// 
// ParameterNotUsedIssue.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 ICSharpCode.NRefactory.Semantics;
using System.Linq;
using ICSharpCode.NRefactory.TypeSystem;
using System.Collections.Generic;
using ICSharpCode.NRefactory.CSharp.Resolver;
using System;

namespace ICSharpCode.NRefactory.CSharp.Refactoring
{
	[IssueDescription ("Unused parameter",
					   Description = "Parameter is never used.",
					   Category = IssueCategories.Redundancies,
					   Severity = Severity.Warning,
					   IssueMarker = IssueMarker.GrayOut)]
	public class ParameterNotUsedIssue : ICodeIssueProvider
	{
		#region ICodeIssueProvider implementation
		public IEnumerable<CodeIssue> GetIssues(BaseRefactoringContext context)
		{
			var delegateVisitor = new GetDelgateUsagesVisitor (context);
			context.RootNode.AcceptVisitor (delegateVisitor);

			return new GatherVisitor (context, delegateVisitor).GetIssues ();
		}
		#endregion

		// Collect all methods that are used as delegate
		class GetDelgateUsagesVisitor : DepthFirstAstVisitor
		{
			BaseRefactoringContext ctx;
			public readonly List<IMethod> UsedMethods = new List<IMethod> ();

			public GetDelgateUsagesVisitor(BaseRefactoringContext ctx)
			{
				this.ctx = ctx;
			}
			
			public override void VisitIdentifierExpression(IdentifierExpression identifierExpression)
			{
				var mgr = ctx.Resolve (identifierExpression) as MethodGroupResolveResult;
				if (mgr != null)
					UsedMethods.AddRange (mgr.Methods);
				base.VisitIdentifierExpression(identifierExpression);
			}

			public override void VisitMemberReferenceExpression(MemberReferenceExpression memberReferenceExpression)
			{
				var mgr = ctx.Resolve (memberReferenceExpression) as MethodGroupResolveResult;
				if (mgr != null)
					UsedMethods.AddRange (mgr.Methods);
				base.VisitMemberReferenceExpression(memberReferenceExpression);
			}
		}

		class GatherVisitor : GatherVisitorBase
		{
			GetDelgateUsagesVisitor usedDelegates;
			public GatherVisitor (BaseRefactoringContext ctx, GetDelgateUsagesVisitor usedDelegates)
				: base (ctx)
			{
				this.usedDelegates = usedDelegates;
			}

			public override void VisitMethodDeclaration(MethodDeclaration methodDeclaration)
			{
				// Only some methods are candidates for the warning

				if (methodDeclaration.Body.IsNull)
					return;
				var methodResolveResult = ctx.Resolve(methodDeclaration) as MemberResolveResult;
				if (methodResolveResult == null)
					return;
				var member = methodResolveResult.Member;
				if (member.IsOverride)
					return;
				if (member.ImplementedInterfaceMembers.Any ())
					return;
				if (usedDelegates.UsedMethods.Any (m => m.Region.Begin == methodDeclaration.StartLocation))
					return;
				foreach (var parameter in methodDeclaration.Parameters)
					parameter.AcceptVisitor (this);
			}

			public override void VisitParameterDeclaration (ParameterDeclaration parameterDeclaration)
			{
 				base.VisitParameterDeclaration (parameterDeclaration);

				if (!(parameterDeclaration.Parent is MethodDeclaration))
					return;

				var resolveResult = ctx.Resolve (parameterDeclaration) as LocalResolveResult;
				if (resolveResult == null)
					return;

				if (ctx.FindReferences (parameterDeclaration.Parent, resolveResult.Variable).Any(r => r.Node != parameterDeclaration))
					return;

				AddIssue (parameterDeclaration.NameToken, ctx.TranslateString ("Parameter is never used"));
			}
		}
	}
}