namespace Rhino.Etl.Core.DataReaders
{
    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Data;

    /// <summary>
    /// Represent a data reader that is based on IEnumerable implementation.
    /// This is important because we can now pass an in memory generated code to code
    /// that requires this, such as the SqlBulkCopy class.
    /// </summary>
    public abstract class EnumerableDataReader : IDataReader
    {
        /// <summary>
        /// The enumerator that we are iterating on.
        /// Required so subclasses can access the current object.
        /// </summary>
        protected readonly IEnumerator enumerator;
        private long rowCount = 0;
        private bool isClosed = false;

        /// <summary>
        /// Initializes a new instance of the <see cref="EnumerableDataReader"/> class.
        /// </summary>
        /// <param name="enumerator">The enumerator.</param>
        protected EnumerableDataReader(IEnumerator enumerator)
        {
            this.enumerator = enumerator;
        }

        /// <summary>
        /// Gets the descriptors for the properties that this instance
        /// is going to handle
        /// </summary>
        /// <value>The property descriptors.</value>
        protected abstract IList<Descriptor> PropertyDescriptors { get; }

        #region IDataReader Members

        /// <summary>
        /// Closes the <see cref="T:System.Data.IDataReader"/> Object.
        /// </summary>
        public void Close()
        {
            DoClose();
            isClosed = true;
        }

        /// <summary>
        /// Perform the actual closing of the reader
        /// </summary>
        protected abstract void DoClose();

        /// <summary>
        /// Returns a <see cref="T:System.Data.DataTable"/> that describes the column metadata of the <see cref="T:System.Data.IDataReader"/>.
        /// </summary>
        /// <remarks>
        /// This is a very trivial implementation, anything that tries to do something really fancy with it
        /// may need more information
        /// </remarks>
        /// <returns>
        /// A <see cref="T:System.Data.DataTable"/> that describes the column metadata.
        /// </returns>
        public DataTable GetSchemaTable()
        {
            DataTable table = new DataTable("schema");
            table.Columns.Add("ColumnName", typeof(string));
            table.Columns.Add("ColumnOrdinal", typeof(int));
            table.Columns.Add("DataType", typeof(Type));

            for (int i = 0; i < PropertyDescriptors.Count; i++)
            {
                table.Rows.Add(
                    PropertyDescriptors[i].Name,
                    i,
                    PropertyDescriptors[i].Type
                    );
            }
            return table;
        }

        /// <summary>
        /// We do not support mutliply result set
        /// </summary>
        /// <returns>
        /// true if there are more rows; otherwise, false.
        /// </returns>
        public bool NextResult()
        {
            return false;
        }

        /// <summary>
        /// Advances the <see cref="T:System.Data.IDataReader"/> to the next record.
        /// </summary>
        /// <returns>
        /// true if there are more rows; otherwise, false.
        /// </returns>
        public bool Read()
        {
            bool next = enumerator.MoveNext();
            if (next)
                rowCount += 1;
            return next;
        }

        /// <summary>
        /// Gets a value indicating the depth of nesting for the current row.
        /// We do not support nesting.
        /// </summary>
        /// <value></value>
        /// <returns>The level of nesting.</returns>
        public int Depth
        {
            get { return 0; }
        }

        /// <summary>
        /// Gets a value indicating whether the data reader is closed.
        /// </summary>
        /// <value></value>
        /// <returns>true if the data reader is closed; otherwise, false.</returns>
        public bool IsClosed
        {
            get { return isClosed; }
        }

        /// <summary>
        /// Gets the number of rows changed, inserted, or deleted by execution of the SQL statement.
        /// </summary>
        /// <value></value>
        /// <returns>The number of rows changed, inserted, or deleted; 0 if no rows were affected or the statement failed; and -1 for SELECT statements.</returns>
        public int RecordsAffected
        {
            get { return -1; }
        }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Close();
        }

        /// <summary>
        /// Gets the name for the field to find.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The name of the field or the empty string (""), if there is no value to return.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public string GetName(int i)
        {
            return PropertyDescriptors[i].Name;
        }

        /// <summary>
        /// Gets the data type information for the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The data type information for the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public string GetDataTypeName(int i)
        {
            return PropertyDescriptors[i].Type.Name;
        }

        /// <summary>
        /// Gets the <see cref="T:System.Type"/> information corresponding to the type of <see cref="T:System.Object"/> that would be returned from <see cref="M:System.Data.IDataRecord.GetValue(System.Int32)"/>.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The <see cref="T:System.Type"/> information corresponding to the type of <see cref="T:System.Object"/> that would be returned from <see cref="M:System.Data.IDataRecord.GetValue(System.Int32)"/>.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public Type GetFieldType(int i)
        {
            return PropertyDescriptors[i].Type;
        }

        /// <summary>
        /// Return the value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The <see cref="T:System.Object"/> which will contain the field value upon return.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public object GetValue(int i)
        {
            return PropertyDescriptors[i].GetValue(enumerator.Current) ?? DBNull.Value;
        }

        /// <summary>
        /// Gets all the attribute fields in the collection for the current record.
        /// </summary>
        /// <param name="values">An array of <see cref="T:System.Object"/> to copy the attribute fields into.</param>
        /// <returns>
        /// The number of instances of <see cref="T:System.Object"/> in the array.
        /// </returns>
        public int GetValues(object[] values)
        {
            for (int i = 0; i < PropertyDescriptors.Count; i++)
            {
                values[i] = PropertyDescriptors[i].GetValue(enumerator.Current);
            }
            return PropertyDescriptors.Count;
        }

        /// <summary>
        /// Return the index of the named field.
        /// </summary>
        /// <param name="name">The name of the field to find.</param>
        /// <returns>The index of the named field.</returns>
        public int GetOrdinal(string name)
        {
            for (int i = 0; i < PropertyDescriptors.Count; i++)
            {
                if (string.Equals(PropertyDescriptors[i].Name, name, StringComparison.InvariantCultureIgnoreCase))
                    return i;
            }
            throw new ArgumentException("There is not property with name: " + name);
        }

        /// <summary>
        /// Gets the value of the specified column as a Boolean.
        /// </summary>
        /// <param name="i">The zero-based column ordinal.</param>
        /// <returns>The value of the column.</returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public bool GetBoolean(int i)
        {
            return (bool)GetValue(i);
        }

        /// <summary>
        /// Gets the 8-bit unsigned integer value of the specified column.
        /// </summary>
        /// <param name="i">The zero-based column ordinal.</param>
        /// <returns>
        /// The 8-bit unsigned integer value of the specified column.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public byte GetByte(int i)
        {
            return (byte)GetValue(i);
        }

        /// <summary>
        /// We do not support this operation
        /// </summary>
        public long GetBytes(int i, long fieldOffset, byte[] buffer, int bufferoffset, int length)
        {
            throw new NotSupportedException();
        }

        /// <summary>
        /// Gets the character value of the specified column.
        /// </summary>
        /// <param name="i">The zero-based column ordinal.</param>
        /// <returns>
        /// The character value of the specified column.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public char GetChar(int i)
        {
            return (char)GetValue(i);
        }

        /// <summary>
        /// We do not support this operation
        /// </summary>
        public long GetChars(int i, long fieldoffset, char[] buffer, int bufferoffset, int length)
        {
            throw new NotSupportedException();
        }

        /// <summary>
        /// Returns the GUID value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>The GUID value of the specified field.</returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public Guid GetGuid(int i)
        {
            return (Guid)GetValue(i);
        }

        /// <summary>
        /// Gets the 16-bit signed integer value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The 16-bit signed integer value of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public short GetInt16(int i)
        {
            return (short)GetValue(i);
        }

        /// <summary>
        /// Gets the 32-bit signed integer value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The 32-bit signed integer value of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public int GetInt32(int i)
        {
            return (int)GetValue(i);
        }

        /// <summary>
        /// Gets the 64-bit signed integer value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The 64-bit signed integer value of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public long GetInt64(int i)
        {
            return (long)GetValue(i);
        }

        /// <summary>
        /// Gets the single-precision floating point number of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The single-precision floating point number of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public float GetFloat(int i)
        {
            return (float)GetValue(i);
        }

        /// <summary>
        /// Gets the double-precision floating point number of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The double-precision floating point number of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public double GetDouble(int i)
        {
            return (double)GetValue(i);
        }

        /// <summary>
        /// Gets the string value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>The string value of the specified field.</returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public string GetString(int i)
        {
            return (string)GetValue(i);
        }

        /// <summary>
        /// Gets the fixed-position numeric value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The fixed-position numeric value of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public decimal GetDecimal(int i)
        {
            return (decimal)GetValue(i);
        }

        /// <summary>
        /// Gets the date and time data value of the specified field.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// The date and time data value of the specified field.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public DateTime GetDateTime(int i)
        {
            return (DateTime)GetValue(i);
        }

        /// <summary>
        /// We do not support nesting
        /// </summary>
        public IDataReader GetData(int i)
        {
            throw new NotSupportedException();
        }

        /// <summary>
        /// Return whether the specified field is set to null.
        /// </summary>
        /// <param name="i">The index of the field to find.</param>
        /// <returns>
        /// true if the specified field is set to null; otherwise, false.
        /// </returns>
        /// <exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>. </exception>
        public bool IsDBNull(int i)
        {
            return GetValue(i) == null || GetValue(i) == DBNull.Value;
        }

        /// <summary>
        /// Gets the number of columns in the current row.
        /// </summary>
        /// <value></value>
        /// <returns>When not positioned in a valid recordset, 0; otherwise, the number of columns in the current record. The default is -1.</returns>
        public int FieldCount
        {
            get { return PropertyDescriptors.Count; }
        }

        /// <summary>
        /// Gets the <see cref="System.Object"/> with the specified i.
        /// </summary>
        /// <value></value>
        public object this[int i]
        {
            get { return GetValue(i); }
        }

        /// <summary>
        /// Gets the <see cref="System.Object"/> with the specified name.
        /// </summary>
        /// <value></value>
        public object this[string name]
        {
            get { return GetValue(GetOrdinal(name)); }
        }

        #endregion
    }
}