/**
    *    Copyright 2009-2015 the original author or authors.
    *
    *    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.apache.ibatis.datasource.pooled;
  
  import java.io.PrintWriter;
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.Proxy;
  import java.sql.Connection;
  import java.sql.DriverManager;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.util.Properties;
  import java.util.logging.Logger;
  
  import javax.sql.DataSource;
  
  import org.apache.ibatis.datasource.unpooled.UnpooledDataSource;
  import org.apache.ibatis.logging.Log;
  import org.apache.ibatis.logging.LogFactory;
  
  /**
   * This is a simple, synchronous, thread-safe database connection pool.
   *
   * @author Clinton Begin
   */
  public class PooledDataSource implements DataSource {
  
    private static final Log log = LogFactory.getLog(PooledDataSource.class);
  
    private final PoolState state = new PoolState(this);
  
    private final UnpooledDataSource dataSource;
  
    // OPTIONAL CONFIGURATION FIELDS
    protected int poolMaximumActiveConnections = 10;
    protected int poolMaximumIdleConnections = 5;
    protected int poolMaximumCheckoutTime = 20000;
    protected int poolTimeToWait = 20000;
    protected String poolPingQuery = "NO PING QUERY SET";
    protected boolean poolPingEnabled = false;
    protected int poolPingConnectionsNotUsedFor = 0;
  
    private int expectedConnectionTypeCode;
  
    public PooledDataSource() {
      dataSource = new UnpooledDataSource();
    }
  
    public PooledDataSource(UnpooledDataSource dataSource) {
      this.dataSource = dataSource;
    }
  
    public PooledDataSource(String driver, String url, String username, String password) {
      dataSource = new UnpooledDataSource(driver, url, username, password);
      expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
    }
  
    public PooledDataSource(String driver, String url, Properties driverProperties) {
      dataSource = new UnpooledDataSource(driver, url, driverProperties);
      expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
    }
  
    public PooledDataSource(ClassLoader driverClassLoader, String driver, String url, String username, String password) {
      dataSource = new UnpooledDataSource(driverClassLoader, driver, url, username, password);
      expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
    }
  
    public PooledDataSource(ClassLoader driverClassLoader, String driver, String url, Properties driverProperties) {
      dataSource = new UnpooledDataSource(driverClassLoader, driver, url, driverProperties);
      expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
    }
  
    @Override
    public Connection getConnection() throws SQLException {
      return popConnection(dataSource.getUsername(), dataSource.getPassword()).getProxyConnection();
    }
  
    @Override
    public Connection getConnection(String username, String password) throws SQLException {
      return popConnection(username, password).getProxyConnection();
    }
  
    @Override
    public void setLoginTimeout(int loginTimeout) throws SQLException {
      DriverManager.setLoginTimeout(loginTimeout);
   }
 
   @Override
   public int getLoginTimeout() throws SQLException {
     return DriverManager.getLoginTimeout();
   }
 
   @Override
   public void setLogWriter(PrintWriter logWriter) throws SQLException {
     DriverManager.setLogWriter(logWriter);
   }
 
   @Override
   public PrintWriter getLogWriter() throws SQLException {
     return DriverManager.getLogWriter();
   }
 
   public void setDriver(String driver) {
     dataSource.setDriver(driver);
     forceCloseAll();
   }
 
   public void setUrl(String url) {
     dataSource.setUrl(url);
     forceCloseAll();
   }
 
   public void setUsername(String username) {
     dataSource.setUsername(username);
     forceCloseAll();
   }
 
   public void setPassword(String password) {
     dataSource.setPassword(password);
     forceCloseAll();
   }
 
   public void setDefaultAutoCommit(boolean defaultAutoCommit) {
     dataSource.setAutoCommit(defaultAutoCommit);
     forceCloseAll();
   }
 
   public void setDefaultTransactionIsolationLevel(Integer defaultTransactionIsolationLevel) {
     dataSource.setDefaultTransactionIsolationLevel(defaultTransactionIsolationLevel);
     forceCloseAll();
   }
 
   public void setDriverProperties(Properties driverProps) {
     dataSource.setDriverProperties(driverProps);
     forceCloseAll();
   }
 
   /*
    * The maximum number of active connections
    *
    * @param poolMaximumActiveConnections The maximum number of active connections
    */
   public void setPoolMaximumActiveConnections(int poolMaximumActiveConnections) {
     this.poolMaximumActiveConnections = poolMaximumActiveConnections;
     forceCloseAll();
   }
 
   /*
    * The maximum number of idle connections
    *
    * @param poolMaximumIdleConnections The maximum number of idle connections
    */
   public void setPoolMaximumIdleConnections(int poolMaximumIdleConnections) {
     this.poolMaximumIdleConnections = poolMaximumIdleConnections;
     forceCloseAll();
   }
 
   /*
    * The maximum time a connection can be used before it *may* be
    * given away again.
    *
    * @param poolMaximumCheckoutTime The maximum time
    */
   public void setPoolMaximumCheckoutTime(int poolMaximumCheckoutTime) {
     this.poolMaximumCheckoutTime = poolMaximumCheckoutTime;
     forceCloseAll();
   }
 
   /*
    * The time to wait before retrying to get a connection
    *
    * @param poolTimeToWait The time to wait
    */
   public void setPoolTimeToWait(int poolTimeToWait) {
     this.poolTimeToWait = poolTimeToWait;
     forceCloseAll();
   }
 
   /*
    * The query to be used to check a connection
    *
    * @param poolPingQuery The query
    */
   public void setPoolPingQuery(String poolPingQuery) {
     this.poolPingQuery = poolPingQuery;
     forceCloseAll();
   }
 
   /*
    * Determines if the ping query should be used.
    *
    * @param poolPingEnabled True if we need to check a connection before using it
    */
   public void setPoolPingEnabled(boolean poolPingEnabled) {
     this.poolPingEnabled = poolPingEnabled;
     forceCloseAll();
   }
 
   /*
    * If a connection has not been used in this many milliseconds, ping the
    * database to make sure the connection is still good.
    *
    * @param milliseconds the number of milliseconds of inactivity that will trigger a ping
    */
   public void setPoolPingConnectionsNotUsedFor(int milliseconds) {
     this.poolPingConnectionsNotUsedFor = milliseconds;
     forceCloseAll();
   }
 
   public String getDriver() {
     return dataSource.getDriver();
   }
 
   public String getUrl() {
     return dataSource.getUrl();
   }
 
   public String getUsername() {
     return dataSource.getUsername();
   }
 
   public String getPassword() {
     return dataSource.getPassword();
   }
 
   public boolean isAutoCommit() {
     return dataSource.isAutoCommit();
   }
 
   public Integer getDefaultTransactionIsolationLevel() {
     return dataSource.getDefaultTransactionIsolationLevel();
   }
 
   public Properties getDriverProperties() {
     return dataSource.getDriverProperties();
   }
 
   public int getPoolMaximumActiveConnections() {
     return poolMaximumActiveConnections;
   }
 
   public int getPoolMaximumIdleConnections() {
     return poolMaximumIdleConnections;
   }
 
   public int getPoolMaximumCheckoutTime() {
     return poolMaximumCheckoutTime;
   }
 
   public int getPoolTimeToWait() {
     return poolTimeToWait;
   }
 
   public String getPoolPingQuery() {
     return poolPingQuery;
   }
 
   public boolean isPoolPingEnabled() {
     return poolPingEnabled;
   }
 
   public int getPoolPingConnectionsNotUsedFor() {
     return poolPingConnectionsNotUsedFor;
   }
 
   /*
    * Closes all active and idle connections in the pool
    */
   public void forceCloseAll() {
     synchronized (state) {
       expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
       for (int i = state.activeConnections.size(); i > 0; i--) {
         try {
           PooledConnection conn = state.activeConnections.remove(i - 1);
           conn.invalidate();
 
           Connection realConn = conn.getRealConnection();
           if (!realConn.getAutoCommit()) {
             realConn.rollback();
           }
           realConn.close();
         } catch (Exception e) {
           // ignore
         }
       }
       for (int i = state.idleConnections.size(); i > 0; i--) {
         try {
           PooledConnection conn = state.idleConnections.remove(i - 1);
           conn.invalidate();
 
           Connection realConn = conn.getRealConnection();
           if (!realConn.getAutoCommit()) {
             realConn.rollback();
           }
           realConn.close();
         } catch (Exception e) {
           // ignore
         }
       }
     }
     if (log.isDebugEnabled()) {
       log.debug("PooledDataSource forcefully closed/removed all connections.");
     }
   }
 
   public PoolState getPoolState() {
     return state;
   }
 
   private int assembleConnectionTypeCode(String url, String username, String password) {
     return ("" + url + username + password).hashCode();
   }
 
   protected void pushConnection(PooledConnection conn) throws SQLException {
 
     synchronized (state) {
       state.activeConnections.remove(conn);
       if (conn.isValid()) {
         if (state.idleConnections.size() < poolMaximumIdleConnections && conn.getConnectionTypeCode() == expectedConnectionTypeCode) {
           state.accumulatedCheckoutTime += conn.getCheckoutTime();
           if (!conn.getRealConnection().getAutoCommit()) {
             conn.getRealConnection().rollback();
           }
           PooledConnection newConn = new PooledConnection(conn.getRealConnection(), this);
           state.idleConnections.add(newConn);
           newConn.setCreatedTimestamp(conn.getCreatedTimestamp());
           newConn.setLastUsedTimestamp(conn.getLastUsedTimestamp());
           conn.invalidate();
           if (log.isDebugEnabled()) {
             log.debug("Returned connection " + newConn.getRealHashCode() + " to pool.");
           }
           state.notifyAll();
         } else {
           state.accumulatedCheckoutTime += conn.getCheckoutTime();
           if (!conn.getRealConnection().getAutoCommit()) {
             conn.getRealConnection().rollback();
           }
           conn.getRealConnection().close();
           if (log.isDebugEnabled()) {
             log.debug("Closed connection " + conn.getRealHashCode() + ".");
           }
           conn.invalidate();
         }
       } else {
         if (log.isDebugEnabled()) {
           log.debug("A bad connection (" + conn.getRealHashCode() + ") attempted to return to the pool, discarding connection.");
         }
         state.badConnectionCount++;
       }
     }
   }
 
   private PooledConnection popConnection(String username, String password) throws SQLException {
     boolean countedWait = false;
     PooledConnection conn = null;
     long t = System.currentTimeMillis();
     int localBadConnectionCount = 0;
 
     while (conn == null) {
       synchronized (state) {
         if (!state.idleConnections.isEmpty()) {
           // Pool has available connection
           conn = state.idleConnections.remove(0);
           if (log.isDebugEnabled()) {
             log.debug("Checked out connection " + conn.getRealHashCode() + " from pool.");
           }
         } else {
           // Pool does not have available connection
           if (state.activeConnections.size() < poolMaximumActiveConnections) {
             // Can create new connection
             conn = new PooledConnection(dataSource.getConnection(), this);
             if (log.isDebugEnabled()) {
               log.debug("Created connection " + conn.getRealHashCode() + ".");
             }
           } else {
             // Cannot create new connection
             PooledConnection oldestActiveConnection = state.activeConnections.get(0);
             long longestCheckoutTime = oldestActiveConnection.getCheckoutTime();
             if (longestCheckoutTime > poolMaximumCheckoutTime) {
               // Can claim overdue connection
               state.claimedOverdueConnectionCount++;
               state.accumulatedCheckoutTimeOfOverdueConnections += longestCheckoutTime;
               state.accumulatedCheckoutTime += longestCheckoutTime;
               state.activeConnections.remove(oldestActiveConnection);
               if (!oldestActiveConnection.getRealConnection().getAutoCommit()) {
                 oldestActiveConnection.getRealConnection().rollback();
               }
               conn = new PooledConnection(oldestActiveConnection.getRealConnection(), this);
               oldestActiveConnection.invalidate();
               if (log.isDebugEnabled()) {
                 log.debug("Claimed overdue connection " + conn.getRealHashCode() + ".");
               }
             } else {
               // Must wait
               try {
                 if (!countedWait) {
                   state.hadToWaitCount++;
                   countedWait = true;
                 }
                 if (log.isDebugEnabled()) {
                   log.debug("Waiting as long as " + poolTimeToWait + " milliseconds for connection.");
                 }
                 long wt = System.currentTimeMillis();
                 state.wait(poolTimeToWait);
                 state.accumulatedWaitTime += System.currentTimeMillis() - wt;
               } catch (InterruptedException e) {
                 break;
               }
             }
           }
         }
         if (conn != null) {
           if (conn.isValid()) {
             if (!conn.getRealConnection().getAutoCommit()) {
               conn.getRealConnection().rollback();
             }
             conn.setConnectionTypeCode(assembleConnectionTypeCode(dataSource.getUrl(), username, password));
             conn.setCheckoutTimestamp(System.currentTimeMillis());
             conn.setLastUsedTimestamp(System.currentTimeMillis());
             state.activeConnections.add(conn);
             state.requestCount++;
             state.accumulatedRequestTime += System.currentTimeMillis() - t;
           } else {
             if (log.isDebugEnabled()) {
               log.debug("A bad connection (" + conn.getRealHashCode() + ") was returned from the pool, getting another connection.");
             }
             state.badConnectionCount++;
             localBadConnectionCount++;
             conn = null;
             if (localBadConnectionCount > (poolMaximumIdleConnections + 3)) {
               if (log.isDebugEnabled()) {
                 log.debug("PooledDataSource: Could not get a good connection to the database.");
               }
               throw new SQLException("PooledDataSource: Could not get a good connection to the database.");
             }
           }
         }
       }
 
     }
 
     if (conn == null) {
       if (log.isDebugEnabled()) {
         log.debug("PooledDataSource: Unknown severe error condition.  The connection pool returned a null connection.");
       }
       throw new SQLException("PooledDataSource: Unknown severe error condition.  The connection pool returned a null connection.");
     }
 
     return conn;
   }
 
   /*
    * Method to check to see if a connection is still usable
    *
    * @param conn - the connection to check
    * @return True if the connection is still usable
    */
   protected boolean pingConnection(PooledConnection conn) {
     boolean result = true;
 
     try {
       result = !conn.getRealConnection().isClosed();
     } catch (SQLException e) {
       if (log.isDebugEnabled()) {
         log.debug("Connection " + conn.getRealHashCode() + " is BAD: " + e.getMessage());
       }
       result = false;
     }
 
     if (result) {
       if (poolPingEnabled) {
         if (poolPingConnectionsNotUsedFor >= 0 && conn.getTimeElapsedSinceLastUse() > poolPingConnectionsNotUsedFor) {
           try {
             if (log.isDebugEnabled()) {
               log.debug("Testing connection " + conn.getRealHashCode() + " ...");
             }
             Connection realConn = conn.getRealConnection();
             Statement statement = realConn.createStatement();
             ResultSet rs = statement.executeQuery(poolPingQuery);
             rs.close();
             statement.close();
             if (!realConn.getAutoCommit()) {
               realConn.rollback();
             }
             result = true;
             if (log.isDebugEnabled()) {
               log.debug("Connection " + conn.getRealHashCode() + " is GOOD!");
             }
           } catch (Exception e) {
             log.warn("Execution of ping query '" + poolPingQuery + "' failed: " + e.getMessage());
             try {
               conn.getRealConnection().close();
             } catch (Exception e2) {
               //ignore
             }
             result = false;
             if (log.isDebugEnabled()) {
               log.debug("Connection " + conn.getRealHashCode() + " is BAD: " + e.getMessage());
             }
           }
         }
       }
     }
     return result;
   }
 
   /*
    * Unwraps a pooled connection to get to the 'real' connection
    *
    * @param conn - the pooled connection to unwrap
    * @return The 'real' connection
    */
   public static Connection unwrapConnection(Connection conn) {
     if (Proxy.isProxyClass(conn.getClass())) {
       InvocationHandler handler = Proxy.getInvocationHandler(conn);
       if (handler instanceof PooledConnection) {
         return ((PooledConnection) handler).getRealConnection();
       }
     }
     return conn;
   }
 
   protected void finalize() throws Throwable {
     forceCloseAll();
     super.finalize();
   }
 
   public <T> T unwrap(Class<T> iface) throws SQLException {
     throw new SQLException(getClass().getName() + " is not a wrapper.");
   }
 
   public boolean isWrapperFor(Class<?> iface) throws SQLException {
     return false;
   }
 
   public Logger getParentLogger() {
     return Logger.getLogger(Logger.GLOBAL_LOGGER_NAME); // requires JDK version 1.6
   }
 
 }