From 6ec6a43e1c990898c8c60d3b8aa718f539165460 Mon Sep 17 00:00:00 2001
From: Laura Hausmann <laura@hausmann.dev>
Date: Tue, 9 Jan 2024 20:00:54 +0100
Subject: [PATCH] WIP: UserResolver

---
 .../Core/Federation/WebFinger/UserResolver.cs | 31 +++++++++++++++++++
 .../Core/Federation/WebFinger/WebFinger.cs    | 23 ++++++--------
 2 files changed, 41 insertions(+), 13 deletions(-)
 create mode 100644 Iceshrimp.Backend/Core/Federation/WebFinger/UserResolver.cs

diff --git a/Iceshrimp.Backend/Core/Federation/WebFinger/UserResolver.cs b/Iceshrimp.Backend/Core/Federation/WebFinger/UserResolver.cs
new file mode 100644
index 00000000..a612e887
--- /dev/null
+++ b/Iceshrimp.Backend/Core/Federation/WebFinger/UserResolver.cs
@@ -0,0 +1,31 @@
+using Iceshrimp.Backend.Core.Database.Tables;
+
+namespace Iceshrimp.Backend.Core.Federation.WebFinger;
+
+public static class UserResolver {
+	private static string AcctToDomain(string acct) =>
+		acct.StartsWith("acct:") && acct.Contains('@')
+			? acct[5..].Split('@')[1]
+			: throw new Exception("Invalid acct");
+
+	/*
+	 * Split domain logic:
+	 * 1. Get WebFinger response for query
+	 * 2. [...]
+	 * TODO: finish description and implement the rest
+	 */
+
+	public static async Task<User> Resolve(string query) {
+		var finger    = new WebFinger(query);
+		var fingerRes = await finger.Resolve();
+		if (fingerRes == null) throw new Exception($"Failed to WebFinger '{query}'");
+		if (finger.Domain != AcctToDomain(fingerRes.Subject)) {
+			//TODO: Logger.info("possible split domain deployment detected, repeating webfinger")
+
+			finger    = new WebFinger(fingerRes.Subject);
+			fingerRes = await finger.Resolve();
+		}
+
+		throw new NotImplementedException("stub method return");
+	}
+}
\ No newline at end of file
diff --git a/Iceshrimp.Backend/Core/Federation/WebFinger/WebFinger.cs b/Iceshrimp.Backend/Core/Federation/WebFinger/WebFinger.cs
index 09051993..c2a15b1a 100644
--- a/Iceshrimp.Backend/Core/Federation/WebFinger/WebFinger.cs
+++ b/Iceshrimp.Backend/Core/Federation/WebFinger/WebFinger.cs
@@ -1,7 +1,6 @@
 using System.Net.Http.Headers;
 using System.Text.Encodings.Web;
 using System.Xml;
-using Iceshrimp.Backend.Core.Configuration;
 using Iceshrimp.Backend.Core.Helpers;
 
 namespace Iceshrimp.Backend.Core.Federation.WebFinger;
@@ -16,18 +15,21 @@ namespace Iceshrimp.Backend.Core.Federation.WebFinger;
  * - doesn't have a query url template
  */
 
+//FIXME: handle cursed person/group acct collisions like https://lemmy.ml/.well-known/webfinger?resource=acct:linux@lemmy.ml
+
 public class WebFinger {
 	private readonly string  _query;
 	private readonly string  _proto;
 	private readonly string  _domain;
-	private readonly string? _username;
 	private          string? _webFingerUrl;
 
+	public string Domain => _domain;
+
 	private string HostMetaUrl              => $"{_proto}://{_domain}/.well-known/host-meta";
 	private string DefaultWebFingerTemplate => $"{_proto}://{_domain}/.well-known/webfinger?resource={{uri}}";
 
 	public WebFinger(string query) {
-		_query = query;
+		_query = query.StartsWith("acct:") ? $"@{query[5..]}" : query;
 		if (_query.StartsWith("http://") || _query.StartsWith("https://")) {
 			var uri = new Uri(_query);
 			_domain = uri.Host;
@@ -37,17 +39,12 @@ public class WebFinger {
 			_proto = "https";
 
 			var split = _query.Split('@');
-			if (split.Length == 2) {
-				throw new Exception("Can't run WebFinger for local user");
-			}
-
-			if (split.Length == 3) {
-				_username = split[1];
-				_domain   = split[2];
-			}
-			else {
+			if (split.Length is < 2 or > 3)
 				throw new Exception("Invalid query");
-			}
+			if (split.Length is 2)
+				throw new Exception("Can't run WebFinger for local user");
+
+			_domain = split[2];
 		}
 		else {
 			throw new Exception("Invalid query");