Add string conversion for tunnel config.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

WireGuard/Models/Interface+Extension.swift

@@ -57,6 +57,20 @@ extension Interface {
         }
     }
 
+    func export() -> String {
+        var exportString = "[Interface]\n"
+        if let privateKey = privateKey {
+            exportString.append("PrivateKey=\(privateKey)")
+        }
+        if listenPort > 0 {
+            exportString.append("ListenPort=\(listenPort)")
+        }
+
+        exportString.append("\n")
+
+        return exportString
+    }
+
 }
 
 enum InterfaceValidationError: Error {

WireGuard/Models/Peer+Extension.swift

@@ -63,6 +63,29 @@ extension Peer {
         }
     }
 
+    func export() -> String {
+        var exportString = "[Peer]\n"
+        if let publicKey = publicKey {
+            exportString.append("PublicKey=\(publicKey)\n")
+        }
+        if let presharedKey = presharedKey {
+            exportString.append("PresharedKey=\(presharedKey)\n")
+        }
+        if let allowedIPs = allowedIPs {
+            exportString.append("AllowedIPs=\(allowedIPs)\n")
+        }
+        if let endpoint = endpoint {
+            exportString.append("Endpoint=\(endpoint)\n")
+        }
+        if persistentKeepalive > 0 {
+            exportString.append("PersistentKeepalive=\(persistentKeepalive)\n")
+        }
+
+        exportString.append("\n")
+
+        return exportString
+    }
+
 }
 
 enum PeerValidationError: Error {

WireGuard/Models/Tunnel+Extension.swift

@@ -159,6 +159,21 @@ extension Tunnel {
         return tunnel
     }
 
+    func export() -> String {
+        var exportString = ""
+        if let interfaceExport = self.interface?.export() {
+            exportString.append(interfaceExport)
+        }
+
+        if let peers = peers?.array as? [Peer] {
+            peers.forEach {
+                exportString.append($0.export())
+            }
+        }
+
+        return exportString
+    }
+
 }
 
 private func base64KeyToHex(_ base64: String?) -> String? {