//---------------------------------------------------------------------
// <copyright file="BindingContext.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//
// @owner  Microsoft
//---------------------------------------------------------------------

using CqtExpression = System.Data.Common.CommandTrees.DbExpression;
using LinqExpression = System.Linq.Expressions.Expression;
using System.Linq.Expressions;
using System.Collections.ObjectModel;
using System.Linq;
using System.Collections.Generic;
using System.Data.Common.CommandTrees;
using System.Data.Metadata.Edm;
using System.Reflection;
using System.Data.Common.EntitySql;
using System.Diagnostics;
using System.Data.Common;
using System.Globalization;
namespace System.Data.Objects.ELinq
{
    /// <summary>
    /// Class containing binding information for an expression converter (associating CQT bindings
    /// with LINQ lambda parameter or LINQ sub-expressions)
    /// </summary>
    /// <remarks>
    /// Usage pattern:
    /// <code>
    /// BindingContext context = ...;
    /// 
    /// // translate a "Where" lamba expression input.Where(i => i.X > 2);
    /// LambdaExpression whereLambda = ...;
    /// CqtExpression inputCqt = Translate(whereLambda.Arguments[1]);
    /// CqtExpression inputBinding = CreateExpressionBinding(inputCqt).Var;
    /// 
    /// // push the scope defined by the parameter 
    /// context.PushBindingScope(new KeyValuePair{ParameterExpression, CqtExpression}(whereLambda.Parameters[0], inputBinding));
    /// 
    /// // translate the expression in this context
    /// CqtExpression result = Translate(whereLambda.Expression);
    /// 
    /// // pop the scope
    /// context.PopBindingScope();
    /// </code>
    /// </remarks>
    internal sealed class BindingContext
    {
        private readonly Stack<Binding> _scopes;

        /// <summary>
        /// Initialize a new binding context
        /// </summary>
        internal BindingContext()
        {
            _scopes = new Stack<Binding>();
        }

        /// <summary>
        /// Set up a new binding scope where parameter expressions map to their paired CQT expressions.
        /// </summary>
        /// <param name="binding">DbExpression/LinqExpression binding</param>
        internal void PushBindingScope(Binding binding)
        {
            _scopes.Push(binding);
        }

        /// <summary>
        /// Removes a scope when leaving a particular sub-expression.
        /// </summary>
        /// <returns>Scope.</returns>
        internal void PopBindingScope()
        {
            _scopes.Pop();
        }

        internal bool TryGetBoundExpression(Expression linqExpression, out CqtExpression cqtExpression)
        {
            cqtExpression = _scopes
                .Where(binding => binding.LinqExpression == linqExpression)
                .Select(binding => binding.CqtExpression)
                .FirstOrDefault();
            return cqtExpression != null;
        }
    }

    /// <summary>
    /// Class describing a LINQ parameter and its bound expression. For instance, in
    /// 
    /// products.Select(p => p.ID)
    /// 
    /// the 'products' query is the bound expression, and 'p' is the parameter.
    /// </summary>
    internal sealed class Binding
    {
        internal Binding(Expression linqExpression, CqtExpression cqtExpression)
        {
            EntityUtil.CheckArgumentNull(linqExpression, "linqExpression");
            EntityUtil.CheckArgumentNull(cqtExpression, "cqtExpression");
            LinqExpression = linqExpression;
            CqtExpression = cqtExpression;
        }

        internal readonly Expression LinqExpression;
        internal readonly CqtExpression CqtExpression;
    }
}