package io.polyfrost.oneconfig.lwjgl;

import java.io.IOException;
import java.io.InputStream;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.SeekableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

import static org.lwjgl.BufferUtils.createByteBuffer;
import static org.lwjgl.system.MemoryUtil.memSlice;

@SuppressWarnings("RedundantCast")
final class IOUtil {

    private IOUtil() {
    }

    private static ByteBuffer resizeBuffer(ByteBuffer buffer, int newCapacity) {
        ByteBuffer newBuffer = createByteBuffer(newCapacity);
        ((Buffer) buffer).flip();
        newBuffer.put(buffer);
        return newBuffer;
    }

     static ByteBuffer resourceToByteBuffer(String resource, int bufferSize) throws IOException {
        ByteBuffer buffer;

        Path path = Paths.get(resource);
        if (Files.isReadable(path)) {
            try (SeekableByteChannel fc = Files.newByteChannel(path)) {
                buffer = createByteBuffer((int)fc.size() + 1);
                while (fc.read(buffer) != -1) {
                    //noinspection UnnecessarySemicolon
                    ;
                }
            }
        } else {
            try (
                    InputStream source = IOUtil.class.getResourceAsStream(resource);
                    ReadableByteChannel rbc = Channels.newChannel(source)
            ) {
                buffer = createByteBuffer(bufferSize);

                while (true) {
                    int bytes = rbc.read(buffer);
                    if (bytes == -1) {
                        break;
                    }
                    if (buffer.remaining() == 0) {
                        buffer = resizeBuffer(buffer, buffer.capacity() * 3 / 2); // 50%
                    }
                }
            }
        }

        ((Buffer) buffer).flip();
        return memSlice(buffer);
    }

}