?/********************************************************
 * 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.Globalization;
  using System.Reflection;

  /// <summary>
  /// SQLite implementation of DbDataReader.
  /// </summary>
  public sealed class SQLiteDataReader : DbDataReader
  {
    /// <summary>
    /// Underlying command this reader is attached to
    /// </summary>
    private SQLiteCommand   _command;
    /// <summary>
    /// Index of the current statement in the command being processed
    /// </summary>
    private int             _activeStatementIndex;
    /// <summary>
    /// Current statement being Read()
    /// </summary>
    private SQLiteStatement _activeStatement;
    /// <summary>
    /// State of the current statement being processed.
    /// -1 = First Step() executed, so the first Read() will be ignored
    ///  0 = Actively reading
    ///  1 = Finished reading
    ///  2 = Non-row-returning statement, no records
    /// </summary>
    private int             _readingState;
    /// <summary>
    /// Number of records affected by the insert/update statements executed on the command
    /// </summary>
    private int             _rowsAffected;
    /// <summary>
    /// Count of fields (columns) in the row-returning statement currently being processed
    /// </summary>
    private int             _fieldCount;
    /// <summary>
    /// Datatypes of active fields (columns) in the current statement, used for type-restricting data
    /// </summary>
    private SQLiteType[]    _fieldTypeArray;

    /// <summary>
    /// The behavior of the datareader
    /// </summary>
    private CommandBehavior _commandBehavior;

    /// <summary>
    /// If set, then dispose of the command object when the reader is finished
    /// </summary>
    internal bool           _disposeCommand;

    /// <summary>
    /// Internal constructor, initializes the datareader and sets up to begin executing statements
    /// </summary>
    /// <param name="cmd">The SQLiteCommand this data reader is for</param>
    /// <param name="behave">The expected behavior of the data reader</param>
    internal SQLiteDataReader(SQLiteCommand cmd, CommandBehavior behave)
    {
      _command = cmd;
      _commandBehavior = behave;
      _activeStatementIndex = -1;
      _activeStatement = null;
      _rowsAffected = -1;
      _fieldCount = -1;

      if (_command != null)
        NextResult();
    }

    /// <summary>
    /// Closes the datareader, potentially closing the connection as well if CommandBehavior.CloseConnection was specified.
    /// </summary>
    public override void Close()
    {
      if (_command != null)
      {
        while (NextResult())
        {
        }
        _command.ClearDataReader();

        if (_disposeCommand)
          ((IDisposable)_command).Dispose();
      }

      // If the datareader's behavior includes closing the connection, then do so here.
      if ((_commandBehavior & CommandBehavior.CloseConnection) != 0)
        _command.Connection.Close();

      _command = null;
      _activeStatement = null;
      _fieldTypeArray = null;
    }

    /// <summary>
    /// Disposes the datareader.  Calls Close() to ensure everything is cleaned up.
    /// </summary>
    protected override void Dispose(bool disposing)
    {
      base.Dispose(disposing);
      GC.SuppressFinalize(this);
    }

    /// <summary>
    /// Throw an error if the datareader is closed
    /// </summary>
    private void CheckClosed()
    {
      if (_command == null)
        throw new InvalidOperationException("DataReader has been closed");
    }

    /// <summary>
    /// Throw an error if a row is not loaded
    /// </summary>
    private void CheckValidRow()
    {
      if (_readingState != 0)
        throw new InvalidOperationException("No current row");
    }

    /// <summary>
    /// Enumerator support
    /// </summary>
    /// <returns>Returns a DbEnumerator object.</returns>
    public override Collections.IEnumerator GetEnumerator()
    {
      return new DbEnumerator(this);
    }

    /// <summary>
    /// Not implemented.  Returns 0
    /// </summary>
    public override int Depth
    {
      get
      {
        CheckClosed();
        return 0;
      }
    }

    /// <summary>
    /// Returns the number of columns in the current resultset
    /// </summary>
    public override int FieldCount
    {
      get
      {
        CheckClosed();
        return _fieldCount;
      }
    }

    /// <summary>
    /// SQLite is inherently un-typed.  All datatypes in SQLite are natively strings.  The definition of the columns of a table
    /// and the affinity of returned types are all we have to go on to type-restrict data in the reader.
    /// 
    /// This function attempts to verify that the type of data being requested of a column matches the datatype of the column.  In
    /// the case of columns that are not backed into a table definition, we attempt to match up the affinity of a column (int, double, string or blob)
    /// to a set of known types that closely match that affinity.  It's not an exact science, but its the best we can do.
    /// </summary>
    /// <returns>
    /// This function throws an InvalidTypeCast() exception if the requested type doesn't match the column's definition or affinity.
    /// </returns>
    /// <param name="i">The index of the column to type-check</param>
    /// <param name="typ">The type we want to get out of the column</param>
    private TypeAffinity VerifyType(int i, DbType typ)
    {
      CheckClosed();
      CheckValidRow();
      TypeAffinity affinity = _activeStatement._sql.ColumnAffinity(_activeStatement, i);

      switch (affinity)
      {
        case TypeAffinity.Int64:
          if (typ == DbType.Int16) return affinity;
          if (typ == DbType.Int32) return affinity;
          if (typ == DbType.Int64) return affinity;
          if (typ == DbType.Boolean) return affinity;
          if (typ == DbType.Byte) return affinity;
          if (typ == DbType.DateTime && _command.Connection._sql._datetimeFormat == SQLiteDateFormats.Ticks) return affinity;
          break;
        case TypeAffinity.Double:
          if (typ == DbType.Single) return affinity;
          if (typ == DbType.Double) return affinity;
          if (typ == DbType.Decimal) return affinity;
          break;
        case TypeAffinity.Text:
          if (typ == DbType.SByte) return affinity;
          if (typ == DbType.String) return affinity;
          if (typ == DbType.SByte) return affinity;
          if (typ == DbType.Guid) return affinity;
          if (typ == DbType.DateTime) return affinity;
          break;
        case TypeAffinity.Blob:
          if (typ == DbType.Guid) return affinity;
          if (typ == DbType.String) return affinity;
          if (typ == DbType.Binary) return affinity;
          break;
      }

      throw new InvalidCastException();
    }

    /// <summary>
    /// Retrieves the column as a boolean value
    /// </summary>
    /// <param name="i">The index of the column to retrieve</param>
    /// <returns>bool</returns>
    public override bool GetBoolean(int i)
    {
      VerifyType(i, DbType.Boolean);
      return Convert.ToBoolean(GetValue(i), CultureInfo.CurrentCulture);
    }

    /// <summary>
    /// Retrieves the column as a single byte value
    /// </summary>
    /// <param name="i">The index of the column to retrieve</param>
    /// <returns>byte</returns>
    public override byte GetByte(int i)
    {
      VerifyType(i, DbType.Byte);
      return Convert.ToByte(_activeStatement._sql.GetInt32(_activeStatement, i));
    }

    /// <summary>
    /// Retrieves a column as an array of bytes (blob)
    /// </summary>
    /// <param name="i">The index of the column to retrieve</param>
    /// <param name="fieldOffset">The zero-based index of where to begin reading the data</param>
    /// <param name="buffer">The buffer to write the bytes into</param>
    /// <param name="bufferoffset">The zero-based index of where to begin writing into the array</param>
    /// <param name="length">The number of bytes to retrieve</param>
    /// <returns>The actual number of bytes written into the array</returns>
    /// <remarks>
    /// To determine the number of bytes in the column, pass a null value for the buffer.  The total length will be returned.
    /// </remarks>
    public override long GetBytes(int i, long fieldOffset, byte[] buffer, int bufferoffset, int length)
    {
      VerifyType(i, DbType.Binary);
      return _activeStatement._sql.GetBytes(_activeStatement, i, (int)fieldOffset, buffer, bufferoffset, length);
    }

    /// <summary>
    /// Returns the column as a single character
    /// </summary>
    /// <param name="i">The index of the column to retrieve</param>
    /// <returns>char</returns>
    public override char GetChar(int i)
    {
      VerifyType(i, DbType.SByte);
      return Convert.ToChar(_activeStatement._sql.GetInt32(_activeStatement, i));
    }

    /// <summary>
    /// Retrieves a column as an array of chars (blob)
    /// </summary>
    /// <param name="i">The index of the column to retrieve</param>
    /// <param name="fieldoffset">The zero-based index of where to begin reading the data</param>
    /// <param name="buffer">The buffer to write the characters into</param>
    /// <param name="bufferoffset">The zero-based index of where to begin writing into the array</param>
    /// <param name="length">The number of bytes to retrieve</param>
    /// <returns>The actual number of characters written into the array</returns>
    /// <remarks>
    /// To determine the number of characters in the column, pass a null value for the buffer.  The total length will be returned.
    /// </remarks>
    public override long GetChars(int i, long fieldoffset, char[] buffer, int bufferoffset, int length)
    {
      VerifyType(i, DbType.String);
      return _activeStatement._sql.GetChars(_activeStatement, i, (int)fieldoffset, buffer, bufferoffset, length);
    }

    /// <summary>
    /// Retrieves the name of the back-end datatype of the column
    /// </summary>