Improve IPAddressRange and add tests

3 files changed, 136 insertions, 35 deletions

diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index acb84d969c..75e3c99ad9 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -58,6 +58,7 @@
 		582BB1B1229569620055B6EF /* CustomNavigationBar.swift in Sources */ = {isa = PBXBuildFile; fileRef = 582BB1B0229569620055B6EF /* CustomNavigationBar.swift */; };
 		582BB1B3229574F40055B6EF /* SettingsAccountCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = 582BB1B2229574F40055B6EF /* SettingsAccountCell.swift */; };
 		582BB1B52295780F0055B6EF /* AccountExpiry.swift in Sources */ = {isa = PBXBuildFile; fileRef = 582BB1B42295780F0055B6EF /* AccountExpiry.swift */; };
+		58341D9D2507826300D2BB19 /* IPAddressRangeTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58341D9C2507826300D2BB19 /* IPAddressRangeTests.swift */; };
 		5835B7CC233B76CB0096D79F /* TunnelManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5835B7CB233B76CB0096D79F /* TunnelManager.swift */; };
 		583BC70724FE4DC500C9DE04 /* Optional+DispatchQueue.swift in Sources */ = {isa = PBXBuildFile; fileRef = 583BC70624FE4DC400C9DE04 /* Optional+DispatchQueue.swift */; };
 		583BC70824FE4DC500C9DE04 /* Optional+DispatchQueue.swift in Sources */ = {isa = PBXBuildFile; fileRef = 583BC70624FE4DC400C9DE04 /* Optional+DispatchQueue.swift */; };
@@ -288,6 +289,7 @@
 		582BB1B0229569620055B6EF /* CustomNavigationBar.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CustomNavigationBar.swift; sourceTree = "<group>"; };
 		582BB1B2229574F40055B6EF /* SettingsAccountCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SettingsAccountCell.swift; sourceTree = "<group>"; };
 		582BB1B42295780F0055B6EF /* AccountExpiry.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccountExpiry.swift; sourceTree = "<group>"; };
+		58341D9C2507826300D2BB19 /* IPAddressRangeTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IPAddressRangeTests.swift; sourceTree = "<group>"; };
 		5835B7CB233B76CB0096D79F /* TunnelManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TunnelManager.swift; sourceTree = "<group>"; };
 		583BC70624FE4DC400C9DE04 /* Optional+DispatchQueue.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Optional+DispatchQueue.swift"; sourceTree = "<group>"; };
 		5840250022B1124600E4CFEC /* IpAddress+Codable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "IpAddress+Codable.swift"; sourceTree = "<group>"; };
@@ -489,6 +491,7 @@
 		58B0A2A1238EE67E00BC001D /* MullvadVPNTests */ = {
 			isa = PBXGroup;
 			children = (
+				58341D9C2507826300D2BB19 /* IPAddressRangeTests.swift */,
 				582AE3112440CA0D00E6733A /* AccountTokenInputTests.swift */,
 				58B0A2A4238EE67E00BC001D /* Info.plist */,
 				584B26F3237434D00073B10E /* RelaySelectorTests.swift */,
@@ -929,6 +932,7 @@
 				5857F23B24C8448600CF6F47 /* OperationProtocol.swift in Sources */,
 				5857F22F24C8404C00CF6F47 /* MullvadRest.swift in Sources */,
 				58B0A2AA238EE6A900BC001D /* RelaySelector.swift in Sources */,
+				58341D9D2507826300D2BB19 /* IPAddressRangeTests.swift in Sources */,
 				5857F23924C8446A00CF6F47 /* AnyOperationObserver.swift in Sources */,
 				5896AE86246D6AD8005B36CB /* CustomDateComponentsFormattingTests.swift in Sources */,
 				5807E2C3243203E700F5FF30 /* String+Split.swift in Sources */,
diff --git a/ios/MullvadVPN/IPAddressRange.swift b/ios/MullvadVPN/IPAddressRange.swift
index fda496714e..712dc4d39e 100644
--- a/ios/MullvadVPN/IPAddressRange.swift
+++ b/ios/MullvadVPN/IPAddressRange.swift
@@ -10,9 +10,45 @@
 import Foundation
 import Network
 
+/// A struct describing an IP address range
 struct IPAddressRange {
     let address: IPAddress
-    var networkPrefixLength: UInt8
+    let networkPrefixLength: UInt8
+
+    init(address: IPAddress, networkPrefixLength: UInt8) {
+        self.address = address
+        self.networkPrefixLength = min(networkPrefixLength, address.maxNetworkPrefixLength)
+    }
+
+    init(string: String) throws {
+        let separatorIndex = string.lastIndex(of: "/") ?? string.endIndex
+        let prefixStartIndex = string.index(separatorIndex, offsetBy: 1, limitedBy: string.endIndex)
+
+        let prefixSubstring = prefixStartIndex.flatMap { string[$0...] }
+        var prefix: UInt8?
+        if let prefixSubstring = prefixSubstring {
+            if let parsedPrefix = UInt8(prefixSubstring) {
+                prefix = parsedPrefix
+            } else {
+                throw IPAddressRangeParseError.parsePrefix(String(prefixSubstring))
+            }
+        }
+
+        let addressString = String(string[..<separatorIndex])
+        if let ipv4Address = IPv4Address(addressString) {
+            self = IPAddressRange(
+                address: ipv4Address,
+                networkPrefixLength: prefix ?? ipv4Address.maxNetworkPrefixLength
+            )
+        } else if let ipv6Address = IPv6Address(addressString) {
+            self = IPAddressRange(
+                address: ipv6Address,
+                networkPrefixLength: prefix ?? ipv6Address.maxNetworkPrefixLength
+            )
+        } else {
+            throw IPAddressRangeParseError.parseAddress(addressString)
+        }
+    }
 }
 
 extension IPAddressRange: Equatable {
@@ -35,44 +71,31 @@ extension IPAddressRange: CustomStringConvertible {
     }
 }
 
-extension IPAddressRange {
-
-    init?(from string: String) {
-        guard let parsed = IPAddressRange.parseAddressString(string) else { return nil }
-        address = parsed.0
-        networkPrefixLength = parsed.1
+private extension IPv4Address {
+    var maxNetworkPrefixLength: UInt8 {
+        return 32
     }
+}
 
-    private static func parseAddressString(_ string: String) -> (IPAddress, UInt8)? {
-        let endOfIPAddress = string.lastIndex(of: "/") ?? string.endIndex
-        let addressString = String(string[string.startIndex ..< endOfIPAddress])
-        let address: IPAddress
-        if let addr = IPv4Address(addressString) {
-            address = addr
-        } else if let addr = IPv6Address(addressString) {
-            address = addr
-        } else {
-            return nil
-        }
+private extension IPv6Address {
+    var maxNetworkPrefixLength: UInt8 {
+        return 128
+    }
+}
 
-        let maxNetworkPrefixLength: UInt8 = address is IPv4Address ? 32 : 128
-        var networkPrefixLength: UInt8
-        if endOfIPAddress < string.endIndex { // "/" was located
-            let indexOfNetworkPrefixLength = string.index(after: endOfIPAddress)
-            guard indexOfNetworkPrefixLength < string.endIndex else { return nil }
-            let networkPrefixLengthSubstring = string[indexOfNetworkPrefixLength ..< string.endIndex]
-            guard let npl = UInt8(networkPrefixLengthSubstring) else { return nil }
-            networkPrefixLength = min(npl, maxNetworkPrefixLength)
+private extension IPAddress {
+    var maxNetworkPrefixLength: UInt8 {
+        if let ipv4Address = self as? IPv4Address {
+            return ipv4Address.maxNetworkPrefixLength
+        } else if let ipv6Address = self as? IPv6Address {
+            return ipv6Address.maxNetworkPrefixLength
         } else {
-            networkPrefixLength = maxNetworkPrefixLength
+            fatalError()
         }
-
-        return (address, networkPrefixLength)
     }
 }
 
 extension IPAddressRange: Codable {
-
     func encode(to encoder: Encoder) throws {
         var container = encoder.singleValueContainer()
 
@@ -83,11 +106,31 @@ extension IPAddressRange: Codable {
         let container = try decoder.singleValueContainer()
         let value = try container.decode(String.self)
 
-        if let addressRange = IPAddressRange(from: value) {
-            self = addressRange
-        } else {
-            throw DecodingError.dataCorruptedError(
-                in: container, debugDescription: "Invalid IPAddressRange representation")
+        do {
+            self = try IPAddressRange(string: value)
+        } catch {
+            let context = DecodingError.Context(
+                codingPath: container.codingPath,
+                debugDescription: "Invalid IPAddressRange representation",
+                underlyingError: error)
+            throw DecodingError.dataCorrupted(context)
+        }
+    }
+}
+
+enum IPAddressRangeParseError: LocalizedError, Equatable {
+    /// A failure to parse the IP address
+    case parseAddress(String)
+
+    /// A failure to parse the network prefix
+    case parsePrefix(String)
+
+    var errorDescription: String? {
+        switch self {
+        case .parseAddress(let addressString):
+            return "Failure to parse the IP address: \(addressString)"
+        case .parsePrefix(let prefixString):
+            return "Failure to parse the network prefix: \(prefixString)"
         }
     }
 }
diff --git a/ios/MullvadVPNTests/IPAddressRangeTests.swift b/ios/MullvadVPNTests/IPAddressRangeTests.swift
new file mode 100644
index 0000000000..37dc3415a2
--- /dev/null
+++ b/ios/MullvadVPNTests/IPAddressRangeTests.swift
@@ -0,0 +1,54 @@
+//
+//  IPAddressRangeTests.swift
+//  MullvadVPNTests
+//
+//  Created by pronebird on 08/09/2020.
+//  Copyright © 2020 Mullvad VPN AB. All rights reserved.
+//
+
+import XCTest
+
+class IPAddressRangeTests: XCTestCase {
+
+    func testParsingValidIPv4AddressRange() throws {
+        let addr = try IPAddressRange(string: "127.0.0.1/32")
+        XCTAssertEqual("\(addr)", "127.0.0.1/32")
+    }
+
+    func testParsingValidIPv6AddressRange() throws {
+        let addr = try IPAddressRange(string: "::1/128")
+        XCTAssertEqual("\(addr)", "::1/128")
+    }
+
+    func testParsingIPv4AddressWithoutNetworkPrefix() throws {
+        let addr = try IPAddressRange(string: "127.0.0.1")
+        XCTAssertEqual("\(addr)", "127.0.0.1/32")
+    }
+
+    func testParsingIPv6AddressWithoutNetworkPrefix() throws {
+        let addr = try IPAddressRange(string: "::1")
+        XCTAssertEqual("\(addr)", "::1/128")
+    }
+
+    func testParsingInvalidIPv4AddressNetworkPrefix() throws {
+        let addr = try IPAddressRange(string: "127.0.0.1/33")
+        XCTAssertEqual("\(addr)", "127.0.0.1/32")
+    }
+
+    func testParsingInvalidIPv6AddressNetworkPrefix() throws {
+        let addr = try IPAddressRange(string: "::1/129")
+        XCTAssertEqual("\(addr)", "::1/128")
+    }
+
+    func testParsingInvalidIPAddress() throws {
+        XCTAssertThrowsError(try IPAddressRange(string: "1.2.3.4.5/32")) { (error) in
+            XCTAssertEqual(error as? IPAddressRangeParseError, IPAddressRangeParseError.parseAddress("1.2.3.4.5"))
+        }
+    }
+
+    func testParsingEmptyNetworkPrefix() throws {
+        XCTAssertThrowsError(try IPAddressRange(string: "::1/")) { (error) in
+            XCTAssertEqual(error as? IPAddressRangeParseError, IPAddressRangeParseError.parsePrefix(""))
+        }
+    }
+}