Updated NETunnelProvider save format

Signed-off-by: Eric Kuck <eric@bluelinelabs.com>

WireGuard/Shared/Model/TunnelConfiguration.swift

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+// Copyright © 2018 WireGuard LLC. All Rights Reserved.
+
+import Foundation
+
+final class TunnelConfiguration {
+    var interface: InterfaceConfiguration
+    let peers: [PeerConfiguration]
+
+    static let keyLength = 32
+
+    init(interface: InterfaceConfiguration, peers: [PeerConfiguration]) {
+        self.interface = interface
+        self.peers = peers
+
+        let peerPublicKeysArray = peers.map { $0.publicKey }
+        let peerPublicKeysSet = Set<Data>(peerPublicKeysArray)
+        if peerPublicKeysArray.count != peerPublicKeysSet.count {
+            fatalError("Two or more peers cannot have the same public key")
+        }
+    }
+}
+
+extension TunnelConfiguration: Codable {
+    enum CodingKeys: String, CodingKey {
+        case interface = "Interface"
+        case peers = "Peer"
+    }
+    
+    convenience init(from decoder: Decoder) throws {
+        let values = try decoder.container(keyedBy: CodingKeys.self)
+        let interface = try values.decode(InterfaceConfiguration.self, forKey: .interface)
+        let peers = try values.decode([PeerConfiguration].self, forKey: .peers)
+        self.init(interface: interface, peers: peers)
+    }
+    
+    func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(interface, forKey: .interface)
+        try container.encode(peers, forKey: .peers)
+    }
+}