// 
// VariableOnlyAssignedIssue.cs
// 
// Author:
//      Mansheng Yang <lightyang0@gmail.com>
// 
// Copyright (c) 2012 Mansheng Yang <lightyang0@gmail.com>
// 
// 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.

using System.Collections.Generic;
using ICSharpCode.NRefactory.TypeSystem;

namespace ICSharpCode.NRefactory.CSharp.Refactoring
{
	public abstract class VariableOnlyAssignedIssue : ICodeIssueProvider
	{
		public abstract IEnumerable<CodeIssue> GetIssues (BaseRefactoringContext context);

		protected static bool TestOnlyAssigned(BaseRefactoringContext ctx, AstNode rootNode, IVariable variable)
		{
			var assignment = false;
			var nonAssignment = false;
			foreach (var result in ctx.FindReferences(rootNode, variable)) {
				var node = result.Node;
				if (node is ParameterDeclaration)
					continue;

				if (node is VariableInitializer) {
					if (!(node as VariableInitializer).Initializer.IsNull)
						assignment = true;
					continue;
				}

				if (node is IdentifierExpression) {
					var parent = node.Parent;
					if (parent is AssignmentExpression) {
						if (((AssignmentExpression)parent).Left == node) {
							assignment = true;
							continue;
						}
					} else if (parent is UnaryOperatorExpression) {
						var op = ((UnaryOperatorExpression)parent).Operator;
						switch (op) {
							case UnaryOperatorType.Increment:
							case UnaryOperatorType.PostIncrement:
							case UnaryOperatorType.Decrement:
							case UnaryOperatorType.PostDecrement:
								assignment = true;
								if (!(parent.Parent is ExpressionStatement))
									nonAssignment = true;
								continue;
						}
					} else if (parent is DirectionExpression) {
						if (((DirectionExpression)parent).FieldDirection == FieldDirection.Out) {
							assignment = true;
							// Using dummy variables is necessary for ignoring
							// out-arguments, so we don't want to warn for those.
							nonAssignment = true;
							continue;
						}
					}
				}
				nonAssignment = true;
			}
			return assignment && !nonAssignment;
		}

	}
}
