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/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2024 Apryse Group NV
    Authors: Apryse Software.

    This program is offered under a commercial and under the AGPL license.
    For commercial licensing, contact us at https://itextpdf.com/sales.  For AGPL licensing, see below.

    AGPL licensing:
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program 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 Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see .
 */
package com.itextpdf.pdfua.checkers.utils;

import com.itextpdf.kernel.pdf.PdfDictionary;
import com.itextpdf.kernel.pdf.PdfName;
import com.itextpdf.kernel.pdf.PdfString;
import com.itextpdf.kernel.pdf.tagging.IStructureNode;
import com.itextpdf.kernel.pdf.tagging.PdfStructElem;
import com.itextpdf.pdfua.exceptions.PdfUAConformanceException;
import com.itextpdf.pdfua.exceptions.PdfUAExceptionMessageConstants;

/**
 * Class that provides methods for checking PDF/UA compliance of Formula elements.
 */
public final class FormulaCheckUtil {

    /**
     * Creates a new {@link FormulaCheckUtil} instance.
     */
    private FormulaCheckUtil() {
        // Empty constructor
    }

    private static boolean hasInvalidValues(PdfString altText, PdfString actualText) {
        String altTextValue = null;
        if (altText != null) {
            altTextValue = altText.getValue();
        }
        String actualTextValue = null;
        if (actualText != null) {
            actualTextValue = actualText.getValue();
        }
        return !(!(altTextValue == null || altTextValue.isEmpty()) || actualTextValue != null);
    }

    /**
     * Handler for checking Formula elements in the TagTree.
     */
    public static class FormulaTagHandler extends ContextAwareTagTreeIteratorHandler {

        /**
         * Creates a new {@link  FormulaTagHandler} instance.
         * @param context The validation context.
         */
        public FormulaTagHandler(PdfUAValidationContext context) {
            super(context);
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public void nextElement(IStructureNode elem) {
            final PdfStructElem structElem = context.getElementIfRoleMatches(PdfName.Formula, elem);
            if (structElem == null) {
                return;
            }
            final PdfDictionary pdfObject = structElem.getPdfObject();
            if (hasInvalidValues(pdfObject.getAsString(PdfName.Alt), pdfObject.getAsString(PdfName.ActualText))) {
                throw new PdfUAConformanceException(PdfUAExceptionMessageConstants.FORMULA_SHALL_HAVE_ALT);
            }
        }
    }

}