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 * CruiseControl, a Continuous Integration Toolkit
 * Copyright (c) 2001, ThoughtWorks, Inc.
 * 200 E. Randolph, 25th Floor
 * Chicago, IL 60601 USA
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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package net.sourceforge.cruisecontrol.config;

import net.sourceforge.cruisecontrol.CruiseControlException;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

import org.apache.log4j.Logger;

/**
 * The interface defining methods responsible for the general resolving of files used
 * to control CruiseControl.
 * 
 * The aim is to limit file system access to a {@link FileResolver} implementation,
 * which is good for testing, but also useful if we wanted to do something like try resolving 
 * paths against different known contexts (e.g. parent directories) rather than being limited 
 * to the working directory.
 * 
 * As the bonus, the resolved files are automatically monitored for changes which cause the 
 * reload of Cruisecontrol configuration.   
 */
public interface FileResolver {

    /**
     * Resolves the path (either absolute or relative to the location of CruiseControl 
     * configuration file).
     * 
     * @param path to file to resolve. 
     * @return stream to read the content of file from.
     * @throws CruiseControlException if file can not be read.
     */
    InputStream getInputStream(String path) throws CruiseControlException;

    
    /**
     * Dummy FileResolver implementation for case when "real" FileResolver is not available.
     * The implementation is straight wrapper for 
     * <code>return new BufferedInputStream(new FileInputStream(path))</code>, nothing more.
     */
    public static final class DummyResolver implements FileResolver {
        private static final Logger LOG = Logger.getLogger(DummyResolver.class);

        /** The implementation of {@link FileResolver#getInputStream(String)} returning raw
         *  stream to read data from */
        public InputStream getInputStream(final String path) throws CruiseControlException {
            LOG.warn("Using dummy resolver for file '" + path + "'. Changes in the file will not be reflected" 
                + "in the project!");
            final File file = new File(path);
            try {
                return new BufferedInputStream(new FileInputStream(file));
            } catch (FileNotFoundException e) {
                throw new CruiseControlException("exception when opening file " + file.getAbsolutePath(), e);
            }
        }
    }
    
}