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 * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.jfr.internal.jfc.model;

import java.io.IOException;
import java.io.Reader;
import java.text.ParseException;
import java.util.ArrayDeque;
import java.util.Deque;
import jdk.internal.org.xml.sax.Attributes;
import jdk.internal.org.xml.sax.InputSource;
import jdk.internal.org.xml.sax.SAXException;
import jdk.internal.org.xml.sax.helpers.DefaultHandler;
import jdk.internal.util.xml.SAXParser;
import jdk.internal.util.xml.impl.SAXParserImpl;

final class Parser {

    static XmlConfiguration parse(Reader reader) throws ParseException, IOException {
        try {
            SAXParser saxParser = new SAXParserImpl();
            ConfigurationHandler handler = new ConfigurationHandler();
            saxParser.parse(new InputSource(reader), handler);
            return handler.configuration;
        } catch (SAXException | IllegalStateException e) {
            throw new ParseException(e.getMessage(), -1);
        }
    }

    private static final class ConfigurationHandler extends DefaultHandler {
        private final Deque<XmlElement> stack = new ArrayDeque<>();
        private final StringBuilder buffer = new StringBuilder();
        private XmlConfiguration configuration;

        @Override
        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            if (configuration == null) {
                if (!qName.equalsIgnoreCase("configuration")) {
                    throw new SAXException("Expected root element to be named 'configuration'");
                }
                configuration = new XmlConfiguration();
                addAttributes(configuration, attributes);
                stack.push(configuration);
                return;
            }
            XmlElement current = stack.peek();
            XmlElement child = current.createChild(qName);
            addAttributes(child, attributes);
            stack.push(child);
        }

        @Override
        public void characters(char ch[], int start, int length) throws SAXException {
            buffer.append(ch, start, length);
        }

        @Override
        public void endElement(String uri, String localName, String qName) {
            String content = buffer.toString().strip();
            if (!content.isEmpty()) {
                stack.peek().setContent(content);
                buffer.setLength(0);
            }

            XmlElement current = stack.peek();
            if (current.getElementName().equalsIgnoreCase(qName)) {
                stack.pop();
            } else {
                throw new IllegalStateException("Unexpected <" + qName + "/>");
            }
        }

        private void addAttributes(XmlElement element, Attributes attributes) {
            for (int i = 0; i < attributes.getLength(); i++) {
                element.setAttribute(attributes.getQName(i), attributes.getValue(i));
            }
        }
    }
}