System.Data.SQLite
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/********************************************************
 * ADO.NET 2.0 Data Provider for SQLite Version 3.X
 * Written by Robert Simpson (robert@blackcastlesoft.com)
 * 
 * Released to the public domain, use at your own risk!
 ********************************************************/

namespace System.Data.SQLite
{
  using System;
  using System.Data;
  using System.Data.Common;
  using System.Collections.Generic;
  using System.ComponentModel;

  /// <summary>
  /// SQLite implementation of DbCommand.
  /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
  [Designer("SQLite.Designer.SQLiteCommandDesigner, SQLite.Designer, Version=1.0.38.1, Culture=neutral, PublicKeyToken=db937bc2d44ff139"), ToolboxItem(true)]
#endif
  public sealed class SQLiteCommand : DbCommand, ICloneable
  {
    /// <summary>
    /// The command text this command is based on
    /// </summary>
    private string _commandText;
    /// <summary>
    /// The connection the command is associated with
    /// </summary>
    private SQLiteConnection _cnn;
    /// <summary>
    /// The version of the connection the command is associated with
    /// </summary>
    private long _version;
    /// <summary>
    /// Indicates whether or not a DataReader is active on the command.
    /// </summary>
    private WeakReference _activeReader;
    /// <summary>
    /// The timeout for the command, kludged because SQLite doesn't support per-command timeout values
    /// </summary>
    internal int _commandTimeout;
    /// <summary>
    /// Designer support
    /// </summary>
    private bool _designTimeVisible;
    /// <summary>
    /// Used by DbDataAdapter to determine updating behavior
    /// </summary>
    private UpdateRowSource _updateRowSource;
    /// <summary>
    /// The collection of parameters for the command
    /// </summary>
    private SQLiteParameterCollection _parameterCollection;
    /// <summary>
    /// The SQL command text, broken into individual SQL statements as they are executed
    /// </summary>
    internal List<SQLiteStatement> _statementList;
    /// <summary>
    /// Unprocessed SQL text that has not been executed
    /// </summary>
    internal string _remainingText;
    /// <summary>
    /// Transaction associated with this command
    /// </summary>
    private SQLiteTransaction _transaction;

    ///<overloads>
    /// Constructs a new SQLiteCommand
    /// </overloads>
    /// <summary>
    /// Default constructor
    /// </summary>
    public SQLiteCommand() :this(null, null)
    {
    }

    /// <summary>
    /// Initializes the command with the given command text
    /// </summary>
    /// <param name="commandText">The SQL command text</param>
    public SQLiteCommand(string commandText) 
      : this(commandText, null, null)
    {
    }

    /// <summary>
    /// Initializes the command with the given SQL command text and attach the command to the specified
    /// connection.
    /// </summary>
    /// <param name="commandText">The SQL command text</param>
    /// <param name="connection">The connection to associate with the command</param>
    public SQLiteCommand(string commandText, SQLiteConnection connection)
      : this(commandText, connection, null)
    {
    }

    /// <summary>
    /// Initializes the command and associates it with the specified connection.
    /// </summary>
    /// <param name="connection">The connection to associate with the command</param>
    public SQLiteCommand(SQLiteConnection connection) 
      : this(null, connection, null)
    {
    }

    private SQLiteCommand(SQLiteCommand source) : this(source.CommandText, source.Connection, source.Transaction)
    {
      CommandTimeout = source.CommandTimeout;
      DesignTimeVisible = source.DesignTimeVisible;
      UpdatedRowSource = source.UpdatedRowSource;

      foreach (SQLiteParameter param in source._parameterCollection)
      {
        Parameters.Add(param.Clone());
      }
    }

    /// <summary>
    /// Initializes a command with the given SQL, connection and transaction
    /// </summary>
    /// <param name="commandText">The SQL command text</param>
    /// <param name="connection">The connection to associate with the command</param>
    /// <param name="transaction">The transaction the command should be associated with</param>
    public SQLiteCommand(string commandText, SQLiteConnection connection, SQLiteTransaction transaction)
    {
      _commandTimeout = 30;
      _parameterCollection = new SQLiteParameterCollection(this);
      _designTimeVisible = true;
      _updateRowSource = UpdateRowSource.None;

      if (commandText != null)
        CommandText = commandText;

      if (connection != null)
      {
        DbConnection = connection;
        _commandTimeout = connection.DefaultTimeout;
      }

      if (transaction != null)
        Transaction = transaction;
    }

    /// <summary>
    /// Disposes of the command and clears all member variables
    /// </summary>
    /// <param name="disposing">Whether or not the class is being explicitly or implicitly disposed</param>
    protected override void Dispose(bool disposing)
    {
      base.Dispose(disposing);

      if (disposing)
      {
        // If a reader is active on this command, don't destroy the command, instead let the reader do it
        SQLiteDataReader reader = null;
        if (_activeReader != null)
        {
          try
          {
            reader = _activeReader.Target as SQLiteDataReader;
          }
          catch(InvalidOperationException)
          {
          }
        }

        if (reader != null)
        {
          reader._disposeCommand = true;
          _activeReader = null;
          return;
        }

        Connection = null;
        _parameterCollection.Clear();
        _commandText = null;
      }
    }

    /// <summary>
    /// Clears and destroys all statements currently prepared
    /// </summary>
    internal void ClearCommands()
    {
      if (_activeReader != null)
      {
        SQLiteDataReader reader = null;
        try
        {
          reader = _activeReader.Target as SQLiteDataReader;
        }
        catch(InvalidOperationException)
        {
        }

        if (reader != null)
          reader.Close();

        _activeReader = null;
      }

      if (_statementList == null) return;

      int x = _statementList.Count;
      for (int n = 0; n < x; n++)
        _statementList[n].Dispose();

      _statementList = null;

      _parameterCollection.Unbind();
    }

    /// <summary>
    /// Builds an array of prepared statements for each complete SQL statement in the command text
    /// </summary>
    internal SQLiteStatement BuildNextCommand()
    {
      SQLiteStatement stmt = null;

      try
      {
        if (_statementList == null)
          _remainingText = _commandText;

        stmt = _cnn._sql.Prepare(_cnn, _remainingText, (_statementList == null) ? null : _statementList[_statementList.Count - 1], (uint)(_commandTimeout * 1000), out _remainingText);
        if (stmt != null)
        {
          stmt._command = this;
          if (_statementList == null)
            _statementList = new List<SQLiteStatement>();

          _statementList.Add(stmt);

          _parameterCollection.MapParameters(stmt);
          stmt.BindParameters();
        }        
        return stmt;
      }
      catch (Exception)
      {
        if (stmt != null)
        {
          if (_statementList.Contains(stmt))
            _statementList.Remove(stmt);

          stmt.Dispose();
        }

        // If we threw an error compiling the statement, we cannot continue on so set the remaining text to null.
        _remainingText = null;

        throw;
      }
    }

    internal SQLiteStatement GetStatement(int index)
    {
      // Haven't built any statements yet
      if (_statementList == null) return BuildNextCommand();

      // If we're at the last built statement and want the next unbuilt statement, then build it
      if (index == _statementList.Count)
      {
        if (String.IsNullOrEmpty(_remainingText) == false) return BuildNextCommand();
        else return null; // No more commands
      }

      SQLiteStatement stmt = _statementList[index];
      stmt.BindParameters();

      return stmt;
    }

    /// <summary>
    /// Not implemented
    /// </summary>
    public override void Cancel()
    {
      if (_activeReader != null)
      {
        SQLiteDataReader reader = _activeReader.Target as SQLiteDataReader;
        if (reader != null)
          reader.Cancel();
      }
    }

    /// <summary>
    /// The SQL command text associated with the command
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [DefaultValue(""), RefreshProperties(RefreshProperties.All), Editor("Microsoft.VSDesigner.Data.SQL.Design.SqlCommandTextEditor, Microsoft.VSDesigner, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", "System.Drawing.Design.UITypeEditor, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
#endif
    public override string CommandText
    {
      get
      {
        return _commandText;
      }
      set
      {
        if (_commandText == value) return;

        if (_activeReader != null && _activeReader.IsAlive)
        {
          throw new InvalidOperationException("Cannot set CommandText while a DataReader is active");
        }

        ClearCommands();
        _commandText = value;

        if (_cnn == null) return;
      }
    }

    /// <summary>
    /// The amount of time to wait for the connection to become available before erroring out
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [DefaultValue((int)30)]
#endif
    public override int CommandTimeout
    {
      get
      {
        return _commandTimeout;
      }
      set
      {
        _commandTimeout = value;
      }
    }

    /// <summary>
    /// The type of the command.  SQLite only supports CommandType.Text
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [RefreshProperties(RefreshProperties.All), DefaultValue(CommandType.Text)]
#endif
    public override CommandType CommandType
    {
      get
      {
        return CommandType.Text;
      }
      set
      {
        if (value != CommandType.Text)
        {
          throw new NotSupportedException();
        }
      }
    }

    /// <summary>
    /// Forwards to the local CreateParameter() function
    /// </summary>
    /// <returns></returns>
    protected override DbParameter CreateDbParameter()
    {
      return CreateParameter();
    }

    /// <summary>
    /// Create a new parameter
    /// </summary>
    /// <returns></returns>
    public new SQLiteParameter CreateParameter()
    {
      return new SQLiteParameter();
    }

    /// <summary>
    /// The connection associated with this command
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [DefaultValue((string)null), Editor("Microsoft.VSDesigner.Data.Design.DbConnectionEditor, Microsoft.VSDesigner, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", "System.Drawing.Design.UITypeEditor, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
#endif
    public new SQLiteConnection Connection
    {
      get { return _cnn; }
      set
      {
        if (_activeReader != null && _activeReader.IsAlive)
          throw new InvalidOperationException("Cannot set Connection while a DataReader is active");

        if (_cnn != null)
        {
          ClearCommands();
          //_cnn.RemoveCommand(this);
        }

        _cnn = value;
        if (_cnn != null)
          _version = _cnn._version;

        //if (_cnn != null)
        //  _cnn.AddCommand(this);
      }
    }

    /// <summary>
    /// Forwards to the local Connection property
    /// </summary>
    protected override DbConnection DbConnection
    {
      get
      {
        return Connection;
      }
      set
      {
        Connection = (SQLiteConnection)value;
      }
    }

    /// <summary>
    /// Returns the SQLiteParameterCollection for the given command
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
#endif
    public new SQLiteParameterCollection Parameters
    {
      get { return _parameterCollection; }
    }

    /// <summary>
    /// Forwards to the local Parameters property
    /// </summary>
    protected override DbParameterCollection DbParameterCollection
    {
      get
      {
        return Parameters;
      }
    }

    /// <summary>
    /// The transaction associated with this command.  SQLite only supports one transaction per connection, so this property forwards to the
    /// command's underlying connection.
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
#endif
    public new SQLiteTransaction Transaction
    {
      get { return _transaction; }
      set
      {
        if (_cnn != null)
        {
          if (_activeReader != null && _activeReader.IsAlive)
            throw new InvalidOperationException("Cannot set Transaction while a DataReader is active");

          if (value != null)
          {
            if (value._cnn != _cnn)
              throw new ArgumentException("Transaction is not associated with the command's connection");
          }
          _transaction = value;
        }
        else
        {
          if (value != null) Connection = value.Connection;
          _transaction = value;
        }
      }
    }

    /// <summary>
    /// Forwards to the local Transaction property
    /// </summary>
    protected override DbTransaction DbTransaction
    {
      get
      {
        return Transaction;
      }
      set
      {
        Transaction = (SQLiteTransaction)value;
      }
    }

    /// <summary>
    /// This function ensures there are no active readers, that we have a valid connection,
    /// that the connection is open, that all statements are prepared and all parameters are assigned
    /// in preparation for allocating a data reader.
    /// </summary>
    private void InitializeForReader()
    {
      if (_activeReader != null && _activeReader.IsAlive)
        throw new InvalidOperationException("DataReader already active on this command");

      if (_cnn == null)
        throw new InvalidOperationException("No connection associated with this command");

      if (_cnn.State != ConnectionState.Open)
        throw new InvalidOperationException("Database is not open");

      // If the version of the connection has changed, clear out any previous commands before starting
      if (_cnn._version != _version)
      {
        _version = _cnn._version;
        ClearCommands();
      }

      // Map all parameters for statements already built
      _parameterCollection.MapParameters(null);

      //// Set the default command timeout
      //_cnn._sql.SetTimeout(_commandTimeout * 1000);
    }

    /// <summary>
    /// Creates a new SQLiteDataReader to execute/iterate the array of SQLite prepared statements
    /// </summary>
    /// <param name="behavior">The behavior the data reader should adopt</param>
    /// <returns>Returns a SQLiteDataReader object</returns>
    protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior)
    {
      return ExecuteReader(behavior);
    }

    /// <summary>
    /// Overrides the default behavior to return a SQLiteDataReader specialization class
    /// </summary>
    /// <param name="behavior">The flags to be associated with the reader</param>
    /// <returns>A SQLiteDataReader</returns>
    public new SQLiteDataReader ExecuteReader(CommandBehavior behavior)
    {
      InitializeForReader();

      SQLiteDataReader rd = new SQLiteDataReader(this, behavior);
      _activeReader = new WeakReference(rd, false);

      return rd;
    }

    /// <summary>
    /// Overrides the default behavior of DbDataReader to return a specialized SQLiteDataReader class
    /// </summary>
    /// <returns>A SQLiteDataReader</returns>
    public new SQLiteDataReader ExecuteReader()
    {
      return ExecuteReader(CommandBehavior.Default);
    }

    /// <summary>
    /// Called by the SQLiteDataReader when the data reader is closed.
    /// </summary>
    internal void ClearDataReader()
    {
      _activeReader = null;
    }

    /// <summary>
    /// Execute the command and return the number of rows inserted/updated affected by it.
    /// </summary>
    /// <returns></returns>
    public override int ExecuteNonQuery()
    {
      using (SQLiteDataReader reader = ExecuteReader(CommandBehavior.SingleRow | CommandBehavior.SingleResult))
      {
        while (reader.NextResult()) ;
        return reader.RecordsAffected;
      }
    }

    /// <summary>
    /// Execute the command and return the first column of the first row of the resultset
    /// (if present), or null if no resultset was returned.
    /// </summary>
    /// <returns>The first column of the first row of the first resultset from the query</returns>
    public override object ExecuteScalar()
    {
      using (SQLiteDataReader reader = ExecuteReader(CommandBehavior.SingleRow | CommandBehavior.SingleResult))
      {
        if (reader.Read())
          return reader[0];
      }
      return null;
    }

    /// <summary>
    /// Does nothing.  Commands are prepared as they are executed the first time, and kept in prepared state afterwards.
    /// </summary>
    public override void Prepare()
    {
    }

    /// <summary>
    /// Sets the method the SQLiteCommandBuilder uses to determine how to update inserted or updated rows in a DataTable.
    /// </summary>
    [DefaultValue(UpdateRowSource.None)]
    public override UpdateRowSource UpdatedRowSource
    {
      get
      {
        return _updateRowSource;
      }
      set
      {
        _updateRowSource = value;
      }
    }

    /// <summary>
    /// Determines if the command is visible at design time.  Defaults to True.
    /// </summary>
#if !PLATFORM_COMPACTFRAMEWORK
    [DesignOnly(true), Browsable(false), DefaultValue(true), EditorBrowsable(EditorBrowsableState.Never)]
#endif
    public override bool DesignTimeVisible
    {
      get
      {
        return _designTimeVisible;
      }
      set
      {
        _designTimeVisible = value;
#if !PLATFORM_COMPACTFRAMEWORK
        TypeDescriptor.Refresh(this);
#endif
      }
    }

    /// <summary>
    /// Clones a command, including all its parameters
    /// </summary>
    /// <returns>A new SQLiteCommand with the same commandtext, connection and parameters</returns>
    public object Clone()
    {
      return new SQLiteCommand(this);
    }
  }
}