/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.xml;

import org.apache.log4j.Appender;
import org.apache.log4j.Layout;
import org.apache.log4j.Level;
import org.apache.log4j.bridge.AppenderAdapter;
import org.apache.log4j.bridge.AppenderWrapper;
import org.apache.log4j.builders.BuilderManager;
import org.apache.log4j.config.Log4j1Configuration;
import org.apache.log4j.config.PropertySetter;
import org.apache.log4j.helpers.OptionConverter;
import org.apache.log4j.spi.AppenderAttachable;
import org.apache.log4j.spi.Configurator;
import org.apache.log4j.spi.ErrorHandler;
import org.apache.log4j.spi.Filter;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.ConfigurationFactory;
import org.apache.logging.log4j.core.config.ConfigurationSource;
import org.apache.logging.log4j.core.config.LoggerConfig;
import org.apache.logging.log4j.core.config.Order;
import org.apache.logging.log4j.core.config.status.StatusConfiguration;
import org.apache.logging.log4j.plugins.Plugin;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.LoaderUtil;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.FactoryConfigurationError;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InterruptedIOException;
import java.io.Reader;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;

/**
 * Constructs a Configuration usable in Log4j 2 from a Log4j 1 configuration file.
 */
@Plugin(name = "Log4j1XmlConfigurationFactory", category = ConfigurationFactory.CATEGORY)
@Order(2)
public class XmlConfigurationFactory extends ConfigurationFactory implements Configurator {
    private static final org.apache.logging.log4j.Logger LOGGER = StatusLogger.getLogger();

    private static final String CONFIGURATION_TAG = "log4j:configuration";
    private static final String OLD_CONFIGURATION_TAG = "configuration";
    private static final String RENDERER_TAG = "renderer";
    private static final String APPENDER_TAG = "appender";
    private static final String APPENDER_REF_TAG = "appender-ref";
    public  static final String PARAM_TAG = "param";
    public static final String LAYOUT_TAG = "layout";
    private static final String CATEGORY = "category";
    private static final String LOGGER_ELEMENT = "logger";
    private static final String CATEGORY_FACTORY_TAG = "categoryFactory";
    private static final String LOGGER_FACTORY_TAG = "loggerFactory";
    public static final String NAME_ATTR = "name";
    private static final String CLASS_ATTR = "class";
    public static final String VALUE_ATTR = "value";
    private static final String ROOT_TAG = "root";
    private static final String LEVEL_TAG = "level";
    private static final String PRIORITY_TAG = "priority";
    public static final String FILTER_TAG = "filter";
    private static final String ERROR_HANDLER_TAG = "errorHandler";
    private static final String REF_ATTR = "ref";
    private static final String ADDITIVITY_ATTR = "additivity";
    private static final String CONFIG_DEBUG_ATTR = "configDebug";
    private static final String INTERNAL_DEBUG_ATTR = "debug";
    private static final String EMPTY_STR = "";
    private static final Class[] ONE_STRING_PARAM = new Class[]{String.class};
    private static final String dbfKey = "javax.xml.parsers.DocumentBuilderFactory";
    private static final String THROWABLE_RENDERER_TAG = "throwableRenderer";
    private static final String SYSTEM_OUT = "System.out";
    private static final String SYSTEM_ERR = "System.err";
    private static final String THREAD_PRINTING_PARAM = "threadprinting";
    private static final String CATEGORY_PREFIXING_PARAM = "categoryprefixing";
    private static final String CONTEXT_PRINTING_PARAM = "contextprinting";
    private static final String DATE_FORMAT_PARAM = "dateformat";
    private static final String TIMEZONE_FORMAT = "timezone";
    public static final String FILE_PARAM = "file";
    public static final String APPEND_PARAM = "append";
    public static final String BUFFERED_IO_PARAM = "bufferedio";
    public static final String BUFFER_SIZE_PARAM = "buffersize";
    public static final String MAX_SIZE_PARAM = "maxfileSize";
    public static final String MAX_BACKUP_INDEX = "maxbackupindex";
    public static final String RELATIVE = "RELATIVE";
    public static final long DEFAULT_DELAY = 60000;
    /**
     * File name prefix for test configurations.
     */
    protected static final String TEST_PREFIX = "log4j-test";

    /**
     * File name prefix for standard configurations.
     */
    protected static final String DEFAULT_PREFIX = "log4j";

    private final BuilderManager manager;

    // key: appenderName, value: appender
    private Map<String, Appender> appenderBag;

    private Properties props = null;

    private final LoggerContext loggerContext;
    private Log4j1Configuration configuration;

    /**
     * No argument constructor.
     */
    public XmlConfigurationFactory() {
        appenderBag = new HashMap<>();
        loggerContext = (LoggerContext) org.apache.logging.log4j.LogManager.getContext(false);
        manager = new BuilderManager();
    }


    private XmlConfigurationFactory(ConfigurationSource source, int monitorIntervalSeconds) {
        appenderBag = new HashMap<>();
        loggerContext = (LoggerContext) org.apache.logging.log4j.LogManager.getContext(false);
        configuration = new Log4j1Configuration(loggerContext, source, monitorIntervalSeconds);
        manager = new BuilderManager();
    }

    @Override
    protected String[] getSupportedTypes() {
        return new String[] {".xml"};
    }

    @Override
    public Configuration getConfiguration(LoggerContext loggerContext, ConfigurationSource source) {
        configuration = new Log4j1Configuration(loggerContext, source, 0);
        doConfigure();
        return configuration;
    }

    public Configuration getConfiguration() {
        return configuration;
    }

    @Override
    protected String getTestPrefix() {
        return TEST_PREFIX;
    }

    @Override
    protected String getDefaultPrefix() {
        return DEFAULT_PREFIX;
    }

    /**
     * Delegates unrecognized content to created instance if
     * it supports UnrecognizedElementParser.
     *
     * @param instance instance, may be null.
     * @param element  element, may not be null.
     * @param props    properties
     * @throws IOException thrown if configuration of owner object
     *                     should be abandoned.
     * @since 1.2.15
     */
    private static void parseUnrecognizedElement(final Object instance, final Element element,
            final Properties props) throws Exception {
        boolean recognized = false;
        if (instance instanceof UnrecognizedElementHandler) {
            recognized = ((UnrecognizedElementHandler) instance).parseUnrecognizedElement(
                    element, props);
        }
        if (!recognized) {
            LOGGER.warn("Unrecognized element {}", element.getNodeName());
        }
    }

    /**
     * Delegates unrecognized content to created instance if
     * it supports UnrecognizedElementParser and catches and
     * logs any exception.
     *
     * @param instance instance, may be null.
     * @param element  element, may not be null.
     * @param props    properties
     * @since 1.2.15
     */
    private static void quietParseUnrecognizedElement(final Object instance,
            final Element element,
            final Properties props) {
        try {
            parseUnrecognizedElement(instance, element, props);
        } catch (Exception ex) {
            if (ex instanceof InterruptedException || ex instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            LOGGER.error("Error in extension content: ", ex);
        }
    }

    /**
     * Like {@link #configureAndWatch(String, long)} except that the
     * default delay is used.
     *
     * @param configFilename A log4j configuration file in XML format.
     */
    public static void configureAndWatch(final String configFilename) {
        configureAndWatch(configFilename, DEFAULT_DELAY);
    }

    /**
     * Read the configuration file <code>configFilename</code> if it
     * exists. Moreover, a thread will be created that will periodically
     * check if <code>configFilename</code> has been created or
     * modified. The period is determined by the <code>delay</code>
     * argument. If a change or file creation is detected, then
     * <code>configFilename</code> is read to configure log4j.
     *
     * @param configFilename A log4j configuration file in XML format.
     * @param delay          The delay in milliseconds to wait between each check.
     */
    public static void configureAndWatch(final String configFilename, final long delay) {
        try {
            File file = new File(configFilename);
            InputStream is = new FileInputStream(file);
            ConfigurationSource source = new ConfigurationSource(is, file);
            int seconds = (int) TimeUnit.MILLISECONDS.toSeconds(delay);
            XmlConfigurationFactory factory = new XmlConfigurationFactory(source, seconds);
            factory.doConfigure();
            org.apache.logging.log4j.core.config.Configurator.reconfigure(factory.getConfiguration());

        } catch (IOException ioe) {
            LOGGER.error("Unable to process configuration file {} due to {}", configFilename, ioe.getMessage());
        }
    }

    /**
     * A static version of doConfigure(String).
     */
    public static void configure(final String filename) throws FactoryConfigurationError {
        configureAndWatch(filename, 0);
    }

    /**
     * A static version of doConfigure(URL).
     */
    public static void configure(final URL url) throws FactoryConfigurationError {
        try {
            InputStream is = url.openStream();
            ConfigurationSource source = new ConfigurationSource(is, url);
            XmlConfigurationFactory factory = new XmlConfigurationFactory(source, 0);
            factory.doConfigure();
            org.apache.logging.log4j.core.config.Configurator.reconfigure(factory.getConfiguration());
        } catch (IOException ioe) {
            LOGGER.error("Unable to process configuration {} due to {}", url.toString(), ioe.getMessage());
        }
    }

    /**
     * Substitutes property value for any references in expression.
     *
     * @param value value from configuration file, may contain
     *              literal text, property references or both
     * @param props properties.
     * @return evaluated expression, may still contain expressions
     * if unable to expand.
     */
    public static String subst(final String value, final Properties props) {
        try {
            return OptionConverter.substVars(value, props);
        } catch (IllegalArgumentException e) {
            LOGGER.warn("Could not perform variable substitution.", e);
            return value;
        }
    }

    /**
     * Sets a parameter based from configuration file content.
     *
     * @param elem       param element, may not be null.
     * @param propSetter property setter, may not be null.
     * @param props      properties
     * @since 1.2.15
     */
    public static void setParameter(final Element elem, final PropertySetter propSetter, final Properties props) {
        String name = subst(elem.getAttribute("name"), props);
        String value = (elem.getAttribute("value"));
        value = subst(OptionConverter.convertSpecialChars(value), props);
        propSetter.setProperty(name, value);
    }

    /**
     * Creates an object and processes any nested param elements
     * but does not call activateOptions.  If the class also supports
     * UnrecognizedElementParser, the parseUnrecognizedElement method
     * will be call for any child elements other than param.
     *
     * @param element       element, may not be null.
     * @param props         properties
     * @param expectedClass interface or class expected to be implemented
     *                      by created class
     * @return created class or null.
     * @throws Exception thrown if the contain object should be abandoned.
     * @since 1.2.15
     */
    public static Object parseElement(final Element element, final Properties props,
            @SuppressWarnings("rawtypes") final Class expectedClass) throws Exception {
        String clazz = subst(element.getAttribute("class"), props);
        Object instance = OptionConverter.instantiateByClassName(clazz,
                expectedClass, null);

        if (instance != null) {
            PropertySetter propSetter = new PropertySetter(instance);
            NodeList children = element.getChildNodes();
            final int length = children.getLength();

            for (int loop = 0; loop < length; loop++) {
                Node currentNode = children.item(loop);
                if (currentNode.getNodeType() == Node.ELEMENT_NODE) {
                    Element currentElement = (Element) currentNode;
                    String tagName = currentElement.getTagName();
                    if (tagName.equals("param")) {
                        setParameter(currentElement, propSetter, props);
                    } else {
                        parseUnrecognizedElement(instance, currentElement, props);
                    }
                }
            }
            return instance;
        }
        return null;
    }

    /**
     * Used internally to parse appenders by IDREF name.
     */
    private Appender findAppenderByName(Document doc, String appenderName) {
        Appender appender = appenderBag.get(appenderName);

        if (appender != null) {
            return appender;
        } else {
            // Doesn't work on DOM Level 1 :
            // Element element = doc.getElementById(appenderName);

            // Endre's hack:
            Element element = null;
            NodeList list = doc.getElementsByTagName("appender");
            for (int t = 0; t < list.getLength(); t++) {
                Node node = list.item(t);
                NamedNodeMap map = node.getAttributes();
                Node attrNode = map.getNamedItem("name");
                if (appenderName.equals(attrNode.getNodeValue())) {
                    element = (Element) node;
                    break;
                }
            }
            // Hack finished.

            if (element == null) {

                LOGGER.error("No appender named [{}] could be found.", appenderName);
                return null;
            } else {
                appender = parseAppender(element);
                if (appender != null) {
                    appenderBag.put(appenderName, appender);
                }
                return appender;
            }
        }
    }

    /**
     * Used internally to parse appenders by IDREF element.
     */
    private Appender findAppenderByReference(Element appenderRef) {
        String appenderName = subst(appenderRef.getAttribute(REF_ATTR));
        Document doc = appenderRef.getOwnerDocument();
        return findAppenderByName(doc, appenderName);
    }

    /**
     * Used internally to parse an appender element.
     */
    private Appender parseAppender(Element appenderElement) {
        String className = subst(appenderElement.getAttribute(CLASS_ATTR));
        LOGGER.debug("Class name: [" + className + ']');
        Appender appender = manager.parseAppender(className, appenderElement, this);
        if (appender == null) {
            appender = buildAppender(className, appenderElement);
        }
        return appender;
    }

    private Appender buildAppender(String className, Element appenderElement) {
            try {
                Appender appender = LoaderUtil.newInstanceOf(className);
                PropertySetter propSetter = new PropertySetter(appender);

                appender.setName(subst(appenderElement.getAttribute(NAME_ATTR)));
                forEachElement(appenderElement.getChildNodes(), (currentElement) -> {
                    // Parse appender parameters
                    switch (currentElement.getTagName()) {
                        case PARAM_TAG:
                            setParameter(currentElement, propSetter);
                            break;
                        case LAYOUT_TAG:
                            appender.setLayout(parseLayout(currentElement));
                            break;
                        case FILTER_TAG:
                            Filter filter = parseFilters(currentElement);
                            if (filter != null) {
                                LOGGER.debug("Adding filter of type [{}] to appender named [{}]",
                                        filter.getClass(), appender.getName());
                                appender.addFilter(filter);
                            }
                            break;
                        case ERROR_HANDLER_TAG:
                            parseErrorHandler(currentElement, appender);
                            break;
                        case APPENDER_REF_TAG:
                            String refName = subst(currentElement.getAttribute(REF_ATTR));
                            if (appender instanceof AppenderAttachable) {
                                AppenderAttachable aa = (AppenderAttachable) appender;
                                Appender child = findAppenderByReference(currentElement);
                                LOGGER.debug("Attaching appender named [{}] to appender named [{}].", refName,
                                        appender.getName());
                                aa.addAppender(child);
                            } else {
                                LOGGER.error("Requesting attachment of appender named [{}] to appender named [{}}]"
                                                + "which does not implement org.apache.log4j.spi.AppenderAttachable.",
                                        refName, appender.getName());
                            }
                            break;
                        default:
                            try {
                                parseUnrecognizedElement(appender, currentElement, props);
                            } catch (Exception ex) {
                                throw new ConsumerException(ex);
                            }
                    }
                });
                propSetter.activate();
                return appender;
            } catch (ConsumerException ex) {
                Throwable t = ex.getCause();
                if (t instanceof InterruptedException || t instanceof InterruptedIOException) {
                    Thread.currentThread().interrupt();
                }
                LOGGER.error("Could not create an Appender. Reported error follows.", t);
            } catch (Exception oops) {
                if (oops instanceof InterruptedException || oops instanceof InterruptedIOException) {
                    Thread.currentThread().interrupt();
                }
                LOGGER.error("Could not create an Appender. Reported error follows.", oops);
            }
            return null;
        }

    /**
     * Used internally to parse an {@link ErrorHandler} element.
     */
    private void parseErrorHandler(Element element, Appender appender) {
        ErrorHandler eh = (ErrorHandler) OptionConverter.instantiateByClassName(
                subst(element.getAttribute(CLASS_ATTR)),
                ErrorHandler.class,
                null);

        if (eh != null) {
            eh.setAppender(appender);

            PropertySetter propSetter = new PropertySetter(eh);
            forEachElement(element.getChildNodes(), (currentElement) -> {
                String tagName = currentElement.getTagName();
                if (tagName.equals(PARAM_TAG)) {
                    setParameter(currentElement, propSetter);
                }
            });
            propSetter.activate();
            appender.setErrorHandler(eh);
        }
    }

    /**
     * Used internally to parse a filter element.
     */
    public Filter parseFilters(Element filterElement) {
        String className = subst(filterElement.getAttribute(CLASS_ATTR));
        LOGGER.debug("Class name: [" + className + ']');
        Filter filter = manager.parseFilter(className, filterElement, this);
        if (filter == null) {
            PropertySetter propSetter = new PropertySetter(filter);
            forEachElement(filterElement.getChildNodes(), (currentElement) -> {
                String tagName = currentElement.getTagName();
                if (tagName.equals(PARAM_TAG)) {
                    setParameter(currentElement, propSetter);
                } else {
                    quietParseUnrecognizedElement(filter, currentElement, props);
                }
            });
            propSetter.activate();
        }
        return filter;
    }

    /**
     * Used internally to parse an category element.
     */
    private void parseCategory(Element loggerElement) {
        // Create a new org.apache.log4j.Category object from the <category> element.
        String catName = subst(loggerElement.getAttribute(NAME_ATTR));
        boolean additivity = OptionConverter.toBoolean(subst(loggerElement.getAttribute(ADDITIVITY_ATTR)), true);
        LoggerConfig loggerConfig = configuration.getLogger(catName);
        if (loggerConfig == null) {
            loggerConfig = new LoggerConfig(catName, org.apache.logging.log4j.Level.ERROR, additivity);
            configuration.addLogger(catName, loggerConfig);
        } else {
            loggerConfig.setAdditive(additivity);
        }
        parseChildrenOfLoggerElement(loggerElement, loggerConfig, false);
    }

    /**
     * Used internally to parse the roor category element.
     */
    private void parseRoot(Element rootElement) {
        LoggerConfig root = configuration.getRootLogger();
        parseChildrenOfLoggerElement(rootElement, root, true);
    }

    /**
     * Used internally to parse the children of a LoggerConfig element.
     */
    private void parseChildrenOfLoggerElement(Element catElement, LoggerConfig loggerConfig, boolean isRoot) {

        final PropertySetter propSetter = new PropertySetter(loggerConfig);
        loggerConfig.getAppenderRefs().clear();
        forEachElement(catElement.getChildNodes(), (currentElement) -> {
            switch (currentElement.getTagName()) {
                case APPENDER_REF_TAG: {
                    Appender appender = findAppenderByReference(currentElement);
                    String refName = subst(currentElement.getAttribute(REF_ATTR));
                    if (appender != null) {
                        LOGGER.debug("Adding appender named [{}] to loggerConfig [{}].", refName,
                                loggerConfig.getName());
                        loggerConfig.addAppender(configuration.getAppender(refName), null, null);
                    } else {
                        LOGGER.debug("Appender named [{}}] not found.", refName);
                    }
                    break;
                }
                case LEVEL_TAG: case PRIORITY_TAG: {
                    parseLevel(currentElement, loggerConfig, isRoot);
                    break;
                }
                case PARAM_TAG: {
                    setParameter(currentElement, propSetter);
                    break;
                }
                default: {
                    quietParseUnrecognizedElement(loggerConfig, currentElement, props);
                }
            }
        });
        propSetter.activate();
    }

    /**
     * Used internally to parse a layout element.
     */
    public Layout parseLayout(Element layoutElement) {
        String className = subst(layoutElement.getAttribute(CLASS_ATTR));
        LOGGER.debug("Parsing layout of class: \"{}\"", className);
        Layout layout = manager.parseLayout(className, layoutElement, this);
        if (layout == null) {
            layout = buildLayout(className, layoutElement);
        }
        return layout;
    }

    private Layout buildLayout(String className, Element layout_element) {
        try {
            Layout layout = LoaderUtil.newInstanceOf(className);
            PropertySetter propSetter = new PropertySetter(layout);
            forEachElement(layout_element.getChildNodes(), (currentElement) -> {
                String tagName = currentElement.getTagName();
                if (tagName.equals(PARAM_TAG)) {
                    setParameter(currentElement, propSetter);
                } else {
                    try {
                        parseUnrecognizedElement(layout, currentElement, props);
                    } catch (Exception ex) {
                        throw new ConsumerException(ex);
                    }
                }
            });

            propSetter.activate();
            return layout;
        } catch (ConsumerException ce) {
            Throwable cause = ce.getCause();
            if (cause instanceof InterruptedException || cause instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            LOGGER.error("Could not create the Layout. Reported error follows.", cause);
        } catch (Exception oops) {
            if (oops instanceof InterruptedException || oops instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            LOGGER.error("Could not create the Layout. Reported error follows.", oops);
        }
        return null;
    }

    /**
     * Used internally to parse a level  element.
     */
    private void parseLevel(Element element, LoggerConfig logger, boolean isRoot) {
        String catName = logger.getName();
        if (isRoot) {
            catName = "root";
        }

        String priStr = subst(element.getAttribute(VALUE_ATTR));
        LOGGER.debug("Level value for {} is [{}}].", catName, priStr);

        if (INHERITED.equalsIgnoreCase(priStr) || NULL.equalsIgnoreCase(priStr)) {
            if (isRoot) {
                LOGGER.error("Root level cannot be inherited. Ignoring directive.");
            } else {
                logger.setLevel(null);
            }
        } else {
            String className = subst(element.getAttribute(CLASS_ATTR));
            if (EMPTY_STR.equals(className)) {
                logger.setLevel(convertLevel(OptionConverter.toLevel(priStr, Level.DEBUG)));
            } else {
                LOGGER.debug("Desired Level sub-class: [{}]", className);
                try {
                    Class<?> clazz = LoaderUtil.loadClass(className);
                    Method toLevelMethod = clazz.getMethod("toLevel", ONE_STRING_PARAM);
                    Level pri = (Level) toLevelMethod.invoke(null, new Object[]{priStr});
                    logger.setLevel(convertLevel(pri));
                } catch (Exception oops) {
                    if (oops instanceof InterruptedException || oops instanceof InterruptedIOException) {
                        Thread.currentThread().interrupt();
                    }
                    LOGGER.error("Could not create level [" + priStr +
                            "]. Reported error follows.", oops);
                    return;
                }
            }
        }
        LOGGER.debug("{} level set to {}", catName,  logger.getLevel());
    }

    private void setParameter(Element elem, PropertySetter propSetter) {
        String name = subst(elem.getAttribute(NAME_ATTR));
        String value = (elem.getAttribute(VALUE_ATTR));
        value = subst(OptionConverter.convertSpecialChars(value));
        propSetter.setProperty(name, value);
    }

    /**
     * Configure log4j by reading in a log4j.dtd compliant XML
     * configuration file.
     */
    private void doConfigure() throws FactoryConfigurationError {
        ConfigurationSource source = configuration.getConfigurationSource();
        ParseAction action = new ParseAction() {
            public Document parse(final DocumentBuilder parser) throws SAXException, IOException {
                InputSource inputSource = new InputSource(source.getInputStream());
                inputSource.setSystemId("dummy://log4j.dtd");
                return parser.parse(inputSource);
            }

            public String toString() {
                return configuration.getConfigurationSource().getLocation();
            }
        };
        doConfigure(action);
    }

    private void doConfigure(final ParseAction action) throws FactoryConfigurationError {
        DocumentBuilderFactory dbf;
        try {
            LOGGER.debug("System property is : {}", OptionConverter.getSystemProperty(dbfKey, null));
            dbf = DocumentBuilderFactory.newInstance();
            LOGGER.debug("Standard DocumentBuilderFactory search succeded.");
            LOGGER.debug("DocumentBuilderFactory is: " + dbf.getClass().getName());
        } catch (FactoryConfigurationError fce) {
            Exception e = fce.getException();
            LOGGER.debug("Could not instantiate a DocumentBuilderFactory.", e);
            throw fce;
        }

        try {
            dbf.setValidating(true);

            DocumentBuilder docBuilder = dbf.newDocumentBuilder();

            docBuilder.setErrorHandler(new SAXErrorHandler());
            docBuilder.setEntityResolver(new Log4jEntityResolver());

            Document doc = action.parse(docBuilder);
            parse(doc.getDocumentElement());
        } catch (Exception e) {
            if (e instanceof InterruptedException || e instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            // I know this is miserable...
            LOGGER.error("Could not parse " + action.toString() + ".", e);
        }
    }

    @Override
    public void doConfigure(InputStream inputStream, LoggerContext loggerContext) {
        try {
            ConfigurationSource source = new ConfigurationSource(inputStream);
            configuration = new Log4j1Configuration(loggerContext, source, 0);
            doConfigure();
        } catch (IOException ioe) {
            LOGGER.error("Unable to process configuration due to {}",  ioe.getMessage());
        }
    }

    @Override
    public void doConfigure(URL url, LoggerContext loggerContext) {
        try {
            ConfigurationSource source = new ConfigurationSource(url.openStream(), url);
            configuration = new Log4j1Configuration(loggerContext, source, 0);
            doConfigure();
        } catch (IOException ioe) {
            LOGGER.error("Unable to process configuration due to {}",  ioe.getMessage());
        }
    }

    /**
     * Used internally to configure the log4j framework by parsing a DOM
     * tree of XML elements based on <a
     * href="doc-files/log4j.dtd">log4j.dtd</a>.
     */
    private void parse(Element element) {
        String rootElementName = element.getTagName();

        if (!rootElementName.equals(CONFIGURATION_TAG)) {
            if (rootElementName.equals(OLD_CONFIGURATION_TAG)) {
                LOGGER.warn("The <" + OLD_CONFIGURATION_TAG +
                        "> element has been deprecated.");
                LOGGER.warn("Use the <" + CONFIGURATION_TAG + "> element instead.");
            } else {
                LOGGER.error("DOM element is - not a <" + CONFIGURATION_TAG + "> element.");
                return;
            }
        }


        String debugAttrib = subst(element.getAttribute(INTERNAL_DEBUG_ATTR));

        LOGGER.debug("debug attribute= \"" + debugAttrib + "\".");
        // if the log4j.dtd is not specified in the XML file, then the
        // "debug" attribute is returned as the empty string.
        String status = "error";
        if (!debugAttrib.equals("") && !debugAttrib.equals("null")) {
            status = OptionConverter.toBoolean(debugAttrib, true) ? "debug" : "error";

        } else {
            LOGGER.debug("Ignoring " + INTERNAL_DEBUG_ATTR + " attribute.");
        }

        String confDebug = subst(element.getAttribute(CONFIG_DEBUG_ATTR));
        if (!confDebug.equals("") && !confDebug.equals("null")) {
            LOGGER.warn("The \"" + CONFIG_DEBUG_ATTR + "\" attribute is deprecated.");
            LOGGER.warn("Use the \"" + INTERNAL_DEBUG_ATTR + "\" attribute instead.");
            status = OptionConverter.toBoolean(confDebug, true) ? "debug" : "error";
        }

        final StatusConfiguration statusConfig = new StatusConfiguration().setStatus(status);
        statusConfig.initialize();

        forEachElement(element.getChildNodes(), (currentElement) -> {
            switch (currentElement.getTagName()) {
                case CATEGORY: case LOGGER_ELEMENT:
                    parseCategory(currentElement);
                    break;
                case ROOT_TAG:
                    parseRoot(currentElement);
                    break;
                case RENDERER_TAG:
                    LOGGER.warn("Renderers are not supported by Log4j 2 and will be ignored.");
                    break;
                case THROWABLE_RENDERER_TAG:
                    LOGGER.warn("Throwable Renderers are not supported by Log4j 2 and will be ignored.");
                    break;
                case CATEGORY_FACTORY_TAG: case LOGGER_FACTORY_TAG:
                    LOGGER.warn("Log4j 1 Logger factories are not supported by Log4j 2 and will be ignored.");
                    break;
                case APPENDER_TAG:
                    Appender appender = parseAppender(currentElement);
                    appenderBag.put(appender.getName(), appender);
                    if (appender instanceof AppenderWrapper) {
                        configuration.addAppender(((AppenderWrapper) appender).getAppender());
                    } else {
                        configuration.addAppender(new AppenderAdapter(appender).getAdapter());
                    }
                    break;
                default:
                    quietParseUnrecognizedElement(null, currentElement, props);
            }
        });
    }

    private org.apache.logging.log4j.Level convertLevel(Level level) {
        if (level == null) {
            return org.apache.logging.log4j.Level.ERROR;
        }
        if (level.isGreaterOrEqual(Level.FATAL)) {
            return org.apache.logging.log4j.Level.FATAL;
        } else if (level.isGreaterOrEqual(Level.ERROR)) {
            return org.apache.logging.log4j.Level.ERROR;
        } else if (level.isGreaterOrEqual(Level.WARN)) {
            return org.apache.logging.log4j.Level.WARN;
        } else if (level.isGreaterOrEqual(Level.INFO)) {
            return org.apache.logging.log4j.Level.INFO;
        } else if (level.isGreaterOrEqual(Level.DEBUG)) {
            return org.apache.logging.log4j.Level.DEBUG;
        } else if (level.isGreaterOrEqual(Level.TRACE)) {
            return org.apache.logging.log4j.Level.TRACE;
        }
        return org.apache.logging.log4j.Level.ALL;
    }

    private String subst(final String value) {
        return configuration.getStrSubstitutor().replace(value);
    }

    public static void forEachElement(NodeList list, Consumer<Element> consumer) {
        final int length = list.getLength();
        for (int loop = 0; loop < length; loop++) {
            Node currentNode = list.item(loop);

            if (currentNode.getNodeType() == Node.ELEMENT_NODE) {
                Element currentElement = (Element) currentNode;
                consumer.accept(currentElement);
            }
        }
    }

    private interface ParseAction {
        Document parse(final DocumentBuilder parser) throws SAXException, IOException;
    }

    private static class SAXErrorHandler implements org.xml.sax.ErrorHandler {
        private static final org.apache.logging.log4j.Logger LOGGER = StatusLogger.getLogger();

        public void error(final SAXParseException ex) {
            emitMessage("Continuable parsing error ", ex);
        }

        public void fatalError(final SAXParseException ex) {
            emitMessage("Fatal parsing error ", ex);
        }

        public void warning(final SAXParseException ex) {
            emitMessage("Parsing warning ", ex);
        }

        private static void emitMessage(final String msg, final SAXParseException ex) {
            LOGGER.warn("{} {} and column {}", msg, ex.getLineNumber(), ex.getColumnNumber());
            LOGGER.warn(ex.getMessage(), ex.getException());
        }
    }

    private static class ConsumerException extends RuntimeException {

        ConsumerException(Exception ex) {
            super(ex);
        }
    }
}