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The DSI utilities are a mishmash of classes accumulated during the last twenty years in projects developed at the DSI (Dipartimento di Scienze dell'Informazione, i.e., Information Sciences Department), now DI (Dipartimento di Informatica, i.e., Informatics Department), of the Universita` degli Studi di Milano.

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package it.unimi.dsi.parser.callback;

/*
 * DSI utilities
 *
 * Copyright (C) 2005-2019 Sebastiano Vigna
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This library is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, see .
 *
 */

import it.unimi.dsi.fastutil.objects.ObjectArrayList;
import it.unimi.dsi.lang.MutableString;
import it.unimi.dsi.parser.Attribute;
import it.unimi.dsi.parser.BulletParser;
import it.unimi.dsi.parser.Element;

import java.util.Map;

/** A builder for composed callbacks.
 *
 * To compose a series of callbacks, you must first create an instance
 * of this class, {@linkplain #add(Callback) add all required callbacks}, and
 * finally {@linkplain #compose() get the composed callback}, which will invoke (in order)
 * the callbacks.
 */

public class ComposedCallbackBuilder {

	/** A sequence of callbacks to be called int turn. */

	private static final class ComposedCallback implements Callback {
		/** The number of callbacks in this composer. */
		final int size;

		/** The callback array. */
		private Callback[] callback;

		/** An array of boolean representing continuation of the corresponding callback in {@link #callback}. */
		private boolean[] cont;

		private final ObjectArrayList callbacks;

		private ComposedCallback(final ObjectArrayList callbacks) {
			super();
			this.callbacks = callbacks;
			this.size = callbacks.size();
			this.cont = new boolean[size];
			this.callback = new Callback[size];
			this.callbacks.toArray(callback);
		}

		@Override
		public void configure(final BulletParser parser) {
			for(int i = 0; i < size; i++) callback[i].configure(parser);
		}

		@Override
		public void startDocument() {
			for(int i = 0; i < size; i++) {
				callback[i].startDocument();
				cont[i] = true;
			}
		}

		@Override
		public boolean startElement(final Element tag, final Map attrList) {
			boolean retValue = false;
			for(int i = 0; i < size; i++) {
				if (cont[i] && ! callback[i].startElement(tag, attrList)) cont[i] = false;
				retValue |= cont[i];
			}
			return retValue;
		}

		@Override
		public boolean endElement(final Element tag) {
			boolean retValue = false;
			for(int i = 0; i < size; i++) {
				if (cont[i] && ! callback[i].endElement(tag)) cont[i] = false;
				retValue |= cont[i];
			}
			return retValue;
		}

		@Override
		public boolean characters(final char[] text, final int offset, final int length, final boolean flowBroken) {
			boolean retValue = false;
			for(int i = 0; i < size; i++) {
				if (cont[i] && ! callback[i].characters(text, offset, length, flowBroken)) cont[i] = false;
				retValue |= cont[i];
			}
			return retValue;
		}

		@Override
		public boolean cdata(final Element element, final char[] text, final int offset, final int length) {
			boolean retValue = false;
			for(int i = 0; i < size; i++) {
				if (cont[i] && ! callback[i].cdata(element, text, offset, length)) cont[i] = false;
				retValue |= cont[i];
			}
			return retValue;
		}

		@Override
		public void endDocument() {
			for(int i = 0; i < size; i++) callback[i].endDocument();
		}
	}

	/** The current list of callbacks. */
	private final ObjectArrayList callbacks = ObjectArrayList.wrap(Callback.EMPTY_CALLBACK_ARRAY);

	/** Creates a new, empty callback composer. */
	public ComposedCallbackBuilder()  {}

	/** Adds a new callback to this builder at a specified position.
	 *
	 * @param position a position in the current callback list.
	 * @param callback a callback.
	 */
	public void add(final int position, final Callback callback) {
		callbacks.add(position, callback);
	}

	/** Adds a new callback to this builder.
	 *
	 * @param callback a callback.
	 */

	public void add(final Callback callback) {
		callbacks.add(callback);
	}

	/** Checks whether this callback builder is empty.
	 *
	 * @return true if this callback builder is empty.
	 */

	public boolean isEmpty() {
		return callbacks.isEmpty();
	}

	/** Returns the number of callbacks in this builder.
	 *
	 * @return the number of callbacks in this composer.
	 */
	public int size() {
		return callbacks.size();
	}

	/** Returns the composed callback produced by this builder.
	 *
	 * @return a composed callback.
	 */
	public Callback compose() {
		if (isEmpty()) return DefaultCallback.getInstance();
		if (size() == 1) return callbacks.get(0);

		return new ComposedCallback(callbacks);
	}
}