/* $HeadURL$
    * $Id$
    *
    * Copyright (c) 2009-2010 DuraSpace
    * http://duraspace.org
    *
    * In collaboration with Topaz Inc.
    * http://www.topazproject.org
    *
   * 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 org.akubraproject.fs;
  
  import com.google.common.collect.AbstractIterator;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.net.URI;
  import java.net.URISyntaxException;
  
  /**
   * Iterates over all files in baseDir (respecting filterPrefix if provided).
   *
   * @author Chris Wilper
   */
  class FSBlobIdIterator extends AbstractIterator<URI> {
    private final Logger log = LoggerFactory.getLogger(FSBlobIdIterator.class);
    private final File baseDir;
    private final String filterPrefix;
    private DirectoryNode currentDir;
  
    FSBlobIdIterator(File baseDir, String filterPrefix) {
      this.baseDir = baseDir;
      this.filterPrefix = filterPrefix;
      currentDir = new DirectoryNode(null, "");
    }
  
    @Override
    protected URI computeNext() {
      while (currentDir != null) {
        DirectoryNode child = currentDir.nextChild();
        if (child == null) {
          // no more children; move up
          currentDir = currentDir.parent;
        } else if (child.isDirectory()) {
          // child is dir; move down
          currentDir = child;
        } else {
          // child is file
          try {
            URI uri = new URI(FSBlob.scheme + ":" + child.path);
            if (filterPrefix == null || uri.toString().startsWith(filterPrefix)) {
              return uri;
            }
          } catch (URISyntaxException e) {
            log.warn("Skipping non-URI-safe file: {}", child.path);
          }
        }
      }
  
      return endOfData(); // exhausted
    }
  
    private class DirectoryNode {
  
      final DirectoryNode parent;
  
      final String path;
  
      private String[] childPaths;
  
      private int childNum;
  
      DirectoryNode(DirectoryNode parent,  // null if root
                    String path) {         // "" if root, "name/" if subdir, "name" if file
        this.parent = parent;
        this.path = path;
        if (isDirectory()) {
          setChildPaths();
        }
      }
  
      private void setChildPaths() {
        File dir;
        if (path.length() == 0) {
          dir = baseDir;
        } else {
          dir = new File(baseDir, path);
       }
       File[] childFiles = dir.listFiles();
       childPaths = new String[childFiles.length];
       for (int i = 0; i < childFiles.length; i++) {
         StringBuilder childPath = new StringBuilder(path);
         childPath.append(childFiles[i].getName());
         if (childFiles[i].isDirectory()) {
           childPath.append("/");
         }
         childPaths[i] = childPath.toString();
       }
     }
 
     boolean isDirectory() {
       return path.length() == 0 || path.endsWith("/");
     }
 
     DirectoryNode nextChild() {
       if (isDirectory()) {
         if (childNum == childPaths.length) {
           return null;  // no more children
         } else {
           return new DirectoryNode(this, childPaths[childNum++]);
         }
       } else {
         return null;   // not a directory
       }
     }
   }
 }