/*

* Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:

*

*/

package com.nokia.mj.impl.rt;

import java.util.Hashtable;

import com.nokia.mj.impl.rt.support.SystemPropertyProvider;

import com.nokia.mj.impl.utils.Logger;

/**

 * A class that will be used to store system properties in CLDC VM.

 * The class is inherited from Hashtable and there will be only one instance

 * of it per VM instance. The VM will replace the original Hashtable with

 * instace of this object which gives us the control when MIDlet is asking

 * for any system property. Original system properties are in the private

 * member and the parent hash table is used to store dynamic handlers.

 *

 * @author Nokia Corporation

 * @version 1.0

 */

class SystemPropertyUtils

{

    private static final String

    PROPERTY_HANDLER_CLASS_PREFIX = "com.nokia.mj.impl.properties.";

    /**

     * Solves the possible dynamic property value. This a utility method

     * to be called by VM dependent sytem properties extension mechanism.

     *

     * The utility will check if the value of the system property indicates

     * that the method is dynamic. if it is not, then the value is returned

     * directly, but if it is, then the value of the dynamic property will

     * be solved by using defined property handler.

     *

     * @param propertyName the name of the system property.

     * @param propertyValue the value of the system property. This must be

     *                      passed as an argument even if the original

     *                      Hashtable is also passed as third argument.

     *                      That can't be used because calling the get method

     *                      of the given Hashtable would lead to forever loop.

     * @param props A hashtable containing the system properties. This is used

     *              to store the "freezed" system property value.

     * @return value of the system property.

     */

    public static Object solvePropertyValue(Object propertyName,

                                            Object propertyValue,

                                            Hashtable systemProperties)

    {

        // Check that the property name and the obtained value are strings

        if (!(propertyName instanceof String) ||

                !(propertyValue instanceof String))

        {

            // Not strings, return the non-string property value.

            return propertyValue;

        }

        String propertyNameStr = (String)propertyName;

        String propertyValueStr = (String)propertyValue;

        try

        {

            // If the property value starts with ':' it is a dynamic property

            if (propertyValueStr != null && propertyValueStr.length() > 0 &&

                    propertyValueStr.charAt(0) == ':')

            {

                // Note for CDC. If some application wants to define some system

                // property value that starts with ':' then it is needed to

                // encode e.g. by using leading ':'.

                if (propertyValueStr.length() > 1 &&

                        propertyValueStr.charAt(1) == ':')

                {

                    return propertyValueStr.substring(1);

                }

                // Strip the dynamic property prefix away.

                final String classEnding = propertyValueStr.substring(1);

                // The result will be the end of the package and of

                // the class name.

                String className = PROPERTY_HANDLER_CLASS_PREFIX +

                                   classEnding;

                try

                {

                    Object providerImpl = clazz.newInstance();

                    boolean isFrozen = false;

                    SystemPropertyProvider systemPropertyProvider =

                        (SystemPropertyProvider)providerImpl;

                    propertyValueStr =

                        systemPropertyProvider.getProperty(propertyNameStr);

                    isFrozen =

                        systemPropertyProvider.isStatic(propertyNameStr);

                    // Freeze the value if the provider wants so

                    if (propertyValueStr != null && isFrozen)

                    {

                        systemProperties.put(propertyNameStr,

                                             propertyValueStr);

                    }

                    return propertyValueStr;

                }

                catch (ClassNotFoundException e)

                {

                    Logger.ELOG(Logger.EUtils, "Dynamic property handler " +

                                className + " was not found for "

                                + propertyName);

                    return "";

                }

            }

            // It wasn't dynamic, so returning the static value.

            return propertyValueStr;

        }

        catch (Throwable t)

        {

            Logger.ELOG(Logger.EUtils, "Error in system properties: Key="

                        + propertyNameStr + ", Val ='" +

                        propertyValueStr, t);

            return "";

        }

    }

}