/*
    * 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.shiro.io;
  
  import org.apache.shiro.util.ClassUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  
  /**
   * Static helper methods for loading {@code Stream}-backed resources.
   *
   * @see #getInputStreamForPath(String)
   * @since 0.2
   */
  public class ResourceUtils {
  
      /**
       * Resource path prefix that specifies to load from a classpath location, value is <b>{@code classpath:}</b>
       */
      public static final String CLASSPATH_PREFIX = "classpath:";
      /**
       * Resource path prefix that specifies to load from a url location, value is <b>{@code url:}</b>
       */
      public static final String URL_PREFIX = "url:";
      /**
       * Resource path prefix that specifies to load from a file location, value is <b>{@code file:}</b>
       */
      public static final String FILE_PREFIX = "file:";
  
      /**
       * Private internal log instance.
       */
      private static final Logger log = LoggerFactory.getLogger(ResourceUtils.class);
  
      /**
       * Prevent instantiation.
       */
      private ResourceUtils() {
      }
  
      /**
       * Returns {@code true} if the resource path is not null and starts with one of the recognized
       * resource prefixes ({@link #CLASSPATH_PREFIX CLASSPATH_PREFIX},
       * {@link #URL_PREFIX URL_PREFIX}, or {@link #FILE_PREFIX FILE_PREFIX}), {@code false} otherwise.
       *
       * @param resourcePath the resource path to check
       * @return {@code true} if the resource path is not null and starts with one of the recognized
       *         resource prefixes, {@code false} otherwise.
       * @since 0.9
       */
      @SuppressWarnings({"UnusedDeclaration"})
      public static boolean hasResourcePrefix(String resourcePath) {
          return resourcePath != null &&
                  (resourcePath.startsWith(CLASSPATH_PREFIX) ||
                          resourcePath.startsWith(URL_PREFIX) ||
                          resourcePath.startsWith(FILE_PREFIX));
      }
  
      /**
       * Returns {@code true} if the resource at the specified path exists, {@code false} otherwise.  This
       * method supports scheme prefixes on the path as defined in {@link #getInputStreamForPath(String)}.
       *
       * @param resourcePath the path of the resource to check.
       * @return {@code true} if the resource at the specified path exists, {@code false} otherwise.
       * @since 0.9
       */
      public static boolean resourceExists(String resourcePath) {
          InputStream stream = null;
          boolean exists = false;
  
          try {
              stream = getInputStreamForPath(resourcePath);
              exists = true;
          } catch (IOException e) {
              stream = null;
          } finally {
              if (stream != null) {
                  try {
                     stream.close();
                 } catch (IOException ignored) {
                 }
             }
         }
 
         return exists;
     }
 
 
     /**
      * Returns the InputStream for the resource represented by the specified path, supporting scheme
      * prefixes that direct how to acquire the input stream
      * ({@link #CLASSPATH_PREFIX CLASSPATH_PREFIX},
      * {@link #URL_PREFIX URL_PREFIX}, or {@link #FILE_PREFIX FILE_PREFIX}).  If the path is not prefixed by one
      * of these schemes, the path is assumed to be a file-based path that can be loaded with a
      * {@link FileInputStream FileInputStream}.
      *
      * @param resourcePath the String path representing the resource to obtain.
      * @return the InputStream for the specified resource.
      * @throws IOException if there is a problem acquiring the resource at the specified path.
      */
     public static InputStream getInputStreamForPath(String resourcePath) throws IOException {
 
         InputStream is;
         if (resourcePath.startsWith(CLASSPATH_PREFIX)) {
             is = loadFromClassPath(stripPrefix(resourcePath));
 
         } else if (resourcePath.startsWith(URL_PREFIX)) {
             is = loadFromUrl(stripPrefix(resourcePath));
 
         } else if (resourcePath.startsWith(FILE_PREFIX)) {
             is = loadFromFile(stripPrefix(resourcePath));
 
         } else {
             is = loadFromFile(resourcePath);
         }
 
         if (is == null) {
             throw new IOException("Resource [" + resourcePath + "] could not be found.");
         }
 
         return is;
     }
 
     private static InputStream loadFromFile(String path) throws IOException {
         if (log.isDebugEnabled()) {
             log.debug("Opening file [" + path + "]...");
         }
         return new FileInputStream(path);
     }
 
     private static InputStream loadFromUrl(String urlPath) throws IOException {
         log.debug("Opening url {}", urlPath);
         URL url = new URL(urlPath);
         return url.openStream();
     }
 
     private static InputStream loadFromClassPath(String path) {
         log.debug("Opening resource from class path [{}]", path);
         return ClassUtils.getResourceAsStream(path);
     }
 
     private static String stripPrefix(String resourcePath) {
         return resourcePath.substring(resourcePath.indexOf(":") + 1);
     }
 
     /**
      * Convenience method that closes the specified {@link InputStream InputStream}, logging any
      * {@link IOException IOException} that might occur. If the {@code InputStream}
      * argument is {@code null}, this method does nothing.  It returns quietly in all cases.
      *
      * @param is the {@code InputStream} to close, logging any {@code IOException} that might occur.
      */
     public static void close(InputStream is) {
         if (is != null) {
             try {
                 is.close();
             } catch (IOException e) {
                 log.warn("Error closing input stream.", e);
             }
         }
     }
 }