package it.cavallium.strangedb.database.blocks;

import it.cavallium.strangedb.database.DatabaseFileIO;
import it.cavallium.strangedb.database.IBlocksIO;
import it.cavallium.strangedb.database.IBlocksMetadata;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.concurrent.CompletionException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import static it.cavallium.strangedb.database.IBlocksMetadata.EMPTY_BLOCK_ID;
import static it.cavallium.strangedb.database.IBlocksMetadata.ERROR_BLOCK_ID;

public class DatabaseBlocksIO implements IBlocksIO {

	private final DatabaseFileIO fileIO;
	private final IBlocksMetadata blocksMetadata;

	public DatabaseBlocksIO(DatabaseFileIO fileIO, IBlocksMetadata blocksMetadata) {
		this.fileIO = fileIO;
		this.blocksMetadata = blocksMetadata;
	}

	@Override
	public long newBlock(int size, ByteBuffer data) throws IOException {
		if (size == 0) {
			return EMPTY_BLOCK_ID;
		}
		if (size < 0) {
			throw new IOException("Trying to create a block with size " + size);
		}
		if (data.limit() < size) {
			throw new IOException("Trying to create a block with size " + size + " but with a buffer of size " + data.limit());
		}
		long index = fileIO.writeAtEnd(size, data);
		return blocksMetadata.newBlock(index, size);
	}

	@Override
	public ByteBuffer readBlock(long blockId) throws IOException {
		if (blockId == EMPTY_BLOCK_ID) {
			return ByteBuffer.wrap(new byte[0]);
		}
		if (blockId == ERROR_BLOCK_ID) {
			throw new IOException("Errored block id");
		}
		if (blockId < 0) {
			throw new IOException("Block id " + blockId + " is not valid");
		}
		BlockInfo blockInfo = blocksMetadata.getBlockInfo(blockId);
		return fileIO.readAt(blockInfo.getIndex(), blockInfo.getSize());
	}

	public ByteBuffer readBlockSizeAndLastElementOfReferencesList(long blockId) throws IOException {
		if (blockId == EMPTY_BLOCK_ID) {
			return ByteBuffer.wrap(new byte[0]);
		}
		if (blockId == ERROR_BLOCK_ID) {
			throw new IOException("Errored block id");
		}
		if (blockId < 0) {
			throw new IOException("Block id " + blockId + " is not valid");
		}
		BlockInfo blockInfo = blocksMetadata.getBlockInfo(blockId);
		if (blockInfo.getSize() >= Integer.BYTES * 2 + Long.BYTES) {
			return fileIO.readAt(blockInfo.getIndex() + blockInfo.getSize() - (Integer.BYTES + Long.BYTES), Integer.BYTES + Long.BYTES);
		} else {
			return fileIO.readAt(blockInfo.getIndex(), blockInfo.getSize());
		}
	}

	@Override
	public void close() {

	}
}