[AltServer] Moves core ConnectionManager logic to AltKit

Refactors ConnectionManager to use arbitrary RequestHandlers and ConnectionHandlers. This allows the core AltServer request logic to be shared across different targets with different connection types.

AltServer/Connections/WirelessConnectionHandler.swift

@@ -0,0 +1,150 @@
+//
+//  WirelessConnectionHandler.swift
+//  AltKit
+//
+//  Created by Riley Testut on 6/1/20.
+//  Copyright © 2020 Riley Testut. All rights reserved.
+//
+
+import Foundation
+import Network
+
+import AltKit
+
+extension WirelessConnectionHandler
+{
+    public enum State
+    {
+        case notRunning
+        case connecting
+        case running(NWListener.Service)
+        case failed(Swift.Error)
+    }
+}
+
+public class WirelessConnectionHandler: ConnectionHandler
+{
+    public var connectionHandler: ((Connection) -> Void)?
+    public var disconnectionHandler: ((Connection) -> Void)?
+    
+    public var stateUpdateHandler: ((State) -> Void)?
+    
+    public private(set) var state: State = .notRunning {
+        didSet {
+            self.stateUpdateHandler?(self.state)
+        }
+    }
+    
+    private lazy var listener = self.makeListener()
+    private let dispatchQueue = DispatchQueue(label: "io.altstore.WirelessConnectionListener", qos: .utility)
+    
+    public func startListening()
+    {
+        switch self.state
+        {
+        case .notRunning, .failed: self.listener.start(queue: self.dispatchQueue)
+        default: break
+        }
+    }
+    
+    public func stopListening()
+    {
+        switch self.state
+        {
+        case .running: self.listener.cancel()
+        default: break
+        }
+    }
+}
+
+private extension WirelessConnectionHandler
+{
+    func makeListener() -> NWListener
+    {
+        let listener = try! NWListener(using: .tcp)
+        
+        let service: NWListener.Service
+        
+        if let serverID = UserDefaults.standard.serverID?.data(using: .utf8)
+        {
+            let txtDictionary = ["serverID": serverID]
+            let txtData = NetService.data(fromTXTRecord: txtDictionary)
+            
+            service = NWListener.Service(name: nil, type: ALTServerServiceType, domain: nil, txtRecord: txtData)
+        }
+        else
+        {
+            service = NWListener.Service(type: ALTServerServiceType)
+        }
+        
+        listener.service = service
+        
+        listener.serviceRegistrationUpdateHandler = { (serviceChange) in
+            switch serviceChange
+            {
+            case .add(.service(let name, let type, let domain, _)):
+                let service = NWListener.Service(name: name, type: type, domain: domain, txtRecord: nil)
+                self.state = .running(service)
+                
+            default: break
+            }
+        }
+        
+        listener.stateUpdateHandler = { (state) in
+            switch state
+            {
+            case .ready: break
+            case .waiting, .setup: self.state = .connecting
+            case .cancelled: self.state = .notRunning
+            case .failed(let error): self.state = .failed(error)
+            @unknown default: break
+            }
+        }
+        
+        listener.newConnectionHandler = { [weak self] (connection) in
+            self?.prepare(connection)
+        }
+        
+        return listener
+    }
+    
+    func prepare(_ nwConnection: NWConnection)
+    {
+        print("Preparing:", nwConnection)
+        
+        // Use same instance for all callbacks.
+        let connection = NetworkConnection(nwConnection)
+        
+        nwConnection.stateUpdateHandler = { [weak self] (state) in
+            switch state
+            {
+            case .setup, .preparing: break
+                
+            case .ready:
+                print("Connected to client:", connection)
+                self?.connectionHandler?(connection)
+                
+            case .waiting:
+                print("Waiting for connection...")
+                
+            case .failed(let error):
+                print("Failed to connect to service \(nwConnection.endpoint).", error)
+                self?.disconnect(connection)
+                
+            case .cancelled:
+                self?.disconnect(connection)
+                
+            @unknown default: break
+            }
+        }
+        
+        nwConnection.start(queue: self.dispatchQueue)
+    }
+    
+    func disconnect(_ connection: Connection)
+    {
+        connection.disconnect()
+        
+        self.disconnectionHandler?(connection)
+    }
+}