Configuration.java

/*
 * @(#)Configuration.java
 *
 * This work is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This work 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 for more details.
 *
 * Copyright (c) 2003 Per Cederberg. All rights reserved.
 */

package net.percederberg.tetris;

import java.awt.Color;
import java.util.Hashtable;

/**
 * A program configuration. This class provides static methods for 
 * simplifying the reading of configuration parameters. It also 
 * provides some methods for transforming string values into more 
 * useful objects.
 * 
 * @author   Per Cederberg, per@percederberg.net
 * @version  1.2
 */
public class Configuration extends Object {

    /**
     * The internal configuration property values. This lookup table
     * is used to avoid setting configuration parameters in the system 
     * properties, as some programs (applets) do not have the security
     * permissions to set system properties.
     */
    private static Hashtable  config = new Hashtable();

    /**
     * Returns a configuration parameter value.
     * 
     * @param key       the configuration parameter key
     * 
     * @return the configuration parameter value, or
     *         null if not set
     */
    public static String getValue(String key) {
        if (config.containsKey(key)) {
            return config.get(key).toString();
        } else {
            try {
                return System.getProperty(key);
            } catch (SecurityException ignore) {
                return null;
            }
        }
    }
    
    /**
     * Returns a configuration parameter value. If the configuration
     * parameter is not set, a default value will be returned instead.
     * 
     * @param key       the configuration parameter key
     * @param def       the default value to use
     * 
     * @return the configuration parameter value, or
     *         the default value if not set
     */
    public static String getValue(String key, String def) {
        String  value = getValue(key);
        
        return (value == null) ? def : value;
    }

    /**
     * Sets a configuration parameter value.
     * 
     * @param key       the configuration parameter key
     * @param value     the configuration parameter value
     */
    public static void setValue(String key, String value) {
        config.put(key, value);
    }

    /**
     * Returns the color configured for the specified key. The key 
     * will be prepended with "tetris.color." and the value will be
     * read from the system properties. The color value must be 
     * specified in hexadecimal web format, i.e. in the "#RRGGBB" 
     * format. If the default color isn't in a valid format, white 
     * will be returned.
     * 
     * @param key       the configuration parameter key
     * @param def       the default value
     * 
     * @return the color specified in the configuration, or 
     *         a default color value
     */
    public static Color getColor(String key, String def) {
        String  value = getValue("tetris.color." + key, def);
        Color   color;
        
        color = parseColor(value);
        if (color != null) {
            return color;
        }
        color = parseColor(def);
        if (color != null) {
            return color;
        } else {
            return Color.white;
        }
    }
    
    /**
     * Parses a web color string. If the color value couldn't be 
     * parsed correctly, null will be returned.
     * 
     * @param value     the color value to parse
     * 
     * @return the color represented by the string, or
     *         null if the string was malformed
     */
    private static Color parseColor(String value) {
        if (!value.startsWith("#")) {
            return null;
        }
        try {
            return new Color(Integer.parseInt(value.substring(1), 16));
        } catch (NumberFormatException ignore) {
            return null;
        }
    }
}