// 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.Generic;
using System.Linq;
using System.Threading;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.LanguageService;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Operations;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp;
 
internal sealed partial class CSharpSemanticFactsService : AbstractSemanticFactsService, ISemanticFactsService
{
    internal static readonly CSharpSemanticFactsService Instance = new();
 
    public override ISyntaxFacts SyntaxFacts => CSharpSyntaxFacts.Instance;
    public override IBlockFacts BlockFacts => CSharpBlockFacts.Instance;
 
    protected override ISemanticFacts SemanticFacts => CSharpSemanticFacts.Instance;
 
    private CSharpSemanticFactsService()
    {
    }
 
    protected override SyntaxToken ToIdentifierToken(string identifier)
        => identifier.ToIdentifierToken();
 
    protected override IEnumerable<ISymbol> GetCollidableSymbols(SemanticModel semanticModel, SyntaxNode location, SyntaxNode container, CancellationToken cancellationToken)
    {
        // Get all the symbols visible to the current location.
        var visibleSymbols = semanticModel.LookupSymbols(location.SpanStart);
 
        // Local function parameter is allowed to shadow variables since C# 8.
        if (semanticModel.Compilation.LanguageVersion().MapSpecifiedToEffectiveVersion() >= LanguageVersion.CSharp8)
        {
            if (SyntaxFacts.IsParameterList(container) && SyntaxFacts.IsLocalFunctionStatement(container.Parent))
            {
                visibleSymbols = visibleSymbols.WhereAsArray(s => !s.MatchesKind(SymbolKind.Local, SymbolKind.Parameter));
            }
        }
 
        // Some symbols in the enclosing block could cause conflicts even if they are not available at the location.
        // E.g. symbols inside if statements / try catch statements.
        var symbolsInBlock = semanticModel.GetAllDeclaredSymbols(container, cancellationToken,
            descendInto: n => ShouldDescendInto(n));
 
        return symbolsInBlock.Concat(visibleSymbols);
 
        // Walk through the enclosing block symbols, but avoid exploring local functions
        //     a) Visible symbols from the local function would be returned by LookupSymbols
        //        (e.g. location is inside a local function, the local function method name).
        //     b) Symbols declared inside the local function do not cause collisions with symbols declared outside them, so avoid considering those symbols.
        // Exclude lambdas as well when the language version is C# 8 or higher because symbols declared inside no longer collide with outer variables.
        bool ShouldDescendInto(SyntaxNode node)
        {
            var isLanguageVersionGreaterOrEqualToCSharp8 = (semanticModel.Compilation as CSharpCompilation)?.LanguageVersion >= LanguageVersion.CSharp8;
            return isLanguageVersionGreaterOrEqualToCSharp8 ? !SyntaxFacts.IsAnonymousOrLocalFunction(node) : !SyntaxFacts.IsLocalFunctionStatement(node);
        }
    }
 
    public bool IsExpressionContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
    {
        return semanticModel.SyntaxTree.IsExpressionContext(
            position,
            semanticModel.SyntaxTree.FindTokenOnLeftOfPosition(position, cancellationToken),
            attributes: true, cancellationToken: cancellationToken, semanticModel: semanticModel);
    }
 
    public bool IsStatementContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
    {
        return semanticModel.SyntaxTree.IsStatementContext(
            position, semanticModel.SyntaxTree.FindTokenOnLeftOfPosition(position, cancellationToken), cancellationToken);
    }
 
    public bool IsTypeContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
        => semanticModel.SyntaxTree.IsTypeContext(position, cancellationToken, semanticModel);
 
    public bool IsNamespaceContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
        => semanticModel.SyntaxTree.IsNamespaceContext(position, cancellationToken, semanticModel);
 
    public bool IsNamespaceDeclarationNameContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
        => semanticModel.SyntaxTree.IsNamespaceDeclarationNameContext(position, cancellationToken);
 
    public bool IsTypeDeclarationContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
    {
        return semanticModel.SyntaxTree.IsTypeDeclarationContext(
            position, semanticModel.SyntaxTree.FindTokenOnLeftOfPosition(position, cancellationToken), cancellationToken);
    }
 
    public bool IsMemberDeclarationContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
    {
        return semanticModel.SyntaxTree.IsMemberDeclarationContext(
            position, semanticModel.SyntaxTree.FindTokenOnLeftOfPosition(position, cancellationToken));
    }
 
    public bool IsGlobalStatementContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
        => semanticModel.SyntaxTree.IsGlobalStatementContext(position, cancellationToken);
 
    public bool IsLabelContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
        => semanticModel.SyntaxTree.IsLabelContext(position, cancellationToken);
 
    public bool IsAttributeNameContext(SemanticModel semanticModel, int position, CancellationToken cancellationToken)
        => semanticModel.SyntaxTree.IsAttributeNameContext(position, cancellationToken);
 
    public CommonConversion ClassifyConversion(SemanticModel semanticModel, SyntaxNode expression, ITypeSymbol destination)
        => semanticModel.ClassifyConversion((ExpressionSyntax)expression, destination).ToCommonConversion();
 
#nullable enable
 
    public IMethodSymbol? TryGetDisposeMethod(SemanticModel semanticModel, SyntaxNode node, CancellationToken cancellationToken)
    {
        var isAsync = false;
        ExpressionSyntax? expression = null;
 
        if (node is UsingStatementSyntax usingStatement)
        {
            isAsync = usingStatement.AwaitKeyword != default;
            expression = usingStatement is { Declaration.Variables: [{ Initializer.Value: { } value }] } ? value : usingStatement.Expression;
        }
        else if (node is LocalDeclarationStatementSyntax { Declaration.Variables: [{ Initializer.Value: { } value }] } localDeclaration)
        {
            isAsync = localDeclaration.AwaitKeyword != default;
            expression = value;
        }
 
        if (expression is null)
            return null;
 
        var type = semanticModel.GetTypeInfo(expression, cancellationToken).Type;
        return FindDisposeMethod(semanticModel.Compilation, type, isAsync);
    }
}