package it.cavallium.strangedb.database.references;

import it.cavallium.strangedb.database.DatabaseFileIO;
import it.cavallium.strangedb.database.IReferencesIO;

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

public class DatabaseReferencesIO implements IReferencesIO {

	private final DatabaseFileIO fileIO;
	private final DatabaseReferencesMetadata referencesMetadata;

	public DatabaseReferencesIO(DatabaseFileIO fileIO, DatabaseReferencesMetadata referencesMetadata) {
		this.fileIO = fileIO;
		this.referencesMetadata = referencesMetadata;
	}

	@Override
	public long allocateReference() throws IOException {
		return referencesMetadata.newReference(0, 0);
	}

	@Override
	public long allocateReference(int size, ByteBuffer data) throws IOException {
		long index = writeToFile(size, data);
		return referencesMetadata.newReference(index, size);
	}

	@Override
	public void writeToReference(long reference, byte cleanerId, int size, ByteBuffer data) throws IOException {
		long index = writeToFile(size, data);
		referencesMetadata.editReference(reference, new ReferenceInfo(index, size, cleanerId));
	}

	@Override
	public ByteBuffer readFromReference(long reference) throws IOException {
		ReferenceInfo referenceInfo = referencesMetadata.getReferenceInfo(reference);
		return fileIO.readAt(referenceInfo.getIndex(), referenceInfo.getSize());
	}

	public ByteBuffer readFromReferenceSizeAndLastElementOfReferencesList(long reference) throws IOException {
		ReferenceInfo referenceInfo = referencesMetadata.getReferenceInfo(reference);
		if (referenceInfo.getSize() >= Integer.BYTES * 2 + Long.BYTES) {
			return fileIO.readAt(referenceInfo.getIndex() + referenceInfo.getSize() - (Integer.BYTES + Long.BYTES), Integer.BYTES + Long.BYTES);
		} else {
			return fileIO.readAt(referenceInfo.getIndex(), referenceInfo.getSize());
		}
	}

	/**
	 *
	 * @param size
	 * @param data
	 * @return index
	 * @throws IOException
	 */
	private long writeToFile(int size, ByteBuffer data) throws IOException {
		if (size == 0 && data == null) return 0;
		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());
		}
		return fileIO.writeAtEnd(size, data);
	}
}