/*
    * 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.net.MalformedURLException;
  import java.net.URI;
  import java.net.URL;
  import java.util.Arrays;
  import java.util.Map;
  
  import org.apache.commons.configuration2.ex.ConfigurationException;
  import org.apache.commons.lang3.ObjectUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * <p>
   * A utility class providing helper methods related to locating files.
   * </p>
   * <p>
   * The methods of this class are used behind the scenes when retrieving configuration files based on different criteria,
   * e.g. URLs, files, or more complex search strategies. They also implement functionality required by the default
   * {@link FileSystem} implementations. Most methods are intended to be used internally only by other classes in the
   * {@code io} package.
   * </p>
   *
   * @since 2.0
   */
  public final class FileLocatorUtils {
      /**
       * Constant for the default {@code FileSystem}. This file system is used by operations of this class if no specific file
       * system is provided. An instance of {@link DefaultFileSystem} is used.
       */
      public static final FileSystem DEFAULT_FILE_SYSTEM = new DefaultFileSystem();
  
      /**
       * Constant for the default {@code FileLocationStrategy}. This strategy is used by the {@code locate()} method if the
       * passed in {@code FileLocator} does not define its own location strategy. The default location strategy is roughly
       * equivalent to the search algorithm used in version 1.x of <em>Commons Configuration</em> (there it was hard-coded
       * though). It behaves in the following way when passed a {@code FileLocator}:
       * <ul>
       * <li>If the {@code FileLocator} has a defined URL, this URL is used as the file's URL (without any further
       * checks).</li>
       * <li>Otherwise, base path and file name stored in the {@code FileLocator} are passed to the current
       * {@code FileSystem}'s {@code locateFromURL()} method. If this results in a URL, it is returned.</li>
       * <li>Otherwise, if the locator's file name is an absolute path to an existing file, the URL of this file is
       * returned.</li>
       * <li>Otherwise, the concatenation of base path and file name is constructed. If this path points to an existing file,
       * its URL is returned.</li>
       * <li>Otherwise, a sub directory of the current user's home directory as defined by the base path is searched for the
       * referenced file. If the file can be found there, its URL is returned.</li>
       * <li>Otherwise, the base path is ignored, and the file name is searched in the current user's home directory. If the
       * file can be found there, its URL is returned.</li>
       * <li>Otherwise, a resource with the name of the locator's file name is searched in the classpath. If it can be found,
       * its URL is returned.</li>
       * <li>Otherwise, the strategy gives up and returns <b>null</b> indicating that the file cannot be resolved.</li>
       * </ul>
       */
      public static final FileLocationStrategy DEFAULT_LOCATION_STRATEGY = initDefaultLocationStrategy();
  
      /** Constant for the file URL protocol */
      private static final String FILE_SCHEME = "file:";
  
      /** The logger. */
      private static final Log LOG = LogFactory.getLog(FileLocatorUtils.class);
  
      /** Property key for the base path. */
      private static final String PROP_BASE_PATH = "basePath";
  
      /** Property key for the encoding. */
      private static final String PROP_ENCODING = "encoding";
  
      /** Property key for the file name. */
      private static final String PROP_FILE_NAME = "fileName";
  
      /** Property key for the file system. */
      private static final String PROP_FILE_SYSTEM = "fileSystem";
  
      /** Property key for the location strategy. */
      private static final String PROP_STRATEGY = "locationStrategy";
  
      /** Property key for the source URL. */
      private static final String PROP_SOURCE_URL = "sourceURL";
 
     /**
      * Private constructor so that no instances can be created.
      */
     private FileLocatorUtils() {
     }
 
     /**
      * Extends a path by another component. The given extension is added to the already existing path adding a separator if
      * necessary.
      *
      * @param path the path to be extended
      * @param ext the extension of the path
      * @return the extended path
      */
     static String appendPath(final String path, final String ext) {
         final StringBuilder fName = new StringBuilder();
         fName.append(path);
 
         // My best friend. Paranoia.
         if (!path.endsWith(File.separator)) {
             fName.append(File.separator);
         }
 
         //
         // We have a relative path, and we have
         // two possible forms here. If we have the
         // "./" form then just strip that off first
         // before continuing.
         //
         if (ext.startsWith("." + File.separator)) {
             fName.append(ext.substring(2));
         } else {
             fName.append(ext);
         }
         return fName.toString();
     }
 
     /**
      * Helper method for constructing a file object from a base path and a file name. This method is called if the base path
      * passed to {@code getURL()} does not seem to be a valid URL.
      *
      * @param basePath the base path
      * @param fileName the file name (must not be <b>null</b>)
      * @return the resulting file
      */
     static File constructFile(final String basePath, final String fileName) {
         final File file;
 
         final File absolute = new File(fileName);
         if (StringUtils.isEmpty(basePath) || absolute.isAbsolute()) {
             file = absolute;
         } else {
             file = new File(appendPath(basePath, fileName));
         }
 
         return file;
     }
 
     /**
      * Tries to convert the specified file to a URL. If this causes an exception, result is <b>null</b>.
      *
      * @param file the file to be converted
      * @return the resulting URL or <b>null</b>
      */
     static URL convertFileToURL(final File file) {
         return convertURIToURL(file.toURI());
     }
 
     /**
      * Tries to convert the specified URI to a URL. If this causes an exception, result is <b>null</b>.
      *
      * @param uri the URI to be converted
      * @return the resulting URL or <b>null</b>
      */
     static URL convertURIToURL(final URI uri) {
         try {
             return uri.toURL();
         } catch (final MalformedURLException e) {
             return null;
         }
     }
 
     /**
      * Creates a fully initialized {@code FileLocator} based on the specified URL.
      *
      * @param src the source {@code FileLocator}
      * @param url the URL
      * @return the fully initialized {@code FileLocator}
      */
     private static FileLocator createFullyInitializedLocatorFromURL(final FileLocator src, final URL url) {
         final FileLocator.FileLocatorBuilder fileLocatorBuilder = fileLocator(src);
         if (src.getSourceURL() == null) {
             fileLocatorBuilder.sourceURL(url);
         }
         if (StringUtils.isBlank(src.getFileName())) {
             fileLocatorBuilder.fileName(getFileName(url));
         }
         if (StringUtils.isBlank(src.getBasePath())) {
             fileLocatorBuilder.basePath(getBasePath(url));
         }
         return fileLocatorBuilder.create();
     }
 
     /**
      * Tries to convert the specified URL to a file object. If this fails, <b>null</b> is returned.
      *
      * @param url the URL
      * @return the resulting file object
      */
     public static File fileFromURL(final URL url) {
         return FileUtils.toFile(url);
     }
 
     /**
      * Returns an uninitialized {@code FileLocatorBuilder} which can be used for the creation of a {@code FileLocator}
      * object. This method provides a convenient way to create file locators using a fluent API as in the following example:
      *
      * <pre>
      * FileLocator locator = FileLocatorUtils.fileLocator().basePath(myBasePath).fileName("test.xml").create();
      * </pre>
      *
      * @return a builder object for defining a {@code FileLocator}
      */
     public static FileLocator.FileLocatorBuilder fileLocator() {
         return fileLocator(null);
     }
 
     /**
      * Returns a {@code FileLocatorBuilder} which is already initialized with the properties of the passed in
      * {@code FileLocator}. This builder can be used to create a {@code FileLocator} object which shares properties of the
      * original locator (e.g. the {@code FileSystem} or the encoding), but points to a different file. An example use case
      * is as follows:
      *
      * <pre>
      * FileLocator loc1 = ...
      * FileLocator loc2 = FileLocatorUtils.fileLocator(loc1)
      *     .setFileName("anotherTest.xml")
      *     .create();
      * </pre>
      *
      * @param src the source {@code FileLocator} (may be <b>null</b>)
      * @return an initialized builder object for defining a {@code FileLocator}
      */
     public static FileLocator.FileLocatorBuilder fileLocator(final FileLocator src) {
         return new FileLocator.FileLocatorBuilder(src);
     }
 
     /**
      * Creates a new {@code FileLocator} object with the properties defined in the given map. The map must be conform to the
      * structure generated by the {@link #put(FileLocator, Map)} method; unexpected data can cause
      * {@code ClassCastException} exceptions. The map can be <b>null</b>, then an uninitialized {@code FileLocator} is
      * returned.
      *
      * @param map the map
      * @return the new {@code FileLocator}
      * @throws ClassCastException if the map contains invalid data
      */
     public static FileLocator fromMap(final Map<String, ?> map) {
         final FileLocator.FileLocatorBuilder builder = fileLocator();
         if (map != null) {
             builder.basePath((String) map.get(PROP_BASE_PATH)).encoding((String) map.get(PROP_ENCODING)).fileName((String) map.get(PROP_FILE_NAME))
                 .fileSystem((FileSystem) map.get(PROP_FILE_SYSTEM)).locationStrategy((FileLocationStrategy) map.get(PROP_STRATEGY))
                 .sourceURL((URL) map.get(PROP_SOURCE_URL));
         }
         return builder.create();
     }
 
     /**
      * Returns a {@code FileLocator} object based on the passed in one whose location is fully defined. This method ensures
      * that all components of the {@code FileLocator} pointing to the file are set in a consistent way. In detail it behaves
      * as follows:
      * <ul>
      * <li>If the {@code FileLocator} has already all components set which define the file, it is returned unchanged.
      * <em>Note:</em> It is not checked whether all components are really consistent!</li>
      * <li>{@link #locate(FileLocator)} is called to determine a unique URL pointing to the referenced file. If this is
      * successful, a new {@code FileLocator} is created as a copy of the passed in one, but with all components pointing to
      * the file derived from this URL.</li>
      * <li>Otherwise, result is <b>null</b>.</li>
      * </ul>
      *
      * @param locator the {@code FileLocator} to be completed
      * @return a {@code FileLocator} with a fully initialized location if possible or <b>null</b>
      */
     public static FileLocator fullyInitializedLocator(final FileLocator locator) {
         if (isFullyInitialized(locator)) {
             // already fully initialized
             return locator;
         }
 
         final URL url = locate(locator);
         return url != null ? createFullyInitializedLocatorFromURL(locator, url) : null;
     }
 
     /**
      * Gets the path without the file name, for example https://xyz.net/foo/bar.xml results in https://xyz.net/foo/
      *
      * @param url the URL from which to extract the path
      * @return the path component of the passed in URL
      */
     static String getBasePath(final URL url) {
         if (url == null) {
             return null;
         }
 
         String s = url.toString();
         if (s.startsWith(FILE_SCHEME) && !s.startsWith("file://")) {
             s = "file://" + s.substring(FILE_SCHEME.length());
         }
 
         if (s.endsWith("/") || StringUtils.isEmpty(url.getPath())) {
             return s;
         }
         return s.substring(0, s.lastIndexOf("/") + 1);
     }
 
     /**
      * Tries to find a resource with the given name in the classpath.
      *
      * @param resourceName the name of the resource
      * @return the URL to the found resource or <b>null</b> if the resource cannot be found
      */
     static URL getClasspathResource(final String resourceName) {
         URL url = null;
         // attempt to load from the context classpath
         final ClassLoader loader = Thread.currentThread().getContextClassLoader();
         if (loader != null) {
             url = loader.getResource(resourceName);
 
             if (url != null) {
                 LOG.debug("Loading configuration from the context classpath (" + resourceName + ")");
             }
         }
 
         // attempt to load from the system classpath
         if (url == null) {
             url = ClassLoader.getSystemResource(resourceName);
 
             if (url != null) {
                 LOG.debug("Loading configuration from the system classpath (" + resourceName + ")");
             }
         }
         return url;
     }
 
     /**
      * Tries to convert the specified base path and file name into a file object. This method is called e.g. by the save()
      * methods of file based configurations. The parameter strings can be relative files, absolute files and URLs as well.
      * This implementation checks first whether the passed in file name is absolute. If this is the case, it is returned.
      * Otherwise further checks are performed whether the base path and file name can be combined to a valid URL or a valid
      * file name. <em>Note:</em> The test if the passed in file name is absolute is performed using
      * {@code java.io.File.isAbsolute()}. If the file name starts with a slash, this method will return <b>true</b> on Unix,
      * but <b>false</b> on Windows. So to ensure correct behavior for relative file names on all platforms you should never
      * let relative paths start with a slash. E.g. in a configuration definition file do not use something like that:
      *
      * <pre>
      * &lt;properties fileName="/subdir/my.properties"/&gt;
      * </pre>
      *
      * Under Windows this path would be resolved relative to the configuration definition file. Under Unix this would be
      * treated as an absolute path name.
      *
      * @param basePath the base path
      * @param fileName the file name (must not be <b>null</b>)
      * @return the file object (<b>null</b> if no file can be obtained)
      */
     static File getFile(final String basePath, final String fileName) {
         // Check if the file name is absolute
         final File f = new File(fileName);
         if (f.isAbsolute()) {
             return f;
         }
 
         // Check if URLs are involved
         URL url;
         try {
             url = new URL(new URL(basePath), fileName);
         } catch (final MalformedURLException mex1) {
             try {
                 url = new URL(fileName);
             } catch (final MalformedURLException mex2) {
                 url = null;
             }
         }
 
         if (url != null) {
             return fileFromURL(url);
         }
 
         return constructFile(basePath, fileName);
     }
 
     /**
      * Extract the file name from the specified URL.
      *
      * @param url the URL from which to extract the file name
      * @return the extracted file name
      */
     static String getFileName(final URL url) {
         if (url == null) {
             return null;
         }
 
         final String path = url.getPath();
 
         if (path.endsWith("/") || StringUtils.isEmpty(path)) {
             return null;
         }
         return path.substring(path.lastIndexOf("/") + 1);
     }
 
     /**
      * Obtains a non-<b>null</b> {@code FileSystem} object from the passed in {@code FileLocator}. If the passed in
      * {@code FileLocator} has a {@code FileSystem} object, it is returned. Otherwise, result is the default
      * {@code FileSystem}.
      *
      * @param locator the {@code FileLocator} (may be <b>null</b>)
      * @return the {@code FileSystem} to be used for this {@code FileLocator}
      */
     static FileSystem getFileSystem(final FileLocator locator) {
         return locator != null ? ObjectUtils.defaultIfNull(locator.getFileSystem(), DEFAULT_FILE_SYSTEM) : DEFAULT_FILE_SYSTEM;
     }
 
     /**
      * Gets a non <b>null</b> {@code FileLocationStrategy} object from the passed in {@code FileLocator}. If the
      * {@code FileLocator} is not <b>null</b> and has a {@code FileLocationStrategy} defined, this strategy is returned.
      * Otherwise, result is the default {@code FileLocationStrategy}.
      *
      * @param locator the {@code FileLocator}
      * @return the {@code FileLocationStrategy} for this {@code FileLocator}
      */
     static FileLocationStrategy getLocationStrategy(final FileLocator locator) {
         return locator != null ? ObjectUtils.defaultIfNull(locator.getLocationStrategy(), DEFAULT_LOCATION_STRATEGY) : DEFAULT_LOCATION_STRATEGY;
     }
 
     /**
      * Creates the default location strategy. This method creates a combined location strategy as described in the comment
      * of the {@link #DEFAULT_LOCATION_STRATEGY} member field.
      *
      * @return the default {@code FileLocationStrategy}
      */
     private static FileLocationStrategy initDefaultLocationStrategy() {
         final FileLocationStrategy[] subStrategies = {new ProvidedURLLocationStrategy(), new FileSystemLocationStrategy(), new AbsoluteNameLocationStrategy(),
             new BasePathLocationStrategy(), new HomeDirectoryLocationStrategy(true), new HomeDirectoryLocationStrategy(false), new ClasspathLocationStrategy()};
         return new CombinedLocationStrategy(Arrays.asList(subStrategies));
     }
 
     /**
      * Returns a flag whether all components of the given {@code FileLocator} describing the referenced file are defined. In
      * order to reference a file, it is not necessary that all components are filled in (for instance, the URL alone is
      * sufficient). For some use cases however, it might be of interest to have different methods for accessing the
      * referenced file. Also, depending on the filled out properties, there is a subtle difference how the file is accessed:
      * If only the file name is set (and optionally the base path), each time the file is accessed a {@code locate()}
      * operation has to be performed to uniquely identify the file. If however the URL is determined once based on the other
      * components and stored in a fully defined {@code FileLocator}, it can be used directly to identify the file. If the
      * passed in {@code FileLocator} is <b>null</b>, result is <b>false</b>.
      *
      * @param locator the {@code FileLocator} to be checked (may be <b>null</b>)
      * @return a flag whether all components describing the referenced file are initialized
      */
     public static boolean isFullyInitialized(final FileLocator locator) {
         if (locator == null) {
             return false;
         }
         return locator.getBasePath() != null && locator.getFileName() != null && locator.getSourceURL() != null;
     }
 
     /**
      * Checks whether the specified {@code FileLocator} contains enough information to locate a file. This is the case if a
      * file name or a URL is defined. If the passed in {@code FileLocator} is <b>null</b>, result is <b>false</b>.
      *
      * @param locator the {@code FileLocator} to check
      * @return a flag whether a file location is defined by this {@code FileLocator}
      */
     public static boolean isLocationDefined(final FileLocator locator) {
         return locator != null && (locator.getFileName() != null || locator.getSourceURL() != null);
     }
 
     /**
      * Locates the provided {@code FileLocator}, returning a URL for accessing the referenced file. This method uses a
      * {@link FileLocationStrategy} to locate the file the passed in {@code FileLocator} points to. If the
      * {@code FileLocator} contains itself a {@code FileLocationStrategy}, it is used. Otherwise, the default
      * {@code FileLocationStrategy} is applied. The strategy is passed the locator and a {@code FileSystem}. The resulting
      * URL is returned. If the {@code FileLocator} is <b>null</b>, result is <b>null</b>.
      *
      * @param locator the {@code FileLocator} to be resolved
      * @return the URL pointing to the referenced file or <b>null</b> if the {@code FileLocator} could not be resolved
      * @see #DEFAULT_LOCATION_STRATEGY
      */
     public static URL locate(final FileLocator locator) {
         if (locator == null) {
             return null;
         }
 
         return getLocationStrategy(locator).locate(getFileSystem(locator), locator);
     }
 
     /**
      * Tries to locate the file referenced by the passed in {@code FileLocator}. If this fails, an exception is thrown. This
      * method works like {@link #locate(FileLocator)}; however, in case of a failed location attempt an exception is thrown.
      *
      * @param locator the {@code FileLocator} to be resolved
      * @return the URL pointing to the referenced file
      * @throws ConfigurationException if the file cannot be resolved
      */
     public static URL locateOrThrow(final FileLocator locator) throws ConfigurationException {
         final URL url = locate(locator);
         if (url == null) {
             throw new ConfigurationException("Could not locate: " + locator);
         }
         return url;
     }
 
     /**
      * Stores the specified {@code FileLocator} in the given map. With the {@link #fromMap(Map)} method a new
      * {@code FileLocator} with the same properties as the original one can be created.
      *
      * @param locator the {@code FileLocator} to be stored
      * @param map the map in which to store the {@code FileLocator} (must not be <b>null</b>)
      * @throws IllegalArgumentException if the map is <b>null</b>
      */
     public static void put(final FileLocator locator, final Map<String, Object> map) {
         if (map == null) {
             throw new IllegalArgumentException("Map must not be null!");
         }
 
         if (locator != null) {
             map.put(PROP_BASE_PATH, locator.getBasePath());
             map.put(PROP_ENCODING, locator.getEncoding());
             map.put(PROP_FILE_NAME, locator.getFileName());
             map.put(PROP_FILE_SYSTEM, locator.getFileSystem());
             map.put(PROP_SOURCE_URL, locator.getSourceURL());
             map.put(PROP_STRATEGY, locator.getLocationStrategy());
         }
     }
 
     /**
      * Convert the specified file into an URL. This method is equivalent to file.toURI().toURL(). It was used to work around
      * a bug in the JDK preventing the transformation of a file into an URL if the file name contains a '#' character. See
      * the issue CONFIGURATION-300 for more details. Now that we switched to JDK 1.4 we can directly use
      * file.toURI().toURL().
      *
      * @param file the file to be converted into an URL
      * @return a URL
      * @throws MalformedURLException If the file protocol handler is not found (should not happen) or if an error occurred
      *         while constructing the URL
      */
     static URL toURL(final File file) throws MalformedURLException {
         return file.toURI().toURL();
     }
 
 }