Tweaks to support decoding Pixelfed instance response

Pachyderm/Model/Instance.swift

@@ -12,19 +12,49 @@ public class Instance: Decodable {
     public let uri: String
     public let title: String
     public let description: String
-    public let email: String
+    public let email: String?
     public let version: String
     public let urls: [String: URL]
-    
-    // pleroma doesn't currently implement these
+    public let thumbnail: URL?
     public let languages: [String]?
+    public let stats: Stats?
+
+    // pleroma doesn't currently implement these
     public let contactAccount: Account?
     
     // MARK: Unofficial additions to the Mastodon API.
-    public let stats: Stats?
-    public let thumbnail: URL?
     public let maxStatusCharacters: Int?
     
+    // we need a custom decoder, because all API-compatible implementations don't return some data in the same format
+    public required init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        self.uri = try container.decode(String.self, forKey: .uri)
+        self.title = try container.decode(String.self, forKey: .title)
+        self.description = try container.decode(String.self, forKey: .description)
+        self.email = try container.decodeIfPresent(String.self, forKey: .email)
+        self.version = try container.decode(String.self, forKey: .version)
+        if let urls = try? container.decodeIfPresent([String: URL].self, forKey: .urls) {
+            self.urls = urls
+        } else {
+            self.urls = [:]
+        }
+        
+        self.languages = try? container.decodeIfPresent([String].self, forKey: .languages)
+        self.contactAccount = try? container.decodeIfPresent(Account.self, forKey: .contactAccount)
+        
+        self.stats = try? container.decodeIfPresent(Stats.self, forKey: .stats)
+        self.thumbnail = try? container.decodeIfPresent(URL.self, forKey: .thumbnail)
+        if let maxStatusCharacters = try? container.decodeIfPresent(Int.self, forKey: .maxStatusCharacters) {
+            self.maxStatusCharacters = maxStatusCharacters
+        } else if let str = try? container.decodeIfPresent(String.self, forKey: .maxStatusCharacters),
+            let maxStatusCharacters = Int(str, radix: 10) {
+            self.maxStatusCharacters = maxStatusCharacters
+        } else {
+            self.maxStatusCharacters = nil
+        }
+        
+    }
+    
     private enum CodingKeys: String, CodingKey {
         case uri
         case title
@@ -32,11 +62,12 @@ public class Instance: Decodable {
         case email
         case version
         case urls
+        case thumbnail
         case languages
+        case stats
+        
         case contactAccount = "contact_account"
         
-        case stats
-        case thumbnail
         case maxStatusCharacters = "max_toot_chars"
     }
 }