// ObservableProperties.java
// $Id: ObservableProperties.java,v 1.3 1996/12/27 13:30:56 abaird Exp $
// (c) COPYRIGHT MIT and INRIA, 1996.
// Please first read the full copyright statement in file COPYRIGHT.html

package w3c.util;

import java.util.* ;
import java.io.File ;

/**
 * An enhanced property class that provides support to monitor changes.
 * This class extends the basic properties class of Java, by providing
 * monitoring support. It also provides more type conversion.
 * @see PropertyMonitoring
 */

public class ObservableProperties extends Properties {
    private static final boolean debug = false;

    PropertyMonitoring observers[]     = null ;
    int                observers_count = 0 ;

    /**
     * Subscribe for property monitoring.
     * @param observer The object that handles the PropertyMonitoring 
     *    interface.
     */
    
    public synchronized void registerObserver (PropertyMonitoring o) {
	// Try looking for an empty slot:
	for (int i = 0 ; i < observers.length ; i++) {
	    if ( observers[i] == null ) {
		observers[i] = o ;
		return ;
	    }
	}
	// Add the observer to the registered oned, resizing array if needed
	if ( observers_count + 1 >= observers.length ) {
	    PropertyMonitoring m[]=new PropertyMonitoring[observers.length*2];
	    System.arraycopy (observers, 0, m, 0, observers.length) ;
	    observers = m ;
	}
	observers[observers_count++] = o;
    }

    /**
     * Unsubscribe this object from the observers list.
     * @param observer The observer to unsubscribe.
     * @return A boolean <strong>true</strong> if object was succesfully 
     *     unsubscribed, <strong>false</strong> otherwise.
     */

    public synchronized boolean unregisterObserver (PropertyMonitoring o) {
	for (int i = 0 ; i < observers.length ; i++) {
	    if ( observers[i] == o ) {
		observers[i] = null ;
		return true ;
	    }
	}
	return false ;
    }
		
    /**
     * Update a property value.
     * Assign a value to a property. If the property value has really changed
     * notify our observers of the change.
     * @param name The name of the property to assign.
     * @param value The new value for this property, or <strong>null</strong>
     *    if the property setting is to be cancelled.
     * @return A boolean <strong>true</strong> if change was accepted by 
     *    our observers, <strong>false</strong> otherwise.
     */
    
    public synchronized boolean putValue (String name, String value) {
	if ( debug )
	    System.out.println("ObservableProperties: put "+name+"="+value);
	// If null value, remove the prop definition:
	if ( value == null ) {
	    super.remove(name) ;
	    return true ;
	}
	// Otherwise, proceed:
	String old = (String) get (value) ;
	if ( (old == null) || (!  old.equals (value)) ) {
	    super.put (name, value) ;
	    for (int i = 0 ; i < observers.length ; i++) {
		if ( observers[i] == null )
		    continue ;
		if ( debug )
		    System.out.println("ObservableProperties: notifies "
				       + observers[i]);
		if ( ! observers[i].propertyChanged (name) ) {
		    if ( old != null )
			super.put (name, old) ;
		    return false ;
		}
	    }
	}
	return true ;
    }
    
    /**
     * Get this property value, as a boolean.
     * @param name The name of the property to be fetched.
     * @param def The default value, if the property isn't defined.
     * @return A Boolean instance.
     */

    public boolean getBoolean(String name, boolean def) {
	String v = getProperty(name, null);
	if ( v != null )
	    return "true".equalsIgnoreCase(v) ? true : false ;
	return def ;
    }

    /**
     * Get this property value, as a String.
     * @param name The name of the property to be fetched.
     * @param def The default value, if the property isn't defined.
     * @return An instance of String.
     */

    public String getString(String name, String def) {
	String v = getProperty (name, null);
	if ( v != null )
	    return v ;
	return def ;
    }

    /**
     * Get this property as a String array.
     * By convention, properties that are get as string arrays should be
     * encoded as a <strong>|</strong> separated list of Strings.
     * @param name The property's name.
     * @param def The default value (if undefined).
     * @return A String array, or <strong>null</strong> if the property
     * is undefined.
     */

    public String[] getStringArray(String name, String def[]) {
	String v = getProperty(name, null);
	if ( v == null )
	    return def;
	// Parse the property value:
	StringTokenizer st    = new StringTokenizer(v, "|");
	int             len   = st.countTokens();
	String          ret[] = new String[len];
	for (int i = 0 ; i < ret.length ; i++) {
	    ret[i] = st.nextToken();
	}
	return ret;
    }

    /**
     * Get this property value, as an integer.
     * @param name The name of the property to be fetched.
     * @param def The default value, if the property isn't defined.
     * @return An integer value.
     */

    public int getInteger(String name, int def) {
	String v = getProperty (name, null);
	if ( v != null ) {
	    try {
		if (v.startsWith("0x")) {
		    return Integer.valueOf(v.substring(2), 16).intValue();
		}
		if (v.startsWith("#")) {
		    return Integer.valueOf(v.substring(1), 16).intValue();
		}
		return Integer.valueOf(v).intValue();
	    } catch (NumberFormatException e) {
	    }
	}
	return def ;
    }

    /**
     * Get this property value, as a double.
     * @param name The name of the property.
     * @param def The default value if undefined.
     * @return A double value.
     */

    public double getDouble(String name, double def) {
	String v = getProperty(name, null);
	if ( v != null ) {
	    try {
		return Double.valueOf(v).doubleValue();
	    } catch (NumberFormatException ex) {
	    }
	}
	return def;
    }

    /**
     * Get this property value, as a File.
     * @param name The name of the property to be fetched.
     * @param def The default value, if the property isn't defined.
     * @return An instance of File.
     */

    public File getFile(String name, File def) {
	String v = getProperty(name, null);
	if ( v != null )
	    return new File (v) ;
	return def ;
    }

    /**
     * Build an httpdProperties instance from a Properties instance.
     * @param props The Properties instance.
     */

    public ObservableProperties(Properties props) {
	super (props) ;
	this.observers       = new PropertyMonitoring[5] ;
	this.observers_count = 0 ;
    }
   
}

 
