// Copyright (c) 2010-2013 AlphaSierraPapa for the SharpDevelop Team
// 
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// 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
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using System;
using System.Threading;
using ICSharpCode.NRefactory.CSharp.TypeSystem;
using ICSharpCode.NRefactory.Semantics;
using ICSharpCode.NRefactory.TypeSystem;

namespace ICSharpCode.NRefactory.CSharp.Resolver
{
	/// <summary>
	/// Helper class that resolves the node at a specified location.
	/// Can be used for implementing tool tips.
	/// </summary>
	public static class ResolveAtLocation
	{
		public static ResolveResult Resolve (ICompilation compilation, CSharpUnresolvedFile unresolvedFile, SyntaxTree syntaxTree, TextLocation location,
		                                    CancellationToken cancellationToken = default(CancellationToken))
		{
			return Resolve (new Lazy<ICompilation>(() => compilation), unresolvedFile, syntaxTree, location, cancellationToken);
		}
		public static ResolveResult Resolve(Lazy<ICompilation> compilation, CSharpUnresolvedFile unresolvedFile, SyntaxTree syntaxTree, TextLocation location,
		                                    CancellationToken cancellationToken = default(CancellationToken))
		{
			AstNode node;
			return Resolve(compilation, unresolvedFile, syntaxTree, location, out node, cancellationToken);
		}
		
		public static ResolveResult Resolve (ICompilation compilation, CSharpUnresolvedFile unresolvedFile, SyntaxTree syntaxTree, TextLocation location, out AstNode node,
		                                    CancellationToken cancellationToken = default(CancellationToken))
		{
			return Resolve (new Lazy<ICompilation>(() => compilation), unresolvedFile, syntaxTree, location, out node, cancellationToken);
		}
		public static ResolveResult Resolve(Lazy<ICompilation> compilation, CSharpUnresolvedFile unresolvedFile, SyntaxTree syntaxTree, TextLocation location, out AstNode node,
		                                    CancellationToken cancellationToken = default(CancellationToken))
		{
			node = syntaxTree.GetNodeAt(location);
			if (node == null || node is ArrayInitializerExpression)
				return null;
			if (node.Parent is UsingAliasDeclaration && node.Role == UsingAliasDeclaration.AliasRole) {
				var r = new CSharpAstResolver(compilation.Value, syntaxTree, unresolvedFile);
				return r.Resolve(((UsingAliasDeclaration)node.Parent).Import, cancellationToken);
			}
			if (CSharpAstResolver.IsUnresolvableNode(node)) {
				if (node is Identifier) {
					node = node.Parent;
				} else if (node.NodeType == NodeType.Token) {
					if (node.Parent is IndexerExpression || node.Parent is ConstructorInitializer || node.Role == IndexerDeclaration.ThisKeywordRole) {
						// There's no other place where one could hover to see the indexer's tooltip,
						// so we need to resolve it when hovering over the '[' or ']'.
						// For constructor initializer, the same applies to the 'base'/'this' token.
						node = node.Parent;
					} else if (node.Parent is BinaryOperatorExpression || node.Parent is UnaryOperatorExpression) {
						// Resolve user-defined operator
						node = node.Parent;
					} else {
						return null;
					}
				} else {
					// don't resolve arbitrary nodes - we don't want to show tooltips for everything
					return null;
				}
			} else {
				// It's a resolvable node.
				// However, we usually don't want to show the tooltip everywhere
				// For example, hovering with the mouse over an empty line between two methods causes
				// node==TypeDeclaration, but we don't want to show any tooltip.
				
				if (!node.GetChildByRole(Roles.Identifier).IsNull) {
					// We'll suppress the tooltip for resolvable nodes if there is an identifier that
					// could be hovered over instead:
					return null;
				}
			}

			if (node == null)
				return null;
			if (node.Parent is ObjectCreateExpression && node.Role == Roles.Type) {
				node = node.Parent;
			} else if (node is ThisReferenceExpression && node.Parent is IndexerExpression) {
				node = node.Parent;
			}

			InvocationExpression parentInvocation = null;
			if ((node is IdentifierExpression || node is MemberReferenceExpression || node is PointerReferenceExpression) && node.Role != Roles.Argument) {
				// we also need to resolve the invocation
				parentInvocation = node.Parent as InvocationExpression;
			}
			
			// TODO: I think we should provide an overload so that an existing CSharpAstResolver can be reused
			CSharpAstResolver resolver = new CSharpAstResolver(compilation.Value, syntaxTree, unresolvedFile);
			ResolveResult rr = resolver.Resolve(node, cancellationToken);
			MethodGroupResolveResult mgrr = rr as MethodGroupResolveResult;
			if (mgrr != null) {
				// For method groups, resolve the parent invocation instead.
				if (parentInvocation != null)
					return resolver.Resolve(parentInvocation);
				if (node is Expression) {
					// If it's not an invocation, try if it's a conversion to a delegate type:
					Conversion c = resolver.GetConversion((Expression)node, cancellationToken);
					if (c.IsMethodGroupConversion)
						return new MemberResolveResult(mgrr.TargetResult, c.Method);
				}
			}
			return rr;
		}
	}
}