// 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 Microsoft.CodeAnalysis.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.CSharp.UseDefaultLiteral;

[DiagnosticAnalyzer(LanguageNames.CSharp)]
internal sealed class CSharpUseDefaultLiteralDiagnosticAnalyzer : AbstractBuiltInUnnecessaryCodeStyleDiagnosticAnalyzer
{
    public CSharpUseDefaultLiteralDiagnosticAnalyzer()
        : base(IDEDiagnosticIds.UseDefaultLiteralDiagnosticId,
               EnforceOnBuildValues.UseDefaultLiteral,
               CSharpCodeStyleOptions.PreferSimpleDefaultExpression,
               new LocalizableResourceString(nameof(CSharpAnalyzersResources.Simplify_default_expression), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)),
               new LocalizableResourceString(nameof(CSharpAnalyzersResources.default_expression_can_be_simplified), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)))
    {
    }

    public override DiagnosticAnalyzerCategory GetAnalyzerCategory()
        => DiagnosticAnalyzerCategory.SemanticSpanAnalysis;

    protected override void InitializeWorker(AnalysisContext context)
        => context.RegisterSyntaxNodeAction(AnalyzeSyntax, SyntaxKind.DefaultExpression);

    private void AnalyzeSyntax(SyntaxNodeAnalysisContext context)
    {
        var preference = context.GetCSharpAnalyzerOptions().PreferSimpleDefaultExpression;
        if (ShouldSkipAnalysis(context, preference.Notification))
            return;

        var cancellationToken = context.CancellationToken;
        var syntaxTree = context.Node.SyntaxTree;
        var parseOptions = (CSharpParseOptions)syntaxTree.Options;
        var defaultExpression = (DefaultExpressionSyntax)context.Node;
        if (!defaultExpression.CanReplaceWithDefaultLiteral(parseOptions, preference.Value, context.SemanticModel, cancellationToken))
            return;

        var fadeSpan = TextSpan.FromBounds(defaultExpression.OpenParenToken.SpanStart, defaultExpression.CloseParenToken.Span.End);

        // Create a normal diagnostic that covers the entire default expression.
        context.ReportDiagnostic(
            DiagnosticHelper.CreateWithLocationTags(
                Descriptor,
                defaultExpression.GetLocation(),
                preference.Notification,
                context.Options,
                additionalLocations: [],
                additionalUnnecessaryLocations: [defaultExpression.SyntaxTree.GetLocation(fadeSpan)]));
    }
}