// 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.Generic;
using Microsoft.AspNetCore.Razor.Language;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Razor;

namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
{
    public sealed class ViewComponentTagHelperDescriptorProvider : RazorEngineFeatureBase, ITagHelperDescriptorProvider
    {
        public int Order { get; set; }

        public void Execute(TagHelperDescriptorProviderContext context)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            var compilation = context.GetCompilation();
            if (compilation == null)
            {
                // No compilation, nothing to do.
                return;
            }

            var vcAttribute = compilation.GetTypeByMetadataName(ViewComponentTypes.ViewComponentAttribute);
            var nonVCAttribute = compilation.GetTypeByMetadataName(ViewComponentTypes.NonViewComponentAttribute);
            if (vcAttribute == null || vcAttribute.TypeKind == TypeKind.Error)
            {
                // Could not find attributes we care about in the compilation. Nothing to do.
                return;
            }

            var types = new List<INamedTypeSymbol>();
            var visitor = new ViewComponentTypeVisitor(vcAttribute, nonVCAttribute, types);

            // We always visit the global namespace.
            visitor.Visit(compilation.Assembly.GlobalNamespace);

            foreach (var reference in compilation.References)
            {
                if (compilation.GetAssemblyOrModuleSymbol(reference) is IAssemblySymbol assembly)
                {
                    if (IsTagHelperAssembly(assembly))
                    {
                        visitor.Visit(assembly.GlobalNamespace);
                    }
                }
            }

            var factory = new ViewComponentTagHelperDescriptorFactory(compilation);
            for (var i = 0; i < types.Count; i++)
            {
                var descriptor = factory.CreateDescriptor(types[i]);

                if (descriptor != null)
                {
                    context.Results.Add(descriptor);
                }
            }
        }

        private bool IsTagHelperAssembly(IAssemblySymbol assembly)
        {
            return assembly.Name != null && !assembly.Name.StartsWith("System.", StringComparison.Ordinal);
        }
    }
}
