// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

namespace System.Data.Entity.Core.Mapping.ViewGeneration.Validation
{
    using System.Collections.Generic;
    using System.Data.Entity.Core.Mapping.ViewGeneration.Structures;
    using System.Text;

    // <summary>
    // Represents a relation signature that lists all projected
    // slots of two cell queries in a cell after projection. So if
    // SPerson1.Disc is present in the cellquery (and part of the where
    // clause) but not in the projected slots, it is missing from a ViewCellRelation
    // </summary>
    internal class ViewCellRelation : CellRelation
    {
        // effects: Creates a view cell relation for "cell" with the
        // projected slots given by slots -- cellNumber is the number of the
        // cell for debugging purposes
        // Also creates the BasicCellRelations for the left and right cell queries
        internal ViewCellRelation(Cell cell, List<ViewCellSlot> slots, int cellNumber)
            : base(cellNumber)
        {
            m_cell = cell;
            m_slots = slots;
            // We create the basiccellrelations  passing this to it so that we have
            // a reference from the basiccellrelations to this
            m_cell.CQuery.CreateBasicCellRelation(this);
            m_cell.SQuery.CreateBasicCellRelation(this);
        }

        private readonly Cell m_cell; // The cell for which this relation exists
        private readonly List<ViewCellSlot> m_slots; // Slots projected from both cell queries

        internal Cell Cell
        {
            get { return m_cell; }
        }

        // requires: slot corresponds to a slot in the corresponding
        // BasicCellRelation
        // effects: Given a slot in the corresponding basicCellRelation,
        // looks up the slot in this viewcellrelation and returns it. Returns
        // null if it does not find the slot in the left or right side of the viewrelation
        internal ViewCellSlot LookupViewSlot(MemberProjectedSlot slot)
        {
            // CHANGE_ADYA_IMPROVE: We could have a dictionary to speed this up
            foreach (var viewSlot in m_slots)
            {
                // If the left or right slots are equal, return the viewSlot
                if (ProjectedSlot.EqualityComparer.Equals(slot, viewSlot.CSlot)
                    ||
                    ProjectedSlot.EqualityComparer.Equals(slot, viewSlot.SSlot))
                {
                    return viewSlot;
                }
            }
            return null;
        }

        protected override int GetHash()
        {
            // Note: Using CLR-Hashcode
            return m_cell.GetHashCode();
            // We need not hash the slots, etc - cell should give us enough
            // differentiation and land the relation into the same bucket
        }

        internal override void ToCompactString(StringBuilder builder)
        {
            builder.Append("ViewRel[");
            m_cell.ToCompactString(builder);
            // StringUtil.ToSeparatedStringSorted(builder, m_slots, ", ");
            builder.Append(']');
        }
    }
}
