an IP address.
     * <p>
     * The IP address is stored in network byte order (i.e., the most
     * significant byte first).
     * </p>
     * @param version the IP address version
     * @param value the value to use
     * @param offset the offset in bytes from the beginning of the byte array
     * @return an IP address
     * @throws IllegalArgumentException if the arguments are invalid
     */
    public static IpAddress valueOf(Version version, byte[] value,
                                    int offset) {
        checkArguments(version, value, offset);
        byte[] bc = Arrays.copyOfRange(value, offset, value.length);
        return IpAddress.valueOf(version, bc);
    }

    /**
     * Converts an IPv4 or IPv6 string literal (e.g., "10.2.3.4" or
     * "1111:2222::8888") into an IP address.
     *
     * @param value an IP address value in string form
     * @return an IP address
     * @throws IllegalArgumentException if the argument is invalid
     */
    public static IpAddress valueOf(String value) {
        InetAddress addr = null;
        try {
            addr = InetAddresses.forString(value);
        } catch (IllegalArgumentException e) {
            final String msg = "Invalid IP address string: " + value;
            throw new IllegalArgumentException(msg);
        }
        byte[] bytes = addr.getAddress();
        if (addr instanceof Inet4Address) {
            return new IpAddress(Version.INET, bytes);
        }
        if (addr instanceof Inet6Address) {
            return new IpAddress(Version.INET6, bytes);
        }
        final String msg = "Unrecognized IP version address string: " + value;
        throw new IllegalArgumentException(msg);
    }

    /**
     * Creates an IP network mask prefix.
     *
     * @param version the IP address version
     * @param prefixLength the length of the mask prefix. Must be in the
     * interval [0, 32] for IPv4, or [0, 128] for IPv6
     * @return a new IP address that contains a mask prefix of the
     * specified length
     * @throws IllegalArgumentException if the arguments are invalid
     */
    public static IpAddress makeMaskPrefix(Version version, int prefixLength) {
        int addrByteLength = byteLength(version);
        int addrBitLength = addrByteLength * Byte.SIZE;

        // Verify the prefix length
        if ((prefixLength < 0) || (prefixLength > addrBitLength)) {
            final String msg = "Invalid IP prefix length: " + prefixLength +
                ". Must be in the interval [0, " + addrBitLength + "].";
            throw new IllegalArgumentException(msg);
        }

        // Number of bytes and extra bits that should be all 1s
        int maskBytes = prefixLength / Byte.SIZE;
        int maskBits = prefixLength % Byte.SIZE;
        byte[] mask = new byte[addrByteLength];

        // Set the bytes and extra bits to 1s
        for (int i = 0; i < maskBytes; i++) {
            mask[i] = (byte) 0xff;              // Set mask bytes to 1s
        }
        for (int i = maskBytes; i < addrByteLength; i++) {
            mask[i] = 0;                        // Set remaining bytes to 0s
        }
        if (maskBits > 0) {
            mask[maskBytes] = (byte) (0xff << (Byte.SIZE - maskBits));
        }
        return new IpAddress(version, mask);
    }

    /**
     * Creates an IP address by masking it with a network mask of given
     * mask length.
     *
     * @param addr the address to mask
     * @param prefixLength the length of the mask prefix. Must be in the
     * interval [0, 32] for IPv4, or [0, 128] for IPv6
     * @return a new IP address that is masked with a mask prefix of the
     * specified length
     * @throws IllegalArgumentException if the prefix length is invalid
     */
    public static IpAddress makeMaskedAddress(final IpAddress addr,
                                              int prefixLength) {
        IpAddress mask = IpAddress.makeMaskPrefix(addr.version(),
                                                  prefixLength);
        byte[] net = new byte[mask.octets.length];

        // Mask each byte
        for (int i = 0; i < net.length; i++) {
            net[i] = (byte) (addr.octets[i] & mask.octets[i]);
        }
        return IpAddress.valueOf(addr.version(), net);
    }

    @Override
    public int compareTo(IpAddress o) {
        // Compare first the version
        if (this.version != o.version) {
            return this.version.compareTo(o.version);
        }

        // Compare the bytes, one-by-one
        for (int i = 0; i < this.octets.length; i++) {
            if (this.octets[i] != o.octets[i]) {
                return UnsignedBytes.compare(this.octets[i], o.octets[i]);
            }
        }
        return 0;       // Equal
    }

    @Override
    public int hashCode() {
        return Objects.hash(version, Arrays.hashCode(octets));
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if ((obj == null) || (getClass() != obj.getClass())) {
            return false;
        }
        IpAddress other = (IpAddress) obj;
        return (version == other.version) &&
            Arrays.equals(octets, other.octets);
    }

    @Override
    /*
     * (non-Javadoc)
     * The string representation of the IP address: "x.x.x.x" for IPv4
     * addresses, or ':' separated string for IPv6 addresses.
     *
     * @see java.lang.Object#toString()
     */
    public String toString() {
        InetAddress inetAddr = null;
        try {
            inetAddr = InetAddress.getByAddress(octets);
        } catch (UnknownHostException e) {
            // Should never happen
            checkState(false, "Internal error: Ip6Address.toString()");
            return "[Invalid IP Address]";
        }
        return InetAddresses.toAddrString(inetAddr);
    }

    /**
     * Gets the IP address name for the IP address version.
     *
     * @param version the IP address version
     * @return the IP address name for the IP address version
     */
    private static String addressName(Version version) {
        switch (version) {
        case INET:
            return "IPv4";
        case INET6:
            return "IPv6";
        default:
            break;
        }
        return "UnknownIP(" + version + ")";
    }

    /**
     * Checks whether the arguments are valid.
     *
     * @param version the IP address version
     * @param value the IP address value stored in a byte array
     * @param offset the offset in bytes from the beginning of the byte
     * array with the address
     * @throws IllegalArgumentException if any of the arguments is invalid
     */
    private static void checkArguments(Version version, byte[] value,
                                       int offset) {
        // Check the offset and byte array length
        int addrByteLength = byteLength(version);
        if ((offset < 0) || (offset + addrByteLength > value.length)) {
            String msg;
            if (value.length < addrByteLength) {
                msg = "Invalid " + addressName(version) +
                    " address array: array length: " + value.length +
                    ". Must be at least " + addrByteLength;
            } else {
                msg = "Invalid " + addressName(version) +
                    " address array: array offset: " + offset +
                    ". Must be in the interval [0, " +
                    (value.length - addrByteLength) + "]";
            }
            throw new IllegalArgumentException(msg);
        }
    }
}