aspnetcore/src/Microsoft.AspNetCore.Mvc.Api.Analyzers/SymbolApiResponseMetadataProvider.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis;

namespace Microsoft.AspNetCore.Mvc.Api.Analyzers
{
    internal static class SymbolApiResponseMetadataProvider
    {
        private const string StatusCodeProperty = "StatusCode";
        private const string StatusCodeConstructorParameter = "statusCode";
        private static readonly IList<DeclaredApiResponseMetadata> DefaultResponseMetadatas = new[]
        {
            DeclaredApiResponseMetadata.ImplicitResponse,
        };

        public static IList<DeclaredApiResponseMetadata> GetDeclaredResponseMetadata(
            in ApiControllerSymbolCache symbolCache,
            IMethodSymbol method)
        {
            var metadataItems = GetResponseMetadataFromMethodAttributes(symbolCache, method);
            if (metadataItems.Count != 0)
            {
                return metadataItems;
            }

            var conventionTypeAttributes = GetConventionTypes(symbolCache, method);
            metadataItems = GetResponseMetadataFromConventions(symbolCache, method, conventionTypeAttributes);

            if (metadataItems.Count == 0)
            {
                // If no metadata can be gleaned either through explicit attributes on the method or via a convention,
                // declare an implicit 200 status code.
                metadataItems = DefaultResponseMetadatas;
            }

            return metadataItems;
        }

        public static ITypeSymbol GetErrorResponseType(
            in ApiControllerSymbolCache symbolCache,
            IMethodSymbol method)
        {
            var errorTypeAttribute =
                method.GetAttributes(symbolCache.ProducesErrorResponseTypeAttribute).FirstOrDefault() ??
                method.ContainingType.GetAttributes(symbolCache.ProducesErrorResponseTypeAttribute).FirstOrDefault() ??
                method.ContainingAssembly.GetAttributes(symbolCache.ProducesErrorResponseTypeAttribute).FirstOrDefault();

            ITypeSymbol errorType = symbolCache.ProblemDetails;
            if (errorTypeAttribute != null && 
                errorTypeAttribute.ConstructorArguments.Length == 1 && 
                errorTypeAttribute.ConstructorArguments[0].Kind == TypedConstantKind.Type &&
                errorTypeAttribute.ConstructorArguments[0].Value is ITypeSymbol typeSymbol)
            {
                errorType = typeSymbol;
            }

            return errorType;
        }

        private static IList<DeclaredApiResponseMetadata> GetResponseMetadataFromConventions(
            in ApiControllerSymbolCache symbolCache,
            IMethodSymbol method,
            IReadOnlyList<ITypeSymbol> conventionTypes)
        {
            var conventionMethod = GetMethodFromConventionMethodAttribute(symbolCache, method);
            if (conventionMethod == null)
            {
                conventionMethod = MatchConventionMethod(symbolCache, method, conventionTypes);
            }

            if (conventionMethod != null)
            {
                return GetResponseMetadataFromMethodAttributes(symbolCache, conventionMethod);
            }

            return Array.Empty<DeclaredApiResponseMetadata>();
        }

        private static IMethodSymbol GetMethodFromConventionMethodAttribute(in ApiControllerSymbolCache symbolCache, IMethodSymbol method)
        {
            var attribute = method.GetAttributes(symbolCache.ApiConventionMethodAttribute, inherit: true)
                .FirstOrDefault();

            if (attribute == null)
            {
                return null;
            }

            if (attribute.ConstructorArguments.Length != 2)
            {
                return null;
            }

            if (attribute.ConstructorArguments[0].Kind != TypedConstantKind.Type ||
                !(attribute.ConstructorArguments[0].Value is ITypeSymbol conventionType))
            {
                return null;
            }

            if (attribute.ConstructorArguments[1].Kind != TypedConstantKind.Primitive ||
                !(attribute.ConstructorArguments[1].Value is string conventionMethodName))
            {
                return null;
            }

            var conventionMethod = conventionType.GetMembers(conventionMethodName)
                .FirstOrDefault(m => m.Kind == SymbolKind.Method && m.IsStatic && m.DeclaredAccessibility == Accessibility.Public);

            return (IMethodSymbol)conventionMethod;
        }

        private static IMethodSymbol MatchConventionMethod(
            in ApiControllerSymbolCache symbolCache,
            IMethodSymbol method,
            IReadOnlyList<ITypeSymbol> conventionTypes)
        {
            foreach (var conventionType in conventionTypes)
            {
                foreach (var conventionMethod in conventionType.GetMembers().OfType<IMethodSymbol>())
                {
                    if (!conventionMethod.IsStatic || conventionMethod.DeclaredAccessibility != Accessibility.Public)
                    {
                        continue;
                    }

                    if (SymbolApiConventionMatcher.IsMatch(symbolCache, method, conventionMethod))
                    {
                        return conventionMethod;
                    }
                }
            }

            return null;
        }

        private static IList<DeclaredApiResponseMetadata> GetResponseMetadataFromMethodAttributes(in ApiControllerSymbolCache symbolCache, IMethodSymbol methodSymbol)
        {
            var metadataItems = new List<DeclaredApiResponseMetadata>();
            var responseMetadataAttributes = methodSymbol.GetAttributes(symbolCache.ProducesResponseTypeAttribute, inherit: true);
            foreach (var attribute in responseMetadataAttributes)
            {
                var statusCode = GetStatusCode(attribute);
                var metadata = DeclaredApiResponseMetadata.ForProducesResponseType(statusCode, attribute, attributeSource: methodSymbol);

                metadataItems.Add(metadata);
            }

            var producesDefaultResponse = methodSymbol.GetAttributes(symbolCache.ProducesDefaultResponseTypeAttribute, inherit: true).FirstOrDefault();
            if (producesDefaultResponse != null)
            {
                metadataItems.Add(DeclaredApiResponseMetadata.ForProducesDefaultResponse(producesDefaultResponse, methodSymbol));
            }

            return metadataItems;
        }

        internal static IReadOnlyList<ITypeSymbol> GetConventionTypes(in ApiControllerSymbolCache symbolCache, IMethodSymbol method)
        {
            var attributes = method.ContainingType.GetAttributes(symbolCache.ApiConventionTypeAttribute).ToArray();
            if (attributes.Length == 0)
            {
                attributes = method.ContainingAssembly.GetAttributes(symbolCache.ApiConventionTypeAttribute).ToArray();
            }

            var conventionTypes = new List<ITypeSymbol>();
            for (var i = 0; i < attributes.Length; i++)
            {
                var attribute = attributes[i];
                if (attribute.ConstructorArguments.Length != 1 ||
                    attribute.ConstructorArguments[0].Kind != TypedConstantKind.Type ||
                    !(attribute.ConstructorArguments[0].Value is ITypeSymbol conventionType))
                {
                    continue;
                }

                conventionTypes.Add(conventionType);
            }

            return conventionTypes;
        }

        internal static int GetStatusCode(AttributeData attribute)
        {
            const int DefaultStatusCode = 200;
            for (var i = 0; i < attribute.NamedArguments.Length; i++)
            {
                var namedArgument = attribute.NamedArguments[i];
                var namedArgumentValue = namedArgument.Value;
                if (string.Equals(namedArgument.Key, StatusCodeProperty, StringComparison.Ordinal) &&
                    namedArgumentValue.Kind == TypedConstantKind.Primitive &&
                    (namedArgumentValue.Type.SpecialType & SpecialType.System_Int32) == SpecialType.System_Int32 &&
                    namedArgumentValue.Value is int statusCode)
                {
                    return statusCode;
                }
            }

            if (attribute.AttributeConstructor == null)
            {
                return DefaultStatusCode;
            }

            var constructorParameters = attribute.AttributeConstructor.Parameters;
            for (var i = 0; i < constructorParameters.Length; i++)
            {
                var parameter = constructorParameters[i];
                if (string.Equals(parameter.Name, StatusCodeConstructorParameter, StringComparison.Ordinal) &&
                    (parameter.Type.SpecialType & SpecialType.System_Int32) == SpecialType.System_Int32)
                {
                    if (attribute.ConstructorArguments.Length < i)
                    {
                        return DefaultStatusCode;
                    }

                    var argument = attribute.ConstructorArguments[i];
                    if (argument.Kind == TypedConstantKind.Primitive && argument.Value is int statusCode)
                    {
                        return statusCode;
                    }
                }
            }

            return DefaultStatusCode;
        }
    }
}