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Tools to assist in the reading of configuration/preferences files in various formats
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.configuration2.io;

import java.io.File;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.URL;

import org.apache.commons.configuration2.ex.ConfigurationException;

/**
 * Abstract layer to allow various types of file systems.
 *
 * @since 1.7
 */
public abstract class FileSystem {
    /** Constant for the default logger. */
    private static final ConfigurationLogger DEFAULT_LOG = ConfigurationLogger.newDummyLogger();

    /** The Logger. */
    private volatile ConfigurationLogger log;

    /** FileSystem options provider. */
    private volatile FileOptionsProvider optionsProvider;

    /**
     * Gets the base path of the given path, for example a directory for a file.
     *
     * @param path the source path.
     * @return the base path.
     */
    public abstract String getBasePath(String path);

    /**
     * Gets the file name of the given path.
     *
     * @param path the source path.
     * @return the file name.
     */
    public abstract String getFileName(String path);

    /**
     * Gets the FileSystem options provider.
     *
     * @return the FileSystem options provider.
     */
    public FileOptionsProvider getFileOptionsProvider() {
        return this.optionsProvider;
    }

    /**
     * Gets an input stream for a URL.
     *
     * @param url the source URL.
     * @return an input stream.
     * @throws ConfigurationException if an problem occurs getting the input stream.
     */
    public abstract InputStream getInputStream(URL url) throws ConfigurationException;

    /**
     * Not abstract for binary compatibility.
     *
     * @param url TODO
     * @param urlConnectionOptions Ignored.
     * @return TODO
     * @throws ConfigurationException TODO
     * @since 2.8.0
     */
    public InputStream getInputStream(final URL url, final URLConnectionOptions urlConnectionOptions) throws ConfigurationException {
        return getInputStream(url);
    }

    /**
     * Gets the logger used by this FileSystem.
     *
     * @return the logger
     */
    public ConfigurationLogger getLogger() {
        final ConfigurationLogger result = log;
        return result != null ? result : DEFAULT_LOG;
    }

    /**
     * Gets an output stream for a File.
     *
     * @param file the source File.
     * @return an output stream.
     * @throws ConfigurationException if an problem occurs getting the output stream.
     */
    public abstract OutputStream getOutputStream(File file) throws ConfigurationException;

    /**
     * Gets an output stream for a URL.
     *
     * @param url the source URL.
     * @return an output stream.
     * @throws ConfigurationException if an problem occurs getting the output stream.
     */
    public abstract OutputStream getOutputStream(URL url) throws ConfigurationException;

    /**
     * Gets a path string for the given input where some values may be null.
     * 
     * The implementation decides on which argument take precedence.
     * 
     *
     * @param file A file.
     * @param url A URL.
     * @param basePath A base path string.
     * @param fileName A file name.
     * @return A path string.
     */
    public abstract String getPath(File file, URL url, String basePath, String fileName);

    /**
     * Gets a URL for a base path and file name.
     *
     * @param basePath The base path.
     * @param fileName The file name.
     * @return a URL.
     * @throws MalformedURLException if a problem occurs creating the URL.
     */
    public abstract URL getURL(String basePath, String fileName) throws MalformedURLException;

    /**
     * Locates a URL for a base path and file name.
     *
     * @param basePath The base path.
     * @param fileName The file name.
     * @return a URL.
     */
    public abstract URL locateFromURL(String basePath, String fileName);

    /**
     * Sets the FileOptionsProvider
     *
     * @param provider The FileOptionsProvider
     */
    public void setFileOptionsProvider(final FileOptionsProvider provider) {
        this.optionsProvider = provider;
    }

    /**
     * Sets the logger to be used by this FileSystem. This method makes it possible for clients to exactly control
     * logging behavior. Per default a logger is set that will ignore all log messages. Derived classes that want to enable
     * logging should call this method during their initialization with the logger to be used. Passing in a null
     * argument disables logging.
     *
     * @param log the new logger
     */
    public void setLogger(final ConfigurationLogger log) {
        this.log = log;
    }
}