/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.buffer;

import io.netty.util.internal.StringUtil;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.ReadOnlyBufferException;
import java.nio.channels.GatheringByteChannel;
import java.nio.channels.ScatteringByteChannel;


/**
 * Read-only ByteBuf which wraps a read-only ByteBuffer.
 */
class ReadOnlyByteBufferBuf extends AbstractReferenceCountedByteBuf {

    protected final ByteBuffer buffer;
    private final ByteBufAllocator allocator;
    private ByteBuffer tmpNioBuf;

    ReadOnlyByteBufferBuf(ByteBufAllocator allocator, ByteBuffer buffer) {
        super(buffer.remaining());
        if (!buffer.isReadOnly()) {
            throw new IllegalArgumentException("must be a readonly buffer: " + StringUtil.simpleClassName(buffer));
        }

        this.allocator = allocator;
        this.buffer = buffer.slice().order(ByteOrder.BIG_ENDIAN);
        writerIndex(this.buffer.limit());
    }

    @Override
    protected void deallocate() { }

    @Override
    public byte getByte(int index) {
        ensureAccessible();
        return _getByte(index);
    }

    @Override
    protected byte _getByte(int index) {
        return buffer.get(index);
    }

    @Override
    public short getShort(int index) {
        ensureAccessible();
        return _getShort(index);
    }

    @Override
    protected short _getShort(int index) {
        return buffer.getShort(index);
    }

    @Override
    public int getUnsignedMedium(int index) {
        ensureAccessible();
        return _getUnsignedMedium(index);
    }

    @Override
    protected int _getUnsignedMedium(int index) {
        return (getByte(index) & 0xff)     << 16 |
               (getByte(index + 1) & 0xff) << 8  |
               getByte(index + 2) & 0xff;
    }

    @Override
    public int getInt(int index) {
        ensureAccessible();
        return _getInt(index);
    }

    @Override
    protected int _getInt(int index) {
        return buffer.getInt(index);
    }

    @Override
    public long getLong(int index) {
        ensureAccessible();
        return _getLong(index);
    }

    @Override
    protected long _getLong(int index) {
        return buffer.getLong(index);
    }

    @Override
    public ByteBuf getBytes(int index, ByteBuf dst, int dstIndex, int length) {
        checkDstIndex(index, length, dstIndex, dst.capacity());
        if (dst.hasArray()) {
            getBytes(index, dst.array(), dst.arrayOffset() + dstIndex, length);
        } else if (dst.nioBufferCount() > 0) {
            for (ByteBuffer bb: dst.nioBuffers(dstIndex, length)) {
                int bbLen = bb.remaining();
                getBytes(index, bb);
                index += bbLen;
            }
        } else {
            dst.setBytes(dstIndex, this, index, length);
        }
        return this;
    }

    @Override
    public ByteBuf getBytes(int index, byte[] dst, int dstIndex, int length) {
        checkDstIndex(index, length, dstIndex, dst.length);

        if (dstIndex < 0 || dstIndex > dst.length - length) {
            throw new IndexOutOfBoundsException(String.format(
                    "dstIndex: %d, length: %d (expected: range(0, %d))", dstIndex, length, dst.length));
        }

        ByteBuffer tmpBuf = internalNioBuffer();
        tmpBuf.clear().position(index).limit(index + length);
        tmpBuf.get(dst, dstIndex, length);
        return this;
    }

    @Override
    public ByteBuf getBytes(int index, ByteBuffer dst) {
        checkIndex(index);
        if (dst == null) {
            throw new NullPointerException("dst");
        }

        int bytesToCopy = Math.min(capacity() - index, dst.remaining());
        ByteBuffer tmpBuf = internalNioBuffer();
        tmpBuf.clear().position(index).limit(index + bytesToCopy);
        dst.put(tmpBuf);
        return this;
    }

    @Override
    public ByteBuf setByte(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    protected void _setByte(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBuf setShort(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    protected void _setShort(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBuf setMedium(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    protected void _setMedium(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBuf setInt(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    protected void _setInt(int index, int value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBuf setLong(int index, long value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    protected void _setLong(int index, long value) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public int capacity() {
        return maxCapacity();
    }

    @Override
    public ByteBuf capacity(int newCapacity) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBufAllocator alloc() {
        return allocator;
    }

    @Override
    public ByteOrder order() {
        return ByteOrder.BIG_ENDIAN;
    }

    @Override
    public ByteBuf unwrap() {
        return null;
    }

    @Override
    public boolean isDirect() {
        return buffer.isDirect();
    }

    @Override
    public ByteBuf getBytes(int index, OutputStream out, int length) throws IOException {
        ensureAccessible();
        if (length == 0) {
            return this;
        }

        if (buffer.hasArray()) {
            out.write(buffer.array(), index + buffer.arrayOffset(), length);
        } else {
            byte[] tmp = new byte[length];
            ByteBuffer tmpBuf = internalNioBuffer();
            tmpBuf.clear().position(index);
            tmpBuf.get(tmp);
            out.write(tmp);
        }
        return this;
    }

    @Override
    public int getBytes(int index, GatheringByteChannel out, int length) throws IOException {
        ensureAccessible();
        if (length == 0) {
            return 0;
        }

        ByteBuffer tmpBuf = internalNioBuffer();
        tmpBuf.clear().position(index).limit(index + length);
        return out.write(tmpBuf);
    }

    @Override
    public ByteBuf setBytes(int index, ByteBuf src, int srcIndex, int length) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBuf setBytes(int index, byte[] src, int srcIndex, int length) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public ByteBuf setBytes(int index, ByteBuffer src) {
        throw new ReadOnlyBufferException();
    }

    @Override
    public int setBytes(int index, InputStream in, int length) throws IOException {
        throw new ReadOnlyBufferException();
    }

    @Override
    public int setBytes(int index, ScatteringByteChannel in, int length) throws IOException {
        throw new ReadOnlyBufferException();
    }

    protected final ByteBuffer internalNioBuffer() {
        ByteBuffer tmpNioBuf = this.tmpNioBuf;
        if (tmpNioBuf == null) {
            this.tmpNioBuf = tmpNioBuf = buffer.duplicate();
        }
        return tmpNioBuf;
    }

    @Override
    public ByteBuf copy(int index, int length) {
        ensureAccessible();
        ByteBuffer src;
        try {
            src = (ByteBuffer) internalNioBuffer().clear().position(index).limit(index + length);
        } catch (IllegalArgumentException ignored) {
            throw new IndexOutOfBoundsException("Too many bytes to read - Need " + (index + length));
        }

        ByteBuffer dst = ByteBuffer.allocateDirect(length);
        dst.put(src);
        dst.order(order());
        dst.clear();
        return new UnpooledDirectByteBuf(alloc(), dst, maxCapacity());
    }

    @Override
    public int nioBufferCount() {
        return 1;
    }

    @Override
    public ByteBuffer[] nioBuffers(int index, int length) {
        return new ByteBuffer[] { nioBuffer(index, length) };
    }

    @Override
    public ByteBuffer nioBuffer(int index, int length) {
        return (ByteBuffer) buffer.duplicate().position(index).limit(index + length);
    }

    @Override
    public ByteBuffer internalNioBuffer(int index, int length) {
        ensureAccessible();
        return (ByteBuffer) internalNioBuffer().clear().position(index).limit(index + length);
    }

    @Override
    public boolean hasArray() {
        return buffer.hasArray();
    }

    @Override
    public byte[] array() {
        return buffer.array();
    }

    @Override
    public int arrayOffset() {
        return buffer.arrayOffset();
    }

    @Override
    public boolean hasMemoryAddress() {
        return false;
    }

    @Override
    public long memoryAddress() {
        throw new UnsupportedOperationException();
    }
}
