ElementBase.java

/*
 * Copyright © 2025 Indiana University
 * All rights reserved.
 *
 * BSD 3-Clause License
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * 
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
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 * 
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 *   this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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package iu.type;

import java.util.ArrayDeque;
import java.util.Objects;
import java.util.Queue;
import java.util.function.Consumer;

import edu.iu.type.IuAnnotatedElement;

/**
 * Provides initialization behavior for type facade elements.
 */
abstract sealed class ElementBase implements IuAnnotatedElement
		permits AnnotatedElementBase, TypeFacade, PropertyFacade {

	private boolean sealed;
	private Queue<Runnable> postInit = new ArrayDeque<>();

	/**
	 * Default constructor, for use by all subclasses extend {@link TypeTemplate}.
	 */
	ElementBase() {
	}

	/**
	 * Constructor for use by {@link TypeTemplate}.
	 * 
	 * @param preInitHook used by {@link TypeFactory}
	 */
	ElementBase(Consumer<TypeTemplate<?, ?>> preInitHook) {
		preInitHook.accept((TypeTemplate<?, ?>) this);
	}

	/**
	 * Checks to verify the element is sealed.
	 * 
	 * <p>
	 * All public methods <em>should</em> invoke this method to verify immutability
	 * before attempting lookups.
	 * </p>
	 * 
	 * @throws IllegalStateException if the element is not sealed.
	 */
	void checkSealed() throws IllegalStateException {
		if (!sealed)
			throw new IllegalStateException("not sealed");
	}

	/**
	 * <em>May</em> be invoked within a base constructor to defer part of
	 * initialization until after the facade instance is fully formed.
	 * 
	 * @param run initialization segment to run after all facade elements are
	 *            populated
	 */
	void postInit(Runnable run) {
		if (sealed)
			run.run();
		else
			postInit.offer(run);
	}

	/**
	 * <em>Should</em> be called at the end of all concrete subclass constructors.
	 */
	void seal() {
		var postInit = Objects.requireNonNull(this.postInit, "already sealed");
		this.sealed = true;
		this.postInit = null;

		while (!postInit.isEmpty())
			postInit.poll().run();
	}

}