org.eclipse.osbp.runtime.common/src/org/eclipse/osbp/runtime/common/session/AbstractSession.java

package org.eclipse.osbp.runtime.common.session;

import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.function.Function;

import org.eclipse.osbp.runtime.common.session.ISessionManager.FutureResult;

/**
 * A base implementation of the session using the SessionUnitOfWork to provide
 * session scope.
 */
public abstract class AbstractSession implements ISession {

	private Type sessionType = Type.MASTER;

	@Override
	public <T> T apply(Function<ISession, T> function) {
		if (function == null) {
			throw new NullPointerException("Function is null!");
		}
		return function.apply(this);
	}

	@Override
	public <T> CompletableFuture<FutureResult<T>> async(final Function<ISession, T> function,
			SessionCallback<T> callback) {
		return async(function, callback, null);
	}

	@Override
	public <T> CompletableFuture<FutureResult<T>> async(Function<ISession, T> function, SessionCallback<T> callback,
			ExecutorService executor) {

		CompletableFuture<T> promise = doAsync(function, executor);

		CompletableFuture<FutureResult<T>> transformer = promise.handle((t, e) -> {
			return new FutureResult<T>(this, t, e);
		});

		CompletableFuture<FutureResult<T>> notifier = transformer.whenComplete((r, t) -> {
			if (callback == null) {
				return;
			}
			callback.accept(r);
		});
		return notifier;

	}

	/**
	 * The implementation needs to synchronize the runnable with the underlying
	 * frameworks. For instance Vaadin UI. This method MUST NOT block.
	 * 
	 * @param function
	 * @param executor
	 */
	protected abstract <T> CompletableFuture<T> doAsync(final Function<ISession, T> function, ExecutorService executor);

	@Override
	public void sendData(Map<String, Object> data) {
		// override if used
	}

	public Type getType() {
		return sessionType;
	}

	public void setType(Type sessionType) {
		this.sessionType = sessionType;
	}

}