// kelondroNaturalOrder.java
// -----------------------
// part of The Kelondro Database
// (C) by Michael Peter Christen; mc@yacy.net
// first published on http://www.anomic.de
// Frankfurt, Germany, 2005
// created 29.12.2005
//
// $LastChangedDate: 2005-09-22 22:01:26 +0200 (Thu, 22 Sep 2005) $
// $LastChangedRevision: 774 $
// $LastChangedBy: orbiter $
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package de.anomic.kelondro;

import java.util.Comparator;

public final class kelondroNaturalOrder extends kelondroAbstractOrder<byte[]> implements kelondroByteOrder, Comparator<byte[]>, Cloneable {
    
    public static final kelondroByteOrder naturalOrder = new kelondroNaturalOrder(true);
    public static final Comparator<String> naturalComparator = new kelondroByteOrder.StringOrder(naturalOrder);
    public kelondroNaturalOrder(final boolean ascending) {
        this.asc = ascending;
        this.zero = null;
    }
    
    public boolean wellformed(final byte[] a) {
        return true;
    }
    
    public boolean wellformed(final byte[] a, final int astart, final int alength) {
        return true;
    }
    
    public final kelondroOrder<byte[]> clone() {
        final kelondroNaturalOrder o = new kelondroNaturalOrder(this.asc);
        o.rotate(this.zero);
        return o;
    }
    
    public static kelondroByteOrder orderBySignature(final String signature) {
        kelondroByteOrder oo = null;
        if (oo == null) oo = kelondroNaturalOrder.bySignature(signature);
        if (oo == null) oo = kelondroBase64Order.bySignature(signature);
        if (oo == null) oo = new kelondroNaturalOrder(true);
        return oo;
    }
    
    public final static kelondroByteOrder bySignature(final String signature) {
        if (signature.equals("nd")) return new kelondroNaturalOrder(false);
        if (signature.equals("nu")) return new kelondroNaturalOrder(true);
        return null;
    }
    
    public final String signature() {
        if (!asc) return "nd";
        if ( asc) return "nu";
        return null;
    }
    
    private final static long cardinalI(final byte[] key) {
        // returns a cardinal number in the range of 0 .. Long.MAX_VALUE
        long c = 0;
        int p = 0;
        while ((p < 8) && (p < key.length)) c = (c << 8) | ((long) key[p++] & 0xFF);
        while (p++ < 8) c = (c << 8);
        c = c >>> 1;
        return c;
    }
    
    public final long cardinal(final byte[] key) {
        if (this.zero == null) return cardinalI(key);
        final long zeroCardinal = cardinalI(this.zero);
        final long keyCardinal = cardinalI(key);
        if (keyCardinal > zeroCardinal) return keyCardinal - zeroCardinal;
        return Long.MAX_VALUE - keyCardinal + zeroCardinal;
    }

    public final static byte[] encodeLong(long c, int length) {
        final byte[] b = new byte[length];
        while (length > 0) {
            b[--length] = (byte) (c & 0xFF);
            c >>= 8;
        }
        return b;
    }

    public final static void encodeLong(long c, final byte[] b, final int offset, int length) {
        assert offset + length <= b.length;
        while (length > 0) {
            b[--length + offset] = (byte) (c & 0xFF);
            c >>= 8;
        }
    }

    public final static long decodeLong(final byte[] s) {
        if (s == null) return 0;
        long c = 0;
        int p = 0;
        while (p < s.length) c = (c << 8) | ((long) s[p++] & 0xFF);
        return c;
    }
    
    public final static long decodeLong(final byte[] s, int offset, final int length) {
        if (s == null) return 0;
        long c = 0;
        final int m = Math.min(s.length, offset + length);
        while (offset < m) c = (c << 8) | ((long) s[offset++] & 0xFF);
        return c;
    }

    private static final int sig(final int x) {
        return (x > 0) ? 1 : (x < 0) ? -1 : 0;
    }
    
    // Compares its two arguments for order.
    // Returns -1, 0, or 1 as the first argument
    // is less than, equal to, or greater than the second.
    // two arrays are also equal if one array is a subset of the other's array
    // with filled-up char(0)-values
    public final int compare(final byte[] a, final byte[] b) {
        return (asc) ? compare0(a, 0, a.length, b, 0, b.length) : compare0(b, 0, b.length, a, 0, a.length);
    }

    public final int compare(final byte[] a, final int aoffset, final int alength, final byte[] b, final int boffset, final int blength) {
        return (asc) ? compare0(a, aoffset, alength, b, boffset, blength) : compare0(b, boffset, blength, a, aoffset, alength);
    }

    public final int compare0(final byte[] a, final int aoffset, final int alength, final byte[] b, final int boffset, final int blength) {
        if (zero == null) return compares(a, aoffset, alength, b, boffset, blength);
        // we have an artificial start point. check all combinations
        final int az = compares(a, aoffset, alength, zero, 0, zero.length); // -1 if a < z; 0 if a == z; 1 if a > z
        final int bz = compares(b, boffset, blength, zero, 0, zero.length); // -1 if b < z; 0 if b == z; 1 if b > z
        if (az == bz) return compares(a, aoffset, alength, b, boffset, blength);
        return sig(az - bz);
    }

    public static final boolean equal(final byte[] a, final byte[] b) {
        if ((a == null) && (b == null)) return true;
        if ((a == null) || (b == null)) return false;
        return compares(a, 0, a.length, b, 0, b.length) == 0;
    }
   
    public static final int compares(final byte[] a, final int aoffset, final int alength, final byte[] b, final int boffset, final int blength) {
        int i = 0;
        final int al = Math.min(alength, a.length - aoffset);
        final int bl = Math.min(blength, b.length - boffset);
        int aa, bb;
        while ((i < al) && (i < bl)) {
            aa = 0xff & a[i + aoffset];
            bb = 0xff & b[i + boffset];
            if (aa > bb) return 1;
            if (aa < bb) return -1;
            // else the bytes are equal and it may go on yet undecided
            i++;
        }
        // compare length
        if (al > bl) return 1;
        if (al < bl) return -1;
        // they are equal
        return 0;
    }

    public static void main(final String[] args) {
        final byte[] t = new byte[12];
        for (int i = 0; i < 12; i++) t[i] = (byte) 255;
        t[0] = (byte) 127;
        final kelondroOrder<byte[]> o = new kelondroNaturalOrder(true);
        System.out.println(o.partition(t, 16));
    }
    
}