using System.Diagnostics.CodeAnalysis;
using System.Threading.RateLimiting;
using System.Xml.Linq;
using Iceshrimp.Backend.Controllers.Federation;
using Iceshrimp.Backend.Controllers.Mastodon.Renderers;
using Iceshrimp.Backend.Controllers.Web.Renderers;
using Iceshrimp.Backend.Core.Configuration;
using Iceshrimp.Backend.Core.Database;
using Iceshrimp.Backend.Core.Federation.WebFinger;
using Iceshrimp.Backend.Core.Helpers.LibMfm.Conversion;
using Iceshrimp.Backend.Core.Middleware;
using Iceshrimp.Backend.Core.Services;
using Iceshrimp.Backend.Core.Services.ImageProcessing;
using Iceshrimp.Backend.SignalR.Authentication;
using Iceshrimp.Shared.Configuration;
using Iceshrimp.Shared.Schemas.Web;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.DataProtection;
using Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption;
using Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption.ConfigurationModel;
using Microsoft.AspNetCore.DataProtection.EntityFrameworkCore;
using Microsoft.AspNetCore.DataProtection.KeyManagement;
using Microsoft.AspNetCore.DataProtection.Repositories;
using Microsoft.AspNetCore.Http.Json;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using Microsoft.OpenApi.Models;
using AuthenticationMiddleware = Iceshrimp.Backend.Core.Middleware.AuthenticationMiddleware;
using AuthorizationMiddleware = Iceshrimp.Backend.Core.Middleware.AuthorizationMiddleware;
using NoteRenderer = Iceshrimp.Backend.Controllers.Web.Renderers.NoteRenderer;
using NotificationRenderer = Iceshrimp.Backend.Controllers.Web.Renderers.NotificationRenderer;
using UserRenderer = Iceshrimp.Backend.Controllers.Web.Renderers.UserRenderer;

namespace Iceshrimp.Backend.Core.Extensions;

public static class ServiceExtensions
{
	public static void AddServices(this IServiceCollection services, IConfiguration configuration)
	{
		// Transient = instantiated per request and class

		// Scoped = instantiated per request
		services
			.AddScoped<ActivityPub.ActivityRenderer>()
			.AddScoped<ActivityPub.UserRenderer>()
			.AddScoped<ActivityPub.NoteRenderer>()
			.AddScoped<ActivityPub.UserResolver>()
			.AddScoped<ActivityPub.ObjectResolver>()
			.AddScoped<ActivityPub.MentionsResolver>()
			.AddScoped<ActivityPub.ActivityDeliverService>()
			.AddScoped<ActivityPub.FederationControlService>()
			.AddScoped<ActivityPub.ActivityHandlerService>()
			.AddScoped<ActivityPub.ActivityFetcherService>()
			.AddScoped<UserService>()
			.AddScoped<NoteService>()
			.AddScoped<EmojiService>()
			.AddScoped<EmojiImportService>()
			.AddScoped<WebFingerService>()
			.AddScoped<SystemUserService>()
			.AddScoped<DriveService>()
			.AddScoped<NotificationService>()
			.AddScoped<DatabaseMaintenanceService>()
			.AddScoped<UserProfileMentionsResolver>()
			.AddScoped<AuthorizedFetchMiddleware>()
			.AddScoped<InboxValidationMiddleware>()
			.AddScoped<AuthenticationMiddleware>()
			.AddScoped<ErrorHandlerMiddleware>()
			.AddScoped<Controllers.Mastodon.Renderers.UserRenderer>()
			.AddScoped<Controllers.Mastodon.Renderers.NoteRenderer>()
			.AddScoped<Controllers.Mastodon.Renderers.NotificationRenderer>()
			.AddScoped<PollRenderer>()
			.AddScoped<PollService>()
			.AddScoped<NoteRenderer>()
			.AddScoped<UserRenderer>()
			.AddScoped<NotificationRenderer>()
			.AddScoped<ActivityPubController>()
			.AddScoped<FollowupTaskService>()
			.AddScoped<InstanceService>()
			.AddScoped<MfmConverter>()
			.AddScoped<UserProfileRenderer>()
			.AddScoped<CacheService>()
			.AddScoped<MetaService>()
			.AddScoped<StorageMaintenanceService>()
			.AddScoped<RelayService>();

		// Singleton = instantiated once across application lifetime
		services
			.AddSingleton<HttpClient, CustomHttpClient>()
			.AddSingleton<HttpRequestService>()
			.AddSingleton<CronService>()
			.AddSingleton<QueueService>()
			.AddSingleton<ObjectStorageService>()
			.AddSingleton<EventService>()
			.AddSingleton<RequestBufferingMiddleware>()
			.AddSingleton<AuthorizationMiddleware>()
			.AddSingleton<RequestVerificationMiddleware>()
			.AddSingleton<RequestDurationMiddleware>()
			.AddSingleton<FederationSemaphoreMiddleware>()
			.AddSingleton<PushService>()
			.AddSingleton<StreamingService>()
			.AddSingleton<ImageProcessor>()
			.AddSingleton<RazorViewRenderService>();

		var config = configuration.GetSection("Storage").Get<Config.StorageSection>() ??
		             throw new Exception("Failed to read storage config section");

		switch (config.MediaProcessing.ImageProcessor)
		{
			case Enums.ImageProcessor.LibVips:
				services.AddSingleton<IImageProcessor, VipsProcessor>();
				services.AddSingleton<IImageProcessor, ImageSharpProcessor>();
				break;
			case Enums.ImageProcessor.ImageSharp:
				services.AddSingleton<IImageProcessor, ImageSharpProcessor>();
				break;
			case Enums.ImageProcessor.None:
				break;
			default:
				throw new ArgumentOutOfRangeException();
		}

		// Hosted services = long running background tasks
		// Note: These need to be added as a singleton as well to ensure data consistency
		services.AddHostedService<CronService>(provider => provider.GetRequiredService<CronService>());
		services.AddHostedService<QueueService>(provider => provider.GetRequiredService<QueueService>());
		services.AddHostedService<PushService>(provider => provider.GetRequiredService<PushService>());
	}

	public static void ConfigureServices(this IServiceCollection services, IConfiguration configuration)
	{
		// @formatter:off
		services.ConfigureWithValidation<Config>(configuration)
		        .ConfigureWithValidation<Config.InstanceSection>(configuration, "Instance")
		        .ConfigureWithValidation<Config.SecuritySection>(configuration, "Security")
		        .ConfigureWithValidation<Config.PerformanceSection>(configuration, "Performance")
		        .ConfigureWithValidation<Config.QueueConcurrencySection>(configuration, "Performance:QueueConcurrency")
		        .ConfigureWithValidation<Config.BackfillSection>(configuration, "Backfill")
		        .ConfigureWithValidation<Config.BackfillRepliesSection>(configuration, "Backfill:Replies")
		        .ConfigureWithValidation<Config.QueueSection>(configuration, "Queue")
		        .ConfigureWithValidation<Config.JobRetentionSection>(configuration, "Queue:JobRetention")
		        .ConfigureWithValidation<Config.DatabaseSection>(configuration, "Database")
		        .ConfigureWithValidation<Config.StorageSection>(configuration, "Storage")
		        .ConfigureWithValidation<Config.LocalStorageSection>(configuration, "Storage:Local")
		        .ConfigureWithValidation<Config.ObjectStorageSection>(configuration, "Storage:ObjectStorage")
		        .ConfigureWithValidation<Config.MediaProcessingSection>(configuration, "Storage:MediaProcessing")
		        .ConfigureWithValidation<Config.ImagePipelineSection>(configuration, "Storage:MediaProcessing:ImagePipeline")
		        .ConfigureWithValidation<Config.ImageFormatConfiguration>(configuration, "Storage:MediaProcessing:ImagePipeline:Original:Local")
		        .ConfigureWithValidation<Config.ImageFormatConfiguration>(configuration, "Storage:MediaProcessing:ImagePipeline:Original:Remote")
		        .ConfigureWithValidation<Config.ImageFormatConfiguration>(configuration, "Storage:MediaProcessing:ImagePipeline:Thumbnail:Local")
		        .ConfigureWithValidation<Config.ImageFormatConfiguration>(configuration, "Storage:MediaProcessing:ImagePipeline:Thumbnail:Remote")
		        .ConfigureWithValidation<Config.ImageFormatConfiguration>(configuration, "Storage:MediaProcessing:ImagePipeline:Public:Local")
		        .ConfigureWithValidation<Config.ImageFormatConfiguration>(configuration, "Storage:MediaProcessing:ImagePipeline:Public:Remote");
		// @formatter:on

		services.Configure<JsonOptions>(options =>
		{
			options.SerializerOptions.PropertyNamingPolicy = JsonSerialization.Options.PropertyNamingPolicy;
			foreach (var converter in JsonSerialization.Options.Converters)
				options.SerializerOptions.Converters.Add(converter);
		});

		services.Configure<Microsoft.AspNetCore.Mvc.JsonOptions>(options =>
		{
			options.JsonSerializerOptions.PropertyNamingPolicy = JsonSerialization.Options.PropertyNamingPolicy;
			foreach (var converter in JsonSerialization.Options.Converters)
				options.JsonSerializerOptions.Converters.Add(converter);
		});
	}

	private static IServiceCollection ConfigureWithValidation<T>(
		this IServiceCollection services, IConfiguration config
	) where T : class
	{
		services.AddOptionsWithValidateOnStart<T>()
		        .Bind(config)
		        .ValidateDataAnnotations();

		return services;
	}

	private static IServiceCollection ConfigureWithValidation<T>(
		this IServiceCollection services, IConfiguration config, string name
	) where T : class
	{
		services.AddOptionsWithValidateOnStart<T>()
		        .Bind(config.GetSection(name))
		        .ValidateDataAnnotations();

		return services;
	}

	public static void AddDatabaseContext(this IServiceCollection services, IConfiguration configuration)
	{
		var config = configuration.GetSection("Database").Get<Config.DatabaseSection>() ??
		             throw new Exception("Failed to initialize database: Failed to load configuration");

		var dataSource = DatabaseContext.GetDataSource(config);
		services.AddDbContext<DatabaseContext>(options => { DatabaseContext.Configure(options, dataSource, config); });
		services.AddKeyedDatabaseContext<DatabaseContext>("cache");
		services.AddDataProtection()
		        .PersistKeysToDbContextAsync<DatabaseContext>()
		        .UseCryptographicAlgorithms(new AuthenticatedEncryptorConfiguration
		        {
			        EncryptionAlgorithm = EncryptionAlgorithm.AES_256_CBC,
			        ValidationAlgorithm = ValidationAlgorithm.HMACSHA256
		        });
	}

	private static void AddKeyedDatabaseContext<T>(
		this IServiceCollection services, string key, ServiceLifetime contextLifetime = ServiceLifetime.Scoped
	) where T : DbContext
	{
		services.TryAdd(new ServiceDescriptor(typeof(T), key, typeof(T), contextLifetime));
	}

	public static void AddSwaggerGenWithOptions(this IServiceCollection services)
	{
		services.AddEndpointsApiExplorer();
		services.AddSwaggerGen(options =>
		{
			options.SupportNonNullableReferenceTypes();

			var version = new Config.InstanceSection().Version;
			options.SwaggerDoc("iceshrimp", new OpenApiInfo { Title  = "Iceshrimp.NET", Version = version });
			options.SwaggerDoc("federation", new OpenApiInfo { Title = "Federation", Version    = version });
			options.SwaggerDoc("mastodon", new OpenApiInfo { Title   = "Mastodon", Version      = version });

			options.AddSecurityDefinition("iceshrimp",
			                              new OpenApiSecurityScheme
			                              {
				                              Name   = "Authorization token",
				                              In     = ParameterLocation.Header,
				                              Type   = SecuritySchemeType.Http,
				                              Scheme = "bearer"
			                              });
			options.AddSecurityDefinition("mastodon",
			                              new OpenApiSecurityScheme
			                              {
				                              Name   = "Authorization token",
				                              In     = ParameterLocation.Header,
				                              Type   = SecuritySchemeType.Http,
				                              Scheme = "bearer"
			                              });

			options.AddFilters();
		});
	}

	public static void AddSlidingWindowRateLimiter(this IServiceCollection services)
	{
		//TODO: rate limit status headers - maybe switch to https://github.com/stefanprodan/AspNetCoreRateLimit?
		//TODO: alternatively just write our own
		services.AddRateLimiter(options =>
		{
			var sliding = new SlidingWindowRateLimiterOptions
			{
				PermitLimit          = 500,
				SegmentsPerWindow    = 60,
				Window               = TimeSpan.FromSeconds(60),
				QueueProcessingOrder = QueueProcessingOrder.OldestFirst,
				QueueLimit           = 0
			};

			var auth = new SlidingWindowRateLimiterOptions
			{
				PermitLimit          = 10,
				SegmentsPerWindow    = 60,
				Window               = TimeSpan.FromSeconds(60),
				QueueProcessingOrder = QueueProcessingOrder.OldestFirst,
				QueueLimit           = 0
			};

			var strict = new SlidingWindowRateLimiterOptions
			{
				PermitLimit          = 3,
				SegmentsPerWindow    = 60,
				Window               = TimeSpan.FromSeconds(60),
				QueueProcessingOrder = QueueProcessingOrder.OldestFirst,
				QueueLimit           = 0
			};

			// @formatter:off
			options.AddPolicy("sliding", ctx => RateLimitPartition.GetSlidingWindowLimiter(ctx.GetRateLimitPartition(false),_ => sliding));
			options.AddPolicy("auth", ctx => RateLimitPartition.GetSlidingWindowLimiter(ctx.GetRateLimitPartition(false), _ => auth));
			options.AddPolicy("strict", ctx => RateLimitPartition.GetSlidingWindowLimiter(ctx.GetRateLimitPartition(true), _ => strict));
			// @formatter:on

			options.OnRejected = async (context, token) =>
			{
				context.HttpContext.Response.StatusCode  = 429;
				context.HttpContext.Response.ContentType = "application/json";
				var res = new ErrorResponse(new Exception())
				{
					Error      = "Too Many Requests",
					StatusCode = 429,
					RequestId  = context.HttpContext.TraceIdentifier
				};
				await context.HttpContext.Response.WriteAsJsonAsync(res, token);
			};
		});
	}

	public static void AddCorsPolicies(this IServiceCollection services)
	{
		services.AddCors(options =>
		{
			options.AddPolicy("well-known", policy =>
			{
				policy.WithOrigins("*")
				      .WithMethods("GET")
				      .WithHeaders("Accept")
				      .WithExposedHeaders("Vary");
			});
			options.AddPolicy("drive", policy =>
			{
				policy.WithOrigins("*")
				      .WithMethods("GET", "HEAD");
			});
			options.AddPolicy("mastodon", policy =>
			{
				policy.WithOrigins("*")
				      .WithMethods("GET", "HEAD", "POST", "PUT", "PATCH", "DELETE", "CONNECT")
				      .WithHeaders("Authorization", "Content-Type", "Idempotency-Key")
				      .WithExposedHeaders("Link", "Connection", "Sec-Websocket-Accept", "Upgrade");
			});
			options.AddPolicy("fallback", policy =>
			{
				policy.WithOrigins("*")
				      .WithMethods("GET", "HEAD", "POST", "PUT", "PATCH", "DELETE", "CONNECT")
				      .WithHeaders("Authorization", "Content-Type", "Idempotency-Key")
				      .WithExposedHeaders("Link", "Connection", "Sec-Websocket-Accept", "Upgrade");
			});
		});
	}

	public static void AddAuthorizationPolicies(this IServiceCollection services)
	{
		services.AddAuthorizationBuilder()
		        .AddPolicy("HubAuthorization", policy =>
		        {
			        policy.Requirements.Add(new HubAuthorizationRequirement());
			        policy.AuthenticationSchemes = ["HubAuthenticationScheme"];
		        });

		services.AddAuthentication(options =>
		{
			options.AddScheme<HubAuthenticationHandler>("HubAuthenticationScheme", null);

			// Add a stub authentication handler to bypass strange ASP.NET Core >=7.0 defaults
			// Ref: https://github.com/dotnet/aspnetcore/issues/44661
			options.AddScheme<IAuthenticationHandler>("StubAuthenticationHandler", null);
		});
	}
}

public static class HttpContextExtensions
{
	public static string GetRateLimitPartition(this HttpContext ctx, bool includeRoute) =>
		(includeRoute ? ctx.Request.Path.ToString() + "#" : "") + (GetRateLimitPartitionInternal(ctx) ?? "");

	private static string? GetRateLimitPartitionInternal(this HttpContext ctx) =>
		ctx.GetUser()?.Id ??
		ctx.Request.Headers["X-Forwarded-For"].FirstOrDefault() ??
		ctx.Connection.RemoteIpAddress?.ToString();
}

#region AsyncDataProtection handlers

/// <summary>
///     Async equivalent of EntityFrameworkCoreDataProtectionExtensions.PersistKeysToDbContext.
///     Required because Npgsql doesn't support the non-async APIs when using connection multiplexing, and the stock
///     version EFCore API calls their blocking equivalents.
/// </summary>
file static class DataProtectionExtensions
{
	public static IDataProtectionBuilder PersistKeysToDbContextAsync<TContext>(this IDataProtectionBuilder builder)
		where TContext : DbContext, IDataProtectionKeyContext
	{
		builder.Services.AddSingleton<IConfigureOptions<KeyManagementOptions>>(services =>
		{
			var loggerFactory = services.GetService<ILoggerFactory>() ?? NullLoggerFactory.Instance;
			return new ConfigureOptions<KeyManagementOptions>(options => options.XmlRepository =
				                                                  new EntityFrameworkCoreXmlRepositoryAsync<
					                                                  TContext>(services, loggerFactory));
		});
		return builder;
	}
}

file sealed class EntityFrameworkCoreXmlRepositoryAsync<TContext> : IXmlRepository
	where TContext : DbContext, IDataProtectionKeyContext
{
	private readonly IServiceProvider _services;

	[DynamicDependency(DynamicallyAccessedMemberTypes.PublicProperties, typeof(DataProtectionKey))]
	public EntityFrameworkCoreXmlRepositoryAsync(IServiceProvider services, ILoggerFactory loggerFactory)
	{
		ArgumentNullException.ThrowIfNull(loggerFactory, nameof(loggerFactory));
		_services = services ?? throw new ArgumentNullException(nameof(services));
	}

	public IReadOnlyCollection<XElement> GetAllElements()
	{
		return GetAllElementsCore().ToBlockingEnumerable().ToList().AsReadOnly();

		async IAsyncEnumerable<XElement> GetAllElementsCore()
		{
			using var scope = _services.CreateScope();
			var @enum = scope.ServiceProvider.GetRequiredService<TContext>()
			                 .DataProtectionKeys
			                 .AsNoTracking()
			                 .AsAsyncEnumerable();

			await foreach (var dataProtectionKey in @enum)
			{
				if (!string.IsNullOrEmpty(dataProtectionKey.Xml))
					yield return XElement.Parse(dataProtectionKey.Xml);
			}
		}
	}

	public void StoreElement(XElement element, string friendlyName)
	{
		using var scope           = _services.CreateAsyncScope();
		using var requiredService = scope.ServiceProvider.GetRequiredService<TContext>();
		requiredService.DataProtectionKeys.Add(new DataProtectionKey
		{
			FriendlyName = friendlyName,
			Xml          = element.ToString(SaveOptions.DisableFormatting)
		});
		requiredService.SaveChangesAsync().Wait();
	}
}

#endregion