package edu.princeton.toy;

import java.awt.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;

import javax.swing.*;

/**
 * TResourceLoader is a convenient library of functions which allow the other classes to easily
 * access resources from within the JAR file.  In centralizing all resource loading, we also give
 * ourselves the ability to change the implementation easily.
 */

public abstract class TResourceLoader
{
    private static Class ANCHOR_CLASS;

    /**
     * The class for the ResourceAnchor.
     */
    static {
        try
        {
            ANCHOR_CLASS = Class.forName("ResourceAnchor");
        }
        catch (ClassNotFoundException e)
        {
            e.printStackTrace();

            JOptionPane.showMessageDialog(
                null,
                "The resource loader cannot load any of Visual X-TOY's resources because your " +
                "JVM does not comply with the Java specification.",
                "JVM Error",
                JOptionPane.ERROR_MESSAGE
                );

            System.exit(-1);
        }
    }

    private static final Toolkit TOOLKIT = Toolkit.getDefaultToolkit();
    private static final ClassLoader LOADER = ANCHOR_CLASS.getClassLoader();

    /**
     * Returns the URL object for a JARed resource.
     *
     * @param path The path of the resource relative to the root of the JAR archive.
     * @return The URL corresponding to the JARed resource.
     */
    public static URL getUrl(String path)
    {
        if (path == null)
            throw new NullPointerException();

        return LOADER.getResource(path);
    }

    /**
     * Returns the Image object for a JARed picture.
     *
     * @param path The path of the picture relative to the root of the JAR archive.
     * @return The Image corresponding to the JARed picture.
     */
    public static Image getImage(String path)
    {
        if (path == null)
            throw new NullPointerException();

        return TOOLKIT.getImage(LOADER.getResource(path));
    }

    /**
     * Returns the InputStream object for a JARed file.
     *
     * @param path The path of the file relative to the root of the JAR archive.
     * @return The InputStream which reads from that file.
     */
    public static InputStream getInputStream(String path) throws IOException
    {
        if (path == null)
            throw new NullPointerException();

        return LOADER.getResource(path).openStream();
    }

    /**
     * Returns the Reader object for a JARed file.
     *
     * @param path The path of the file relative to the root of the JAR archive.
     * @return The Reader which reads from that file.
     */
    public static Reader getReader(String path) throws IOException
    {
        if (path == null)
            throw new NullPointerException();

        return new InputStreamReader(LOADER.getResource(path).openStream());
    }

    /**
     * Returns the BufferedReader object for a JARed file.
     *
     * @param path The path of the file relative to the root of the JAR archive.
     * @return The BufferedReader which reads from that file.
     */
    public static BufferedReader getBufferedReader(String path) throws IOException
    {
        if (path == null)
            throw new NullPointerException();

        return new BufferedReader(new InputStreamReader(LOADER.getResource(path).openStream()));
    }
}