Copyright (c) 2004, 2018 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2004, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.core.util;

import org.eclipse.jdt.internal.core.JavaElement;

public class MementoTokenizer {
	public static final String COUNT = Character.toString(JavaElement.JEM_COUNT);
	public static final String JAVAPROJECT = Character.toString(JavaElement.JEM_JAVAPROJECT);
	public static final String PACKAGEFRAGMENTROOT = Character.toString(JavaElement.JEM_PACKAGEFRAGMENTROOT);
	public static final String PACKAGEFRAGMENT = Character.toString(JavaElement.JEM_PACKAGEFRAGMENT);
	public static final String FIELD = Character.toString(JavaElement.JEM_FIELD);
	public static final String METHOD = Character.toString(JavaElement.JEM_METHOD);
	public static final String INITIALIZER = Character.toString(JavaElement.JEM_INITIALIZER);
	public static final String COMPILATIONUNIT = Character.toString(JavaElement.JEM_COMPILATIONUNIT);
	public static final String CLASSFILE = Character.toString(JavaElement.JEM_CLASSFILE);
	public static final String MODULAR_CLASSFILE = Character.toString(JavaElement.JEM_MODULAR_CLASSFILE);
	public static final String TYPE = Character.toString(JavaElement.JEM_TYPE);
	public static final String MODULE = Character.toString(JavaElement.JEM_MODULE);
	public static final String PACKAGEDECLARATION = Character.toString(JavaElement.JEM_PACKAGEDECLARATION);
	public static final String IMPORTDECLARATION = Character.toString(JavaElement.JEM_IMPORTDECLARATION);
	public static final String LOCALVARIABLE = Character.toString(JavaElement.JEM_LOCALVARIABLE);
	public static final String TYPE_PARAMETER = Character.toString(JavaElement.JEM_TYPE_PARAMETER);
	public static final String ANNOTATION = Character.toString(JavaElement.JEM_ANNOTATION);
	public static final String LAMBDA_EXPRESSION = Character.toString(JavaElement.JEM_LAMBDA_EXPRESSION);
	public static final String LAMBDA_METHOD = Character.toString(JavaElement.JEM_LAMBDA_METHOD);
	public static final String STRING = Character.toString(JavaElement.JEM_STRING);
	public static final String CLASSPATH_ATTRIBUTE = JAVAPROJECT+PACKAGEFRAGMENTROOT;

	private final char[] memento;
	private final int length;
	private int index = 0;

	public MementoTokenizer(String memento) {
		this.memento = memento.toCharArray();
		this.length = this.memento.length;
	}

	public boolean hasMoreTokens() {
		return this.index < this.length;
	}

	public String nextToken() {
		int start = this.index;
		StringBuffer buffer = null;
		switch (this.memento[this.index++]) {
			case JavaElement.JEM_ESCAPE:
				buffer = new StringBuffer();
				buffer.append(this.memento[this.index]);
				start = ++this.index;
				break;
			case JavaElement.JEM_COUNT:
				return COUNT;
			case JavaElement.JEM_JAVAPROJECT:
				// Also covers JavaElement#JEM_DELIMITER_ESCAPE, in which case, 
				// we seek ahead by one char and check if it's an escaped delimiter
				// and if that's true, we return that as the token. 
				// Else, we decide that JEM_JAVAPROJECT is the current token.
				if (this.index < this.length) {
					char nextChar = this.memento[this.index++];
					switch(nextChar) {
						case JavaElement.JEM_LAMBDA_EXPRESSION:
							return LAMBDA_EXPRESSION;
						case JavaElement.JEM_LAMBDA_METHOD:
							return LAMBDA_METHOD;
						case JavaElement.JEM_STRING:
							return STRING;
						case JavaElement.JEM_PACKAGEFRAGMENTROOT:
							return CLASSPATH_ATTRIBUTE;
						default:
							this.index--;
							break;
					}
				}
				return JAVAPROJECT;
			case JavaElement.JEM_PACKAGEFRAGMENTROOT:
				return PACKAGEFRAGMENTROOT;
			case JavaElement.JEM_PACKAGEFRAGMENT:
				return PACKAGEFRAGMENT;
			case JavaElement.JEM_FIELD:
				return FIELD;
			case JavaElement.JEM_METHOD:
				return METHOD;
			case JavaElement.JEM_INITIALIZER:
				return INITIALIZER;
			case JavaElement.JEM_COMPILATIONUNIT:
				return COMPILATIONUNIT;
			case JavaElement.JEM_CLASSFILE:
				return CLASSFILE;
			case JavaElement.JEM_MODULAR_CLASSFILE:
				return MODULAR_CLASSFILE;
			case JavaElement.JEM_TYPE:
				return TYPE;
			case JavaElement.JEM_MODULE:
				return MODULE;
			case JavaElement.JEM_PACKAGEDECLARATION:
				return PACKAGEDECLARATION;
			case JavaElement.JEM_IMPORTDECLARATION:
				return IMPORTDECLARATION;
			case JavaElement.JEM_LOCALVARIABLE:
				return LOCALVARIABLE;
			case JavaElement.JEM_TYPE_PARAMETER:
				return TYPE_PARAMETER;
			case JavaElement.JEM_ANNOTATION:
				return ANNOTATION;
		}
		loop: while (this.index < this.length) {
			switch (this.memento[this.index]) {
				case JavaElement.JEM_ESCAPE:
					if (buffer == null) buffer = new StringBuffer();
					buffer.append(this.memento, start, this.index - start);
					start = ++this.index;
					if (this.memento[this.index] == JavaElement.JEM_MODULE)
						return buffer.toString();
					break;
				case JavaElement.JEM_COUNT:
				case JavaElement.JEM_JAVAPROJECT:
				case JavaElement.JEM_PACKAGEFRAGMENTROOT:
				case JavaElement.JEM_PACKAGEFRAGMENT:
				case JavaElement.JEM_FIELD:
				case JavaElement.JEM_METHOD:
				case JavaElement.JEM_INITIALIZER:
				case JavaElement.JEM_COMPILATIONUNIT:
				case JavaElement.JEM_CLASSFILE:
				case JavaElement.JEM_TYPE:
				case JavaElement.JEM_MODULE:
				case JavaElement.JEM_PACKAGEDECLARATION:
				case JavaElement.JEM_IMPORTDECLARATION:
				case JavaElement.JEM_LOCALVARIABLE:
				case JavaElement.JEM_TYPE_PARAMETER:
				case JavaElement.JEM_ANNOTATION:
					break loop;
			}
			this.index++;
		}
		if (buffer != null) {
			buffer.append(this.memento, start, this.index - start);
			return buffer.toString();
		} else {
			return new String(this.memento, start, this.index - start);
		}
	}

	public String getStringDelimitedBy(String delimiter) {
		String token = nextToken();
		if (token == delimiter)
			return ""; //$NON-NLS-1$
		String separator = nextToken();
		assert separator == delimiter;
		return token;
	}
}