﻿// 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.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeGeneration;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.GenerateMember.GenerateEnumMember
{
    internal abstract partial class AbstractGenerateEnumMemberService<TService, TSimpleNameSyntax, TExpressionSyntax>
    {
        private partial class State
        {
            // public TypeDeclarationSyntax ContainingTypeDeclaration { get; private set; }
            public INamedTypeSymbol TypeToGenerateIn { get; private set; } = null!;

            // Just the name of the method.  i.e. "Goo" in "Goo" or "X.Goo"
            public SyntaxToken IdentifierToken { get; private set; }
            public TSimpleNameSyntax SimpleName { get; private set; } = null!;
            public TExpressionSyntax SimpleNameOrMemberAccessExpression { get; private set; } = null!;

            public static async Task<State?> GenerateAsync(
                TService service,
                SemanticDocument document,
                SyntaxNode node,
                CancellationToken cancellationToken)
            {
                var state = new State();
                if (!await state.TryInitializeAsync(service, document, node, cancellationToken).ConfigureAwait(false))
                    return null;

                return state;
            }

            private async Task<bool> TryInitializeAsync(
                TService service,
                SemanticDocument document,
                SyntaxNode node,
                CancellationToken cancellationToken)
            {
                if (service.IsIdentifierNameGeneration(node))
                {
                    if (!TryInitializeIdentifierName(service, document, (TSimpleNameSyntax)node, cancellationToken))
                        return false;
                }
                else
                {
                    return false;
                }

                // Ok.  It either didn't bind to any symbols, or it bound to a symbol but with
                // errors.  In the former case we definitely want to offer to generate a field.  In
                // the latter case, we want to generate a field *unless* there's an existing member
                // with the same name.  Note: it's ok if there's an existing field with the same
                // name.
                var existingMembers = TypeToGenerateIn.GetMembers(IdentifierToken.ValueText);
                if (existingMembers.Any())
                {
                    // TODO: Code coverage There was an existing member that the new member would
                    // clash with.  
                    return false;
                }

                cancellationToken.ThrowIfCancellationRequested();
                var sourceType = await SymbolFinder.FindSourceDefinitionAsync(TypeToGenerateIn, document.Project.Solution, cancellationToken).ConfigureAwait(false) as INamedTypeSymbol;
                if (!ValidateTypeToGenerateIn(sourceType, true, EnumType))
                    return false;

                TypeToGenerateIn = sourceType;
                return CodeGenerator.CanAdd(document.Project.Solution, TypeToGenerateIn, cancellationToken);
            }

            private bool TryInitializeIdentifierName(
                TService service,
                SemanticDocument semanticDocument,
                TSimpleNameSyntax identifierName,
                CancellationToken cancellationToken)
            {
                SimpleName = identifierName;
                if (!service.TryInitializeIdentifierNameState(semanticDocument, identifierName, cancellationToken,
                        out var identifierToken, out var simpleNameOrMemberAccessExpression))
                {
                    return false;
                }

                IdentifierToken = identifierToken;
                SimpleNameOrMemberAccessExpression = simpleNameOrMemberAccessExpression;

                var semanticModel = semanticDocument.SemanticModel;
                var semanticFacts = semanticDocument.Document.GetRequiredLanguageService<ISemanticFactsService>();
                var syntaxFacts = semanticDocument.Document.GetRequiredLanguageService<ISyntaxFactsService>();
                if (semanticFacts.IsWrittenTo(semanticModel, SimpleNameOrMemberAccessExpression, cancellationToken) ||
                    syntaxFacts.IsInNamespaceOrTypeContext(SimpleNameOrMemberAccessExpression))
                {
                    return false;
                }

                // Now, try to bind the invocation and see if it succeeds or not.  if it succeeds and
                // binds uniquely, then we don't need to offer this quick fix.
                cancellationToken.ThrowIfCancellationRequested();
                var containingType = semanticModel.GetEnclosingNamedType(identifierToken.SpanStart, cancellationToken);
                if (containingType == null)
                    return false;

                var semanticInfo = semanticModel.GetSymbolInfo(SimpleNameOrMemberAccessExpression, cancellationToken);
                if (semanticInfo.Symbol != null)
                    return false;

                // Either we found no matches, or this was ambiguous. Either way, we might be able
                // to generate a method here.  Determine where the user wants to generate the method
                // into, and if it's valid then proceed.
                if (!TryDetermineTypeToGenerateIn(
                        semanticDocument, containingType, simpleNameOrMemberAccessExpression, cancellationToken,
                        out var typeToGenerateIn, out var isStatic, out var isColorColorCase))
                {
                    return false;
                }

                if (!isStatic && !isColorColorCase)
                    return false;

                TypeToGenerateIn = typeToGenerateIn;
                return true;
            }
        }
    }
}
