strangedb/src/main/java/org/warp/jcwdb/ann/DBArrayList.java

package org.warp.jcwdb.ann;

import it.unimi.dsi.fastutil.longs.LongArrayList;

import java.io.IOError;
import java.io.IOException;
import java.util.StringJoiner;

public abstract class DBArrayList<T> extends DBObject {

	private final Object indicesAccessLock = new Object();

	@DBField(id = 0, type = DBDataType.UID_LIST)
	private LongArrayList indices;

	public DBArrayList() {
		super();
	}

	public DBArrayList(JCWDatabase database) throws IOException {
		super(database);
	}

	@Override
	public void initialize() {
		indices = new LongArrayList();
	}

	public T get(int index) {
		synchronized (indicesAccessLock) {
			try {
				long uid = indices.getLong(index);
				return loadItem(uid);
			} catch (IOException e) {
				throw new IOError(e);
			}
		}
	}

	public void add(T value) {
		long uid = database.getDataLoader().allocateNullValue();
		synchronized (indicesAccessLock) {
			indices.add(uid);
			try {
				writeItemToDisk(uid, value);
			} catch (IOException e) {
				throw new IOError(e);
			}
		}
	}

	public void update(int index, T value) {
		synchronized (indicesAccessLock) {
			set(index, value);
		}
	}

	public void set(int index, T value) {
		long uid = database.getDataLoader().allocateNullValue();
		synchronized (indicesAccessLock) {
			indices.set(index, uid);
			try {
				writeItemToDisk(uid, value);
			} catch (IOException e) {
				throw new IOError(e);
			}
		}
	}

	public void add(int index, T value) {
		long uid = database.getDataLoader().allocateNullValue();
		synchronized (indicesAccessLock) {
			indices.add(index, uid);
			try {
				writeItemToDisk(uid, value);
			} catch (IOException e) {
				throw new IOError(e);
			}
		}
	}

	public T getLast() {
		synchronized (indicesAccessLock) {
			if (indices.size() > 0) {
				return get(indices.size() - 1);
			} else {
				return null;
			}
		}
	}

	public boolean isEmpty() {
		synchronized (indicesAccessLock) {
			return indices.size() <= 0;
		}
	}

	public int size() {
		synchronized (indicesAccessLock) {
			return indices.size();
		}
	}

	protected abstract T loadItem(long uid) throws IOException;

	protected abstract void writeItemToDisk(long uid, T item) throws IOException;

	@Override
	public String toString() {
		return new StringJoiner(", ", DBArrayList.class.getSimpleName() + "[", "]")
						.add(indices.size() + " items")
						.toString();
	}
}