[AltKit] Replaces dedicated AltKit module with shared files across targets

Treating AltKit as a full module resulted in more complexity than necessary, when we really just wanted to share some files between different targets. Now we can share individual files across modules as-needed without AltKit overhead.

Shared/Server Protocol/CodableServerError.swift

@@ -0,0 +1,126 @@
+//
+//  CodableServerError.swift
+//  AltKit
+//
+//  Created by Riley Testut on 3/5/20.
+//  Copyright © 2020 Riley Testut. All rights reserved.
+//
+
+import Foundation
+
+// Can only automatically conform ALTServerError.Code to Codable, not ALTServerError itself
+extension ALTServerError.Code: Codable {}
+
+extension CodableServerError
+{
+    enum UserInfoValue: Codable
+    {
+        case string(String)
+        case error(NSError)
+        
+        public init(from decoder: Decoder) throws
+        {
+            let container = try decoder.singleValueContainer()
+
+            if
+                let data = try? container.decode(Data.self),
+                let error = try? NSKeyedUnarchiver.unarchivedObject(ofClass: NSError.self, from: data)
+            {
+                self = .error(error)
+            }
+            else if let string = try? container.decode(String.self)
+            {
+                self = .string(string)
+            }
+            else
+            {
+                throw DecodingError.dataCorruptedError(in: container, debugDescription: "UserInfoValue value cannot be decoded")
+            }
+        }
+        
+        func encode(to encoder: Encoder) throws
+        {
+            var container = encoder.singleValueContainer()
+            
+            switch self
+            {
+            case .string(let string): try container.encode(string)
+            case .error(let error):
+                guard let data = try? NSKeyedArchiver.archivedData(withRootObject: error, requiringSecureCoding: true) else {
+                    let context = EncodingError.Context(codingPath: container.codingPath, debugDescription: "UserInfoValue value \(self) cannot be encoded")
+                    throw EncodingError.invalidValue(self, context)
+                }
+                
+                try container.encode(data)
+            }
+        }
+    }
+}
+
+struct CodableServerError: Codable
+{
+    var error: ALTServerError {
+        return ALTServerError(self.errorCode, userInfo: self.userInfo ?? [:])
+    }
+    
+    private var errorCode: ALTServerError.Code
+    private var userInfo: [String: Any]?
+    
+    private enum CodingKeys: String, CodingKey
+    {
+        case errorCode
+        case userInfo
+    }
+
+    init(error: ALTServerError)
+    {
+        self.errorCode = error.code
+        
+        var userInfo = error.userInfo
+        if let localizedRecoverySuggestion = (error as NSError).localizedRecoverySuggestion
+        {
+            userInfo[NSLocalizedRecoverySuggestionErrorKey] = localizedRecoverySuggestion
+        }
+        
+        if !userInfo.isEmpty
+        {
+            self.userInfo = userInfo
+        }
+    }
+    
+    init(from decoder: Decoder) throws
+    {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        
+        let errorCode = try container.decode(Int.self, forKey: .errorCode)
+        self.errorCode = ALTServerError.Code(rawValue: errorCode) ?? .unknown
+        
+        let rawUserInfo = try container.decodeIfPresent([String: UserInfoValue].self, forKey: .userInfo)
+        
+        let userInfo = rawUserInfo?.mapValues { (value) -> Any in
+            switch value
+            {
+            case .string(let string): return string
+            case .error(let error): return error
+            }
+        }
+        self.userInfo = userInfo
+    }
+    
+    func encode(to encoder: Encoder) throws
+    {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(self.error.code.rawValue, forKey: .errorCode)
+        
+        let rawUserInfo = self.userInfo?.compactMapValues { (value) -> UserInfoValue? in
+            switch value
+            {
+            case let string as String: return .string(string)
+            case let error as NSError: return .error(error)
+            default: return nil
+            }
+        }
+        try container.encodeIfPresent(rawUserInfo, forKey: .userInfo)
+    }
+}
+