// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp.Utilities;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.LanguageServices;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Simplification;
using Roslyn.Utilities;
using MonoDevelop.CSharp.CodeFixes;
using ICSharpCode.NRefactory6.CSharp;

namespace MonoDevelop.CSharp.CodeFixes
{
	[ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.AddUsingOrImport), Shared]
	class CSharpAddImportCodeFixProvider : AbstractAddImportCodeFixProvider
	{
		/// <summary>
		/// name does not exist in context
		/// </summary>
		private const string CS0103 = "CS0103";

		/// <summary>
		/// type or namespace could not be found
		/// </summary>
		private const string CS0246 = "CS0246";

		/// <summary>
		/// wrong number of type args
		/// </summary>
		private const string CS0305 = "CS0305";

		/// <summary>
		/// type does not contain a definition of method or extension method
		/// </summary>
		private const string CS1061 = "CS1061";

		/// <summary>
		/// cannot find implementation of query pattern
		/// </summary>
		private const string CS1935 = "CS1935";

		/// <summary>
		/// The non-generic type 'A' cannot be used with type arguments
		/// </summary>
		private const string CS0308 = "CS0308";

		/// <summary>
		/// 'A' is inaccessible due to its protection level
		/// </summary>
		private const string CS0122 = "CS0122";

		/// <summary>
		/// The using alias 'A' cannot be used with type arguments
		/// </summary>
		private const string CS0307 = "CS0307";

		/// <summary>
		/// 'A' is not an attribute class
		/// </summary>
		private const string CS0616 = "CS0616";

		/// <summary>
		/// ; expected.
		/// </summary>
		private const string CS1002 = "CS1002";

		/// <summary>
		/// Syntax error, 'A' expected
		/// </summary>
		private const string CS1003 = "CS1003";

		/// <summary>
		/// cannot convert from 'int' to 'string'
		/// </summary>
		private const string CS1503 = "CS1503";

		/// <summary>
		/// XML comment on 'construct' has syntactically incorrect cref attribute 'name'
		/// </summary>
		private const string CS1574 = "CS1574";

		/// <summary>
		/// Invalid type for parameter 'parameter number' in XML comment cref attribute
		/// </summary>
		private const string CS1580 = "CS1580";

		/// <summary>
		/// Invalid return type in XML comment cref attribute
		/// </summary>
		private const string CS1581 = "CS1581";

		/// <summary>
		/// XML comment has syntactically incorrect cref attribute
		/// </summary>
		private const string CS1584 = "CS1584";

		public override ImmutableArray<string> FixableDiagnosticIds
		{
			get
			{
				return ImmutableArray.Create(
					CS0103,
					CS0246,
					CS0305,
					CS1061,
					CS1935,
					CS0308,
					CS0122,
					CS0307,
					CS0616,
					CS1002,
					CS1003,
					CS1503,
					CS1574,
					CS1580,
					CS1581,
					CS1584);
			}
		}

		protected override bool IgnoreCase
		{
			get { return false; }
		}

		protected override bool CanAddImport(SyntaxNode node, CancellationToken cancellationToken)
		{
			if (cancellationToken.IsCancellationRequested)
			{
				return false;
			}

			return node.CanAddUsingDirectives(cancellationToken);
		}

		protected override bool CanAddImportForMethod(Diagnostic diagnostic, ref SyntaxNode node)
		{
			switch (diagnostic.Id)
			{
			case CS1061:
				if (node.IsKind(SyntaxKind.ConditionalAccessExpression))
				{
					node = (node as ConditionalAccessExpressionSyntax).WhenNotNull;
				}
				else if (node.IsKind(SyntaxKind.MemberBindingExpression))
				{
					node = (node as MemberBindingExpressionSyntax).Name;
				}
				else if (node.Parent.IsKind(SyntaxKind.CollectionInitializerExpression))
				{
					return true;
				}

				break;
			case CS0122:
				break;

			case CS1503:
				//// look up its corresponding method name
				var parent = node.GetAncestor<InvocationExpressionSyntax>();
				if (parent == null)
				{
					return false;
				}

				var method = parent.Expression as MemberAccessExpressionSyntax;
				if (method != null)
				{
					node = method.Name;
				}

				break;

			default:
				return false;
			}

			var simpleName = node as SimpleNameSyntax;
			if (!simpleName.IsParentKind(SyntaxKind.SimpleMemberAccessExpression) &&
				!simpleName.IsParentKind(SyntaxKind.MemberBindingExpression))
			{
				return false;
			}

			var memberAccess = simpleName.Parent as MemberAccessExpressionSyntax;
			var memberBinding = simpleName.Parent as MemberBindingExpressionSyntax;
			if (memberAccess.IsParentKind(SyntaxKind.SimpleMemberAccessExpression) ||
				memberAccess.IsParentKind(SyntaxKind.ElementAccessExpression) ||
				memberBinding.IsParentKind(SyntaxKind.SimpleMemberAccessExpression) ||
				memberBinding.IsParentKind(SyntaxKind.ElementAccessExpression))
			{
				return false;
			}

			if (!node.IsMemberAccessExpressionName())
			{
				return false;
			}

			return true;
		}

		protected override bool CanAddImportForNamespace(Diagnostic diagnostic, ref SyntaxNode node)
		{
			return false;
		}

		protected override bool CanAddImportForQuery(Diagnostic diagnostic, ref SyntaxNode node)
		{
			if (diagnostic.Id != CS1935)
			{
				return false;
			}

			return node.AncestorsAndSelf().Any(n => n is QueryExpressionSyntax && !(n.Parent is QueryContinuationSyntax));
		}

		protected override bool CanAddImportForType(Diagnostic diagnostic, ref SyntaxNode node)
		{
			switch (diagnostic.Id)
			{
			case CS0103:
			case CS0246:
			case CS0305:
			case CS0308:
			case CS0122:
			case CS0307:
			case CS0616:
			case CS1003:
			case CS1580:
			case CS1581:
				break;

			case CS1002:
				//// only lookup errors inside ParenthesizedLambdaExpression e.g., () => { ... }
				if (node.Ancestors().OfType<ParenthesizedLambdaExpressionSyntax>().Any())
				{
					if (node is SimpleNameSyntax)
					{
						break;
					}
					else if (node is BlockSyntax || node is MemberAccessExpressionSyntax || node is BinaryExpressionSyntax)
					{
						var last = node.DescendantNodes().OfType<SimpleNameSyntax>().LastOrDefault();
						if (!TryFindStandaloneType(ref node))
						{
							node = node.DescendantNodes().OfType<SimpleNameSyntax>().FirstOrDefault();
						}
						else
						{
							node = last;
						}
					}
				}
				else
				{
					return false;
				}

				break;

			case CS1574:
			case CS1584:
				var cref = node as QualifiedCrefSyntax;
				if (cref != null)
				{
					node = cref.Container;
				}

				break;

			default:
				return false;
			}

			return TryFindStandaloneType(ref node);
		}

		private static bool TryFindStandaloneType(ref SyntaxNode node)
		{
			var qn = node as QualifiedNameSyntax;
			if (qn != null)
			{
				node = GetLeftMostSimpleName(qn);
			}

			var simpleName = node as SimpleNameSyntax;
			return simpleName.LooksLikeStandaloneTypeName();
		}

		private static SimpleNameSyntax GetLeftMostSimpleName(QualifiedNameSyntax qn)
		{
			while (qn != null)
			{
				var left = qn.Left;
				var simpleName = left as SimpleNameSyntax;
				if (simpleName != null)
				{
					return simpleName;
				}

				qn = left as QualifiedNameSyntax;
			}

			return null;
		}

		protected override ISet<INamespaceSymbol> GetNamespacesInScope(
			SemanticModel semanticModel,
			SyntaxNode node,
			CancellationToken cancellationToken)
		{
			return semanticModel.GetUsingNamespacesInScope(node);
		}

		protected override ITypeSymbol GetQueryClauseInfo(
			SemanticModel semanticModel,
			SyntaxNode node,
			CancellationToken cancellationToken)
		{
			var query = node.AncestorsAndSelf().OfType<QueryExpressionSyntax>().First();

			if (InfoBoundSuccessfully(semanticModel.GetQueryClauseInfo(query.FromClause, cancellationToken)))
			{
				return null;
			}

			foreach (var clause in query.Body.Clauses)
			{
				if (InfoBoundSuccessfully(semanticModel.GetQueryClauseInfo(clause, cancellationToken)))
				{
					return null;
				}
			}

			if (InfoBoundSuccessfully(semanticModel.GetSymbolInfo(query.Body.SelectOrGroup, cancellationToken)))
			{
				return null;
			}

			var fromClause = query.FromClause;
			return semanticModel.GetTypeInfo(fromClause.Expression, cancellationToken).Type;
		}

		private bool InfoBoundSuccessfully(SymbolInfo symbolInfo)
		{
			return InfoBoundSuccessfully(symbolInfo.Symbol);
		}

		private bool InfoBoundSuccessfully(QueryClauseInfo semanticInfo)
		{
			return InfoBoundSuccessfully(semanticInfo.OperationInfo);
		}

		private static bool InfoBoundSuccessfully(ISymbol operation)
		{
			operation = operation.GetOriginalUnreducedDefinition();
			return operation != null;
		}

		protected override string GetDescription(INamespaceOrTypeSymbol namespaceSymbol, SemanticModel semanticModel, SyntaxNode contextNode)
		{
			var root = GetCompilationUnitSyntaxNode(contextNode);

			// No localization necessary
			string externAliasString;
			if (TryGetExternAliasString(namespaceSymbol, semanticModel, root, out externAliasString))
			{
				return string.Format ("extern alias {0};", externAliasString);
			}

			string namespaceString;
			if (TryGetNamespaceString(namespaceSymbol, root, false, null, out namespaceString))
			{
				return string.Format ("using {0};", namespaceString);
			}

			// If we get here then neither a namespace or a an extern alias can be added.
			// There is no valid string to show to the user and there is 
			// likely a bug in that we should know about.
			throw new InvalidOperationException ();
		}

		protected override async Task<Document> AddImportAsync(
			SyntaxNode contextNode,
			INamespaceOrTypeSymbol namespaceSymbol,
			Document document,
			bool placeSystemNamespaceFirst,
			CancellationToken cancellationToken)
		{
			var root = GetCompilationUnitSyntaxNode(contextNode, cancellationToken);
			var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
			var simpleUsingDirective = GetUsingDirective(root, namespaceSymbol, semanticModel, fullyQualify: false);
			var externAliasUsingDirective = GetExternAliasUsingDirective(root, namespaceSymbol, semanticModel);
			if (externAliasUsingDirective != null)
			{
				root = root.AddExterns(
					externAliasUsingDirective
					.WithAdditionalAnnotations(Formatter.Annotation));
			}

			if (simpleUsingDirective != null)
			{
				// Because of the way usings can be nested inside of namespace declarations,
				// we need to check if the usings must be fully qualified so as not to be
				// ambiguous with the containing namespace. 
				if (UsingsAreContainedInNamespace(contextNode))
				{
					// When we add usings we try and place them, as best we can, where the user
					// wants them according to their settings.  This means we can't just add the fully-
					// qualified usings and expect the simplifier to take care of it, the usings have to be
					// simplified before we attempt to add them to the document.
					// You might be tempted to think that we could call 
					//   AddUsings -> Simplifier -> SortUsings
					// But this will clobber the users using settings without asking.  Instead we create a new
					// Document and check if our using can be simplified.  Worst case we need to back out the 
					// fully qualified change and reapply with the simple name.
					var fullyQualifiedUsingDirective = GetUsingDirective(root, namespaceSymbol, semanticModel, fullyQualify: true);
					SyntaxNode newRoot = root.AddUsingDirective(
						fullyQualifiedUsingDirective, contextNode, placeSystemNamespaceFirst,
						Formatter.Annotation);
					var newDocument = document.WithSyntaxRoot(newRoot);
					var newSemanticModel = await newDocument.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
					newRoot = await newDocument.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
					var newUsing = newRoot
						.DescendantNodes().OfType<UsingDirectiveSyntax>().Where(uds => uds.IsEquivalentTo(fullyQualifiedUsingDirective, topLevel: true)).Single();
					var speculationAnalyzer = new SpeculationAnalyzer(newUsing.Name, simpleUsingDirective.Name, newSemanticModel, cancellationToken);
					if (speculationAnalyzer.ReplacementChangesSemantics())
					{
						// Not fully qualifying the using causes to refer to a different namespace so we need to keep it as is.
						return newDocument;
					}
					else
					{
						// It does not matter if it is fully qualified or simple so lets return the simple name.
						return document.WithSyntaxRoot(root.AddUsingDirective(
							simpleUsingDirective, contextNode, placeSystemNamespaceFirst,
							Formatter.Annotation));
					}
				}
				else
				{
					// simple form
					return document.WithSyntaxRoot(root.AddUsingDirective(
						simpleUsingDirective, contextNode, placeSystemNamespaceFirst,
						Formatter.Annotation));
				}
			}

			return document.WithSyntaxRoot(root);
		}

		private static ExternAliasDirectiveSyntax GetExternAliasUsingDirective(CompilationUnitSyntax root, INamespaceOrTypeSymbol namespaceSymbol, SemanticModel semanticModel)
		{
			string externAliasString;
			if (TryGetExternAliasString(namespaceSymbol, semanticModel, root, out externAliasString))
			{
				return SyntaxFactory.ExternAliasDirective(SyntaxFactory.Identifier(externAliasString));
			}

			return null;
		}

		private UsingDirectiveSyntax GetUsingDirective(CompilationUnitSyntax root, INamespaceOrTypeSymbol namespaceSymbol, SemanticModel semanticModel, bool fullyQualify)
		{
			string namespaceString;
			string externAliasString;
			TryGetExternAliasString(namespaceSymbol, semanticModel, root, out externAliasString);
			if (externAliasString != null)
			{
				if (TryGetNamespaceString(namespaceSymbol, root, false, externAliasString, out namespaceString))
				{
					return SyntaxFactory.UsingDirective(SyntaxFactory.ParseName(namespaceString));
				}

				return null;
			}

			if (TryGetNamespaceString(namespaceSymbol, root, fullyQualify, null, out namespaceString))
			{
				return SyntaxFactory.UsingDirective(SyntaxFactory.ParseName(namespaceString));
			}

			return null;
		}

		private bool UsingsAreContainedInNamespace(SyntaxNode contextNode)
		{
			return contextNode.GetAncestor<NamespaceDeclarationSyntax>()?.DescendantNodes().OfType<UsingDirectiveSyntax>().FirstOrDefault() != null;
		}

		private static bool TryGetExternAliasString(INamespaceOrTypeSymbol namespaceSymbol, SemanticModel semanticModel, CompilationUnitSyntax root, out string externAliasString)
		{
			externAliasString = null;
			var metadataReference = semanticModel.Compilation.GetMetadataReference(namespaceSymbol.ContainingAssembly);
			if (metadataReference == null)
			{
				return false;
			}

			var properties = metadataReference.Properties;
			var aliases = properties.Aliases;
			if (aliases.IsDefaultOrEmpty)
			{
				return false;
			}

			aliases = properties.Aliases.Where(a => a != MetadataReferenceProperties.GlobalAlias).ToImmutableArray();
			if (!aliases.Any())
			{
				return false;
			}

			externAliasString = aliases.First();
			return ShouldAddExternAlias(aliases, root);
		}

		private static bool TryGetNamespaceString(INamespaceOrTypeSymbol namespaceSymbol, CompilationUnitSyntax root, bool fullyQualify, string alias, out string namespaceString)
		{
			namespaceString = fullyQualify
				? namespaceSymbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)
				: namespaceSymbol.ToDisplayString();

			if (alias != null)
			{
				namespaceString = alias + "::" + namespaceString;
			}

			return ShouldAddUsing(namespaceString, root);
		}

		private static bool ShouldAddExternAlias(ImmutableArray<string> aliases, CompilationUnitSyntax root)
		{
			var identifiers = root.DescendantNodes().OfType<ExternAliasDirectiveSyntax>().Select(e => e.Identifier.ToString());
			var externAliases = aliases.Where(a => identifiers.Contains(a));
			return !externAliases.Any();
		}

		private static bool ShouldAddUsing(string usingDirective, CompilationUnitSyntax root)
		{
			return !root.Usings.Select(u => u.Name.ToString()).Contains(usingDirective);
		}

		private static CompilationUnitSyntax GetCompilationUnitSyntaxNode(SyntaxNode contextNode, CancellationToken cancellationToken = default(CancellationToken))
		{
			return (CompilationUnitSyntax)contextNode.SyntaxTree.GetRoot(cancellationToken);
		}

		protected override bool IsViableExtensionMethod(IMethodSymbol method, SyntaxNode expression, SemanticModel semanticModel, CancellationToken cancellationToken)
		{
			var leftExpression = expression.GetExpressionOfMemberAccessExpression() ?? expression.GetExpressionOfConditionalMemberAccessExpression();
			if (leftExpression == null)
			{
				if (expression.IsKind(SyntaxKind.CollectionInitializerExpression))
				{
					leftExpression = expression.GetAncestor<ObjectCreationExpressionSyntax>();
				}
				else
				{
					return false;
				}
			}

			var semanticInfo = semanticModel.GetTypeInfo(leftExpression, cancellationToken);
			var leftExpressionType = semanticInfo.Type;

			return leftExpressionType != null && method.ReduceExtensionMethod(leftExpressionType) != null;
		}

		protected override IEnumerable<ITypeSymbol> GetProposedTypes(string name, List<ITypeSymbol> accessibleTypeSymbols, SemanticModel semanticModel, ISet<INamespaceSymbol> namespacesInScope)
		{
			if (accessibleTypeSymbols == null)
			{
				yield break;
			}

			foreach (var typeSymbol in accessibleTypeSymbols)
			{
				if ((typeSymbol != null) && (typeSymbol.ContainingType != null) && typeSymbol.ContainingType.IsStatic)
				{
					yield return typeSymbol.ContainingType;
				}
			}
		}

		internal override bool IsViableField(IFieldSymbol field, SyntaxNode expression, SemanticModel semanticModel, CancellationToken cancellationToken)
		{
			return IsViablePropertyOrField(field, expression, semanticModel, cancellationToken);
		}

		internal override bool IsViableProperty(IPropertySymbol property, SyntaxNode expression, SemanticModel semanticModel, CancellationToken cancellationToken)
		{
			return IsViablePropertyOrField(property, expression, semanticModel, cancellationToken);
		}

		private bool IsViablePropertyOrField(ISymbol propertyOrField, SyntaxNode expression, SemanticModel semanticModel, CancellationToken cancellationToken)
		{
			if (!propertyOrField.IsStatic)
			{
				return false;
			}

			var leftName = (expression as MemberAccessExpressionSyntax)?.Expression as SimpleNameSyntax;
			if (leftName == null)
			{
				return false;
			}

			return string.Compare(propertyOrField.ContainingType.Name, leftName.Identifier.Text, this.IgnoreCase) == 0;
		}

		internal override bool IsAddMethodContext(SyntaxNode node, SemanticModel semanticModel)
		{
			if (node.Parent.IsKind(SyntaxKind.CollectionInitializerExpression))
			{
				var objectCreationExpressionSyntax = node.GetAncestor<ObjectCreationExpressionSyntax>();
				if (objectCreationExpressionSyntax == null)
				{
					return false;
				}

				return true;
			}

			return false;
		}
	}
}