// XmlApp.java: base class for Æfred demos.
// NO WARRANTY! See README, and copyright below.
// $Id$
// Modified 11/8/98 to add package statement.
package com.microstar.xml.demo;

import java.net.MalformedURLException;
import java.net.URL;

import com.microstar.xml.XmlHandler;
import com.microstar.xml.XmlParser;

/**
 * Base class for Ælfred demonstration applications.
 * <p>This class fills in the basic interface, and provides
 * an I/O infrastructure for simple applications and applets.
 * @author Copyright (c) 1997, 1998 by Microstar Software Ltd.;
 * @author written by David Megginson &lt;dmeggins@microstar.com&gt;
 * @version 1.1
 * @since Ptolemy II 0.2
 * @see com.microstar.xml.XmlParser
 * @see com.microstar.xml.XmlHandler
 * @see EventDemo
 * @see TimerDemo
 * @see DtdDemo
 * @see StreamDemo
 */
public class XmlApp implements XmlHandler {
    /**
     * Flag to show whether we're running as an applet or application.
     */
    public boolean isApplet = false;

    public XmlParser parser;

    //////////////////////////////////////////////////////////////////////
    // Implementation of XmlParser interface.
    //
    // The following methods provide a full skeleton implementation of the
    // XmlHandler interface, so that subclasses can override only
    // the methods they need.
    //////////////////////////////////////////////////////////////////////

    /**
     * Resolve an external entity.
     * <p>This method could generate a new URL by looking up the
     * public identifier in a hash table, or it could replace the
     * URL supplied with a different, local one; for now, however,
     * just return the URL supplied.
     * @see com.microstar.xml.XmlHandler#resolveEntity
     */
    @Override
    public Object resolveEntity(String publicId, String systemId) {
        return null;
    }

    @Override
    public void startExternalEntity(String systemId) {
    }

    @Override
    public void endExternalEntity(String systemId) {
    }

    /**
     * Handle the start of the document.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * <p>This method will always be called first.
     * @see com.microstar.xml.XmlHandler#startDocument
     */
    @Override
    public void startDocument() {
    }

    /**
     * Handle the end the document.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * <p>This method will always be called last.
     * @see com.microstar.xml.XmlHandler#endDocument
     */
    @Override
    public void endDocument() {
    }

    /**
     * Handle a DOCTYPE declaration.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * <p>Well-formed XML documents might not have one of these.
     * <p>The query methods in XmlParser will return useful
     * values only after this callback.
     * @see com.microstar.xml.XmlHandler#doctypeDecl
     */
    @Override
    public void doctypeDecl(String name, String pubid, String sysid) {
    }

    /**
     * Handle an attribute value specification.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * @see com.microstar.xml.XmlHandler#attribute
     */
    @Override
    public void attribute(String name, String value, boolean isSpecified) {
    }

    /**
     * Handle the start of an element.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * @see com.microstar.xml.XmlHandler#startElement
     */
    @Override
    public void startElement(String name) {
    }

    /**
     * Handle the end of an element.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * @see com.microstar.xml.XmlHandler#endElement
     */
    @Override
    public void endElement(String name) {
    }

    /**
     * Handle character data.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * @see com.microstar.xml.XmlHandler#charData
     */
    @Override
    public void charData(char[] ch, int start, int length) {
    }

    /**
     * Handle ignorable whitespace.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * @see com.microstar.xml.XmlHandler#ignorableWhitespace
     */
    @Override
    public void ignorableWhitespace(char[] ch, int start, int length) {
    }

    /**
     * Handle a processing instruction.
     * <p>Do nothing for now.  Subclasses can override this method
     * if they want to take a specific action.
     * @see com.microstar.xml.XmlHandler#processingInstruction
     */
    @Override
    public void processingInstruction(String target, String data) {
    }

    /**
     * Handle a parsing error.
     * <p>By default, print a message and throw an Error.
     * <p>Subclasses can override this method if they want to do something
     * different.
     * @see com.microstar.xml.XmlHandler#error
     */
    @Override
    public void error(String message, String url, int line, int column) {
        displayText("FATAL ERROR: " + message);
        displayText("  at " + url + ": line " + line + " column " + column);
        throw new Error(message);
    }

    //////////////////////////////////////////////////////////////////////
    // General utility methods.
    //////////////////////////////////////////////////////////////////////

    /**
     * Start a parse in application mode.
     * <p>Output will go to STDOUT.
     * @see #displayText(String)
     * @see com.microstar.xml.XmlParser#parse(String, String, String)
     */
    void doParse(String url) throws java.lang.Exception {
        /* String docURL = */makeAbsoluteURL(url);

        // create the parser
        parser = new XmlParser();
        parser.setHandler(this);
        parser.parse(makeAbsoluteURL(url), null, (String) null);
    }

    static String makeAbsoluteURL(String url) throws MalformedURLException {
        URL baseURL;

        String currentDirectory = System.getProperty("user.dir");

        String fileSep = System.getProperty("file.separator");
        String file = currentDirectory.replace(fileSep.charAt(0), '/') + '/';

        if (file.charAt(0) != '/') {
            file = "/" + file;
        }

        baseURL = new URL("file", null, file);
        return new URL(baseURL, url).toString();
    }

    /**
     * Display text on STDOUT or in an applet TextArea.
     */
    void displayText(String text) {
        System.out.println(text);
    }

    /**
     * Escape a string for printing.
     */
    String escape(char[] ch, int length) {
        StringBuffer out = new StringBuffer();

        for (int i = 0; i < length; i++) {
            switch (ch[i]) {
            case '\\':
                out.append("\\\\");
                break;

            case '\n':
                out.append("\\n");
                break;

            case '\t':
                out.append("\\t");
                break;

            case '\r':
                out.append("\\r");
                break;

            case '\f':
                out.append("\\f");
                break;

            default:
                out.append(ch[i]);
                break;
            }
        }

        return out.toString();
    }
}

// end of XmlApp.java