/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Apache License, Version 2.0, please send an email to 

 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 

 * by the terms of the Apache License, Version 2.0.

 *

 * You must not remove this notice, or any other, from this software.

 *

 *

 * ***************************************************************************/



#if !CLR2

using System.Linq.Expressions;

#else

using Microsoft.Scripting.Ast;

#endif



using System;

using System.Collections.Generic;

using System.Dynamic;

using System.Collections.ObjectModel;

using Microsoft.Scripting.Utils;



namespace Microsoft.Scripting.Ast {

    public sealed class BlockBuilder : ExpressionCollectionBuilder<Expression> {

        public BlockBuilder() {

        }



        /// <summary>

        /// Returns <c>null</c> if no expression was added into the builder.

        /// If only a single expression was added returns it.

        /// Otherwise returns a <see cref="BlockExpression"/> containing the expressions added to the builder.

        /// </summary>

        public Expression ToExpression() {

            switch (Count) {

                case 0: return null;

                case 1: return Expression0;

                case 2: return Expression.Block(Expression0, Expression1);

                case 3: return Expression.Block(Expression0, Expression1, Expression2);

                case 4: return Expression.Block(Expression0, Expression1, Expression2, Expression3);

                default: return Expression.Block(Expressions);

            }

        }



        public static implicit operator Expression(BlockBuilder/*!*/ block) {

            return block.ToExpression();

        }

    }

}