// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Immutable;
using System.Linq;
using Analyzer.Utilities;
using Analyzer.Utilities.Extensions;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Diagnostics;

namespace Microsoft.CodeQuality.Analyzers.ApiDesignGuidelines
{
    using static MicrosoftCodeQualityAnalyzersResources;

    /// <summary>
    /// CA1021: <inheritdoc cref="AvoidOutParametersTitle"/>
    /// </summary>
    [DiagnosticAnalyzer(LanguageNames.CSharp, LanguageNames.VisualBasic)]
    public sealed class AvoidOutParameters : DiagnosticAnalyzer
    {
        internal const string RuleId = "CA1021";

        internal static readonly DiagnosticDescriptor Rule = DiagnosticDescriptorHelper.Create(
            RuleId,
            CreateLocalizableResourceString(nameof(AvoidOutParametersTitle)),
            CreateLocalizableResourceString(nameof(AvoidOutParametersMessage)),
            DiagnosticCategory.Design,
            RuleLevel.Disabled,
            description: CreateLocalizableResourceString(nameof(AvoidOutParametersDescription)),
            isPortedFxCopRule: true,
            isDataflowRule: false,
            isEnabledByDefaultInAggressiveMode: false);

        public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(Rule);

        public override void Initialize(AnalysisContext context)
        {
            context.EnableConcurrentExecution();
            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);

            context.RegisterCompilationStartAction(context =>
            {
                var outAttributeType = context.Compilation.GetOrCreateTypeByMetadataName(WellKnownTypeNames.SystemRuntimeInteropServicesOutAttribute);
                var analyzer = new MethodAnalyzer(outAttributeType);

                context.RegisterSymbolAction(analyzer.Analyze, SymbolKind.Method);
            });
        }

        private class MethodAnalyzer
        {
            private readonly INamedTypeSymbol? outAttributeSymbol;

            public MethodAnalyzer(INamedTypeSymbol? outAttributeSymbol)
            {
                this.outAttributeSymbol = outAttributeSymbol;
            }

            public void Analyze(SymbolAnalysisContext analysisContext)
            {
                var methodSymbol = (IMethodSymbol)analysisContext.Symbol;
                if (methodSymbol.IsOverride ||
                    !analysisContext.Options.MatchesConfiguredVisibility(Rule, methodSymbol, analysisContext.Compilation) ||
                    methodSymbol.IsImplementationOfAnyInterfaceMember())
                {
                    return;
                }

                var numberOfOutParams = methodSymbol.Parameters.Count(IsOutParameter);

                if (numberOfOutParams >= 1 &&
                    !IsTryPatternMethod(methodSymbol, numberOfOutParams) &&
                    !IsDeconstructPattern(methodSymbol))
                {
                    analysisContext.ReportDiagnostic(methodSymbol.CreateDiagnostic(Rule));
                }
            }

            private bool IsOutParameter(IParameterSymbol parameterSymbol) =>
                parameterSymbol.RefKind == RefKind.Out ||
                // Handle VB.NET special case for out parameters
                (parameterSymbol.RefKind == RefKind.Ref && parameterSymbol.HasAnyAttribute(outAttributeSymbol));

            private bool IsTryPatternMethod(IMethodSymbol methodSymbol, int numberOfOutParams) =>
                methodSymbol.Name.StartsWith("Try", StringComparison.Ordinal) &&
                methodSymbol.ReturnType.SpecialType == SpecialType.System_Boolean &&
                !methodSymbol.Parameters.IsEmpty &&
                IsOutParameter(methodSymbol.Parameters[^1]) &&
                numberOfOutParams == 1;

            private bool IsDeconstructPattern(IMethodSymbol methodSymbol)
            {
                if (!methodSymbol.Name.Equals("Deconstruct", StringComparison.Ordinal) ||
                    !methodSymbol.ReturnsVoid ||
                    methodSymbol.Parameters.IsEmpty)
                {
                    return false;
                }

                // The first parameter of a Deconstruct method can either be this XXX or out XXX
                if (!methodSymbol.IsExtensionMethod &&
                    !IsOutParameter(methodSymbol.Parameters[0]))
                {
                    return false;
                }

                return methodSymbol.Parameters.Skip(1).All(IsOutParameter);
            }
        }
    }
}