/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */


package javax.xml.parsers;

import java.io.InputStream;
import java.io.IOException;
import java.io.File;
import java.io.FileInputStream;

import java.util.Properties;
import java.io.BufferedReader;
import java.io.InputStreamReader;

/**
 * Defines a factory API that enables applications to obtain a
 * parser that produces DOM object trees from XML documents.
 *
 * @since JAXP 1.0
 * @version 1.0
 * @author Rajiv Mordani
 * @author James Davidson
 */

public abstract class DocumentBuilderFactory {
    /** The default property name according to the JAXP spec */
    private static final String defaultPropName =
        "javax.xml.parsers.DocumentBuilderFactory";

    private boolean validating = false;
    private boolean namespaceAware = false;
    private boolean whitespace = false;
    private boolean expandEntityRef = true;
    private boolean ignoreComments = false;
    private boolean coalescing = false;
    
    protected DocumentBuilderFactory () {
    
    }

    /**
     * Obtain a new instance of a
     * <code>DocumentBuilderFactory</code>. This static method creates
     * a new factory instance.
     * This method uses the following ordered lookup procedure to determine
     * the <code>DocumentBuilderFactory</code> implementation class to
     * load:
     * <ul>
     * <li>
     * Use the <code>javax.xml.parsers.DocumentBuilderFactory</code> system
     * property.
     * </li>
     * <li>
     * Use the JAVA_HOME(the parent directory where jdk is
     * installed)/lib/jaxp.properties for a property file that contains the
     * name of the implementation class keyed on the same value as the
     * system property defined above.
     * </li>
     * <li>
     * Use the Services API (as detailed in teh JAR specification), if
     * available, to determine the classname. The Services API will look
     * for a classname in the file
     * <code>META-INF/services/javax.xml.parsers.DocumentBuilderFactory</code>
     * in jars available to the runtime.
     * </li>
     * <li>
     * Platform default <code>DocumentBuilderFactory</code> instance.
     * </li>
     * </ul>
     *
     * Once an application has obtained a reference to a
     * <code>DocumentBuilderFactory</code> it can use the factory to
     * configure and obtain parser instances.
     *
     * @exception FactoryConfigurationError if the implementation is not
     * available or cannot be instantiated.
     */    
    
    public static DocumentBuilderFactory newInstance() {
        String factoryImplName = findFactory(defaultPropName,
                                             "org.apache.crimson.jaxp.DocumentBuilderFactoryImpl");
        // the default can be removed after services are tested well enough

        if (factoryImplName == null) {
            throw new FactoryConfigurationError(
                "No default implementation found");
        }

        DocumentBuilderFactory factoryImpl;
        try {
            Class clazz = getClassForName(factoryImplName);
            factoryImpl = (DocumentBuilderFactory)clazz.newInstance();
        } catch  (ClassNotFoundException cnfe) {
            throw new FactoryConfigurationError(cnfe);
        } catch (IllegalAccessException iae) {
            throw new FactoryConfigurationError(iae);
        } catch (InstantiationException ie) {
            throw new FactoryConfigurationError(ie);
        }
        return factoryImpl;
    }

    /** a zero length Object array used in getClassForName() */
    private static final Object NO_OBJS[] = new Object[0];
    /** the Method object for getContextClassLoader */
    private static java.lang.reflect.Method getCCL;
    
    static {
	try { 
	    getCCL = Thread.class.getMethod("getContextClassLoader",
					    new Class[0]);
	} catch (Exception e) {
	    getCCL = null;
	}
    }
    
    private static Class getClassForName(String className )
        throws ClassNotFoundException
    {
	if (getCCL != null) {
	    try {
		ClassLoader contextClassLoader =
		    (ClassLoader) getCCL.invoke(Thread.currentThread(),
						NO_OBJS);
		return contextClassLoader.loadClass(className);
	    } catch (ClassNotFoundException cnfe) {
		// nothing, try again with Class.forName 
	    } catch (Exception e) {
		getCCL = null; // don't try again
		// fallback
	    }
	}
	
	return Class.forName(className);
    }

    
    /**
     * Creates a new instance of a DocumentBuilder using the
     * currently configured parameters.
     *
     * @exception ParserConfigurationException if a DocumentBuilder
     * cannot be created which satisfies the configuration requested
     */
    
    public abstract DocumentBuilder newDocumentBuilder()
        throws ParserConfigurationException;
    
    
    /**
     * Specifies that the parser produced by this code will
     * provide support for XML namespaces. By default the value of this is set 
     * to <code>false</code>
     */
    
    public void setNamespaceAware(boolean awareness) {
        this.namespaceAware = awareness;
    }

    /**
     * Specifies that the parser produced by this code will
     * validate documents as they are parsed. By default the value of this
     * is set to <code>false</code>
     */
    
    public void setValidating(boolean validating) {
        this.validating = validating;
    }

    /**
     * Specifies that the parsers created by this  factory must eliminate
     * whitespace in element content (sometimes known loosely as 
     * 'ignorable whitespace') when parsing XML documents (see XML Rec
     * 2.10). Note that only whitespace which is directly contained within
     * element content that has an element only content model (see XML
     * Rec 3.2.1) will be eliminated. Due to reliance on the content model
     * this setting requires the parser to be in validating mode. By default 
     * the value of this is set to <code>false</code>
     */

    public void setIgnoringElementContentWhitespace(boolean whitespace) {
        this.whitespace = whitespace;
    }

    /**
     * Specifies that the parser produced by this code will
     * expand entity reference nodes. By default the value of this is set to 
     * <code>true</code>
     */
    
    public void setExpandEntityReferences(boolean expandEntityRef) {
        this.expandEntityRef = expandEntityRef;
    }

    /**
     * Specifies that the parser produced by this code will
     * ignore comments. By default the value of this is set to <code>false
     * </code>
     */
    
    public void setIgnoringComments(boolean ignoreComments) {
        this.ignoreComments = ignoreComments;
    }

    /**
     * Specifies that the parser produced by this code will
     * convert CDATA nodes to Text nodes and append it to the 
     * adjacent (if any) text node. By default the value of this is set to 
     * <code>false</code>
     */
    
    public void setCoalescing(boolean coalescing) {
        this.coalescing = coalescing;
    }

    /**
     * Indicates whether or not the factory is configured to produce
     * parsers which are namespace aware.
     */
    
    public boolean isNamespaceAware() {
        return namespaceAware;
    }

    /**
     * Indicates whether or not the factory is configured to produce
     * parsers which validate the XML content during parse.
     */
    
    public boolean isValidating() {
        return validating;
    }

    /**
     * Indicates whether or not the factory is configured to produce
     * parsers which ignore ignorable whitespace in element content.
     */
    
    public boolean isIgnoringElementContentWhitespace() {
        return whitespace;
    }

    /**
     * Indicates whether or not the factory is configured to produce
     * parsers which expand entity reference nodes.
     */
    
    public boolean isExpandEntityReferences() {
        return expandEntityRef;
    }

    /**
     * Indicates whether or not the factory is configured to produce
     * parsers which ignores comments.
     */
    
    public boolean isIgnoringComments() {
        return ignoreComments;
    }

    /**
     * Indicates whether or not the factory is configured to produce
     * parsers which converts CDATA nodes to Text nodes and appends it to
     * the adjacent (if any) Text node.
     */
    
    public boolean isCoalescing() {
        return coalescing;
    }

    /**
     * Allows the user to set specific attributes on the underlying 
     * implementation.
     * @param name The name of the attribute.
     * @param value The value of the attribute.
     * @exception IllegalArgumentException thrown if the underlying 
     * implementation doesn't recognize the attribute.
     */
    public abstract void setAttribute(String name, Object value) 
                        throws IllegalArgumentException;

    /**
     * Allows the user to retrieve specific attributes on the underlying 
     * implementation.
     * @param name The name of the attribute.
     * @return value The value of the attribute.
     * @exception IllegalArgumentException thrown if the underlying 
     * implementation doesn't recognize the attribute.
     */
    public abstract Object getAttribute(String name)
                        throws IllegalArgumentException;
    
    // -------------------- private methods --------------------
    // This code is duplicated in all factories.
    // Keep it in sync or move it to a common place 
    // Because it's small probably it's easier to keep it here
    /** Avoid reading all the files when the findFactory
        method is called the second time ( cache the result of
        finding the default impl )
    */
    private static String foundFactory=null;

    /** Temp debug code - this will be removed after we test everything
     */
    private static boolean debug=false;
    static {
	try {
	    debug=System.getProperty( "jaxp.debug" ) != null;
	} catch(SecurityException se ) {}
    }

    /** Private implementation method - will find the implementation
        class in the specified order.
        @param factoryId   Name of the factory interface
        @param xmlProperties Name of the properties file based on JAVA/lib
        @param defaultFactory Default implementation, if nothing else is found
    */
    private static String findFactory(String factoryId, 
                                      String defaultFactory)
    {
        // Use the system property first
        try {
            String systemProp =
                System.getProperty( factoryId );
            if( systemProp!=null) {
                if( debug ) 
                    System.err.println("JAXP: found system property" +
                                       systemProp );
                return systemProp;
            }
            
        }catch (SecurityException se) {
        }

        if( foundFactory!=null)
            return foundFactory;
        
        // try to read from $java.home/lib/xml.properties
        try {
            String javah=System.getProperty( "java.home" );
            String configFile = javah + File.separator +
                "lib" + File.separator + "jaxp.properties";
            File f=new File( configFile );
            if( f.exists()) {
                Properties props=new Properties();
                props.load( new FileInputStream(f));
                foundFactory=props.getProperty( factoryId );
                if( debug )
                    System.err.println("JAXP: found java.home property " +
                                       foundFactory );
                if(foundFactory!=null )
                    return foundFactory;
            }
        } catch(Exception ex ) {
            if( debug ) ex.printStackTrace();
        }

        String serviceId = "META-INF/services/" + factoryId;
        // try to find services in CLASSPATH
        try {
            ClassLoader cl=DocumentBuilderFactory.class.getClassLoader();
            InputStream is=null;
            if( cl == null ) {
                is=ClassLoader.getSystemResourceAsStream( serviceId );
            } else {
                is=cl.getResourceAsStream( serviceId );
            }
            
            if( is!=null ) {
                if( debug )
                    System.err.println("JAXP: found  " +
                                       serviceId);
                BufferedReader rd=new BufferedReader( new
                    InputStreamReader(is));
                
                foundFactory=rd.readLine();
                rd.close();

                if( debug )
                    System.err.println("JAXP: loaded from services: " +
                                       foundFactory );
                if( foundFactory != null &&
                    !  "".equals( foundFactory) ) {
                    return foundFactory;
                }
            }
        } catch( Exception ex ) {
            if( debug ) ex.printStackTrace();
        }

        return defaultFactory;
    }

}