package org.avaje.datasource.pool;

import org.avaje.datasource.delegate.ConnectionDelegator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Savepoint;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Map;

/**
 * Is a connection that belongs to a DataSourcePool.
 * <p/>
 * <p>
 * It is designed to be part of DataSourcePool. Closing the connection puts it
 * back into the pool.
 * </p>
 * <p/>
 * <p>
 * It defaults autoCommit and Transaction Isolation to the defaults of the
 * DataSourcePool.
 * </p>
 * <p/>
 * <p>
 * It has caching of Statements and PreparedStatements. Remembers the last
 * statement that was executed. Keeps statistics on how long it is in use.
 * </p>
 */
public class PooledConnection extends ConnectionDelegator {

  private static final Logger logger = LoggerFactory.getLogger(PooledConnection.class);

  private static final String IDLE_CONNECTION_ACCESSED_ERROR = "Pooled Connection has been accessed whilst idle in the pool, via method: ";

  /**
   * Marker for when connection is closed due to exceeding the max allowed age.
   */
  private static final String REASON_MAXAGE = "maxAge";

  /**
   * Marker for when connection is closed due to exceeding the max inactive time.
   */
  private static final String REASON_IDLE = "idleTime";

  /**
   * Marker for when the connection is closed due to a reset.
   */
  private static final String REASON_RESET = "reset";

  /**
   * Set when connection is idle in the pool. In general when in the pool the
   * connection should not be modified.
   */
  private static final int STATUS_IDLE = 88;

  /**
   * Set when connection given to client.
   */
  private static final int STATUS_ACTIVE = 89;

  /**
   * Set when commit() or rollback() called.
   */
  private static final int STATUS_ENDED = 87;

  /**
   * Name used to identify the PooledConnection for logging.
   */
  private final String name;

  /**
   * The pool this connection belongs to.
   */
  private final ConnectionPool pool;

  /**
   * The underlying connection.
   */
  private final Connection connection;

  /**
   * The time this connection was created.
   */
  private final long creationTime;

  /**
   * Cache of the PreparedStatements
   */
  private final PstmtCache pstmtCache;

  private final Object pstmtMonitor = new Object();

  /**
   * Helper for statistics collection.
   */
  private final PooledConnectionStatistics stats = new PooledConnectionStatistics();

  /**
   * The status of the connection. IDLE, ACTIVE or ENDED.
   */
  private int status = STATUS_IDLE;

  /**
   * The reason for a connection closing.
   */
  private String closeReason;

  /**
   * Set this to true if the connection will be busy for a long time.
   * <p>
   * This means it should skip the suspected connection pool leak checking.
   * </p>
   */
  private boolean longRunning;

  /**
   * Flag to indicate that this connection had errors and should be checked to
   * make sure it is okay.
   */
  private boolean hadErrors;

  private boolean resetAutoCommit;

  /**
   * The last start time. When the connection was given to a thread.
   */
  private long startUseTime;

  /**
   * The last end time of this connection. This is to calculate the usage
   * time.
   */
  private long lastUseTime;

  private long exeStartNanos;

  /**
   * The last statement executed by this connection.
   */
  private String lastStatement;

  /**
   * The non avaje method that created the connection.
   */
  private String createdByMethod;

  /**
   * Used to find connection pool leaks.
   */
  private StackTraceElement[] stackTrace;

  private final int maxStackTrace;

  /**
   * Slot position in the BusyConnectionBuffer.
   */
  private int slotId;

  private boolean resetIsolationReadOnlyRequired;


  /**
   * Construct the connection that can refer back to the pool it belongs to.
   * <p>
   * close() will return the connection back to the pool , while
   * closeDestroy() will close() the underlining connection properly.
   * </p>
   */
  public PooledConnection(ConnectionPool pool, int uniqueId, Connection connection) {
    super(connection);

    this.pool = pool;
    this.connection = connection;
    this.name = pool.getName() + "" + uniqueId;
    this.pstmtCache = new PstmtCache(pool.getPstmtCacheSize());
    this.maxStackTrace = pool.getMaxStackTraceSize();
    this.creationTime = System.currentTimeMillis();
    this.lastUseTime = creationTime;
  }

  /**
   * For testing the pool without real connections.
   */
  protected PooledConnection(String name) {
    super(null);
    this.name = name;
    this.pool = null;
    this.connection = null;
    this.pstmtCache = null;
    this.maxStackTrace = 0;
    this.creationTime = System.currentTimeMillis();
    this.lastUseTime = creationTime;
  }

  /**
   * Return the slot position in the busy buffer.
   */
  int getSlotId() {
    return slotId;
  }

  /**
   * Set the slot position in the busy buffer.
   */
  void setSlotId(int slotId) {
    this.slotId = slotId;
  }

  /**
   * Return a string to identify the connection.
   */
  String getName() {
    return name;
  }

  private String getNameSlot() {
    return name + ":" + slotId;
  }

  public String toString() {
    return getDescription();
  }

  private long getBusySeconds() {
    return (System.currentTimeMillis() - startUseTime) / 1000;
  }

  String getDescription() {
    return "name[" + name + "] slot[" + slotId + "] startTime[" + getStartUseTime() + "] busySeconds[" + getBusySeconds() + "] createdBy[" + getCreatedByMethod() + "] stmt[" + getLastStatement() + "]";
  }

  String getFullDescription() {
    return "name[" + name + "] slot[" + slotId + "] startTime[" + getStartUseTime() + "] busySeconds[" + getBusySeconds() + "] stackTrace[" + getStackTraceAsString() + "] stmt[" + getLastStatement() + "]";
  }

  PooledConnectionStatistics getStatistics() {
    return stats;
  }

  /**
   * Return true if the connection should be treated as long running (skip connection pool leak check).
   */
  boolean isLongRunning() {
    return longRunning;
  }

  /**
   * Set this to true if the connection is a long running connection and should skip the
   * 'suspected connection pool leak' checking.
   */
  public void setLongRunning(boolean longRunning) {
    this.longRunning = longRunning;
  }

  /**
   * Close the connection fully NOT putting in back into the pool.
   * <p>
   * The logErrors parameter exists so that expected errors are not logged
   * such as when the database is known to be down.
   * </p>
   *
   * @param logErrors if false then don't log errors when closing
   */
  void closeConnectionFully(boolean logErrors) {

    if (pool != null) {
      // allow collection of load statistics
      pool.reportClosingConnection(this);
    }

    if (logger.isDebugEnabled()) {
      logger.debug("Closing Connection[{}] slot[{}] reason[{}] stats: {} , pstmtStats: {} ", name, slotId, closeReason, stats.getValues(false), pstmtCache.getDescription());
    }

    try {
      if (connection.isClosed()) {
        // Typically the JDBC Driver has its own JVM shutdown hook and already
        // closed the connections in our DataSource pool so making this DEBUG level
        logger.debug("Closing Connection[{}] that is already closed?", name);
        return;
      }
    } catch (SQLException ex) {
      if (logErrors) {
        logger.error("Error checking if connection [" + getNameSlot() + "] is closed", ex);
      }
    }

    try {
      for (ExtendedPreparedStatement ps : pstmtCache.values()) {
        ps.closeDestroy();
      }

    } catch (SQLException ex) {
      if (logErrors) {
        logger.warn("Error when closing connection Statements", ex);
      }
    }

    try {
      connection.close();
    } catch (SQLException ex) {
      if (logErrors || logger.isDebugEnabled()) {
        logger.error("Error when fully closing connection [" + getFullDescription() + "]", ex);
      }
    }
  }

  /**
   * Creates a wrapper ExtendedStatement so that I can get the executed sql. I
   * want to do this so that I can get the slowest query statments etc, and
   * log that information.
   */
  public Statement createStatement() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "createStatement()");
    }
    try {
      return connection.createStatement();
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public Statement createStatement(int resultSetType, int resultSetConcurreny) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "createStatement()");
    }
    try {
      return connection.createStatement(resultSetType, resultSetConcurreny);

    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  /**
   * Return a PreparedStatement back into the cache.
   */
  void returnPreparedStatement(ExtendedPreparedStatement pstmt) {

    synchronized (pstmtMonitor) {
      if (!pstmtCache.returnStatement(pstmt)) {
        try {
          // Already an entry in the cache with the exact same SQL...
          pstmt.closeDestroy();

        } catch (SQLException e) {
          logger.error("Error closing Pstmt", e);
        }
      }
    }
  }

  /**
   * This will try to use a cache of PreparedStatements.
   */
  public PreparedStatement prepareStatement(String sql, int returnKeysFlag) throws SQLException {
    StringBuilder cacheKey = new StringBuilder(sql.length() + 50);
    cacheKey.append(sql);
    cacheKey.append(':').append(currentSchema);
    cacheKey.append(':').append(returnKeysFlag);
    return prepareStatement(sql, true, returnKeysFlag, cacheKey.toString());
  }

  /**
   * This will try to use a cache of PreparedStatements.
   */
  public PreparedStatement prepareStatement(String sql) throws SQLException {
    StringBuilder cacheKey = new StringBuilder(sql.length() + 50);
    cacheKey.append(sql);
    cacheKey.append(':').append(currentSchema);
    return prepareStatement(sql, false, 0, cacheKey.toString());
  }

  /**
   * This will try to use a cache of PreparedStatements.
   */
  private PreparedStatement prepareStatement(String sql, boolean useFlag, int flag, String cacheKey) throws SQLException {

    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "prepareStatement()");
    }
    try {
      synchronized (pstmtMonitor) {
        lastStatement = sql;

        // try to get a matching cached PStmt from the cache.
        ExtendedPreparedStatement pstmt = pstmtCache.remove(cacheKey);

        if (pstmt != null) {
          return pstmt;
        }

        // create a new PreparedStatement
        PreparedStatement actualPstmt;
        if (useFlag) {
          actualPstmt = connection.prepareStatement(sql, flag);
        } else {
          actualPstmt = connection.prepareStatement(sql);
        }
        return new ExtendedPreparedStatement(this, actualPstmt, sql, cacheKey);
      }

    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurreny) throws SQLException {

    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "prepareStatement()");
    }
    try {
      // no caching when creating PreparedStatements this way
      lastStatement = sql;
      return connection.prepareStatement(sql, resultSetType, resultSetConcurreny);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  /**
   * Reset the connection for returning to the client. Resets the status,
   * startUseTime and hadErrors.
   */
  void resetForUse() {
    this.status = STATUS_ACTIVE;
    this.startUseTime = System.currentTimeMillis();
    this.exeStartNanos = System.nanoTime();
    this.createdByMethod = null;
    this.lastStatement = null;
    this.hadErrors = false;
    this.longRunning = false;
  }

  /**
   * When an error occurs during use add it the connection.
   * <p>
   * Any PooledConnection that has an error is checked to make sure it works
   * before it is placed back into the connection pool.
   * </p>
   */
  void markWithError() {
    hadErrors = true;
  }

  /**
   * close the connection putting it back into the connection pool.
   * <p>
   * Note that to ensure that the next transaction starts at the correct time
   * a commit() or rollback() should be called. If neither has occured at this
   * time then a rollback() is used (to end the transaction).
   * </p>
   * <p>
   * To close the connection fully use closeConnectionFully().
   * </p>
   */
  public void close() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "close()");
    }

    long durationNanos = System.nanoTime() - exeStartNanos;
    stats.add(durationNanos, hadErrors);

    if (hadErrors) {
      if (!pool.validateConnection(this)) {
        // the connection is BAD, remove it, close it and test the pool
        pool.returnConnectionForceClose(this);
        return;
      }
    }

    try {
      // reset the autoCommit back if client code changed it
      if (resetAutoCommit) {
        connection.setAutoCommit(pool.isAutoCommit());
        resetAutoCommit = false;
      }
      // Generally resetting Isolation level seems expensive.
      // Hence using resetIsolationReadOnlyRequired flag
      // performance reasons.
      if (resetIsolationReadOnlyRequired) {
        resetIsolationReadOnly();
        resetIsolationReadOnlyRequired = false;
      }

      // the connection is assumed GOOD so put it back in the pool
      lastUseTime = System.currentTimeMillis();
      // connection.clearWarnings();
      status = STATUS_IDLE;
      pool.returnConnection(this);

    } catch (Exception ex) {
      // the connection is BAD, remove it, close it and test the pool
      logger.warn("Error when trying to return connection to pool, closing fully.", ex);
      pool.returnConnectionForceClose(this);
    }
  }

  private void resetIsolationReadOnly() throws SQLException {
    // reset the transaction isolation if the client code changed it
    //noinspection MagicConstant
    if (connection.getTransactionIsolation() != pool.getTransactionIsolation()) {
      //noinspection MagicConstant
      connection.setTransactionIsolation(pool.getTransactionIsolation());
    }
    // reset readonly to false
    if (connection.isReadOnly()) {
      connection.setReadOnly(false);
    }
  }

  protected void finalize() throws Throwable {
    try {
      if (connection != null && !connection.isClosed()) {
        // connect leak?
        logger.warn("Closing Connection on finalize() - {}", getFullDescription());
        closeConnectionFully(false);
      }
    } catch (Exception e) {
      logger.error("Error when finalize is closing a connection? (unexpected)", e);
    }
    super.finalize();
  }

  /**
   * Return true if the connection is too old.
   */
  private boolean exceedsMaxAge(long maxAgeMillis) {
    if (maxAgeMillis > 0 && (creationTime < (System.currentTimeMillis() - maxAgeMillis))) {
      this.closeReason = REASON_MAXAGE;
      return true;
    }
    return false;
  }

  boolean shouldTrimOnReturn(long lastResetTime, long maxAgeMillis) {
    if (creationTime <= lastResetTime) {
      this.closeReason = REASON_RESET;
      return true;
    }
    return exceedsMaxAge(maxAgeMillis);
  }

  /**
   * Return true if the connection has been idle for too long or is too old.
   */
  boolean shouldTrim(long usedSince, long createdSince) {
    if (lastUseTime < usedSince) {
      // been idle for too long so trim it
      this.closeReason = REASON_IDLE;
      return true;
    }
    if (createdSince > 0 && createdSince > creationTime) {
      // exceeds max age so trim it
      this.closeReason = REASON_MAXAGE;
      return true;
    }
    return false;
  }

  /**
   * Return the time the connection was passed to the client code.
   * <p>
   * Used to detect busy connections that could be leaks.
   * </p>
   */
  private long getStartUseTime() {
    return startUseTime;
  }

  /**
   * Returns the time the connection was last used.
   * <p>
   * Used to close connections that have been idle for some time. Typically 5
   * minutes.
   * </p>
   */
  long getLastUsedTime() {
    return lastUseTime;
  }

  /**
   * Returns the last sql statement executed.
   */
  private String getLastStatement() {
    return lastStatement;
  }

  /**
   * Called by ExtendedStatement to trace the sql being executed.
   * <p>
   * Note with addBatch() this will not really work.
   * </p>
   */
  void setLastStatement(String lastStatement) {
    this.lastStatement = lastStatement;
    if (logger.isTraceEnabled()) {
      logger.trace(".setLastStatement[" + lastStatement + "]");
    }
  }


  /**
   * Also note the read only status needs to be reset when put back into the
   * pool.
   */
  public void setReadOnly(boolean readOnly) throws SQLException {
    // A bit loose not checking for STATUS_IDLE
    // if (status == STATUS_IDLE) {
    // throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR +
    // "setReadOnly()");
    // }
    resetIsolationReadOnlyRequired = true;
    connection.setReadOnly(readOnly);
  }

  /**
   * Also note the Isolation level needs to be reset when put back into the
   * pool.
   */
  public void setTransactionIsolation(int level) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "setTransactionIsolation()");
    }
    try {
      resetIsolationReadOnlyRequired = true;
      connection.setTransactionIsolation(level);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  //
  //
  // Simple wrapper methods which pass a method call onto the acutal
  // connection object. These methods are safe-guarded to prevent use of
  // the methods whilst the connection is in the connection pool.
  //
  //
  public void clearWarnings() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "clearWarnings()");
    }
    connection.clearWarnings();
  }

  public void commit() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "commit()");
    }
    try {
      status = STATUS_ENDED;
      connection.commit();
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public boolean getAutoCommit() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "getAutoCommit()");
    }
    return connection.getAutoCommit();
  }

  public String getCatalog() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "getCatalog()");
    }
    return connection.getCatalog();
  }

  public DatabaseMetaData getMetaData() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "getMetaData()");
    }
    return connection.getMetaData();
  }

  public int getTransactionIsolation() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "getTransactionIsolation()");
    }
    return connection.getTransactionIsolation();
  }

  public Map<String, Class<?>> getTypeMap() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "getTypeMap()");
    }
    return connection.getTypeMap();
  }

  public SQLWarning getWarnings() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "getWarnings()");
    }
    return connection.getWarnings();
  }

  public boolean isClosed() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "isClosed()");
    }
    return connection.isClosed();
  }

  public boolean isReadOnly() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "isReadOnly()");
    }
    return connection.isReadOnly();
  }

  public String nativeSQL(String sql) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "nativeSQL()");
    }
    lastStatement = sql;
    return connection.nativeSQL(sql);
  }

  public CallableStatement prepareCall(String sql) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "prepareCall()");
    }
    lastStatement = sql;
    return connection.prepareCall(sql);
  }

  public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurreny) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "prepareCall()");
    }
    lastStatement = sql;
    return connection.prepareCall(sql, resultSetType, resultSetConcurreny);
  }

  public void rollback() throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "rollback()");
    }
    try {
      status = STATUS_ENDED;
      connection.rollback();
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public void setAutoCommit(boolean autoCommit) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "setAutoCommit()");
    }
    try {
      connection.setAutoCommit(autoCommit);
      resetAutoCommit = true;
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public void setCatalog(String catalog) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "setCatalog()");
    }
    connection.setCatalog(catalog);
  }

  public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
    if (status == STATUS_IDLE) {
      throw new SQLException(IDLE_CONNECTION_ACCESSED_ERROR + "setTypeMap()");
    }
    connection.setTypeMap(map);
  }

  public Savepoint setSavepoint() throws SQLException {
    try {
      return connection.setSavepoint();
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public Savepoint setSavepoint(String savepointName) throws SQLException {
    try {
      return connection.setSavepoint(savepointName);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public void rollback(Savepoint sp) throws SQLException {
    try {
      connection.rollback(sp);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public void releaseSavepoint(Savepoint sp) throws SQLException {
    try {
      connection.releaseSavepoint(sp);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public void setHoldability(int i) throws SQLException {
    try {
      connection.setHoldability(i);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public int getHoldability() throws SQLException {
    try {
      return connection.getHoldability();
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public Statement createStatement(int i, int x, int y) throws SQLException {
    try {
      return connection.createStatement(i, x, y);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public PreparedStatement prepareStatement(String s, int i, int x, int y) throws SQLException {
    try {
      return connection.prepareStatement(s, i, x, y);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public PreparedStatement prepareStatement(String s, int[] i) throws SQLException {
    try {
      return connection.prepareStatement(s, i);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public PreparedStatement prepareStatement(String s, String[] s2) throws SQLException {
    try {
      return connection.prepareStatement(s, s2);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  public CallableStatement prepareCall(String s, int i, int x, int y) throws SQLException {
    try {
      return connection.prepareCall(s, i, x, y);
    } catch (SQLException ex) {
      markWithError();
      throw ex;
    }
  }

  /**
   * Returns the method that created the connection.
   * <p>
   * Used to help finding connection pool leaks.
   * </p>
   */
  private String getCreatedByMethod() {
    if (createdByMethod != null) {
      return createdByMethod;
    }
    if (stackTrace == null) {
      return null;
    }

    for (int j = 0; j < stackTrace.length; j++) {
      String methodLine = stackTrace[j].toString();
      if (!skipElement(methodLine)) {
        createdByMethod = methodLine;
        return createdByMethod;
      }
    }

    return null;
  }

  private boolean skipElement(String methodLine) {
    if (methodLine.startsWith("java.lang.")) {
      return true;
    } else if (methodLine.startsWith("java.util.")) {
      return true;
    } else if (methodLine.startsWith("org.avaje.datasource.")) {
      return true;
    }
    return methodLine.startsWith("com.avaje.ebean");
  }

  /**
   * Set the stack trace to help find connection pool leaks.
   */
  void setStackTrace(StackTraceElement[] stackTrace) {
    this.stackTrace = stackTrace;
  }

  /**
   * Return the stackTrace as a String for logging purposes.
   */
  private String getStackTraceAsString() {
    StackTraceElement[] stackTrace = getStackTrace();
    if (stackTrace == null) {
      return "";
    }
    return Arrays.toString(stackTrace);
  }

  /**
   * Return the full stack trace that got the connection from the pool. You
   * could use this if getCreatedByMethod() doesn't work for you.
   */
  private StackTraceElement[] getStackTrace() {

    if (stackTrace == null) {
      return null;
    }

    // filter off the top of the stack that we are not interested in
    ArrayList<StackTraceElement> filteredList = new ArrayList<StackTraceElement>();
    boolean include = false;
    for (int i = 0; i < stackTrace.length; i++) {
      if (!include && !skipElement(stackTrace[i].toString())) {
        include = true;
      }
      if (include && filteredList.size() < maxStackTrace) {
        filteredList.add(stackTrace[i]);
      }
    }
    return filteredList.toArray(new StackTraceElement[filteredList.size()]);

  }

}