/*
    * Copyright 2004-2007 Brian McCallister
    *
    * 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.skife.jdbi.v2.tweak.transactions;
  
  import org.skife.jdbi.v2.Handle;
  import org.skife.jdbi.v2.exceptions.TransactionException;
  import org.skife.jdbi.v2.tweak.TransactionHandler;
  
  import java.sql.Connection;
  import java.sql.SQLException;
  import java.sql.Savepoint;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  /**
   * This <code>TransactionHandler</code> uses local JDBC transactions
   * demarcated explicitely on the handle and passed through to be handled
   * directly on the JDBC Connection instance.
   */
  public class LocalTransactionHandler implements TransactionHandler
  {
      private ConcurrentHashMap<Handle, LocalStuff> localStuff = new ConcurrentHashMap<Handle, LocalStuff>();
  
      /**
       * Called when a transaction is started
       */
      public void begin(Handle handle)
      {
          try {
              boolean initial = handle.getConnection().getAutoCommit();
              localStuff.put(handle, new LocalStuff(initial));
              handle.getConnection().setAutoCommit(false);
          }
          catch (SQLException e) {
              throw new TransactionException("Failed to start transaction", e);
          }
      }
  
      /**
       * Called when a transaction is committed
       */
      public void commit(Handle handle)
      {
          try {
              handle.getConnection().commit();
              final LocalStuff stuff = localStuff.remove(handle);
              if (stuff != null) {
                  handle.getConnection().setAutoCommit(stuff.getInitialAutocommit());
                  stuff.getCheckpoints().clear();
              }
          }
          catch (SQLException e) {
              throw new TransactionException("Failed to commit transaction", e);
          }
          finally {
              // prevent memory leak if commit throws an exception
              if (localStuff.containsKey(handle)) {
                  localStuff.remove(handle);
              }
          }
      }
  
      /**
       * Called when a transaction is rolled back
       */
      public void rollback(Handle handle)
      {
          try {
              handle.getConnection().rollback();
              final LocalStuff stuff = localStuff.remove(handle);
              if (stuff != null) {
                  handle.getConnection().setAutoCommit(stuff.getInitialAutocommit());
                  stuff.getCheckpoints().clear();
              }
          }
          catch (SQLException e) {
              throw new TransactionException("Failed to rollback transaction", e);
          }
          finally {
              // prevent memory leak if rollback throws an exception
              if (localStuff.containsKey(handle)) {
                  localStuff.remove(handle);
              }
          }
     }
 
     /**
      * Create a new checkpoint (savepoint in JDBC terminology)
      *
      * @param handle the handle on which the transaction is being checkpointed
      * @param name   The name of the chckpoint, used to rollback to or release late
      */
     public void checkpoint(Handle handle, String name)
     {
         final Connection conn = handle.getConnection();
         try {
             final Savepoint savepoint = conn.setSavepoint(name);
             localStuff.get(handle).getCheckpoints().put(name, savepoint);
         }
         catch (SQLException e) {
             throw new TransactionException(String.format("Unable to create checkpoint %s", name), e);
         }
     }
 
     public void release(Handle handle, String name)
     {
         final Connection conn = handle.getConnection();
         try {
             final Savepoint savepoint = localStuff.get(handle).getCheckpoints().remove(name);
             if (savepoint == null) {
                 throw new TransactionException(String.format("Attempt to rollback to non-existant savepoint, '%s'",
                                                              name));
             }
             conn.releaseSavepoint(savepoint);
         }
         catch (SQLException e) {
             throw new TransactionException(String.format("Unable to create checkpoint %s", name), e);
         }
     }
 
     /**
      * Roll back to a named checkpoint
      *
      * @param handle the handle the rollback is being performed on
      * @param name   the name of the checkpoint to rollback to
      */
     public void rollback(Handle handle, String name)
     {
         final Connection conn = handle.getConnection();
         try {
             final Savepoint savepoint = localStuff.get(handle).getCheckpoints().remove(name);
             if (savepoint == null) {
                 throw new TransactionException(String.format("Attempt to rollback to non-existant savepoint, '%s'",
                                                              name));
             }
             conn.rollback(savepoint);
         }
         catch (SQLException e) {
             throw new TransactionException(String.format("Unable to create checkpoint %s", name), e);
         }
     }
 
     /**
      * Called to test if a handle is in a transaction
      */
     public boolean isInTransaction(Handle handle)
     {
         try {
             return !handle.getConnection().getAutoCommit();
         }
         catch (SQLException e) {
             throw new TransactionException("Failed to test for transaction status", e);
         }
     }
 
     private static class LocalStuff
     {
         private final Map<String, Savepoint> checkpoints = new HashMap<String, Savepoint>();
         private final boolean initialAutocommit;
 
         public LocalStuff(boolean initial)
         {
             this.initialAutocommit = initial;
         }
 
         public Map<String, Savepoint> getCheckpoints()
         {
             return checkpoints;
         }
 
         public boolean getInitialAutocommit()
         {
             return initialAutocommit;
         }
     }
 }