Resolve Mastodon remote status links

Closes #384

Tusker/Screens/Conversation/ConversationViewController.swift

@@ -11,6 +11,13 @@ import Pachyderm
 import WebURL
 import WebURLFoundationExtras
 
+private let mastodonRemoteStatusRegex = try! NSRegularExpression(pattern: "^/@.+@.+/\\d{18}")
+private func isLikelyMastodonRemoteStatus(url: URL) -> Bool {
+    let path = url.path
+    let range = NSRange(location: 0, length: path.utf16.count)
+    return mastodonRemoteStatusRegex.numberOfMatches(in: path, range: range) == 1
+}
+
 class ConversationViewController: UIViewController {
     
     weak var mastodonController: MastodonController!
@@ -210,11 +217,24 @@ class ConversationViewController: UIViewController {
         indicator.startAnimating()
         state = .loading(indicator)
         
-        let url = WebURL(url)!.serialized(excludingFragment: true)
+        let effectiveURL: String
-        let request = Client.search(query: url, types: [.statuses], resolve: true)
+        class RedirectBlocker: NSObject, URLSessionTaskDelegate {
+            func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest, completionHandler: @escaping (URLRequest?) -> Void) {
+                completionHandler(nil)
+            }
+        }
+        if isLikelyMastodonRemoteStatus(url: url),
+           let (_, response) = try? await URLSession.shared.data(from: url, delegate: RedirectBlocker()),
+           let location = (response as? HTTPURLResponse)?.value(forHTTPHeaderField: "location") {
+            effectiveURL = location
+        } else {
+            effectiveURL = WebURL(url)!.serialized(excludingFragment: true)
+        }
+        
+        let request = Client.search(query: effectiveURL, types: [.statuses], resolve: true)
         do {
             let (results, _) = try await mastodonController.run(request)
-            guard let status = results.statuses.first(where: { $0.url?.serialized() == url }) else {
+            guard let status = results.statuses.first(where: { $0.url?.serialized() == effectiveURL }) else {
                 throw UnableToResolveError()
             }
             _ = mastodonController.persistentContainer.addOrUpdateOnViewContext(status: status)

Tusker/TuskerNavigationDelegate.swift

@@ -205,6 +205,7 @@ enum PopoverSource {
 private let statusPathRegex = try! NSRegularExpression(
     pattern:
            "(^/@[a-z0-9_]+/\\d{18})"        // mastodon
+        + "|(^/@.+@.+/\\d{18})"             // mastodon remote
         + "|(^/notice/[a-z0-9]{18})"        // pleroma
         + "|(^/notes/[a-z0-9]{10})"         // misskey
         + "|(^/p/[a-z0-9_]+/\\d{18})"       // pixelfed