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/*
   Copyright 2016 Jörg Prante

   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.xbib.marc.io;

import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

/**
 * A byte array, wrapped in a {@link BytesReference}.
 */
public class BytesArray implements BytesReference {

    private static final String EMPTY_STRING = "";

    private byte[] bytes;

    private int offset;

    private int length;

    /**
     * Create {@link BytesArray} from a byte array.
     * @param bytes the byte array
     */
    public BytesArray(byte[] bytes) {
        this.bytes = bytes;
        this.offset = 0;
        this.length = bytes.length;
    }

    /**
     * Create {@link BytesArray} from a part of a byte array.
     * @param bytes the byte array
     * @param offset the offset
     * @param length the length
     */
    public BytesArray(byte[] bytes, int offset, int length) {
        this.bytes = bytes;
        this.offset = offset;
        this.length = length;
    }


    @Override
    public byte get(int index) {
        return bytes[offset + index];
    }

    @Override
    public int length() {
        return length;
    }

    @Override
    public int indexOf(byte b, int offset, int len) {
        if (offset < 0 || (offset + length) > this.length) {
            throw new IllegalArgumentException();
        }
        for (int i = offset; i < offset + len; i++) {
            if (bytes[i] == b) {
                return i;
            }
        }
        return -1;
    }

    @Override
    public BytesReference slice(int from, int length) {
        if (from < 0 || (from + length) > this.length) {
            throw new IllegalArgumentException("can't slice a buffer with length [" + this.length +
                    "], with slice parameters from [" + from + "], length [" + length + "]");
        }
        return new BytesArray(bytes, offset + from, length);
    }

    @Override
    public byte[] toBytes() {
        if (offset == 0 && bytes.length == length) {
            return bytes;
        }
        return Arrays.copyOfRange(bytes, offset, offset + length);
    }

    @Override
    public String toUtf8() {
        if (length == 0) {
            return EMPTY_STRING;
        }
        return new String(bytes, offset, length, StandardCharsets.UTF_8);
    }

    /**
     * Split byte array by a separator byte.
     * @param sep the separator
     * @return a list of byte arrays
     */
    public List split(byte sep) {
        List l = new LinkedList<>();
        int start = 0;
        for (int i = 0; i < bytes.length; i++) {
            if (sep == bytes[i]) {
                byte[] b = Arrays.copyOfRange(bytes, start, i);
                if (b.length > 0) {
                    l.add(b);
                }
                start = i + 1;
                i = start;
            }
        }
        l.add(Arrays.copyOfRange(bytes, start, bytes.length));
        return l;
    }
}