// 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.Collections.Immutable;
using Microsoft.CodeAnalysis.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
 
namespace Microsoft.CodeAnalysis.CSharp.SimplifyPropertyPattern;
 
/// <summary>
/// Looks for code of the form:
/// 
///     <c>x is { a: { b: ... } }</c>
///     
/// and converts it to:
/// 
///     <c>x is { a.b: ... }</c>
/// </summary>
[DiagnosticAnalyzer(LanguageNames.CSharp)]
internal class CSharpSimplifyPropertyPatternDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
{
    public CSharpSimplifyPropertyPatternDiagnosticAnalyzer()
        : base(IDEDiagnosticIds.SimplifyPropertyPatternDiagnosticId,
               EnforceOnBuildValues.SimplifyPropertyPattern,
               CSharpCodeStyleOptions.PreferExtendedPropertyPattern,
               new LocalizableResourceString(nameof(CSharpAnalyzersResources.Property_pattern_can_be_simplified), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)),
               new LocalizableResourceString(nameof(CSharpAnalyzersResources.Simplify_property_pattern), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)))
    {
    }
 
    public override DiagnosticAnalyzerCategory GetAnalyzerCategory()
        => DiagnosticAnalyzerCategory.SemanticSpanAnalysis;
 
    protected override void InitializeWorker(AnalysisContext context)
    {
        context.RegisterCompilationStartAction(compilationContext =>
        {
            // Dotted property patterns are only available in C# 10.0 and above.  Don't offer this refactoring
            // in projects targeting a lesser version.
 
            if (compilationContext.Compilation.LanguageVersion() < LanguageVersion.CSharp10)
                return;
 
            context.RegisterSyntaxNodeAction(AnalyzeSubpattern, SyntaxKind.Subpattern);
        });
    }
 
    private void AnalyzeSubpattern(SyntaxNodeAnalysisContext syntaxContext)
    {
        // Bail immediately if the user has disabled this feature.
        var styleOption = syntaxContext.GetCSharpAnalyzerOptions().PreferExtendedPropertyPattern;
        if (!styleOption.Value || ShouldSkipAnalysis(syntaxContext, styleOption.Notification))
            return;
 
        var subpattern = (SubpatternSyntax)syntaxContext.Node;
        if (!SimplifyPropertyPatternHelpers.IsSimplifiable(subpattern, out _, out var expressionColon))
            return;
 
        // If the diagnostic is not hidden, then just place the user visible part
        // on the local being initialized with the lambda.
        syntaxContext.ReportDiagnostic(DiagnosticHelper.Create(
            Descriptor,
            expressionColon.GetLocation(),
            styleOption.Notification,
            syntaxContext.Options,
            ImmutableArray.Create(subpattern.GetLocation()),
            properties: null));
    }
}