// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Collections.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.UseIsNullCheck
{
    internal abstract class AbstractUseIsNullCheckForReferenceEqualsCodeFixProvider<TExpressionSyntax>
        : SyntaxEditorBasedCodeFixProvider
        where TExpressionSyntax : SyntaxNode
    {
        public override ImmutableArray<string> FixableDiagnosticIds
            => ImmutableArray.Create(IDEDiagnosticIds.UseIsNullCheckDiagnosticId);
 
        protected abstract string GetTitle(bool negated, ParseOptions options);
 
        protected abstract SyntaxNode CreateNullCheck(TExpressionSyntax argument, bool isUnconstrainedGeneric);
        protected abstract SyntaxNode CreateNotNullCheck(TExpressionSyntax argument);
 
        private static bool IsSupportedDiagnostic(Diagnostic diagnostic)
            => diagnostic.Properties[UseIsNullConstants.Kind] == UseIsNullConstants.ReferenceEqualsKey;
 
        public override Task RegisterCodeFixesAsync(CodeFixContext context)
        {
            var diagnostic = context.Diagnostics.First();
            if (IsSupportedDiagnostic(diagnostic))
            {
                var negated = diagnostic.Properties.ContainsKey(UseIsNullConstants.Negated);
                var title = GetTitle(negated, diagnostic.Location.SourceTree!.Options);
                context.RegisterCodeFix(
                    CodeAction.Create(title, GetDocumentUpdater(context), title),
                    context.Diagnostics);
            }
 
            return Task.CompletedTask;
        }
 
        protected override Task FixAllAsync(
            Document document, ImmutableArray<Diagnostic> diagnostics,
            SyntaxEditor editor, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)
        {
            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
 
            // Order in reverse so we process inner diagnostics before outer diagnostics.
            // Otherwise, we won't be able to find the nodes we want to replace if they're
            // not there once their parent has been replaced.
            foreach (var diagnostic in diagnostics.OrderByDescending(d => d.Location.SourceSpan.Start))
            {
                if (!IsSupportedDiagnostic(diagnostic))
                    continue;
 
                var invocation = diagnostic.AdditionalLocations[0].FindNode(getInnermostNodeForTie: true, cancellationToken: cancellationToken);
                var negate = diagnostic.Properties.ContainsKey(UseIsNullConstants.Negated);
                var isUnconstrainedGeneric = diagnostic.Properties.ContainsKey(UseIsNullConstants.UnconstrainedGeneric);
 
                var arguments = syntaxFacts.GetArgumentsOfInvocationExpression(invocation);
                var argument = syntaxFacts.IsNullLiteralExpression(syntaxFacts.GetExpressionOfArgument(arguments[0]))
                    ? (TExpressionSyntax)syntaxFacts.GetExpressionOfArgument(arguments[1])
                    : (TExpressionSyntax)syntaxFacts.GetExpressionOfArgument(arguments[0]);
 
                var toReplace = negate ? invocation.GetRequiredParent() : invocation;
                var replacement = negate
                    ? CreateNotNullCheck(argument)
                    : CreateNullCheck(argument, isUnconstrainedGeneric);
 
                editor.ReplaceNode(
                    toReplace,
                    replacement.WithTriviaFrom(toReplace));
            }
 
            return Task.CompletedTask;
        }
    }
}