From af8345d8c9626e196655942294d39ae8c9e60a45 Mon Sep 17 00:00:00 2001
From: Miss Pasture <miss@pasture.moe>
Date: Sat, 17 Jul 2021 20:26:45 -0400
Subject: [PATCH] Remote follow

---
 .../Models/WebFingerData.cs                   | 21 ++++++++
 src/BirdsiteLive.Domain/ActivityPubService.cs | 10 ++++
 .../Controllers/UsersController.cs            | 50 ++++++++++++++++++-
 src/BirdsiteLive/Views/Users/Index.cshtml     |  7 ++-
 4 files changed, 86 insertions(+), 2 deletions(-)
 create mode 100644 src/BirdsiteLive.ActivityPub/Models/WebFingerData.cs

diff --git a/src/BirdsiteLive.ActivityPub/Models/WebFingerData.cs b/src/BirdsiteLive.ActivityPub/Models/WebFingerData.cs
new file mode 100644
index 0000000..31dc1b8
--- /dev/null
+++ b/src/BirdsiteLive.ActivityPub/Models/WebFingerData.cs
@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace BirdsiteLive.ActivityPub.Models
+{
+    public class WebFingerData
+    {
+        public List<string> aliases { get; set; }
+
+        public List<WebFingerLink> links { get; set; }
+    }
+
+    public class WebFingerLink
+    {
+        public string href { get; set; }
+        public string rel { get; set; }
+        public string type { get; set; }
+        public string template { get; set; }
+    }
+}
diff --git a/src/BirdsiteLive.Domain/ActivityPubService.cs b/src/BirdsiteLive.Domain/ActivityPubService.cs
index 37fe0b5..71a1457 100644
--- a/src/BirdsiteLive.Domain/ActivityPubService.cs
+++ b/src/BirdsiteLive.Domain/ActivityPubService.cs
@@ -21,6 +21,7 @@ namespace BirdsiteLive.Domain
         Task<HttpStatusCode> PostDataAsync<T>(T data, string targetHost, string actorUrl, string inbox = null);
         Task PostNewNoteActivity(Note note, string username, string noteId, string targetHost,
             string targetInbox);
+        Task<WebFingerData> WebFinger(string account);
     }
 
     public class ActivityPubService : IActivityPubService
@@ -118,5 +119,14 @@ namespace BirdsiteLive.Domain
             response.EnsureSuccessStatusCode();
             return response.StatusCode;
         }
+
+        public async Task<WebFingerData> WebFinger(string account)
+        {
+            var httpClient = _httpClientFactory.CreateClient();
+            var result = await httpClient.GetAsync("https://" + account.Split('@')[1] + "/.well-known/webfinger?resource=acct:" + account);
+            var content = await result.Content.ReadAsStringAsync();
+
+            return JsonConvert.DeserializeObject<WebFingerData>(content);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/BirdsiteLive/Controllers/UsersController.cs b/src/BirdsiteLive/Controllers/UsersController.cs
index 91b63c7..753a141 100644
--- a/src/BirdsiteLive/Controllers/UsersController.cs
+++ b/src/BirdsiteLive/Controllers/UsersController.cs
@@ -30,16 +30,18 @@ namespace BirdsiteLive.Controllers
         private readonly IUserService _userService;
         private readonly IStatusService _statusService;
         private readonly InstanceSettings _instanceSettings;
+        private readonly IActivityPubService _activityPubService;
         private readonly ILogger<UsersController> _logger;
 
         #region Ctor
-        public UsersController(ITwitterUserService twitterUserService, IUserService userService, IStatusService statusService, InstanceSettings instanceSettings, ITwitterTweetsService twitterTweetService, ILogger<UsersController> logger)
+        public UsersController(ITwitterUserService twitterUserService, IUserService userService, IStatusService statusService, InstanceSettings instanceSettings, ITwitterTweetsService twitterTweetService, IActivityPubService activityPubService, ILogger<UsersController> logger)
         {
             _twitterUserService = twitterUserService;
             _userService = userService;
             _statusService = statusService;
             _instanceSettings = instanceSettings;
             _twitterTweetService = twitterTweetService;
+            _activityPubService = activityPubService;
             _logger = logger;
         }
         #endregion
@@ -188,5 +190,51 @@ namespace BirdsiteLive.Controllers
         {
             return header.ToDictionary<KeyValuePair<string, StringValues>, string, string>(h => h.Key.ToLowerInvariant(), h => h.Value);
         }
+
+        [Route("/users/{actor}/remote_follow")]
+        [HttpPost]
+        public async Task<IActionResult> RemoteFollow(string actor)
+        {
+            StringValues webfingerValues;
+
+            if (!Request.Form.TryGetValue("webfinger", out webfingerValues)) return BadRequest();
+
+            var webfinger = webfingerValues.First();
+
+            if (webfinger.Length < 1 || actor.Length < 1) return BadRequest();
+
+            if (webfinger[0] == '@') webfinger = webfinger[1..];
+
+            if (webfinger.IndexOf("@") < 0 || ! new Regex("^[A-Za-z0-9_]*$").IsMatch(webfinger.Split('@')[0]) || ! new Regex("^[A-Za-z0-9_]*$").IsMatch(actor) || Uri.CheckHostName(webfinger.Split('@')[1]) == UriHostNameType.Unknown)
+            {
+                return BadRequest();
+            }
+
+            WebFingerData webfingerData;
+
+            try
+            {
+                webfingerData = await _activityPubService.WebFinger(webfinger);
+            }
+            catch(Exception e)
+            {
+                _logger.LogError("Could not WebFinger {user}: {exception}", webfinger, e);
+                return NotFound();
+            }
+
+            string redirectLink = "";
+
+            foreach(var link in webfingerData.links)
+            {
+                if(link.rel == "http://ostatus.org/schema/1.0/subscribe" && link.template.Length > 0)
+                {
+                    redirectLink = link.template.Replace("{uri}", "https://" + _instanceSettings.Domain + "/users/" + actor);
+                }
+            }
+
+            if (redirectLink == "") return NotFound();
+
+            return Redirect(redirectLink);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/BirdsiteLive/Views/Users/Index.cshtml b/src/BirdsiteLive/Views/Users/Index.cshtml
index 945964a..d0bce7a 100644
--- a/src/BirdsiteLive/Views/Users/Index.cshtml
+++ b/src/BirdsiteLive/Views/Users/Index.cshtml
@@ -40,7 +40,12 @@
     else
     {
         <div>
-            <p>Search this handle to find it in your instance:</p>
+            <form action="/users/@ViewData.Model.Acct/remote_follow" method="post">
+                <input type="text" class="form-control mb-2" placeholder="your handle, i.e. @@pasture@@pl.gamers.exposed" name="webfinger" />
+                <input type="submit" class="btn btn-primary w-100 mb-2" value="Remote follow" />
+            </form>
+
+            <p>or search this handle to find it in your instance:</p>
 
             <input type="text" name="textbox" value="@ViewData.Model.InstanceHandle" onclick="this.select()" class="form-control" readonly />
         </div>