Store the raw JSON payload from the getRelays API call

ios/MullvadREST/ApiHandlers/RESTAPIProxy.swift

@@ -107,13 +107,14 @@ extension REST {
                     switch httpStatus {
                     case let httpStatus where httpStatus.isSuccess:
                         return .decoding {
-                            let serverRelays = try self.responseDecoder.decode(
+                            // Discarding result since we're only interested in knowing that it's parseable.
+                            _ = try self.responseDecoder.decode(
                                 ServerRelaysResponse.self,
                                 from: data
                             )
                             let newEtag = response.value(forHTTPHeaderField: HTTPHeader.etag)
 
-                            return .newContent(newEtag, serverRelays)
+                            return .newContent(newEtag, data)
                         }
 
                     case .notModified where etag != nil:
@@ -284,7 +285,7 @@ extension REST {
 
     public enum ServerRelaysCacheResponse {
         case notModified
-        case newContent(_ etag: String?, _ value: ServerRelaysResponse)
+        case newContent(_ etag: String?, _ rawData: Data)
     }
 
     private struct CreateApplePaymentRequest: Encodable {

ios/MullvadREST/Relay/CachedRelays.swift

@@ -8,7 +8,7 @@
 
 import Foundation
 
-/// A struct that represents the relay cache on disk
+/// A struct that represents the relay cache in memory
 public struct CachedRelays: Codable, Equatable {
     /// E-tag returned by server
     public let etag: String?

ios/MullvadREST/Relay/IPOverrideWrapper.swift

@@ -18,21 +18,23 @@ public class IPOverrideWrapper: RelayCacheProtocol {
         self.ipOverrideRepository = ipOverrideRepository
     }
 
-    public func read() throws -> CachedRelays {
+    public func read() throws -> StoredRelays {
         let cache = try relayCache.read()
         let relayResponse = apply(overrides: ipOverrideRepository.fetchAll(), to: cache.relays)
+        let rawData = try REST.Coding.makeJSONEncoder().encode(relayResponse)
 
-        return CachedRelays(relays: relayResponse, updatedAt: cache.updatedAt)
+        return try StoredRelays(etag: cache.etag, rawData: rawData, updatedAt: cache.updatedAt)
     }
 
-    public func readPrebundledRelays() throws -> CachedRelays {
+    public func readPrebundledRelays() throws -> StoredRelays {
         let prebundledRelays = try relayCache.readPrebundledRelays()
         let relayResponse = apply(overrides: ipOverrideRepository.fetchAll(), to: prebundledRelays.relays)
+        let rawData = try REST.Coding.makeJSONEncoder().encode(relayResponse)
 
-        return CachedRelays(relays: relayResponse, updatedAt: prebundledRelays.updatedAt)
+        return try StoredRelays(etag: prebundledRelays.etag, rawData: rawData, updatedAt: prebundledRelays.updatedAt)
     }
 
-    public func write(record: CachedRelays) throws {
+    public func write(record: StoredRelays) throws {
         try relayCache.write(record: record)
     }
 

ios/MullvadREST/Relay/RelayCache.swift

@@ -12,59 +12,66 @@ import MullvadTypes
 public protocol RelayCacheProtocol {
     /// Reads from a cached list,
     /// which falls back to reading from prebundled relays if there was no cache hit
-    func read() throws -> CachedRelays
+    func read() throws -> StoredRelays
     /// Reads the relays file that were prebundled with the app installation.
     ///
     /// > Warning: Prefer `read()` over this unless there is an explicit need to read
     /// relays from the bundle, because those might contain stale data.
-    func readPrebundledRelays() throws -> CachedRelays
-    func write(record: CachedRelays) throws
+    func readPrebundledRelays() throws -> StoredRelays
+    func write(record: StoredRelays) throws
 }
 
 /// - Warning: `RelayCache` should not be used directly. It should be used through `IPOverrideWrapper` to have
 /// ip overrides applied.
 public final class RelayCache: RelayCacheProtocol {
-    private let fileCache: any FileCacheProtocol<CachedRelays>
+    private let fileURL: URL
+    private let fileCache: any FileCacheProtocol<StoredRelays>
 
     /// Designated initializer
     public init(cacheDirectory: URL) {
-        fileCache = FileCache(fileURL: cacheDirectory.appendingPathComponent("relays.json", isDirectory: false))
+        fileURL = cacheDirectory.appendingPathComponent("relays.json", isDirectory: false)
+        fileCache = FileCache(fileURL: fileURL)
     }
 
     /// Initializer that accepts a custom FileCache implementation. Used in tests.
-    init(fileCache: some FileCacheProtocol<CachedRelays>) {
+    init(fileCache: some FileCacheProtocol<StoredRelays>) {
+        fileURL = FileManager.default.temporaryDirectory.appendingPathComponent("relays.json", isDirectory: false)
         self.fileCache = fileCache
     }
 
-    /// Safely read the cache file from disk using file coordinator and fallback to prebundled
-    /// relays in case if the relay cache file is missing.
-    public func read() throws -> CachedRelays {
+    /// Safely read the cache file from disk using file coordinator and fallback in the following manner:
+    /// 1. If there is a file but it's not decodable, try to parse into the old cache format. If it's still
+    ///    not decodable, read the pre-bundled data.
+    /// 2. If there is no file, read from the pre-bundled data.
+    public func read() throws -> StoredRelays {
         do {
             return try fileCache.read()
-        } catch {
-            if error is DecodingError || (error as? CocoaError)?.code == .fileReadNoSuchFile {
+        } catch is DecodingError {
+            do {
+                let oldFormatFileCache = FileCache<CachedRelays>(fileURL: fileURL)
+                return try StoredRelays(cachedRelays: try oldFormatFileCache.read())
+            } catch {
                 return try readPrebundledRelays()
-            } else {
-                throw error
             }
+        } catch {
+            return try readPrebundledRelays()
         }
     }
 
     /// Safely write the cache file on disk using file coordinator.
-    public func write(record: CachedRelays) throws {
+    public func write(record: StoredRelays) throws {
         try fileCache.write(record)
     }
 
     /// Read pre-bundled relays file from disk.
-    public func readPrebundledRelays() throws -> CachedRelays {
+    public func readPrebundledRelays() throws -> StoredRelays {
         guard let prebundledRelaysFileURL = Bundle(for: Self.self).url(forResource: "relays", withExtension: "json")
         else { throw CocoaError(.fileNoSuchFile) }
 
         let data = try Data(contentsOf: prebundledRelaysFileURL)
-        let relays = try REST.Coding.makeJSONDecoder().decode(REST.ServerRelaysResponse.self, from: data)
 
-        return CachedRelays(
-            relays: relays,
+        return try StoredRelays(
+            rawData: data,
             updatedAt: Date(timeIntervalSince1970: 0)
         )
     }

ios/MullvadREST/Relay/StoredRelays.swift

@@ -0,0 +1,43 @@
+//
+//  StoredRelays.swift
+//  MullvadVPNUITests
+//
+//  Created by Jon Petersson on 2024-09-09.
+//  Copyright © 2024 Mullvad VPN AB. All rights reserved.
+//
+
+import Foundation
+
+/// A struct that represents the relay cache on disk
+public struct StoredRelays: Codable, Equatable {
+    /// E-tag returned by server
+    public let etag: String?
+
+    /// The raw relay JSON data stored within the cache entry
+    public let rawData: Data
+
+    /// The date when this cache was last updated
+    public let updatedAt: Date
+
+    /// Relays parsed from the JSON data
+    public let relays: REST.ServerRelaysResponse
+
+    /// `CachedRelays` representation
+    public var cachedRelays: CachedRelays {
+        CachedRelays(etag: etag, relays: relays, updatedAt: updatedAt)
+    }
+
+    public init(etag: String? = nil, rawData: Data, updatedAt: Date) throws {
+        self.etag = etag
+        self.rawData = rawData
+        self.updatedAt = updatedAt
+        relays = try REST.Coding.makeJSONDecoder().decode(REST.ServerRelaysResponse.self, from: rawData)
+    }
+
+    public init(cachedRelays: CachedRelays) throws {
+        etag = cachedRelays.etag
+        rawData = try REST.Coding.makeJSONEncoder().encode(cachedRelays.relays)
+        updatedAt = cachedRelays.updatedAt
+        relays = cachedRelays.relays
+    }
+}

ios/MullvadREST/Transport/Shadowsocks/ShadowsocksRelaySelector.swift

@@ -43,6 +43,6 @@
 
     public func getBridges() throws -> REST.ServerShadowsocks? {
         let cachedRelays = try relayCache.read()
-        return RelaySelector.Shadowsocks.tcpBridge(from: cachedRelays.relays)
+        return RelaySelector.Shadowsocks.tcpBridge(from: try cachedRelays.relays)
     }
 }

ios/MullvadVPN.xcodeproj/project.pbxproj

@@ -577,6 +577,7 @@
 		7A9FA1422A2E3306000B728D /* CheckboxView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7A9FA1412A2E3306000B728D /* CheckboxView.swift */; };
 		7A9FA1442A2E3FE5000B728D /* CheckableSettingsCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7A9FA1432A2E3FE5000B728D /* CheckableSettingsCell.swift */; };
 		7AA513862BC91C6B00D081A4 /* LogRotationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7AA513852BC91C6B00D081A4 /* LogRotationTests.swift */; };
+		7AA7046A2C8EFE2B0045699D /* StoredRelays.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7AA704682C8EFE050045699D /* StoredRelays.swift */; };
 		7AB2B6702BA1EB8C00B03E3B /* ListCustomListViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7AB2B66E2BA1EB8C00B03E3B /* ListCustomListViewController.swift */; };
 		7AB2B6712BA1EB8C00B03E3B /* ListCustomListCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7AB2B66F2BA1EB8C00B03E3B /* ListCustomListCoordinator.swift */; };
 		7AB3BEB52BD7A6CB00E34384 /* LocationViewControllerWrapper.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7AB3BEB42BD7A6CB00E34384 /* LocationViewControllerWrapper.swift */; };
@@ -1888,6 +1889,7 @@
 		7A9FA1412A2E3306000B728D /* CheckboxView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CheckboxView.swift; sourceTree = "<group>"; };
 		7A9FA1432A2E3FE5000B728D /* CheckableSettingsCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CheckableSettingsCell.swift; sourceTree = "<group>"; };
 		7AA513852BC91C6B00D081A4 /* LogRotationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LogRotationTests.swift; sourceTree = "<group>"; };
+		7AA704682C8EFE050045699D /* StoredRelays.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StoredRelays.swift; sourceTree = "<group>"; };
 		7AB2B66E2BA1EB8C00B03E3B /* ListCustomListViewController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ListCustomListViewController.swift; sourceTree = "<group>"; };
 		7AB2B66F2BA1EB8C00B03E3B /* ListCustomListCoordinator.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ListCustomListCoordinator.swift; sourceTree = "<group>"; };
 		7AB3BEB42BD7A6CB00E34384 /* LocationViewControllerWrapper.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LocationViewControllerWrapper.swift; sourceTree = "<group>"; };
@@ -4159,6 +4161,7 @@
 				7AEBA5292C2179F20018BEC5 /* RelaySelectorWrapper.swift */,
 				F0B894F02BF751E300817A42 /* RelayWithDistance.swift */,
 				F0B894EE2BF751C500817A42 /* RelayWithLocation.swift */,
+				7AA704682C8EFE050045699D /* StoredRelays.swift */,
 			);
 			path = Relay;
 			sourceTree = "<group>";
@@ -5190,6 +5193,7 @@
 				A90763B32B2857D50045ADF0 /* Socks5Authentication.swift in Sources */,
 				06799ADB28F98E4800ACD94E /* RESTProxyFactory.swift in Sources */,
 				F0DDE4182B220458006B57A7 /* ShadowsocksConfiguration.swift in Sources */,
+				7AA7046A2C8EFE2B0045699D /* StoredRelays.swift in Sources */,
 				06799AF228F98E4800ACD94E /* RESTAccessTokenManager.swift in Sources */,
 				A90763B12B2857D50045ADF0 /* Socks5Endpoint.swift in Sources */,
 				06799AF328F98E4800ACD94E /* RESTAuthenticationProxy.swift in Sources */,

ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift

@@ -63,7 +63,7 @@ final class RelayCacheTracker: RelayCacheTrackerProtocol {
         cache = relayCache
 
         do {
-            cachedRelays = try cache.read()
+            cachedRelays = try cache.read().cachedRelays
             try hotfixRelaysThatDoNotHaveDaita()
         } catch {
             logger.error(
@@ -89,8 +89,8 @@ final class RelayCacheTracker: RelayCacheTrackerProtocol {
         // If the cached relays already have daita information, this fix is not necessary
         guard daitaPropertyMissing else { return }
 
-        let preBundledRelays = try cache.readPrebundledRelays()
-        let preBundledDaitaRelays = preBundledRelays.relays.wireguard.relays.filter { $0.daita == true }
+        let preBundledRelays = try cache.readPrebundledRelays().relays
+        let preBundledDaitaRelays = preBundledRelays.wireguard.relays.filter { $0.daita == true }
         var cachedRelaysWithFixedDaita = cachedRelays.relays.wireguard.relays
 
         // For each daita enabled relay in the prebundled relays
@@ -119,9 +119,19 @@ final class RelayCacheTracker: RelayCacheTrackerProtocol {
             bridge: cachedRelays.relays.bridge
         )
 
-        let updatedCachedRelays = CachedRelays(relays: updatedRelays, updatedAt: Date())
+        let updatedRawRelayData = try REST.Coding.makeJSONEncoder().encode(updatedRelays)
+        let updatedCachedRelays = try StoredRelays(
+            etag: cachedRelays.etag,
+            rawData: updatedRawRelayData,
+            updatedAt: cachedRelays.updatedAt
+        )
+
         try cache.write(record: updatedCachedRelays)
-        self.cachedRelays = updatedCachedRelays
+        self.cachedRelays = CachedRelays(
+            etag: cachedRelays.etag,
+            relays: updatedRelays,
+            updatedAt: cachedRelays.updatedAt
+        )
     }
 
     func startPeriodicUpdates() {
@@ -196,7 +206,7 @@ final class RelayCacheTracker: RelayCacheTrackerProtocol {
     }
 
     func refreshCachedRelays() throws {
-        let newCachedRelays = try cache.read()
+        let newCachedRelays = try cache.read().cachedRelays
 
         relayCacheLock.lock()
         cachedRelays = newCachedRelays
@@ -244,8 +254,8 @@ final class RelayCacheTracker: RelayCacheTrackerProtocol {
         -> Result<RelaysFetchResult, Error> {
         result.tryMap { response -> RelaysFetchResult in
             switch response {
-            case let .newContent(etag, relays):
-                try self.storeResponse(etag: etag, relays: relays)
+            case let .newContent(etag, rawData):
+                try self.storeResponse(etag: etag, rawData: rawData)
 
                 return .newContent
 
@@ -262,18 +272,14 @@ final class RelayCacheTracker: RelayCacheTrackerProtocol {
         }
     }
 
-    private func storeResponse(etag: String?, relays: REST.ServerRelaysResponse) throws {
-        let numRelays = relays.wireguard.relays.count
-
-        logger.info("Downloaded \(numRelays) relays.")
-
-        let newCachedRelays = CachedRelays(
+    private func storeResponse(etag: String?, rawData: Data) throws {
+        let newCachedData = try StoredRelays(
             etag: etag,
-            relays: relays,
+            rawData: rawData,
             updatedAt: Date()
         )
 
-        try cache.write(record: newCachedRelays)
+        try cache.write(record: newCachedData)
         try refreshCachedRelays()
     }
 

ios/MullvadVPNTests/MullvadREST/Relay/RelayCacheTests.swift

@@ -12,7 +12,7 @@ import XCTest
 final class RelayCacheTests: XCTestCase {
     func testReadCache() throws {
         let fileCache = MockFileCache(
-            initialState: .exists(CachedRelays(relays: .mock(), updatedAt: .distantPast))
+            initialState: .exists(try StoredRelays(rawData: try .mock(), updatedAt: .distantPast))
         )
         let cache = RelayCache(fileCache: fileCache)
         let relays = try XCTUnwrap(cache.read())
@@ -22,17 +22,17 @@ final class RelayCacheTests: XCTestCase {
 
     func testWriteCache() throws {
         let fileCache = MockFileCache(
-            initialState: .exists(CachedRelays(relays: .mock(), updatedAt: .distantPast))
+            initialState: .exists(try StoredRelays(rawData: try .mock(), updatedAt: .distantPast))
         )
         let cache = RelayCache(fileCache: fileCache)
-        let newCachedRelays = CachedRelays(relays: .mock(), updatedAt: Date())
+        let newCachedRelays = try StoredRelays(rawData: try .mock(), updatedAt: Date())
 
         try cache.write(record: newCachedRelays)
         XCTAssertEqual(fileCache.getState(), .exists(newCachedRelays))
     }
 
     func testReadPrebundledRelaysWhenNoCacheIsStored() throws {
-        let fileCache = MockFileCache<CachedRelays>(initialState: .fileNotFound)
+        let fileCache = MockFileCache<StoredRelays>(initialState: .fileNotFound)
         let cache = RelayCache(fileCache: fileCache)
 
         XCTAssertNoThrow(try cache.read())
@@ -42,7 +42,7 @@ final class RelayCacheTests: XCTestCase {
 extension REST.ServerRelaysResponse {
     static func mock(
         serverRelays: [REST.ServerRelay] = [],
-        brideRelays: [REST.BridgeRelay] = []
+        bridgeRelays: [REST.BridgeRelay] = []
     ) -> Self {
         REST.ServerRelaysResponse(
             locations: [:],
@@ -52,7 +52,17 @@ extension REST.ServerRelaysResponse {
                 portRanges: [],
                 relays: serverRelays
             ),
-            bridge: REST.ServerBridges(shadowsocks: [], relays: brideRelays)
+            bridge: REST.ServerBridges(shadowsocks: [], relays: bridgeRelays)
         )
     }
 }
+
+extension Data {
+    static func mock(
+        serverRelays: [REST.ServerRelay] = [],
+        bridgeRelays: [REST.BridgeRelay] = []
+    ) throws -> Data {
+        let relays = REST.ServerRelaysResponse.mock(serverRelays: serverRelays, bridgeRelays: bridgeRelays)
+        return try REST.Coding.makeJSONEncoder().encode(relays)
+    }
+}