// 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.FindSymbols;
using Microsoft.CodeAnalysis.FindSymbols.Finders;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.ChangeSignature;

/// <summary>
/// For ChangeSignature, FAR on a delegate invoke method must cascade to BeginInvoke, 
/// cascade through method group conversions, and discover implicit invocations that do not
/// mention the string "Invoke" or the delegate type itself. This implementation finds these
/// symbols by binding most identifiers and invocation expressions in the solution. 
/// </summary>
/// <remarks>
/// TODO: Rewrite this to track backward through references instead of binding everything
/// </remarks>
internal sealed class DelegateInvokeMethodReferenceFinder : AbstractReferenceFinder<IMethodSymbol>
{
    public static readonly DelegateInvokeMethodReferenceFinder Instance = new();

    private DelegateInvokeMethodReferenceFinder()
    {
    }

    protected override bool CanFind(IMethodSymbol symbol)
        => symbol.MethodKind == MethodKind.DelegateInvoke;

    protected override async ValueTask<ImmutableArray<ISymbol>> DetermineCascadedSymbolsAsync(
        IMethodSymbol symbol,
        Solution solution,
        FindReferencesSearchOptions options,
        CancellationToken cancellationToken)
    {
        using var _ = ArrayBuilder<ISymbol>.GetInstance(out var result);

        var beginInvoke = symbol.ContainingType.GetMembers(WellKnownMemberNames.DelegateBeginInvokeName).FirstOrDefault();
        if (beginInvoke != null)
            result.Add(beginInvoke);

        // All method group references
        foreach (var project in solution.Projects)
        {
            foreach (var document in project.Documents)
            {
                var changeSignatureService = document.GetRequiredLanguageService<AbstractChangeSignatureService>();
                var cascaded = await changeSignatureService.DetermineCascadedSymbolsFromDelegateInvokeAsync(
                    symbol, document, cancellationToken).ConfigureAwait(false);
                result.AddRange(cascaded);
            }
        }

        return result.ToImmutableAndClear();
    }

    protected override Task DetermineDocumentsToSearchAsync<TData>(
        IMethodSymbol symbol,
        HashSet<string>? globalAliases,
        Project project,
        IImmutableSet<Document>? documents,
        Action<Document, TData> processResult,
        TData processResultData,
        FindReferencesSearchOptions options,
        CancellationToken cancellationToken)
    {
        foreach (var document in project.Documents)
            processResult(document, processResultData);

        return Task.CompletedTask;
    }

    protected override void FindReferencesInDocument<TData>(
        IMethodSymbol methodSymbol,
        FindReferencesDocumentState state,
        Action<FinderLocation, TData> processResult,
        TData processResultData,
        FindReferencesSearchOptions options,
        CancellationToken cancellationToken)
    {
        // FAR on the Delegate type and use those results to find Invoke calls

        var syntaxFacts = state.SyntaxFacts;

        var root = state.Root;
        var nodes = root.DescendantNodes();

        var invocations = nodes.Where(syntaxFacts.IsInvocationExpression)
            .Where(e => state.SemanticModel.GetSymbolInfo(e, cancellationToken).Symbol?.OriginalDefinition == methodSymbol);

        foreach (var node in invocations)
            processResult(CreateFinderLocation(node, state, cancellationToken), processResultData);

        foreach (var node in nodes)
        {
            if (!syntaxFacts.IsAnonymousFunctionExpression(node))
                continue;

            var convertedType = (ISymbol?)state.SemanticModel.GetTypeInfo(node, cancellationToken).ConvertedType;
            if (convertedType != null)
            {
                convertedType = SymbolFinder.FindSourceDefinitionAsync(convertedType, state.Solution, cancellationToken).WaitAndGetResult_CanCallOnBackground(cancellationToken) ?? convertedType;
            }

            if (convertedType == methodSymbol.ContainingType)
            {
                var finderLocation = CreateFinderLocation(node, state, cancellationToken);
                processResult(finderLocation, processResultData);
            }
        }

        return;

        static FinderLocation CreateFinderLocation(SyntaxNode node, FindReferencesDocumentState state, CancellationToken cancellationToken)
        {
            return new FinderLocation(
                node,
                new ReferenceLocation(
                    state.Document,
                    alias: null,
                    node.GetLocation(),
                    isImplicit: false,
                    GetSymbolUsageInfo(node, state, cancellationToken),
                    GetAdditionalFindUsagesProperties(node, state),
                    CandidateReason.None));
        }
    }
}