/*

  * $Source$

  * $Revision$

  *

  * Copyright (C) 2000 William Chesters

  *

  * Part of Melati (http://melati.org), a framework for the rapid

  * development of clean, maintainable web applications.

  *

  * Melati is free software; Permission is granted to copy, distribute

  * and/or modify this software under the terms either:

  *

  * a) 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,

  *

  *    or

  *

  * b) any version of the Melati Software License, as published

  *    at http://melati.org

  *

  * You should have received a copy of the GNU General Public License and

  * the Melati Software License along with this program;

  * if not, write to the Free Software Foundation, Inc.,

  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the

  * GNU General Public License and visit http://melati.org to obtain the

  * Melati Software License.

  *

  * Feel free to contact the Developers of Melati (http://melati.org),

  * if you would like to work out a different arrangement than the options

  * outlined here.  It is our intention to allow Melati to be used by as

  * wide an audience as possible.

  *

  * This program 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.

  *

  * Contact details for copyright holder:

  *

  *     William Chesters <williamc AT paneris.org>

  *     http://paneris.org/~williamc

  *     Obrechtstraat 114, 2517VX Den Haag, The Netherlands

  */

 package org.melati.util;

 import java.util.Hashtable;

 import java.util.Properties;

 import java.io.File;

 import java.io.InputStream;

 import java.io.FileInputStream;

 import java.io.IOException;

 import java.io.FileNotFoundException;

 /**

  * Useful things to do with properties files.

  */

 public final class PropertiesUtils {

   private PropertiesUtils() {}

   /**

    * Get a {@link Properties} object from a file.

    * 

    * @param path a {@link File} path name

    * @return a {@link Properties} object

    * @throws IOException if there is a problem loading the file

    */

   public static Properties fromFile(File path) throws IOException {

     InputStream data = new FileInputStream(path);

     Properties them = new Properties();

     try {

       them.load(data);

     } catch (IOException e) {

       throw new IOException("Corrupt properties file `" + path + "': " +

       e.getMessage());

     }

     return them;

   }

   public static Properties fromResource(Class<?> clazz)

         throws IOException {

     String name = clazz.getCanonicalName() + ".properties";

     return fromResource(clazz, name);

   }

   /**

    * Get a {@link Properties} object from a {@link Class}.

    * 

    * 

    * @param clazz the {@link Class} to look up

    * @param name the property file name

    * @return a {@link Properties} object

    * @throws IOException if the file cannot load or is not found

    */

   public static Properties fromResource(Class<?> clazz, String name)

       throws IOException {

     InputStream is = clazz.getResourceAsStream(name);

     if (is == null)

       throw new FileNotFoundException(name + ": is it in CLASSPATH?");

     Properties them = new Properties();

     try {

       them.load(is);

     } catch (IOException e) {

       throw new IOException("Corrupt properties file `" + name + "': " +

       e.getMessage());

     }

     return them;

   }

   /**

    * Return a property.

    * 

    * @param properties the {@link Properties} object to look in 

    * @param propertyName the property to get 

    * @return the property value

    * @throws NoSuchPropertyException if the property is not set

    */

   public static String getOrDie(Properties properties, String propertyName)

       throws NoSuchPropertyException {

     String value = properties.getProperty(propertyName);

     if (value == null)

       throw new NoSuchPropertyException(properties, propertyName);

     return value;

   }

   /**

    * Get a property or return the supplied default.

    * 

    * @param properties the {@link Properties} object to look in 

    * @param propertyName the property to get 

    * @param def the default to return if not found

    * @return the property value

    */

   public static String getOrDefault(Properties properties, 

                                     String propertyName, String def) {

     String value = properties.getProperty(propertyName);

     if (value == null) return def;

     return value;

   }

   /**

    * Get an Integer property.

    * 

    * @param properties the {@link Properties} object to look in 

    * @param propertyName the property to get 

    * @return the int property value 

    * @throws NoSuchPropertyException if it is not found

    * @throws FormatPropertyException if it is not an Integer 

    */

   public static int getOrDie_int(Properties properties, String propertyName)

       throws NoSuchPropertyException, FormatPropertyException {

     String string = getOrDie(properties, propertyName);

     try {

       return Integer.parseInt(string);

     }

     catch (NumberFormatException e) {

       throw new FormatPropertyException(properties, propertyName, string,

       "an integer", e);

     }

   }

   /**

    * Get an Integer property from a {@link Properties} object or make a fuss. 

    * 

    * @param properties a {@link Properties} 

    * @param propertyName the name of the property

    * @param def cater for multiple definitions, with increment numbers

    * @return the property as an int 

    * @throws FormatPropertyException if it is not an Integer 

    */

   public static int getOrDefault_int(Properties properties, 

                                      String propertyName, int def)

       throws FormatPropertyException {

     String string = getOrDefault(properties, propertyName, ""+def);

     try {

       return Integer.parseInt(string);

     }

     catch (NumberFormatException e) {

       throw new FormatPropertyException(properties, propertyName, string,

       "an integer", e);

     }

   }

   private static Hashtable<String, Object> instantiatedClassesCache = new Hashtable<String, Object>();

   /**

    * Instantiate an interface.

    * 

    * @param className the name of the class

    * @param interfaceClassName the interface Class name

    * @return a new object

    * @throws InstantiationPropertyException 

    *   if the named class does not descend from the interface

    */

   public static Object instanceOfNamedClass(String className, String interfaceClassName)

       throws InstantiationPropertyException {

     Object cached = instantiatedClassesCache.get(className);

     if (cached != null)

       return cached;

     try {

       Class<?> clazz = Class.forName(className);

       if (interfaceClassName != null) {

         Class<?> interfaceClass = Class.forName(interfaceClassName);

         if (!interfaceClass.isAssignableFrom(clazz))

           throw new ClassCastException(

                 clazz + " is not descended from " + interfaceClass);

       }

       Object it = clazz.newInstance();

       instantiatedClassesCache.put(className, it);

       return it;

     } catch (Exception e) {

       throw new InstantiationPropertyException(className, e);

     }

   }

   /**

    * Instantiate a Class.

    * 

    * @param properties a {@link Properties} 

    * @param propertyName the name of the property

    * @param interfaceClassName     the interface name

    * @param defaultName  a default concrete class if the property is undefined

    * @return a new Object

    * @throws InstantiationPropertyException if there is a problem

    */

   public static Object instanceOfNamedClass(Properties properties, 

                                             String propertyName,

                                             String interfaceClassName, 

                                             String defaultName)

   throws InstantiationPropertyException {

     String className =  (String)properties.get(propertyName);

     return instanceOfNamedClass(className == null ? defaultName : className, interfaceClassName);

   }

 }