#region license
//
//	(C) 2007 - 2008 Novell, Inc. http://www.novell.com
//	(C) 2007 - 2008 Jb Evain http://evain.net
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
#endregion

using System;
using System.Collections;
using System.Collections.Generic;

using Mono.Cecil.Cil;

using Cecil.Decompiler.Ast;

namespace Cecil.Decompiler.Steps {

	class VariableComparer : IEqualityComparer {

		public static readonly IEqualityComparer Instance = new VariableComparer ();

		public bool Equals (object x, object y)
		{
			if (x == y)
				return true;

			if (x == null)
				return y == null;

			var x_arg_ref = x as ArgumentReferenceExpression;
			var y_arg_ref = y as ArgumentReferenceExpression;

			if (x_arg_ref != null && y_arg_ref != null)
				return x_arg_ref.Parameter == y_arg_ref.Parameter;

			var x_var_ref = x as VariableReferenceExpression;
			var y_var_ref = y as VariableReferenceExpression;

			if (x_var_ref != null && y_var_ref != null)
				return x_var_ref.Variable == y_var_ref.Variable;

			return false;
		}

		public int GetHashCode (object obj)
		{
			return obj.GetHashCode ();
		}
	}

	class SelfAssignement : BaseCodeTransformer, IDecompilationStep {

		public static readonly IDecompilationStep Instance = new SelfAssignement ();

		const string TargetKey = "Target";
		const string OperatorKey = "Operator";

		static readonly Pattern.ICodePattern SelfAssignmentPattern = new Pattern.Assignment {
			Bind = assign => new Pattern.MatchData (TargetKey, assign.Target),
			Expression = new Pattern.Binary {
				Bind = binary => new Pattern.MatchData (OperatorKey, binary.Operator),
				Left = new Pattern.ContextData { Name = TargetKey, Comparer = VariableComparer.Instance },
				Right = new Pattern.Literal { Value = 1 }
			}
		};

		public override ICodeNode VisitAssignExpression (AssignExpression node)
		{
			var result = Pattern.CodePattern.Match (SelfAssignmentPattern, node);
			if (!result.Success)
				return base.VisitAssignExpression (node);

			var target = (Expression) result [TargetKey];
			var @operator = (BinaryOperator) result [OperatorKey];

			switch (@operator) {
			case BinaryOperator.Add:
			case BinaryOperator.Subtract:
				return new UnaryExpression (
					GetCorrespondingOperator (@operator), target);
			default:
				return base.VisitAssignExpression (node);
			}
		}

		static UnaryOperator GetCorrespondingOperator (BinaryOperator @operator)
		{
			switch (@operator) {
			case BinaryOperator.Add:
				return UnaryOperator.PostIncrement;
			case BinaryOperator.Subtract:
				return UnaryOperator.PostDecrement;
			default:
				throw new ArgumentException ();
			}
		}

		public BlockStatement Process (DecompilationContext context, BlockStatement body)
		{
			return (BlockStatement) VisitBlockStatement (body);
		}
	}
}
