Replace semaphore with DispatchGroup

This makes UnknownType the one to wait until the registration
is complete. Once the registration is complete, UnknownType will
be free to begin encoding and decoding.

This is a better solution, but it's still not perfect. A better solution
might be to make APIClientService wait until the registration
is complete.

Author: MasterJ93

Sources/ATProtoKit/ATProtoKit.swift

@@ -167,22 +167,20 @@ public class ATProtoKit: ATProtoKitConfiguration, ATRecordConfiguration {
         self.sessionConfiguration = sessionConfiguration
         self.logger = session?.logger
 
+        // Mark the beginning of registration.
         // This is to fix a bug from the following issue: https://github.com/MasterJ93/ATProtoKit/issues/75
-        // The thread may be blocked if the code within the Task block doesn't complete in a reasonable timeframe.
-        // This should hopefully be a temporary fix until there's a better solution that doesn't block the
-        // UI-related threads.
-        let semaphore = DispatchSemaphore(value: 0)
+        // as well as this issue: https://github.com/MasterJ93/ATProtoKit/issues/102
+        ATRecordTypeRegistry.registrationGroup.enter()
 
         Task { [recordLexicons] in
             if canUseBlueskyRecords && !(ATRecordTypeRegistry.areBlueskyRecordsRegistered) {
                 _ = await ATRecordTypeRegistry(blueskyLexiconTypes: recordLexicons)
                 await ATRecordTypeRegistry.setBlueskyRecordsRegistered(true)
             }
 
-            semaphore.signal()
+            // Registration complete – signal waiting threads.
+            ATRecordTypeRegistry.registrationGroup.leave()
         }
-
-        semaphore.wait()
     }
 
     /// Determines the appropriate Personal Data Server (PDS) URL.

Sources/ATProtoKit/Utilities/ATRecordProtocol.swift

@@ -129,6 +129,9 @@ public actor ATRecordTypeRegistry {
     /// - Warning: Don't touch this property; this should only be used for ``ATProtoKit``.
     public static var areBlueskyRecordsRegistered = false
 
+    /// Global dispatch group to signal when registration is complete.
+    public static let registrationGroup = DispatchGroup()
+
     /// Initializes the registry with an array of record types.
     ///
     /// - Parameter types: An array of ``ATRecordProtocol``-conforming `struct`s.
@@ -266,6 +269,16 @@ public enum UnknownType: Sendable, Codable {
     ///     \- the JSON object is invalid
     @_documentation(visibility: private)
     public init(from decoder: Decoder) throws {
+        // Before we decode anything, we need to check that ATRecordTypeRegistry is ready.
+        // It shouldn't ever take more than 3 seconds to be ready, but in the rare case that it is,
+        // indeed, not ready, we need to end this early.
+        let waitResult = ATRecordTypeRegistry.registrationGroup.wait(timeout: .now() + 3)
+        if waitResult == .timedOut {
+            throw DecodingError.dataCorrupted(
+                DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Record registry not ready")
+            )
+        }
+
         let container = try decoder.container(keyedBy: DynamicCodingKeys.self)
 
         if let typeKey = DynamicCodingKeys(stringValue: "$type"),
@@ -425,6 +438,16 @@ public enum UnknownType: Sendable, Codable {
     /// Inherited from `Encoder`.
     @_documentation(visibility: private)
     public func encode(to encoder: Encoder) throws {
+        // Before we encode anything, we need to check that ATRecordTypeRegistry is ready.
+        // It shouldn't ever take more than 3 seconds to be ready, but in the rare case that it is,
+        // indeed, not ready, we need to end this early.
+        let waitResult = ATRecordTypeRegistry.registrationGroup.wait(timeout: .now() + 3)
+        if waitResult == .timedOut {
+            throw EncodingError.invalidValue(self,
+                                             EncodingError.Context(codingPath: encoder.codingPath,
+                                                                   debugDescription: "Record registry not ready"))
+        }
+
         var container = encoder.singleValueContainer()
 
         switch self {