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Internet scale, high-performance RESTful Services in Java
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/*
    Copyright 2010, Strategic Gains, Inc.

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

		http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
*/
package com.strategicgains.restexpress.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

import com.strategicgains.restexpress.exception.ConfigurationException;

/**
 * @author kevwil
 * @author toddf
 * @since Dec 16, 2010
 */
public abstract class Environment
{
	private static final String ENVIRONMENT_DIR = "config/";
	private static final String PROPERTIES_FILENAME = "/environment.properties";
	private static final String DEFAULT_ENVIRONMENT = "dev";

	public static  T fromDefault(Class type)
	throws FileNotFoundException, IOException
	{
		return from(DEFAULT_ENVIRONMENT, type);
	}

	public static  T from(String environmentName, Class type)
	throws FileNotFoundException, IOException
	{
		T instance = newEnvironment(type);

		if (environmentName != null)
		{
			instance.load(ENVIRONMENT_DIR + environmentName + PROPERTIES_FILENAME);
		}

		return instance;
	}

	protected void load(String filename)
	throws ConfigurationException, FileNotFoundException, IOException
	{
//		log.debug("loading environment properties from " + environmentFile);
		Properties p = readProperties(filename);
		fillValues(p);
	}
	
	protected abstract void fillValues(Properties p)
	throws ConfigurationException;

	protected Properties readProperties(String environmentFile)
	throws FileNotFoundException,
	    IOException
	{
		FileInputStream fis = null;
		try
		{
			File envFile = new File(environmentFile);
			Properties properties = new Properties();
			fis = new FileInputStream(envFile);
			properties.load(fis);
			return properties;
		}
		catch (FileNotFoundException e)
		{
//			log.error("could not find properties file: " + e.getLocalizedMessage());
			throw e;
		}
		catch (IOException e)
		{
//			log.error("error reading properties file: ", e);
			throw e;
		}
		finally
		{
			try
			{
				if (fis != null)
				{
					fis.close();
				}
			}
			catch (IOException e)
			{
				// too late to care at this point
			}
		}
	}

	private static  T newEnvironment(Class type)
    {
		T instance = null;

	    try
        {
	        instance = type.newInstance();
        }
        catch (InstantiationException e)
        {
	        e.printStackTrace();
        }
        catch (IllegalAccessException e)
        {
	        e.printStackTrace();
        }

        return instance;
    }
}