#:sdk Microsoft.NET.Sdk.Web
#:property PublishAot=false
#:property InvariantGlobalization=true
#:property Nullable=disable

// flood: a crowd of fake servers for the pasture's load runs (tools/pasture/load.sh).
//   flood serve                 answers as flood1..N.test: each host's actors (/users/u<i>, with their keys), WebFinger,
//                               NodeInfo, empty collections, and inboxes that answer any Follow with a signed Accept
//   flood run [options]         sends signed activities from those actors to PrivaPub's shared inbox at a set rate and
//                               prints, as JSON, what it sent and how PrivaPub answered
// Both read the actors' keys from the state directory (made by the first `serve`), so they speak as the same actors.
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Globalization;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;

var state = Environment.GetEnvironmentVariable("FLOOD_STATE") ?? "/state";
var hosts = int.Parse(Environment.GetEnvironmentVariable("FLOOD_HOSTS") ?? "20", CultureInfo.InvariantCulture);
var perHost = int.Parse(Environment.GetEnvironmentVariable("FLOOD_ACTORS") ?? "10", CultureInfo.InvariantCulture);
var keys = Keys.Load(state, hosts, perHost);

if (args.Length > 0 && args[0] == "run")
	return await Run.Start(args[1..], keys);

var builder = WebApplication.CreateBuilder();
builder.Logging.SetMinimumLevel(LogLevel.Warning);
builder.WebHost.UseUrls("http://0.0.0.0:8080");
var app = builder.Build();
var http = Signer.Client();

app.MapGet("/users/{name}", (HttpContext context, string name) =>
	keys.Find(context.Request.Host.Host, name) is { } actor ? Json(Actor(actor)) : Results.NotFound());
app.MapGet("/users/{name}/{collection}", (HttpContext context, string name, string collection) =>
	keys.Find(context.Request.Host.Host, name) is { } actor && collection is "followers" or "following" or "outbox"
		? Json(new JsonObject { ["@context"] = "https://www.w3.org/ns/activitystreams", ["id"] = $"{actor.Id}/{collection}", ["type"] = "OrderedCollection", ["totalItems"] = 0 })
		: Results.NotFound());
app.MapGet("/.well-known/webfinger", (HttpContext context, string resource) =>
{
	var handle = resource?.StartsWith("acct:", StringComparison.Ordinal) == true ? resource[5..] : resource;
	var parts = handle?.Split('@') ?? [];
	return parts.Length == 2 && keys.Find(parts[1], parts[0]) is { } actor
		? Results.Json(new { subject = "acct:" + handle, links = new[] { new { rel = "self", type = "application/activity+json", href = actor.Id } } },
			contentType: "application/jrd+json")
		: Results.NotFound();
});
app.MapGet("/.well-known/nodeinfo", (HttpContext context) => Results.Json(new
{
	links = new[] { new { rel = "http://nodeinfo.diaspora.software/ns/schema/2.0", href = $"https://{context.Request.Host.Host}/nodeinfo/2.0" } }
}));
app.MapGet("/nodeinfo/2.0", () => Results.Json(new
{
	version = "2.0", software = new { name = "flood", version = "1" }, protocols = new[] { "activitypub" },
	usage = new { users = new { total = perHost } }, openRegistrations = false
}));
app.MapPost("/inbox", (Delegate)Inbox);
app.MapPost("/users/{name}/inbox", (Delegate)Inbox);
app.Run();
return 0;

// a Follow of one of ours is accepted, signed by the followed actor, at the follower's inbox; anything else is taken
async Task<IResult> Inbox(HttpContext context)
{
	var activity = await JsonNode.ParseAsync(context.Request.Body);
	if (activity?["type"]?.GetValue<string>() == "Follow" && activity["object"]?.GetValue<string>() is { } followed
		&& keys.ById(followed) is { } actor && activity["actor"]?.GetValue<string>() is { } follower)
		_ = Task.Run(async () =>
		{
			var inbox = (await Signer.Get(http, follower, actor))?["inbox"]?.GetValue<string>();
			if (inbox == null)
				return;
			var accept = new JsonObject
			{
				["@context"] = "https://www.w3.org/ns/activitystreams", ["id"] = $"{actor.Id}/accepts/{Guid.NewGuid():N}",
				["type"] = "Accept", ["actor"] = actor.Id, ["object"] = activity.DeepClone()
			};
			await Signer.Post(http, inbox, accept, actor);
		});
	return Results.Accepted();
}

static IResult Json(JsonNode document) => Results.Text(document.ToJsonString(), "application/activity+json");

static JsonObject Actor(FloodActor actor) => new()
{
	["@context"] = new JsonArray("https://www.w3.org/ns/activitystreams", "https://w3id.org/security/v1"),
	["id"] = actor.Id,
	["type"] = "Person",
	["preferredUsername"] = actor.Name,
	["name"] = $"Flood {actor.Name} of {actor.Host}",
	["inbox"] = actor.Id + "/inbox",
	["outbox"] = actor.Id + "/outbox",
	["followers"] = actor.Id + "/followers",
	["following"] = actor.Id + "/following",
	["endpoints"] = new JsonObject { ["sharedInbox"] = $"https://{actor.Host}/inbox" },
	["publicKey"] = new JsonObject { ["id"] = actor.Id + "#main-key", ["owner"] = actor.Id, ["publicKeyPem"] = actor.PublicPem }
};

sealed record FloodActor(string Host, string Name, string PrivatePem, string PublicPem)
{
	public string Id => $"https://{Host}/users/{Name}";
}

sealed class Keys(List<FloodActor> actors)
{
	public IReadOnlyList<FloodActor> All => actors;

	public FloodActor Find(string host, string name) => actors.FirstOrDefault(a => a.Host == host && a.Name == name);

	public FloodActor ById(string id) => actors.FirstOrDefault(a => a.Id == id);

	public static Keys Load(string state, int hosts, int perHost)
	{
		var path = Path.Combine(state, "keys.json");
		if (File.Exists(path))
			return new Keys(JsonSerializer.Deserialize<List<FloodActor>>(File.ReadAllText(path)));
		var actors = new List<FloodActor>();
		for (var h = 1; h <= hosts; h++)
			for (var i = 0; i < perHost; i++)
			{
				using var rsa = RSA.Create(2048);
				actors.Add(new FloodActor($"flood{h}.test", $"u{i}", rsa.ExportPkcs8PrivateKeyPem(), rsa.ExportSubjectPublicKeyInfoPem()));
			}
		Directory.CreateDirectory(state);
		File.WriteAllText(path, JsonSerializer.Serialize(actors));
		return new Keys(actors);
	}
}

// draft-cavage rsa-sha256, as PrivaPub signs and checks it: (request-target) host date [digest]
static class Signer
{
	public static HttpClient Client() => new(new SocketsHttpHandler { MaxConnectionsPerServer = 128, PooledConnectionLifetime = TimeSpan.FromMinutes(5) })
	{
		Timeout = TimeSpan.FromSeconds(60)
	};

	static string Signature(FloodActor actor, string signingString, string headers)
	{
		using var rsa = RSA.Create();
		rsa.ImportFromPem(actor.PrivatePem);
		var signature = Convert.ToBase64String(rsa.SignData(Encoding.UTF8.GetBytes(signingString), HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1));
		return $"keyId=\"{actor.Id}#main-key\",algorithm=\"rsa-sha256\",headers=\"{headers}\",signature=\"{signature}\"";
	}

	public static async Task<HttpStatusCode> Post(HttpClient http, string inbox, JsonNode activity, FloodActor actor)
	{
		var uri = new Uri(inbox);
		var body = Encoding.UTF8.GetBytes(activity.ToJsonString());
		var date = DateTime.UtcNow.ToString("r", CultureInfo.InvariantCulture);
		var digest = "SHA-256=" + Convert.ToBase64String(SHA256.HashData(body));
		using var request = new HttpRequestMessage(HttpMethod.Post, uri) { Content = new ByteArrayContent(body) };
		request.Content.Headers.TryAddWithoutValidation("Content-Type", "application/activity+json");
		request.Headers.TryAddWithoutValidation("Date", date);
		request.Headers.TryAddWithoutValidation("Digest", digest);
		request.Headers.TryAddWithoutValidation("Signature",
			Signature(actor, $"(request-target): post {uri.PathAndQuery}\nhost: {uri.Host}\ndate: {date}\ndigest: {digest}", "(request-target) host date digest"));
		try
		{
			using var response = await http.SendAsync(request);
			return response.StatusCode;
		}
		catch (Exception)
		{
			return 0;
		}
	}

	public static async Task<JsonNode> Get(HttpClient http, string url, FloodActor actor)
	{
		var uri = new Uri(url);
		var date = DateTime.UtcNow.ToString("r", CultureInfo.InvariantCulture);
		using var request = new HttpRequestMessage(HttpMethod.Get, uri);
		request.Headers.TryAddWithoutValidation("Accept", "application/activity+json");
		request.Headers.TryAddWithoutValidation("Date", date);
		request.Headers.TryAddWithoutValidation("Signature", Signature(actor, $"(request-target): get {uri.PathAndQuery}\nhost: {uri.Host}\ndate: {date}", "(request-target) host date"));
		try
		{
			using var response = await http.SendAsync(request);
			return response.IsSuccessStatusCode ? JsonNode.Parse(await response.Content.ReadAsStringAsync()) : null;
		}
		catch (Exception)
		{
			return null;
		}
	}
}

// the load: activities at a rate, each from a random actor, to PrivaPub's shared inbox
static class Run
{
	public static async Task<int> Start(string[] args, Keys keys)
	{
		var options = args.Select(a => a.Split('=', 2)).Where(p => p.Length == 2).ToDictionary(p => p[0].TrimStart('-'), p => p[1]);
		var target = options.GetValueOrDefault("target", "https://privapub.test");
		var rate = double.Parse(options.GetValueOrDefault("rate", "20"), CultureInfo.InvariantCulture);
		var seconds = double.Parse(options.GetValueOrDefault("seconds", "60"), CultureInfo.InvariantCulture);
		var personas = options.GetValueOrDefault("personas", "").Split(',', StringSplitOptions.RemoveEmptyEntries);
		var posts = options.TryGetValue("posts", out var postsFile) && File.Exists(postsFile)
			? File.ReadAllLines(postsFile).Where(l => l.Length > 0).ToArray() : [];
		var mix = options.GetValueOrDefault("mix", "create=80,like=20").Split(',')
			.Select(p => p.Split('=')).ToDictionary(p => p[0], p => double.Parse(p[1], CultureInfo.InvariantCulture));
		var inbox = target.TrimEnd('/') + "/human-centipede";
		var http = Signer.Client();
		var random = new Random(4127);
		var gate = new SemaphoreSlim(int.Parse(options.GetValueOrDefault("concurrency", "64"), CultureInfo.InvariantCulture));
		var results = new ConcurrentBag<(string Kind, int Status, double Ms)>();
		var pending = new List<Task>();
		var clock = Stopwatch.StartNew();
		var total = (int)(rate * seconds);
		for (var n = 0; n < total; n++)
		{
			var due = TimeSpan.FromSeconds(n / rate);
			if (due > clock.Elapsed)
				await Task.Delay(due - clock.Elapsed);
			var actor = keys.All[random.Next(keys.All.Count)];
			var kind = Pick(mix, random);
			var activity = kind switch
			{
				"like" when posts.Length > 0 => Like(actor, posts[random.Next(posts.Length)]),
				"follow" when personas.Length > 0 => Follow(actor, personas[random.Next(personas.Length)]),
				_ => Create(actor, personas, n)
			};
			await gate.WaitAsync();
			pending.Add(Task.Run(async () =>
			{
				var sent = Stopwatch.StartNew();
				var status = await Signer.Post(http, inbox, activity, actor);
				results.Add((activity["type"]!.GetValue<string>(), (int)status, sent.Elapsed.TotalMilliseconds));
				gate.Release();
			}));
		}
		await Task.WhenAll(pending);
		var elapsed = clock.Elapsed.TotalSeconds;
		var latencies = results.Select(r => r.Ms).Order().ToArray();
		double Percentile(double p) => latencies.Length == 0 ? 0 : latencies[Math.Min(latencies.Length - 1, (int)Math.Ceiling(p * latencies.Length) - 1)];
		Console.WriteLine(new JsonObject
		{
			["sent"] = results.Count,
			["seconds"] = Math.Round(elapsed, 1),
			["rate"] = Math.Round(results.Count / elapsed, 1),
			["byType"] = new JsonObject(results.GroupBy(r => r.Kind).Select(g => KeyValuePair.Create(g.Key, (JsonNode)g.Count()))),
			["byStatus"] = new JsonObject(results.GroupBy(r => r.Status.ToString(CultureInfo.InvariantCulture)).Select(g => KeyValuePair.Create(g.Key, (JsonNode)g.Count()))),
			["p50Ms"] = Math.Round(Percentile(0.5), 1),
			["p95Ms"] = Math.Round(Percentile(0.95), 1),
			["p99Ms"] = Math.Round(Percentile(0.99), 1),
			["maxMs"] = Math.Round(latencies.LastOrDefault(), 1)
		}.ToJsonString());
		return 0;
	}

	static string Pick(Dictionary<string, double> mix, Random random)
	{
		var roll = random.NextDouble() * mix.Values.Sum();
		foreach (var (kind, weight) in mix)
			if ((roll -= weight) <= 0)
				return kind;
		return mix.Keys.First();
	}

	static JsonObject Create(FloodActor actor, string[] personas, int n)
	{
		var id = $"{actor.Id}/notes/{Guid.NewGuid():N}";
		var mentioned = personas.Length == 0 ? null : personas[n % personas.Length];
		var note = new JsonObject
		{
			["id"] = id, ["type"] = "Note", ["attributedTo"] = actor.Id,
			["content"] = $"<p>flood note {n}{(mentioned == null ? "" : $" for <a href=\"{mentioned}\" class=\"mention\">@someone</a>")}</p>",
			["published"] = DateTime.UtcNow.ToString("o", CultureInfo.InvariantCulture),
			["to"] = new JsonArray("https://www.w3.org/ns/activitystreams#Public"),
			["cc"] = mentioned == null ? new JsonArray(actor.Id + "/followers") : new JsonArray(actor.Id + "/followers", mentioned),
			["tag"] = mentioned == null ? new JsonArray() : new JsonArray(new JsonObject { ["type"] = "Mention", ["href"] = mentioned })
		};
		return new JsonObject
		{
			["@context"] = "https://www.w3.org/ns/activitystreams", ["id"] = id + "/activity", ["type"] = "Create",
			["actor"] = actor.Id, ["to"] = note["to"]!.DeepClone(), ["cc"] = note["cc"]!.DeepClone(), ["object"] = note
		};
	}

	static JsonObject Like(FloodActor actor, string post) => new()
	{
		["@context"] = "https://www.w3.org/ns/activitystreams", ["id"] = $"{actor.Id}/likes/{Guid.NewGuid():N}",
		["type"] = "Like", ["actor"] = actor.Id, ["object"] = post
	};

	static JsonObject Follow(FloodActor actor, string persona) => new()
	{
		["@context"] = "https://www.w3.org/ns/activitystreams", ["id"] = $"{actor.Id}/follows/{Guid.NewGuid():N}",
		["type"] = "Follow", ["actor"] = actor.Id, ["object"] = persona
	};
}