ExpressionParser.java

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/*
 * This file is part of JXClient, the Fullscreen Java Crossfire Client.
 *
 * JXClient is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * JXClient 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with JXClient; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Copyright (C) 2005-2008 Yann Chachkoff
 * Copyright (C) 2006-2017,2019-2023 Andreas Kirschbaum
 * Copyright (C) 2010-2012,2014-2018,2020-2023 Nicolas Weeger
 */
 
package com.realtime.crossfire.jxclient.skin.io;
 
import com.realtime.crossfire.jxclient.gui.gui.Expression;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.jetbrains.annotations.NotNull;
 
public class ExpressionParser {
 
    @NotNull
    private static final Pattern PATTERN_EXPR = Pattern.compile("(.+?) *([+-]) *(.+)");
 
    @NotNull
    private static final Pattern PATTERN_TERM1 = Pattern.compile("([0-9.]+) *[*] *([A-Z_]+)");
 
    @NotNull
    private static final Pattern PATTERN_TERM2 = Pattern.compile("([A-Z_]+) *[*] *([0-9.]+)");
 
    private ExpressionParser() {
    }
 
    public static int parseInt(@NotNull final String str) throws IOException {
        return parseExpression(str).evaluateConstant();
    }
 
    @NotNull
    public static Expression parseExpression(@NotNull final String str) throws IOException {
        Matcher matcherExpr = PATTERN_EXPR.matcher(str);
        if (!matcherExpr.matches()) {
            return parseTerm(str);
        }
 
        Expression expr = parseTerm(matcherExpr.group(1));
        while (true) {
            final boolean negative = switch (matcherExpr.group(2)) {
                case "+" -> false;
                case "-" -> true;
                default -> throw new AssertionError("unrecognized operator: "+matcherExpr.group(2));
            };
 
            final Matcher matcherExpr2 = PATTERN_EXPR.matcher(matcherExpr.group(3));
            if (!matcherExpr2.matches()) {
                return new Expression(expr, negative, parseTerm(matcherExpr.group(3)));
            }
 
            matcherExpr = matcherExpr2;
            expr = new Expression(expr, negative, parseTerm(matcherExpr.group(1)));
        }
    }
 
    @NotNull
    private static Expression parseTerm(@NotNull final String str) throws IOException {
        try {
            return new Expression(Integer.parseInt(str), 0, 0, 0, 0);
        } catch (final NumberFormatException ignored) {
        }
 
        switch (str) {
        case "WIDTH":
            return new Expression(0, 1, 0, 0, 0);
 
        case "HEIGHT":
            return new Expression(0, 0, 1, 0, 0);
 
        case "PREF_WIDTH":
            return new Expression(0, 0, 0, 1, 0);
 
        case "PREF_HEIGHT":
            return new Expression(0, 0, 0, 0, 1);
 
        case "WIDTH/2":
            return new Expression(0, 0.5F, 0, 0, 0);
 
        case "HEIGHT/2":
            return new Expression(0, 0, 0.5F, 0, 0);
 
        case "PREF_WIDTH/2":
            return new Expression(0, 0, 0, 0.5F, 0);
 
        case "PREF_HEIGHT/2":
            return new Expression(0, 0, 0, 0, 0.5F);
        }
 
        final Matcher matcherTerm1 = PATTERN_TERM1.matcher(str);
        if (matcherTerm1.matches()) {
            return parseTerm(matcherTerm1.group(1), matcherTerm1.group(2));
        }
 
        final Matcher matcherTerm2 = PATTERN_TERM2.matcher(str);
        if (matcherTerm2.matches()) {
            return parseTerm(matcherTerm2.group(2), matcherTerm2.group(1));
        }
 
        throw new IOException("syntax error in '"+str+"'");
    }
 
    @NotNull
    private static Expression parseTerm(@NotNull final String factor, @NotNull final String constant) throws IOException {
        final float factor2;
        try {
            factor2 = Float.parseFloat(factor);
        } catch (final NumberFormatException ex) {
            throw new IOException("invalid value '"+factor+"'", ex);
        }
 
        switch (constant) {
        case "WIDTH":
            return new Expression(0, factor2, 0, 0, 0);
 
        case "HEIGHT":
            return new Expression(0, 0, factor2, 0, 0);
 
        case "PREF_WIDTH":
            return new Expression(0, 0, 0, factor2, 0);
 
        case "PREF_HEIGHT":
            return new Expression(0, 0, 0, 0, factor2);
        }
 
        throw new IOException("invalid constant '"+constant+"'");
    }
 
}