SocialPub/PrivaPub/Api/Mastodon/Controllers/InstanceController.cs

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;

using MongoDB.Entities;

using PrivaPub.Api.Mastodon.Infrastructure;
using PrivaPub.Domain.Privacy;
using PrivaPub.Federation.Actors;
using PrivaPub.Infrastructure;
using PrivaPub.Models.User;

using PostEntity = PrivaPub.Models.Post.Post;

namespace PrivaPub.Api.Mastodon.Controllers
{
	public class InstanceController : MastodonController
	{
		public const string Version = "4.2.0 (compatible; PrivaPub)";
		const string Description = "A small ActivityPub server where one private login keeps several unlinkable public personas.";

		readonly ILocalActorService _localActors;
		readonly IOptionsMonitor<RegistrationOptions> _registrations;

		public InstanceController(ILocalActorService localActors, IOptionsMonitor<RegistrationOptions> registrations)
		{
			_localActors = localActors;
			_registrations = registrations;
		}

		bool Open => _registrations.CurrentValue.IsOpen;

		// the languages this server is set up for (AppConfiguration:SupportedLanguages), "en" when none are named
		public static IReadOnlyList<string> LanguageCodes(IServiceProvider services)
		{
			var configured = services.GetRequiredService<Microsoft.Extensions.Options.IOptionsMonitor<Models.AppConfiguration>>().CurrentValue.SupportedLanguages;
			var codes = (configured ?? new List<string>()).Where(c => !string.IsNullOrWhiteSpace(c)).Select(c => c.Split('-')[0].ToLowerInvariant()).Distinct().ToList();
			return codes.Count == 0 ? new[] { "en" } : codes;
		}

		string Domain => new Uri(_localActors.BaseAddress).Authority;

		// where clients open their streams (StreamingController): this server, as ws or wss
		string Streaming => new UriBuilder(_localActors.BaseAddress) { Scheme = _localActors.BaseAddress.StartsWith("https", StringComparison.OrdinalIgnoreCase) ? "wss" : "ws" }
			.Uri.GetLeftPart(UriPartial.Authority);

		// every limit is what the server enforces, read from where it is enforced
		static object Statuses => new { max_characters = PrivaPub.Domain.Statuses.StatusService.MaxCharacters, max_media_attachments = 4, characters_reserved_per_url = 23 };

		object MediaAttachments
		{
			get
			{
				var media = HttpContext.RequestServices.GetRequiredService<IOptionsMonitor<PrivaPub.Domain.Media.MediaOptions>>().CurrentValue;
				return new
				{
					supported_mime_types = PrivaPub.Domain.Media.MediaService.SupportedTypes,
					image_size_limit = media.MaxImageBytes,
					image_matrix_limit = media.MaxPixels,
					video_size_limit = media.MaxVideoBytes,
					video_frame_rate_limit = (int)media.MaxFrameRate,
					video_matrix_limit = media.MaxVideoPixels
				};
			}
		}

		static object Polls => new
		{
			max_options = PrivaPub.Domain.Statuses.PollService.MaxOptions,
			max_characters_per_option = PrivaPub.Domain.Statuses.PollService.MaxOptionLength,
			min_expiration = PrivaPub.Domain.Statuses.PollService.MinExpiration,
			max_expiration = PrivaPub.Domain.Statuses.PollService.MaxExpiration
		};

		[HttpGet("/api/v1/instance"), AllowAnonymous]
		public async Task<IActionResult> V1(CancellationToken token)
		{
			var users = await Counted.Users(token);
			var statuses = await Counted.LocalPosts(token);
			var domains = await KnownServers(token);
			return Json(new
			{
				uri = Domain,
				title = "PrivaPub",
				short_description = Description,
				description = Description,
				email = string.Empty,
				version = Version,
				urls = new { streaming_api = Streaming },
				stats = new { user_count = users, status_count = statuses, domain_count = domains },
				thumbnail = $"{_localActors.BaseAddress}/media/missing-header.png",
				languages = LanguageCodes(HttpContext.RequestServices),
				registrations = Open,
				approval_required = false,
				invites_enabled = true,//a group invitation always creates an account
				configuration = new { accounts = new { max_featured_tags = 0 }, statuses = Statuses, media_attachments = MediaAttachments, polls = Polls },
				contact_account = default(object),
				rules = Array.Empty<object>()
			});
		}

		// the servers we have exchanged activities with, as the statistics count them. Which ones is not published
		// (/instance/peers stays empty, as on a Mastodon with its peers API off): on a small server it would say who its
		// personas talk to.
		static async Task<long> KnownServers(CancellationToken token) =>
			await DB.Default.CountAsync<Models.Jobs.RemoteInstance>(i => i.Seen == "touched", token);

		[HttpGet("/api/v2/instance"), AllowAnonymous]
		public async Task<IActionResult> V2(CancellationToken token) => Json(new
		{
			domain = Domain,
			title = "PrivaPub",
			version = Version,
			api_versions = new { mastodon = 7 },
			source_url = "https://git.thepra.dev/thepra/SocialPub",
			description = Description,
			usage = new { users = new { active_month = await Counted.ActiveUsers(30, token) } },
			thumbnail = new { url = $"{_localActors.BaseAddress}/media/missing-header.png" },
			languages = LanguageCodes(HttpContext.RequestServices),
			configuration = new
			{
				urls = new { streaming = Streaming },
				accounts = new { max_featured_tags = 0, max_pinned_statuses = StatusesController.MaxPins },
				statuses = Statuses,
				media_attachments = MediaAttachments,
				polls = Polls,
				translation = new { enabled = false }
			},
			registrations = new { enabled = Open, approval_required = false, message = Open ? default : RegistrationOptions.ClosedMessage },
			contact = new { email = string.Empty, account = default(object) },
			rules = Array.Empty<object>()
		});

		[HttpGet("/api/v1/instance/peers"), AllowAnonymous]
		public IActionResult Peers() => Json(Array.Empty<string>());

		[HttpGet("/api/v1/instance/activity"), AllowAnonymous]
		public IActionResult Activity() => Json(Array.Empty<object>());

		[HttpGet("/api/v1/instance/rules"), AllowAnonymous]
		public IActionResult Rules() => Json(Array.Empty<object>());

		[HttpGet("/api/v1/instance/extended_description"), AllowAnonymous]
		public IActionResult ExtendedDescription() => Json(new { updated_at = MastodonJson.Day(DateTime.UtcNow), content = $"<p>{Description}</p>" });
	}
}