/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.common.io.stream;

import org.apache.lucene.util.BytesRef;

import java.io.EOFException;
import java.io.IOException;

/**
 * Resettable {@link StreamInput} that wraps a byte array. It is heavily inspired in Lucene's
 * {@link org.apache.lucene.store.ByteArrayDataInput}.
 */
public final class ByteArrayStreamInput extends StreamInput {

    private byte[] bytes;
    private int pos;
    private int limit;

    public ByteArrayStreamInput() {
        reset(BytesRef.EMPTY_BYTES);
    }

    public ByteArrayStreamInput(byte[] bytes) {
        reset(bytes);
    }

    @Override
    public String readString() throws IOException {
        final int chars = readArraySize();
        String string = tryReadStringFromBytes(bytes, pos, limit, chars);
        if (string != null) {
            return string;
        }
        return doReadString(chars);
    }

    @Override
    public int read() throws IOException {
        if (limit - pos <= 0) {
            return -1;
        }
        return readByte() & 0xFF;
    }

    public void reset(byte[] bytes) {
        reset(bytes, 0, bytes.length);
    }

    public int length() {
        return limit;
    }

    public int getPosition() {
        return pos;
    }

    public void setPosition(int pos) {
        this.pos = pos;
    }

    public void reset(byte[] bytes, int offset, int len) {
        this.bytes = bytes;
        pos = offset;
        limit = offset + len;
    }

    public void skipBytes(long count) {
        pos += (int) count;
    }

    @Override
    public long skip(long n) throws IOException {
        if (n <= 0L) {
            return 0L;
        }
        int available = available();
        if (n < available) {
            pos += (int) n;
            return n;
        }
        pos = limit;
        return available;
    }

    @Override
    public void close() {
        // No-op
    }

    @Override
    public int available() {
        return limit - pos;
    }

    @Override
    protected void ensureCanReadBytes(int length) throws EOFException {
        final int available = limit - pos;
        if (length > available) {
            throwEOF(length, available);
        }
    }

    @Override
    public byte readByte() {
        return bytes[pos++];
    }

    @Override
    public void readBytes(byte[] b, int offset, int len) {
        System.arraycopy(bytes, pos, b, offset, len);
        pos += len;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        final int available = limit - pos;
        if (available <= 0) {
            return -1;
        }
        int toRead = Math.min(len, available);
        readBytes(b, off, toRead);
        return toRead;
    }
}