package git.artdeell.arcdns;

import java.net.InetAddress;
import java.net.UnknownHostException;

public class CacheUtilCommons {
    public static final long NEVER_EXPIRATION = Long.MAX_VALUE;
    static InetAddress[] toInetAddressArray(String host, String[] ips) throws UnknownHostException {
        InetAddress[] addresses = new InetAddress[ips.length];
        for (int i = 0; i < addresses.length; i++) {
            addresses[i] = InetAddress.getByAddress(host, ip2ByteArray(ips[i]));
        }
        return addresses;
    }
    private static final String INVALID_IP_V6_ADDRESS = ": invalid IPv6 address";
    private static final String INVALID_IP_ADDRESS = ": invalid IP address";

    static byte[] ip2ByteArray(String ip) {
        boolean ipv6Expected = false;
        if (ip.charAt(0) == '[') {
            // This is supposed to be an IPv6 literal
            if (ip.length() > 2 && ip.charAt(ip.length() - 1) == ']') {
                ip = ip.substring(1, ip.length() - 1);
                ipv6Expected = true;
            } else {
                // This was supposed to be a IPv6 address, but it's not!
                throw new IllegalArgumentException(ip + INVALID_IP_V6_ADDRESS);
            }
        }

        if (Character.digit(ip.charAt(0), 16) != -1 || (ip.charAt(0) == ':')) {
            // see if it is IPv4 address
            byte[] address = textToNumericFormatV4(ip);
            if (address != null) return address;

            // see if it is IPv6 address
            // Check if a numeric or string zone id is present
            address = textToNumericFormatV6(ip);
            if (address != null) return address;

            if (ipv6Expected) {
                throw new IllegalArgumentException(ip + INVALID_IP_V6_ADDRESS);
            } else {
                throw new IllegalArgumentException(ip + INVALID_IP_ADDRESS);
            }
        } else {
            throw new IllegalArgumentException(ip + INVALID_IP_ADDRESS);
        }
    }
    private static final int INADDR4SZ = 4;
    private static final int INADDR16SZ = 16;
    private static final int INT16SZ = 2;

    /*
     * Converts IPv4 address in its textual presentation form
     * into its numeric binary form.
     *
     * @param src a String representing an IPv4 address in standard format
     * @return a byte array representing the IPv4 numeric address
     */
    @SuppressWarnings("fallthrough")
    static byte[] textToNumericFormatV4(String src)
    {
        byte[] res = new byte[INADDR4SZ];

        long tmpValue = 0;
        int currByte = 0;
        boolean newOctet = true;

        int len = src.length();
        if (len == 0 || len > 15) {
            return null;
        }
        /*
         * When only one part is given, the value is stored directly in
         * the network address without any byte rearrangement.
         *
         * When a two part address is supplied, the last part is
         * interpreted as a 24-bit quantity and placed in the right
         * most three bytes of the network address. This makes the
         * two part address format convenient for specifying Class A
         * network addresses as net.host.
         *
         * When a three part address is specified, the last part is
         * interpreted as a 16-bit quantity and placed in the right
         * most two bytes of the network address. This makes the
         * three part address format convenient for specifying
         * Class B net- work addresses as 128.net.host.
         *
         * When four parts are specified, each is interpreted as a
         * byte of data and assigned, from left to right, to the
         * four bytes of an IPv4 address.
         *
         * We determine and parse the leading parts, if any, as single
         * byte values in one pass directly into the resulting byte[],
         * then the remainder is treated as a 8-to-32-bit entity and
         * translated into the remaining bytes in the array.
         */
        for (int i = 0; i < len; i++) {
            char c = src.charAt(i);
            if (c == '.') {
                if (newOctet || tmpValue < 0 || tmpValue > 0xff || currByte == 3) {
                    return null;
                }
                res[currByte++] = (byte) (tmpValue & 0xff);
                tmpValue = 0;
                newOctet = true;
            } else {
                int digit = Character.digit(c, 10);
                if (digit < 0) {
                    return null;
                }
                tmpValue *= 10;
                tmpValue += digit;
                newOctet = false;
            }
        }
        if (newOctet || tmpValue < 0 || tmpValue >= (1L << ((4 - currByte) * 8))) {
            return null;
        }
        switch (currByte) {
            case 0:
                res[0] = (byte) ((tmpValue >> 24) & 0xff);
            case 1:
                res[1] = (byte) ((tmpValue >> 16) & 0xff);
            case 2:
                res[2] = (byte) ((tmpValue >>  8) & 0xff);
            case 3:
                res[3] = (byte) ((tmpValue >>  0) & 0xff);
        }
        return res;
    }

    /*
     * Convert IPv6 presentation level address to network order binary form.
     * credit:
     *  Converted from C code from Solaris 8 (inet_pton)
     *
     * Any component of the string following a per-cent % is ignored.
     *
     * @param src a String representing an IPv6 address in textual format
     * @return a byte array representing the IPv6 numeric address
     */
    static byte[] textToNumericFormatV6(String src)
    {
        // Shortest valid string is "::", hence at least 2 chars
        if (src.length() < 2) {
            return null;
        }

        int colonp;
        char ch;
        boolean saw_xdigit;
        int val;
        char[] srcb = src.toCharArray();
        byte[] dst = new byte[INADDR16SZ];

        int srcb_length = srcb.length;
        int pc = src.indexOf ('%');
        if (pc == srcb_length -1) {
            return null;
        }

        if (pc != -1) {
            srcb_length = pc;
        }

        colonp = -1;
        int i = 0, j = 0;
        /* Leading :: requires some special handling. */
        if (srcb[i] == ':')
            if (srcb[++i] != ':')
                return null;
        int curtok = i;
        saw_xdigit = false;
        val = 0;
        while (i < srcb_length) {
            ch = srcb[i++];
            int chval = Character.digit(ch, 16);
            if (chval != -1) {
                val <<= 4;
                val |= chval;
                if (val > 0xffff)
                    return null;
                saw_xdigit = true;
                continue;
            }
            if (ch == ':') {
                curtok = i;
                if (!saw_xdigit) {
                    if (colonp != -1)
                        return null;
                    colonp = j;
                    continue;
                } else if (i == srcb_length) {
                    return null;
                }
                if (j + INT16SZ > INADDR16SZ)
                    return null;
                dst[j++] = (byte) ((val >> 8) & 0xff);
                dst[j++] = (byte) (val & 0xff);
                saw_xdigit = false;
                val = 0;
                continue;
            }
            if (ch == '.' && ((j + INADDR4SZ) <= INADDR16SZ)) {
                String ia4 = src.substring(curtok, srcb_length);
                /* check this IPv4 address has 3 dots, ie. A.B.C.D */
                int dot_count = 0, index=0;
                while ((index = ia4.indexOf ('.', index)) != -1) {
                    dot_count ++;
                    index ++;
                }
                if (dot_count != 3) {
                    return null;
                }
                byte[] v4addr = textToNumericFormatV4(ia4);
                if (v4addr == null) {
                    return null;
                }
                for (int k = 0; k < INADDR4SZ; k++) {
                    dst[j++] = v4addr[k];
                }
                saw_xdigit = false;
                break;  /* '\0' was seen by inet_pton4(). */
            }
            return null;
        }
        if (saw_xdigit) {
            if (j + INT16SZ > INADDR16SZ)
                return null;
            dst[j++] = (byte) ((val >> 8) & 0xff);
            dst[j++] = (byte) (val & 0xff);
        }

        if (colonp != -1) {
            int n = j - colonp;

            if (j == INADDR16SZ)
                return null;
            for (i = 1; i <= n; i++) {
                dst[INADDR16SZ - i] = dst[colonp + n - i];
                dst[colonp + n - i] = 0;
            }
            j = INADDR16SZ;
        }
        if (j != INADDR16SZ)
            return null;
        byte[] newdst = convertFromIPv4MappedAddress(dst);
        if (newdst != null) {
            return newdst;
        } else {
            return dst;
        }
    }

    /*
     * Convert IPv4-Mapped address to IPv4 address. Both input and
     * returned value are in network order binary form.
     *
     * @param src a String representing an IPv4-Mapped address in textual format
     * @return a byte array representing the IPv4 numeric address
     */
    private static byte[] convertFromIPv4MappedAddress(byte[] addr) {
        if (isIPv4MappedAddress(addr)) {
            byte[] newAddr = new byte[INADDR4SZ];
            System.arraycopy(addr, 12, newAddr, 0, INADDR4SZ);
            return newAddr;
        }
        return null;
    }

    /**
     * Utility routine to check if the InetAddress is an
     * IPv4 mapped IPv6 address.
     *
     * @return a <code>boolean</code> indicating if the InetAddress is
     * an IPv4 mapped IPv6 address; or false if address is IPv4 address.
     */
    private static boolean isIPv4MappedAddress(byte[] addr) {
        if (addr.length < INADDR16SZ) {
            return false;
        }
        if ((addr[0] == 0x00) && (addr[1] == 0x00) &&
                (addr[2] == 0x00) && (addr[3] == 0x00) &&
                (addr[4] == 0x00) && (addr[5] == 0x00) &&
                (addr[6] == 0x00) && (addr[7] == 0x00) &&
                (addr[8] == 0x00) && (addr[9] == 0x00) &&
                (addr[10] == (byte)0xff) &&
                (addr[11] == (byte)0xff))  {
            return true;
        }
        return false;
    }
    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    //
    // Below source code is copied from commons-lang-3.12.0:
    //
    // https://github.com/apache/commons-lang/blob/rel/commons-lang-3.12.0/src/main/java/org/apache/commons/lang3/SystemUtils.java
    //
    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

    @SuppressWarnings({"CommentedOutCode", "SameParameterValue"})
    private static String getSystemProperty(final String property) {
        try {
            return System.getProperty(property);
        } catch (final SecurityException ex) {
            // we are not allowed to look at this property
            // System.err.println("Caught a SecurityException reading the system property '" + property
            //   + "'; the SystemUtils property value will default to null.");
            return null;
        }
    }

}