// 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;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.FindSymbols.Finders;

/// <summary>
/// For finding explicit calls to a constructor via "this(...)" or "base(...)".
/// </summary>
internal sealed class ExplicitConstructorInitializerSymbolReferenceFinder
    : ExplicitOrImplicitConstructorInitializerSymbolReferenceFinder
{
    public static readonly ExplicitConstructorInitializerSymbolReferenceFinder Instance = new();

    private ExplicitConstructorInitializerSymbolReferenceFinder()
    {
    }

    protected override bool CheckIndex(Document document, string name, SyntaxTreeIndex index)
    {
        if (index.ContainsExplicitBaseConstructorInitializer)
        {
            // if we have `partial class C { ... : base(...) }` we have to assume it might be a match, as the base
            // type reference might be in a another part of the partial in another file.
            if (index.ContainsPartialClass)
                return true;

            // Otherwise, if it doesn't have any partial types, ensure that the base type name is referenced in the
            // same file.  e.g. `partial class C : B { ... base(...) }`.   This allows us to greatly filter down the
            // number of matches, presuming that most inheriting types in a project are not themselves partial.
            if (index.ProbablyContainsIdentifier(name))
                return true;
        }

        if (index.ProbablyContainsIdentifier(name))
        {
            if (index.ContainsThisConstructorInitializer)
            {
                return true;
            }
            else if (document.Project.Language == LanguageNames.VisualBasic && index.ProbablyContainsIdentifier("New"))
            {
                // "New" can be explicitly accessed in xml doc comments to reference a constructor.
                return true;
            }
        }

        return false;
    }

    protected sealed override void FindReferencesInDocument<TData>(
        IMethodSymbol methodSymbol,
        FindReferencesDocumentState state,
        Action<FinderLocation, TData> processResult,
        TData processResultData,
        FindReferencesSearchOptions options,
        CancellationToken cancellationToken)
    {
        var tokens = state.Cache.GetConstructorInitializerTokens(cancellationToken);
        if (state.SemanticModel.Language == LanguageNames.VisualBasic)
            tokens = tokens.Concat(FindMatchingIdentifierTokens(state, "New", cancellationToken)).Distinct();

        var totalTokens = tokens.WhereAsArray(
            static (token, tuple) => TokensMatch(tuple.state, token, tuple.methodSymbol.ContainingType.Name, tuple.cancellationToken),
            (state, methodSymbol, cancellationToken));

        FindReferencesInTokens(methodSymbol, state, totalTokens, processResult, processResultData, cancellationToken);
        return;

        // local functions
        static bool TokensMatch(
            FindReferencesDocumentState state,
            SyntaxToken token,
            string typeName,
            CancellationToken cancellationToken)
        {
            var semanticModel = state.SemanticModel;
            var syntaxFacts = state.SyntaxFacts;

            if (syntaxFacts.IsBaseConstructorInitializer(token))
            {
                var containingType = semanticModel.GetEnclosingNamedType(token.SpanStart, cancellationToken);
                return containingType != null && containingType.BaseType != null && containingType.BaseType.Name == typeName;
            }
            else if (syntaxFacts.IsThisConstructorInitializer(token))
            {
                var containingType = semanticModel.GetEnclosingNamedType(token.SpanStart, cancellationToken);
                return containingType != null && containingType.Name == typeName;
            }
            else if (semanticModel.Language == LanguageNames.VisualBasic && token.IsPartOfStructuredTrivia())
            {
                return true;
            }

            return false;
        }
    }
}