// Copyright (C) 2003-2010 Xtensive LLC.

// All rights reserved.

// For conditions of distribution and use, see license.

// Created by: Elena Vakhtina

// Created:    2009.04.01



using System;

using System.Collections.Generic;

using Xtensive.Core.Collections;

using Xtensive.Core.Internals.DocTemplates;

using Xtensive.Storage.Rse.Resources;

using System.Linq;



namespace Xtensive.Storage.Rse.Providers.Compilable

{

  /// <summary>

  /// Produces concatenation between <see cref="BinaryProvider.Left"/> and 

  /// <see cref="BinaryProvider.Right"/> sources.

  /// </summary>

  [Serializable]

  public class ConcatProvider : BinaryProvider

  {

    protected override RecordSetHeader BuildHeader()

    {

      EnsureConcatIsPossible();

      var mappedColumnIndexes = new List<int>();

      var columns = new List<Column>();

      for (int i = 0; i < Left.Header.Columns.Count; i++) {

        var leftColumn = Left.Header.Columns[i];

        var rightColumn = Right.Header.Columns[i];

        if (leftColumn is MappedColumn && rightColumn is MappedColumn) {

          var leftMappedColumn = (MappedColumn) leftColumn;

          var rightMappedColumn = (MappedColumn) rightColumn;

          if (leftMappedColumn.ColumnInfoRef.Equals(rightMappedColumn.ColumnInfoRef)) {

            columns.Add(leftMappedColumn);

            mappedColumnIndexes.Add(i);

            }

          else

            columns.Add(new SystemColumn(leftColumn.Name, leftColumn.Index, leftColumn.Type));

        }

        else

          columns.Add(new SystemColumn(leftColumn.Name, leftColumn.Index, leftColumn.Type));

      }

      var columnGroups = Left.Header.ColumnGroups.Where(cg => cg.Keys.All(mappedColumnIndexes.Contains)).ToList();



      return new RecordSetHeader(

        Left.Header.TupleDescriptor, 

        columns, 

        columnGroups,

        null,

        null);

    }



    /// <exception cref="InvalidOperationException">Something went wrong.</exception>

    private void EnsureConcatIsPossible()

    {

      var left = Left.Header.TupleDescriptor;

      var right = Right.Header.TupleDescriptor;

      if (!left.Equals(right))

        throw new InvalidOperationException(String.Format(Strings.ExXCantBeExecuted, "Concatenation"));

    }



    /// <inheritdoc/>

    protected override DirectionCollection<int> CreateExpectedColumnsOrdering()

    {

      return EmptyOrder;

    }





    // Constructors



    /// <summary>

    ///  <see cref="ClassDocTemplate.Ctor" copy="true"/>

    /// </summary>

    /// <param name="left">The left provider to intersect.</param>

    /// <param name="right">The right provider to intersect.</param>

    public ConcatProvider(CompilableProvider left, CompilableProvider right)

      : base(ProviderType.Concat, left, right)

    {

    }

  }

}