package it.cavallium.strangedb.database.references;

import it.cavallium.strangedb.database.IReferencesIO;
import it.cavallium.strangedb.database.blocks.DatabaseBlocksIO;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.concurrent.locks.ReentrantReadWriteLock;

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

public class DatabaseReferencesIO implements IReferencesIO {

	private final DatabaseBlocksIO blocksIO;
	private final DatabaseReferencesMetadata referencesMetadata;
	private ReentrantReadWriteLock lock = new ReentrantReadWriteLock(false);

	public DatabaseReferencesIO(DatabaseBlocksIO blocksIO, DatabaseReferencesMetadata referencesMetadata) {
		this.blocksIO = blocksIO;
		this.referencesMetadata = referencesMetadata;
	}

	@Override
	public long allocateReference() throws IOException {
		return referencesMetadata.newReference(EMPTY_BLOCK_ID);
	}

	@Override
	public long allocateReference(int size, ByteBuffer data) throws IOException {
		long blockId = (size == 0) ? EMPTY_BLOCK_ID : blocksIO.newBlock(size, data);
		return referencesMetadata.newReference(blockId);
	}

	@Override
	public void writeToReference(long reference, byte cleanerId, int size, ByteBuffer data) throws IOException {
		long blockId = (size == 0) ? EMPTY_BLOCK_ID : blocksIO.newBlock(size, data);
		lock.writeLock().lock();
		try {
			referencesMetadata.editReference(reference, cleanerId, blockId);
		} finally {
			lock.writeLock().unlock();
		}
	}

	@Override
	public ByteBuffer readFromReference(long reference) throws IOException {
		long blockId;
		lock.readLock().lock();
		try {
			blockId = referencesMetadata.getReferenceBlockId(reference);
		} finally {
			lock.readLock().unlock();
		}
		return blocksIO.readBlock(blockId);
	}

	public ByteBuffer readFromReferenceSizeAndLastElementOfReferencesList(long reference) throws IOException {
		long blockId;
		lock.readLock().lock();
		try {
			blockId = referencesMetadata.getReferenceBlockId(reference);
		} finally {
			lock.readLock().unlock();
		}
		return blocksIO.readBlockSizeAndLastElementOfReferencesList(blockId);
	}
}