package org.warp.jcwdb;

import java.io.IOException;
import java.util.function.Function;

/**
 * You must have only a maximum of 1 reference for each index
 * @param <T>
 */
public class EntryReference<T> implements Castable {
	private final JCWDatabase.EntryReferenceTools db;
	private final long entryIndex;
	private final DBTypeParser<T> parser;
	private T value;
	private volatile boolean closed;
	private final Object closeLock = new Object();

	public EntryReference(JCWDatabase.EntryReferenceTools db, long entryId, DBTypeParser<T> parser) throws IOException {
		this.db = db;
		this.entryIndex = entryId;
		this.parser = parser;
		this.value = db.read(entryId, parser.getReader());
	}

	public EntryReference(JCWDatabase.EntryReferenceTools db, long entryId, DBTypeParser<T> parser, T value) {
		this.db = db;
		this.entryIndex = entryId;
		this.parser = parser;
		this.value = value;
	}

	public DBTypeParser<T> getParser() {
		return parser;
	}

	public long getIndex() {
		return entryIndex;
	}
	
	public long calculateHash() {
		return parser.calculateHash(value);
	}

	/**
	 * Note that this method won't be called when closing without saving
	 * @throws IOException
	 */
	public void save() throws IOException {
		if (!closed) {
			db.write(entryIndex, parser.getWriter(value));
		}
	}

	public void editValue(Function<T, T> editFunction) throws IOException {
		this.value = editFunction.apply(this.value);
		this.save();
	}

	/**
	 * Use editValue instead
	 * @return
	 */
	@Deprecated()
	public T getValue() {
		return this.value;
	}

	/**
	 * DO NOT ATTEMPT TO MODIFY THE VALUE RETURNED
	 * @return
	 */
	public T getValueUnsafe() {
		return this.value;
	}

	@Override
	public <T> T cast() {
		return (T) this;
	}

	protected void close() throws IOException {
		if (closed) {
			return;
		}
		synchronized (closeLock) {
			if (closed) {
				return;
			}

			save();

			closed = true;
		}
	}

	public void closeWithoutSaving() {
		if (closed) {
			return;
		}
		synchronized (closeLock) {
			if (closed) {
				return;
			}

			closed = true;
		}
	}
}