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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.lang;

/*
 * DSI utilities
 *
 * Copyright (C) 2016-2018 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 com.martiansoftware.jsap.ParseException;
import com.martiansoftware.jsap.StringParser;

/**
 * A {@link com.martiansoftware.jsap.StringParser StringParser} that makes the user choose among
 * items of a Java {@code enum}.
 *
 * Optionally, parsed strings can be normalized to upper case.
 * Thus, if the enum elements are defined in uppercase, the parser will be in practice
 * case-independent.
 *
 * 
A typical usage example for an {@code ExampleEnum} with an item {@code A} that is going to be the default:
 * 
 * new FlaggedOption("example",
 *     EnumStringParser.getParser(ExampleEnum.class, true),
 *     ExampleEnum.A.name(), JSAP.NOT_REQUIRED, 'e', "example",
 *     Arrays.toString(ExampleEnum.values()))
 * 
 */

public class EnumStringParser> extends StringParser {
	private final Class enumClass;
	private final boolean toUpper;

	/** Returns the enum item obtained by passing the argument to {@link Enum#valueOf(Class, String)}.
	 *
	 * @param s an enum item name.
	 * @return the enum item returned by {@link Enum#valueOf(Class, String)} (possibly
	 * after upper casing {@code s}).
	 */
	@Override
	@SuppressWarnings({ "unchecked" })
	public E parse(String s) throws ParseException {
		try {
			return (E) enumClass.getMethod("valueOf", String.class).invoke(null, toUpper ? s.toUpperCase() : s);
		} catch (Exception e) {
			throw (new ParseException("Unknown value '" + s + "'.", e));
		}
	}

	private EnumStringParser(Class enumClass, final boolean toUpper) {
		this.enumClass = enumClass;
		this.toUpper = toUpper;
	}

	/**
	 * Returns an enum parser.
	 *
	 * @param enumClass an {@code enum} class whose values
	 * @param toUpper tells the parser to upper case the strings to be parsed.
	 */
	public static > EnumStringParser getParser(final Class enumClass, final boolean toUpper) throws IllegalArgumentException {
		return new EnumStringParser<>(enumClass, toUpper);
	}

	/**
	 * Returns an enum parser that does not normalize to upper case.
	 *
	 * @param enumClass an {@code enum} class whose values
	 */
	public static > EnumStringParser getParser(final Class enumClass) throws IllegalArgumentException {
		return getParser(enumClass, false);
	}
}