// 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 System.Threading;
using Microsoft.CodeAnalysis.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.CodeGeneration;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Options;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.UseExpressionBody;

[DiagnosticAnalyzer(LanguageNames.CSharp)]
internal sealed class UseExpressionBodyDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
{
    public const string FixesError = nameof(FixesError);

    private readonly ImmutableArray<SyntaxKind> _syntaxKinds;

    private static readonly ImmutableArray<UseExpressionBodyHelper> _helpers = UseExpressionBodyHelper.Helpers;

    public UseExpressionBodyDiagnosticAnalyzer()
        : base(GetSupportedDescriptorsWithOptions())
    {
        _syntaxKinds = _helpers.SelectManyAsArray(h => h.SyntaxKinds);
    }

    private static ImmutableArray<(DiagnosticDescriptor, IOption2)> GetSupportedDescriptorsWithOptions()
    {
        var builder = new FixedSizeArrayBuilder<(DiagnosticDescriptor, IOption2)>(_helpers.Length);
        foreach (var helper in _helpers)
        {
            var descriptor = CreateDescriptorWithId(helper.DiagnosticId, helper.EnforceOnBuild, hasAnyCodeStyleOption: true, helper.UseExpressionBodyTitle, helper.UseExpressionBodyTitle);
            builder.Add((descriptor, helper.Option));
        }

        return builder.MoveToImmutable();
    }

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

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

    private void AnalyzeSyntax(SyntaxNodeAnalysisContext context)
    {
        var cancellationToken = context.CancellationToken;
        var options = context.GetCSharpAnalyzerOptions().GetCodeGenerationOptions();

        var nodeKind = context.Node.Kind();

        // Don't offer a fix on an accessor, if we would also offer it on the property/indexer.
        if (UseExpressionBodyForAccessorsHelper.Instance.SyntaxKinds.Contains(nodeKind))
        {
            var grandparent = context.Node.GetRequiredParent().GetRequiredParent();

            if (grandparent.Kind() == SyntaxKind.PropertyDeclaration &&
                AnalyzeSyntax(options, grandparent, context, UseExpressionBodyForPropertiesHelper.Instance, cancellationToken) != null)
            {
                return;
            }

            if (grandparent.Kind() == SyntaxKind.IndexerDeclaration &&
                AnalyzeSyntax(options, grandparent, context, UseExpressionBodyForIndexersHelper.Instance, cancellationToken) != null)
            {
                return;
            }
        }

        foreach (var helper in _helpers)
        {
            cancellationToken.ThrowIfCancellationRequested();

            if (helper.SyntaxKinds.Contains(nodeKind))
            {
                var diagnostic = AnalyzeSyntax(options, context.Node, context, helper, cancellationToken);
                if (diagnostic != null)
                {
                    context.ReportDiagnostic(diagnostic);
                    return;
                }
            }
        }
    }

    private Diagnostic? AnalyzeSyntax(
        CSharpCodeGenerationOptions options, SyntaxNode declaration, SyntaxNodeAnalysisContext context, UseExpressionBodyHelper helper, CancellationToken cancellationToken)
    {
        var preference = helper.GetExpressionBodyPreference(options);
        if (ShouldSkipAnalysis(context, preference.Notification))
            return null;

        var severity = preference.Notification.Severity;

        if (helper.CanOfferUseExpressionBody(preference, declaration, forAnalyzer: true, cancellationToken))
        {
            var location = severity.WithDefaultSeverity(DiagnosticSeverity.Hidden) == ReportDiagnostic.Hidden
                ? declaration.GetLocation()
                : helper.GetDiagnosticLocation(declaration);

            var additionalLocations = ImmutableArray.Create(declaration.GetLocation());
            var properties = ImmutableDictionary<string, string?>.Empty.Add(nameof(UseExpressionBody), "");
            return DiagnosticHelper.Create(
                CreateDescriptorWithId(helper.DiagnosticId, helper.EnforceOnBuild, hasAnyCodeStyleOption: true, helper.UseExpressionBodyTitle, helper.UseExpressionBodyTitle),
                location, preference.Notification, context.Options, additionalLocations: additionalLocations, properties: properties);
        }

        if (helper.CanOfferUseBlockBody(preference, declaration, forAnalyzer: true, out var fixesError, out var expressionBody))
        {
            // They have an expression body.  Create a diagnostic to convert it to a block
            // if they don't want expression bodies for this member.  
            var location = severity.WithDefaultSeverity(DiagnosticSeverity.Hidden) == ReportDiagnostic.Hidden
                ? declaration.GetLocation()
                : expressionBody.GetLocation();

            var properties = ImmutableDictionary<string, string?>.Empty;
            if (fixesError)
                properties = properties.Add(FixesError, "");

            var additionalLocations = ImmutableArray.Create(declaration.GetLocation());
            return DiagnosticHelper.Create(
                CreateDescriptorWithId(helper.DiagnosticId, helper.EnforceOnBuild, hasAnyCodeStyleOption: true, helper.UseBlockBodyTitle, helper.UseBlockBodyTitle),
                location, preference.Notification, context.Options, additionalLocations: additionalLocations, properties: properties);
        }

        return null;
    }
}