/*
 *    Copyright (c) 2020-2025, Aayush Atharva
 *
 *    Brotli4j 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 com.aayushatharva.brotli4j.decoder;

import com.aayushatharva.brotli4j.common.annotations.Local;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.PooledByteBufAllocator;

import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * Multiple decoding methods using Netty Buffer.
 * Make sure to add it as dependency before using this class
 *
 * @see <a href="https://search.maven.org/artifact/io.netty/netty-buffer/">Netty Buffer</a>
 */
@Local
public final class Decoders {

    /**
     * Decodes the given data buffer.
     *
     * @param compressed   {@link ByteBuffer} source - will be read in full (position == limit after this call).
     * @param decompressed {@link ByteBuffer} destination - compressed data will be filled in beginning at position, up to remaining bytes; position is updated
     * @return {@link DirectDecompress} instance - upon return, only the status code is still valid
     * @throws IOException Thrown in case of error during decoding
     */
    @Local
    public static DirectDecompress decompress(ByteBuffer compressed, ByteBuffer decompressed) throws IOException {
        ByteBuf src = PooledByteBufAllocator.DEFAULT.directBuffer();
        ByteBuf dst = PooledByteBufAllocator.DEFAULT.buffer();

        try {
            src.writeBytes(compressed);
            final DirectDecompress result = decompress(src, dst);
            dst.readBytes(decompressed);
            return result;
        } finally {
            src.release();
            dst.release();
        }
    }

    /**
     * Decodes the given data buffer.
     *
     * @param compressed   {@link ByteBuf} source
     * @param decompressed {@link ByteBuf} destination
     * @return {@link DirectDecompress} instance
     * @throws IOException Thrown in case of error during encoding
     */
    @Local
    public static DirectDecompress decompress(ByteBuf compressed, ByteBuf decompressed) throws IOException {
        int compressedBytes = compressed.readableBytes();
        DecoderJNI.Wrapper decoder = new DecoderJNI.Wrapper(compressedBytes);
        try {
            decoder.getInputBuffer().put(compressed.nioBuffer());
            decoder.push(compressedBytes);
            while (decoder.getStatus() != DecoderJNI.Status.DONE) {
                switch (decoder.getStatus()) {
                    case OK:
                        decoder.push(0);
                        break;

                    case NEEDS_MORE_OUTPUT:
                        ByteBuffer buffer = decoder.pull();
                        decompressed.writeBytes(buffer);
                        break;

                    case NEEDS_MORE_INPUT:
                        // Give decoder a chance to process the remaining of the buffered byte.
                        decoder.push(0);
                        // If decoder still needs input, this means that stream is truncated.
                        if (decoder.getStatus() == DecoderJNI.Status.NEEDS_MORE_INPUT) {
                            return new DirectDecompress(decoder.getStatus(), null, null);
                        }
                        break;

                    default:
                        return new DirectDecompress(decoder.getStatus(), null, null);
                }
            }
        } finally {
            decoder.destroy();
        }
        return new DirectDecompress(decoder.getStatus(), null, decompressed);
    }
}
