feat(apple): collect transfers held for this device

Adds the opt-in foreground check and an explicit Check now, the waiting-to-
be-delivered list on the sender side, and honest reporting when a send could
not be delivered: a closed app is a delay, not a success nobody received.

The setting is off by default and its footer states that checking reveals
app-open times to remembered devices, since that is the reason it is a
setting at all.

Records in the design doc that this shipped as one global toggle rather than
the per-contact opt-in originally specified.

apple/Tests/ContactsModelTests.swift

@@ -235,7 +235,13 @@ final class ContactsModelTests: XCTestCase {
 			fileSystemService: files
 		)
 		gateway.sendToContactResult = .success(
-			Share(transferId: 1, ticket: "vnd1:x", transferName: "doc", contentHash: "h", fileCount: 1, totalSize: 2)
+			ContactSendOutcome(
+				share: Share(
+					transferId: 1, ticket: "vnd1:x", transferName: "doc",
+					contentHash: "h", fileCount: 1, totalSize: 2
+				),
+				delivered: true
+			)
 		)
 
 		model.chooseFilesToSend(to: "peer")
@@ -276,6 +282,98 @@ final class ContactsModelTests: XCTestCase {
 		XCTAssertTrue(gateway.sentToContacts.isEmpty)
 	}
 
+	/// Polling is opt-in: it tells every contact the app was opened.
+	func testForegroundCheckIsSkippedUnlessEnabled() async {
+		let gateway = FakeCoreGateway()
+		let (model, _) = makeModel(gateway)
+
+		await model.checkForOffersOnForeground()
+
+		XCTAssertEqual(gateway.pollCount, 0)
+	}
+
+	func testForegroundCheckRunsOnceEnabled() async {
+		let gateway = FakeCoreGateway()
+		let (model, preferences) = makeModel(gateway)
+
+		model.setCheckForOffersOnOpen(true)
+		await model.checkForOffersOnForeground()
+
+		XCTAssertEqual(gateway.pollCount, 1)
+		XCTAssertTrue(preferences.preferences.checkForOffersOnOpen)
+	}
+
+	/// The explicit "check now" ignores the setting: the user just asked.
+	func testExplicitCheckRunsEvenWhenTheSettingIsOff() async {
+		let gateway = FakeCoreGateway()
+		gateway.pollResult = .success(2)
+		let (model, _) = makeModel(gateway)
+
+		let collected = await model.collectWaitingOffers()
+
+		XCTAssertEqual(collected, 2)
+		XCTAssertEqual(gateway.pollCount, 1)
+	}
+
+	/// A transfer that could not be delivered is reported as waiting, not as a
+	/// success nobody has received.
+	func testAnUndeliveredSendIsReportedAsWaiting() async {
+		let gateway = FakeCoreGateway()
+		let files = FakeFileSystemService()
+		let defaults = UserDefaults(suiteName: "contacts-held-\(UUID().uuidString)")!
+		let preferences = AppPreferencesRepository(
+			defaults: defaults,
+			fallback: AppPreferencesDefaults(
+				username: "tester",
+				receiveFolder: ReceiveFolder(kind: .fileSystemPath, value: "/tmp", displayName: "Downloads"),
+				themeMode: .system
+			)
+		)
+		let messages = UiMessageController()
+		let model = ContactsModel(
+			repository: gateway,
+			messages: messages,
+			preferences: preferences,
+			fileSystemService: files
+		)
+		gateway.sendToContactResult = .success(
+			ContactSendOutcome(
+				share: Share(
+					transferId: 1, ticket: "vnd1:x", transferName: "doc",
+					contentHash: "h", fileCount: 1, totalSize: 2
+				),
+				delivered: false
+			)
+		)
+
+		model.chooseFilesToSend(to: "peer")
+		await model.onFilesPicked([
+			PickedShareFile(value: "/tmp/doc.txt", displayName: "doc.txt", isDirectory: false)
+		])
+
+		XCTAssertEqual(messages.current?.tone, .info)
+	}
+
+	func testHeldOffersAreLoadedForDisplay() async {
+		let gateway = FakeCoreGateway()
+		gateway.heldOffersResult = .success([
+			HeldOfferModel(
+				offerId: "held-1",
+				endpointId: "peer",
+				transferId: 1,
+				transferName: "doc",
+				fileCount: 1,
+				totalBytes: 2,
+				createdAt: 0
+			)
+		])
+		let (model, _) = makeModel(gateway)
+
+		await model.refresh()
+
+		XCTAssertEqual(model.state.heldOffers.map(\.offerId), ["held-1"])
+	}
+
 	func testUnreachableContactIsSurfacedForRepairing() async {
 		let gateway = FakeCoreGateway()
 		gateway.contactsResult = .success([contact("peer", canSend: false)])

apple/Tests/Fakes.swift

@@ -90,7 +90,10 @@ final class FakeCoreGateway: CoreGateway {
 	var respondToPairingResult: Result<Bool, Error> = .success(true)
 	/// Ticket handed back when an offer is accepted; nil models a declined one.
 	var offerTicket: String? = "vnd1:offered"
-	var sendToContactResult: Result<Share, Error> = .failure(TestError.unimplemented)
+	var sendToContactResult: Result<ContactSendOutcome, Error> = .failure(TestError.unimplemented)
+	var heldOffersResult: Result<[HeldOfferModel], Error> = .success([])
+	var pollResult: Result<UInt64, Error> = .success(0)
+	private(set) var pollCount = 0
 	var forgetContactResult: Result<Void, Error> = .success(())
 	var blockedResult: Result<[String], Error> = .success([])
 
@@ -129,10 +132,15 @@ final class FakeCoreGateway: CoreGateway {
 		sources: [ShareSource],
 		transferName: String,
 		senderName: String
-	) async -> Result<Share, Error> {
+	) async -> Result<ContactSendOutcome, Error> {
 		sentToContacts.append(endpointId)
 		return sendToContactResult
 	}
+	func heldOffers() async -> Result<[HeldOfferModel], Error> { heldOffersResult }
+	func pollContactsForOffers() async -> Result<UInt64, Error> {
+		pollCount += 1
+		return pollResult
+	}
 	func forgetContact(endpointId: String) async -> Result<Void, Error> {
 		forgottenContacts.append(endpointId)
 		return forgetContactResult
@@ -168,13 +176,14 @@ final class FakeFileSystemService: FileSystemService {
 	func canRevealReceiveFolder(_ folder: ReceiveFolder) -> Bool { false }
 	private(set) var shareDestinations: [ShareDestination] = []
 
-	func sharePickedFiles(repository: CoreGateway, files: [PickedShareFile], transferName: String, senderName: String, destination: ShareDestination) async -> Result<Share, Error> {
+	func sharePickedFiles(repository: CoreGateway, files: [PickedShareFile], transferName: String, senderName: String, destination: ShareDestination) async -> Result<ContactSendOutcome, Error> {
 		shareDestinations.append(destination)
 		switch destination {
 		case .invitation(let accessPolicy):
 			return await repository.shareSources(
 				[], transferName: transferName, senderName: senderName, accessPolicy: accessPolicy
 			)
+			.map { ContactSendOutcome(share: $0, delivered: true) }
 		case .contact(let endpointId):
 			return await repository.sendToContact(
 				endpointId: endpointId, sources: [], transferName: transferName, senderName: senderName