Model: IPAddressRange: Converting to and from String

Signed-off-by: Roopesh Chander <roop@roopc.net>

WireGuard/WireGuard/Model/IPAddressRange.swift

@@ -15,6 +15,37 @@ struct IPAddressRange {
     var networkPrefixLength: UInt8
 }
 
+// MARK: Converting to and from String
+// For use in the UI
+
+extension IPAddressRange {
+    init?(from string: String) {
+        guard let indexOfSlash = string.lastIndex(of: "/") else { return nil }
+        let indexOfNetworkPrefixLength = string.index(after: indexOfSlash)
+        guard (indexOfNetworkPrefixLength < string.endIndex) else { return nil }
+        let addressString = String(string[string.startIndex ..< indexOfSlash])
+        if let addr = IPv4Address(addressString) {
+            address = addr
+        } else if let addr = IPv6Address(addressString) {
+            address = addr
+        } else {
+            return nil
+        }
+        let networkPrefixLengthSubstring = string[indexOfNetworkPrefixLength ..< string.endIndex]
+        if let npl = UInt8(networkPrefixLengthSubstring) {
+            networkPrefixLength = npl
+        } else {
+            return nil
+        }
+    }
+    func stringRepresentation() -> String {
+        return "\(address)/\(networkPrefixLength)"
+    }
+}
+
+// MARK: Codable
+// For serializing to disk
+
 @available(OSX 10.14, iOS 12.0, *)
 extension IPAddressRange: Codable {
     public func encode(to encoder: Encoder) throws {