// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Buffers;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Components.Discovery;
using Microsoft.AspNetCore.Components.Endpoints.Infrastructure;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Primitives;
using static Microsoft.AspNetCore.Internal.LinkerFlags;
 
namespace Microsoft.AspNetCore.Components.Endpoints;
 
internal class RazorComponentEndpointDataSource<[DynamicallyAccessedMembers(Component)] TRootComponent> : EndpointDataSource
{
    private readonly object _lock = new();
    private readonly List<Action<EndpointBuilder>> _conventions = [];
    private readonly List<Action<EndpointBuilder>> _finallyConventions = [];
    private readonly List<Action<ComponentApplicationBuilder>> _componentApplicationBuilderActions = [];
    private readonly RazorComponentDataSourceOptions _options = new();
    private readonly IEndpointRouteBuilder _endpointRouteBuilder;
    private readonly ResourceCollectionResolver _resourceCollectionResolver;
    private readonly RenderModeEndpointProvider[] _renderModeEndpointProviders;
    private readonly RazorComponentEndpointFactory _factory;
    private readonly HotReloadService? _hotReloadService;
    private List<Endpoint>? _endpoints;
    private CancellationTokenSource _cancellationTokenSource;
    private IChangeToken _changeToken;
    private IDisposable? _disposableChangeToken;   // THREADING: protected by _lock
 
    // Internal for testing.
    internal List<Action<EndpointBuilder>> Conventions => _conventions;
    internal List<Action<ComponentApplicationBuilder>> ComponentApplicationBuilderActions => _componentApplicationBuilderActions;
    internal CancellationTokenSource ChangeTokenSource => _cancellationTokenSource;
 
    public RazorComponentEndpointDataSource(
        IEnumerable<RenderModeEndpointProvider> renderModeEndpointProviders,
        IEndpointRouteBuilder endpointRouteBuilder,
        RazorComponentEndpointFactory factory,
        HotReloadService? hotReloadService = null)
    {
        _endpointRouteBuilder = endpointRouteBuilder;
        _resourceCollectionResolver = new ResourceCollectionResolver(endpointRouteBuilder);
        _renderModeEndpointProviders = renderModeEndpointProviders.ToArray();
        _factory = factory;
        _hotReloadService = hotReloadService;
        DefaultBuilder = new RazorComponentsEndpointConventionBuilder(
            _lock,
            endpointRouteBuilder,
            _options,
            _conventions,
            _finallyConventions,
            _componentApplicationBuilderActions);
 
        _cancellationTokenSource = new CancellationTokenSource();
        _changeToken = new CancellationChangeToken(_cancellationTokenSource.Token);
    }
 
    internal RazorComponentsEndpointConventionBuilder DefaultBuilder { get; }
 
    public override IReadOnlyList<Endpoint> Endpoints
    {
        get
        {
            // Note it is important that this is lazy, since we only want to create the endpoints after the user had a chance to populate
            // the list of conventions.
            // The order is as follows:
            // * MapRazorComponents gets called and the data source gets created.
            // * The RazorComponentEndpointConventionBuilder is returned and the user gets a chance to call on it to add conventions.
            // * The first request arrives and the DfaMatcherBuilder accesses the data sources to get the endpoints.
            // * The endpoints get created and the conventions get applied.
            Initialize();
            Debug.Assert(_changeToken != null);
            Debug.Assert(_endpoints != null);
            return _endpoints;
        }
    }
 
    internal RazorComponentDataSourceOptions Options => _options;
 
    private void Initialize()
    {
        if (_endpoints == null)
        {
            lock (_lock)
            {
                if (_endpoints == null)
                {
                    UpdateEndpoints();
                }
            }
        }
    }
 
    private void UpdateEndpoints()
    {
        const string ResourceCollectionKey = "__ResourceCollectionKey";
 
        lock (_lock)
        {
            _disposableChangeToken?.Dispose();
            _disposableChangeToken = null;
 
            var endpoints = new List<Endpoint>();
 
            var componentApplicationBuilder = new ComponentApplicationBuilder();
 
            foreach (var action in ComponentApplicationBuilderActions)
            {
                action?.Invoke(componentApplicationBuilder);
            }
 
            var context = componentApplicationBuilder.Build();
 
            var configuredRenderModesMetadata = new ConfiguredRenderModesMetadata(
                [.. Options.ConfiguredRenderModes]);
 
            var endpointContext = new RazorComponentEndpointUpdateContext(endpoints, _options);
 
            DefaultBuilder.OnBeforeCreateEndpoints(endpointContext);
 
            AddBlazorWebEndpoints(endpoints);
 
            foreach (var definition in context.Pages)
            {
                _factory.AddEndpoints(
                    endpoints,
                    typeof(TRootComponent),
                    definition,
                    _conventions,
                    _finallyConventions,
                    configuredRenderModesMetadata);
            }
 
            // Extract the endpoint collection from any of the endpoints
            var resourceCollection = endpoints.Count > 0 ? endpoints[^1].Metadata.GetMetadata<ResourceAssetCollection>() : null;
 
            ICollection<IComponentRenderMode> renderModes = Options.ConfiguredRenderModes;
            foreach (var renderMode in renderModes)
            {
                var found = false;
                foreach (var provider in _renderModeEndpointProviders)
                {
                    var builder = _endpointRouteBuilder.CreateApplicationBuilder();
                    builder.Properties[ResourceCollectionKey] = resourceCollection;
                    if (provider.Supports(renderMode))
                    {
                        found = true;
                        RenderModeEndpointProvider.AddEndpoints(
                            endpoints,
                            typeof(TRootComponent),
                            provider.GetEndpointBuilders(renderMode, builder),
                            renderMode,
                            _conventions,
                            _finallyConventions);
                    }
                }
 
                if (!found)
                {
                    throw new InvalidOperationException($"Unable to find a provider for the render mode: {renderMode.GetType().FullName}. This generally " +
                        "means that a call to 'AddInteractiveWebAssemblyComponents' or 'AddInteractiveServerComponents' is missing. " +
                        "For example, change builder.Services.AddRazorComponents() to builder.Services.AddRazorComponents().AddInteractiveServerComponents().");
                }
            }
 
            var oldCancellationTokenSource = _cancellationTokenSource;
            _endpoints = endpoints;
            _cancellationTokenSource = new CancellationTokenSource();
            _changeToken = new CancellationChangeToken(_cancellationTokenSource.Token);
            oldCancellationTokenSource?.Cancel();
            oldCancellationTokenSource?.Dispose();
            if (_hotReloadService is { MetadataUpdateSupported: true })
            {
                _disposableChangeToken = ChangeToken.OnChange(_hotReloadService.GetChangeToken, UpdateEndpoints);
            }
        }
    }
 
    private void AddBlazorWebEndpoints(List<Endpoint> endpoints)
    {
        List<EndpointBuilder> blazorWebEndpoints = [
            OpaqueRedirection.GetBlazorOpaqueRedirectionEndpoint()];
 
        foreach (var endpoint in blazorWebEndpoints)
        {
            foreach (var convention in _conventions)
            {
                convention(endpoint);
            }
 
            foreach (var convention in _finallyConventions)
            {
                convention(endpoint);
            }
 
            endpoints.Add(endpoint.Build());
        }
    }
 
    public override IChangeToken GetChangeToken()
    {
        Initialize();
        Debug.Assert(_changeToken != null);
        Debug.Assert(_endpoints != null);
        return _changeToken;
    }
}