/*
    *  Copyright 2001-2009 Stephen Colebourne
    *
    *  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.joda.time.tz;
  
  import java.io.DataInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.lang.ref.SoftReference;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  import java.util.concurrent.ConcurrentHashMap;
  
  import org.joda.time.DateTimeZone;
  
  /**
   * ZoneInfoProvider loads compiled data files as generated by
   * {@link ZoneInfoCompiler}.
   * <p>
   * ZoneInfoProvider is thread-safe and publicly immutable.
   *
   * @author Brian S O'Neill
   * @since 1.0
   */
  public class ZoneInfoProvider implements Provider {
  
      /** The directory where the files are held. */
      private final File iFileDir;
      /** The resource path. */
      private final String iResourcePath;
      /** The class loader to use. */
      private final ClassLoader iLoader;
      /** Maps ids to strings or SoftReferences to DateTimeZones. */
      private final Map<String, Object> iZoneInfoMap;
  
      /**
       * ZoneInfoProvider searches the given directory for compiled data files.
       *
       * @throws IOException if directory or map file cannot be read
       */
      public ZoneInfoProvider(File fileDir) throws IOException {
          if (fileDir == null) {
              throw new IllegalArgumentException("No file directory provided");
          }
          if (!fileDir.exists()) {
              throw new IOException("File directory doesn't exist: " + fileDir);
          }
          if (!fileDir.isDirectory()) {
              throw new IOException("File doesn't refer to a directory: " + fileDir);
          }
  
          iFileDir = fileDir;
          iResourcePath = null;
          iLoader = null;
  
          iZoneInfoMap = loadZoneInfoMap(openResource("ZoneInfoMap"));
      }
  
      /**
       * ZoneInfoProvider searches the given ClassLoader resource path for
       * compiled data files. Resources are loaded from the ClassLoader that
       * loaded this class.
       *
       * @throws IOException if directory or map file cannot be read
       */
      public ZoneInfoProvider(String resourcePath) throws IOException {
          this(resourcePath, null, false);
      }
  
      /**
       * ZoneInfoProvider searches the given ClassLoader resource path for
       * compiled data files.
       *
       * @param loader ClassLoader to load compiled data files from. If null,
       * use system ClassLoader.
       * @throws IOException if directory or map file cannot be read
       */
      public ZoneInfoProvider(String resourcePath, ClassLoader loader)
          throws IOException
      {
          this(resourcePath, loader, true);
      }
  
      /**
      * @param favorSystemLoader when true, use the system class loader if
      * loader null. When false, use the current class loader if loader is null.
      */
     private ZoneInfoProvider(String resourcePath,
                              ClassLoader loader, boolean favorSystemLoader) 
         throws IOException
     {
         if (resourcePath == null) {
             throw new IllegalArgumentException("No resource path provided");
         }
         if (!resourcePath.endsWith("/")) {
             resourcePath += '/';
         }
 
         iFileDir = null;
         iResourcePath = resourcePath;
 
         if (loader == null && !favorSystemLoader) {
             loader = getClass().getClassLoader();
         }
 
         iLoader = loader;
 
         iZoneInfoMap = loadZoneInfoMap(openResource("ZoneInfoMap"));
     }
 
     //-----------------------------------------------------------------------
     /**
      * If an error is thrown while loading zone data, uncaughtException is
      * called to log the error and null is returned for this and all future
      * requests.
      * 
      * @param id  the id to load
      * @return the loaded zone
      */
     public DateTimeZone getZone(String id) {
         if (id == null) {
             return null;
         }
 
         Object obj = iZoneInfoMap.get(id);
         if (obj == null) {
             return null;
         }
 
         if (id.equals(obj)) {
             // Load zone data for the first time.
             return loadZoneData(id);
         }
 
         if (obj instanceof SoftReference<?>) {
             @SuppressWarnings("unchecked")
             SoftReference<DateTimeZone> ref = (SoftReference<DateTimeZone>) obj;
             DateTimeZone tz = ref.get();
             if (tz != null) {
                 return tz;
             }
             // Reference cleared; load data again.
             return loadZoneData(id);
         }
 
         // If this point is reached, mapping must link to another.
         return getZone((String)obj);
     }
 
     /**
      * Gets a list of all the available zone ids.
      * 
      * @return the zone ids
      */
     public Set<String> getAvailableIDs() {
         // Return a copy of the keys rather than an umodifiable collection.
         // This prevents ConcurrentModificationExceptions from being thrown by
         // some JVMs if zones are opened while this set is iterated over.
         return new TreeSet<String>(iZoneInfoMap.keySet());
     }
 
     /**
      * Called if an exception is thrown from getZone while loading zone data.
      * 
      * @param ex  the exception
      */
     protected void uncaughtException(Exception ex) {
         Thread t = Thread.currentThread();
         t.getThreadGroup().uncaughtException(t, ex);
     }
 
     /**
      * Opens a resource from file or classpath.
      * 
      * @param name  the name to open
      * @return the input stream
      * @throws IOException if an error occurs
      */
     private InputStream openResource(String name) throws IOException {
         InputStream in;
         if (iFileDir != null) {
             in = new FileInputStream(new File(iFileDir, name));
         } else {
             String path = iResourcePath.concat(name);
             if (iLoader != null) {
                 in = iLoader.getResourceAsStream(path);
             } else {
                 in = ClassLoader.getSystemResourceAsStream(path);
             }
             if (in == null) {
                 StringBuilder buf = new StringBuilder(40)
                     .append("Resource not found: \"")
                     .append(path)
                     .append("\" ClassLoader: ")
                     .append(iLoader != null ? iLoader.toString() : "system");
                 throw new IOException(buf.toString());
             }
         }
         return in;
     }
 
     /**
      * Loads the time zone data for one id.
      * 
      * @param id  the id to load
      * @return the zone
      */
     private DateTimeZone loadZoneData(String id) {
         InputStream in = null;
         try {
             in = openResource(id);
             DateTimeZone tz = DateTimeZoneBuilder.readFrom(in, id);
             iZoneInfoMap.put(id, new SoftReference<DateTimeZone>(tz));
             return tz;
         } catch (IOException ex) {
             uncaughtException(ex);
             iZoneInfoMap.remove(id);
             return null;
         } finally {
             try {
                 if (in != null) {
                     in.close();
                 }
             } catch (IOException ex) {
             }
         }
     }
 
     //-----------------------------------------------------------------------
     /**
      * Loads the zone info map.
      * 
      * @param in  the input stream
      * @return the map
      */
     private static Map<String, Object> loadZoneInfoMap(InputStream in) throws IOException {
         Map<String, Object> map = new ConcurrentHashMap<String, Object>();
         DataInputStream din = new DataInputStream(in);
         try {
             readZoneInfoMap(din, map);
         } finally {
             try {
                 din.close();
             } catch (IOException ex) {
             }
         }
         map.put("UTC", new SoftReference<DateTimeZone>(DateTimeZone.UTC));
         return map;
     }
 
     /**
      * Reads the zone info map from file.
      * 
      * @param din  the input stream
      * @param zimap  gets filled with string id to string id mappings
      */
     private static void readZoneInfoMap(DataInputStream din, Map<String, Object> zimap) throws IOException {
         // Read the string pool.
         int size = din.readUnsignedShort();
         String[] pool = new String[size];
         for (int i=0; i<size; i++) {
             pool[i] = din.readUTF().intern();
         }
 
         // Read the mappings.
         size = din.readUnsignedShort();
         for (int i=0; i<size; i++) {
             try {
                 zimap.put(pool[din.readUnsignedShort()], pool[din.readUnsignedShort()]);
             } catch (ArrayIndexOutOfBoundsException ex) {
                 throw new IOException("Corrupt zone info map");
             }
         }
     }
 
 }