// 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.Threading;
using System.Threading.Tasks;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.FindSymbols.Finders;
 
internal sealed class MethodTypeParameterSymbolReferenceFinder : AbstractTypeParameterSymbolReferenceFinder
{
    protected override bool CanFind(ITypeParameterSymbol symbol)
        => symbol.TypeParameterKind == TypeParameterKind.Method;
 
    protected override ValueTask<ImmutableArray<ISymbol>> DetermineCascadedSymbolsAsync(
        ITypeParameterSymbol symbol,
        Solution solution,
        FindReferencesSearchOptions options,
        CancellationToken cancellationToken)
    {
        var method = (IMethodSymbol)symbol.ContainingSymbol;
        var ordinal = method.TypeParameters.IndexOf(symbol);
 
        if (ordinal >= 0)
        {
            if (method.PartialDefinitionPart != null && ordinal < method.PartialDefinitionPart.TypeParameters.Length)
                return new([method.PartialDefinitionPart.TypeParameters[ordinal]]);
 
            if (method.PartialImplementationPart != null && ordinal < method.PartialImplementationPart.TypeParameters.Length)
                return new([method.PartialImplementationPart.TypeParameters[ordinal]]);
        }
 
        return new([]);
    }
 
    protected sealed override Task DetermineDocumentsToSearchAsync<TData>(
        ITypeParameterSymbol symbol,
        HashSet<string>? globalAliases,
        Project project,
        IImmutableSet<Document>? documents,
        Action<Document, TData> processResult,
        TData processResultData,
        FindReferencesSearchOptions options,
        CancellationToken cancellationToken)
    {
        // Type parameters are only found in documents that have both their name, and the name
        // of its owning method.  NOTE(cyrusn): We have to check in multiple files because of
        // partial types.  A type parameter can be referenced across all the parts. NOTE(cyrusn):
        // We look for type parameters by name.  This means if the same type parameter has a
        // different name in different parts that we won't find it. However, this only happens
        // in error situations.  It is not legal in C# to use a different name for a type
        // parameter in different parts.
        //
        // Also, we only look for files that have the name of the owning type.  This helps filter
        // down the set considerably.
        Contract.ThrowIfNull(symbol.DeclaringMethod);
        return FindDocumentsAsync(project, documents, processResult, processResultData, cancellationToken, symbol.Name,
            GetMemberNameWithoutInterfaceName(symbol.DeclaringMethod.Name),
            symbol.DeclaringMethod.ContainingType.Name);
    }
 
    private static string GetMemberNameWithoutInterfaceName(string fullName)
    {
        var index = fullName.LastIndexOf('.');
        return index > 0 ? fullName[(index + 1)..] : fullName;
    }
}