// 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.Frozen;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Remote;
using Microsoft.CodeAnalysis.Shared.Collections;
using Microsoft.CodeAnalysis.SourceGeneration;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis;
 
// Cache of list of analyzer references to whether or not they have source generators.  Keyed based off
// IReadOnlyList<AnalyzerReference> so that we can cache the value even as project-states fork based on 
// document edits.
using AnalyzerReferenceMap = ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, AsyncLazy<bool>>;
 
internal sealed partial class SolutionCompilationState
{
    private sealed record SourceGeneratorMap(
        ImmutableArray<ISourceGenerator> SourceGenerators,
        FrozenDictionary<ISourceGenerator, AnalyzerReference> SourceGeneratorToAnalyzerReference);
 
    /// <summary>
    /// Cached mapping from language (only C#/VB since those are the only languages that support analyzers) to the lists
    /// of analyzer references (see <see cref="ProjectState.AnalyzerReferences"/>) to all the <see
    /// cref="ISourceGenerator"/>s produced by those references.  This should only be created and cached on the OOP side
    /// of things so that we don't cause source generators to be loaded (and fixed) within VS (which is .net framework
    /// only).
    /// </summary>
    private static readonly ConditionalWeakTable<ProjectState, SourceGeneratorMap> s_projectStateToSourceGeneratorsMap = new();
 
    /// <summary>
    /// Cached information about if a project has source generators or not.  Note: this is distinct from <see
    /// cref="s_projectStateToSourceGeneratorsMap"/> as we want to be able to compute it by calling over to our OOP
    /// process (if present) and having it make the determination, without the host necessarily loading generators
    /// itself.
    /// </summary>
    private static readonly Dictionary<string, AnalyzerReferenceMap> s_languageToAnalyzerReferenceMap = new()
    {
        { LanguageNames.CSharp, new() },
        { LanguageNames.VisualBasic, new() },
    };
 
    /// <summary>
    /// This method should only be called in a .net core host like our out of process server.
    /// </summary>
    private static ImmutableArray<ISourceGenerator> GetSourceGenerators(ProjectState projectState)
    {
        var map = GetSourceGeneratorMap(projectState);
        return map is null ? [] : map.SourceGenerators;
    }
 
    /// <summary>
    /// This method should only be called in a .net core host like our out of process server.
    /// </summary>
    private static AnalyzerReference GetAnalyzerReference(ProjectState projectState, ISourceGenerator sourceGenerator)
    {
        // We must be talking about a project that supports compilations, since we already got a source generator from it.
        Contract.ThrowIfFalse(projectState.SupportsCompilation);
 
        var map = GetSourceGeneratorMap(projectState);
 
        // It should not be possible for this to be null. We have the source generator, as such we must have mapped from
        // the project state to the SG info for it.
        Contract.ThrowIfNull(map);
 
        return map.SourceGeneratorToAnalyzerReference[sourceGenerator];
    }
 
    private static SourceGeneratorMap? GetSourceGeneratorMap(ProjectState projectState)
    {
        if (!projectState.SupportsCompilation)
            return null;
 
        return s_projectStateToSourceGeneratorsMap.GetValue(projectState, ComputeSourceGenerators);
 
        static SourceGeneratorMap ComputeSourceGenerators(ProjectState projectState)
        {
            using var generators = TemporaryArray<ISourceGenerator>.Empty;
            using var _ = PooledDictionary<ISourceGenerator, AnalyzerReference>.GetInstance(out var generatorToAnalyzerReference);
 
            foreach (var reference in projectState.AnalyzerReferences)
            {
                foreach (var generator in reference.GetGenerators(projectState.Language).Distinct())
                {
                    generators.Add(generator);
                    generatorToAnalyzerReference.Add(generator, reference);
                }
            }
 
            return new(generators.ToImmutableAndClear(), generatorToAnalyzerReference.ToFrozenDictionary());
        }
    }
 
    public async Task<bool> HasSourceGeneratorsAsync(ProjectId projectId, CancellationToken cancellationToken)
    {
        var projectState = this.SolutionState.GetRequiredProjectState(projectId);
        if (projectState.AnalyzerReferences.Count == 0)
            return false;
 
        if (!RemoteSupportedLanguages.IsSupported(projectState.Language))
            return false;
 
        var analyzerReferenceMap = s_languageToAnalyzerReferenceMap[projectState.Language];
        if (!analyzerReferenceMap.TryGetValue(projectState.AnalyzerReferences, out var lazy))
        {
            // Extracted into local function to prevent allocations in the case where we find a value in the cache.
            lazy = GetLazy(analyzerReferenceMap, projectState);
        }
 
        return await lazy.GetValueAsync(cancellationToken).ConfigureAwait(false);
 
        AsyncLazy<bool> GetLazy(AnalyzerReferenceMap analyzerReferenceMap, ProjectState projectState)
            => analyzerReferenceMap.GetValue(
                projectState.AnalyzerReferences,
                _ => AsyncLazy.Create(
                    cancellationToken => ComputeHasSourceGeneratorsAsync(this, projectState, cancellationToken)));
 
        static async Task<bool> ComputeHasSourceGeneratorsAsync(
            SolutionCompilationState solution, ProjectState projectState, CancellationToken cancellationToken)
        {
            var client = await RemoteHostClient.TryGetClientAsync(solution.Services, cancellationToken).ConfigureAwait(false);
            // If in proc, just load the generators and see if we have any.
            if (client is null)
                return GetSourceGenerators(projectState).Any();
 
            // Out of process, call to the remote to figure this out.
            var projectId = projectState.Id;
            var projectStateChecksums = await projectState.GetStateChecksumsAsync(cancellationToken).ConfigureAwait(false);
            var analyzerReferences = projectStateChecksums.AnalyzerReferences.Children;
 
            var result = await client.TryInvokeAsync<IRemoteSourceGenerationService, bool>(
                solution,
                projectId,
                (service, solution, cancellationToken) => service.HasGeneratorsAsync(solution, projectId, analyzerReferences, projectState.Language, cancellationToken),
                cancellationToken).ConfigureAwait(false);
            return result.HasValue && result.Value;
        }
    }
}