refactor: own daily currency calculation lifetime

2026-10-16 14:59:00 +02:00
parent c8b2e8e0c5
commit a6ea75821b
5 changed files with 177 additions and 59 deletions
@@ -0,0 +1,74 @@
+import ConjureKit
+import Foundation
+import Testing
+
+@MainActor
+private final class RateRequests {
+    var pending: [CheckedContinuation<CurrencyRates, any Error>] = []
+    func fetch() async throws -> CurrencyRates {
+        try await withCheckedThrowingContinuation { pending.append($0) }
+    }
+}
+
+@MainActor
+private func waitForRates(_ condition: () -> Bool) async throws {
+    // Scheduling deadline only; calculation freshness uses the injected clock.
+    for _ in 0..<1_000 {
+        if condition() { return }
+        try await Task.sleep(for: .milliseconds(1))
+    }
+    try #require(condition(), "Currency calculation did not reach the expected state")
+}
+
+@Test @MainActor
+func currencyLifetimeSharesRefreshAndPreservesStaleCopyUntilFailure() async throws {
+    var calendar = Calendar(identifier: .gregorian)
+    calendar.timeZone = TimeZone(secondsFromGMT: 0)!
+    var now = calendar.date(from: DateComponents(year: 2026, month: 1, day: 2, hour: 12))!
+    let requests = RateRequests()
+    let calculation = CurrencyCalculation(now: { now }, calendar: calendar, fetch: { try await requests.fetch() })
+    var completions = 0
+    calculation.changed = { completions += 1 }
+    let snapshot = CurrencyRates(date: "2026-01-02", rates: ["eur": 1, "usd": 2, "dkk": 8])
+
+    calculation.update("100 USD to DKK")
+    #expect(calculation.isCurrency)
+    #expect(calculation.result?.copyValue == nil)
+    try await waitForRates { requests.pending.count == 1 }
+    calculation.update("50 USD to DKK")
+    requests.pending[0].resume(returning: snapshot)
+    try await waitForRates { completions == 1 }
+    #expect(calculation.result?.copyValue == "200 DKK")
+    calculation.update("100 USD to DKK")
+    #expect(calculation.result?.copyValue == "400 DKK")
+    #expect(requests.pending.count == 1)
+
+    now = calendar.date(byAdding: .day, value: 1, to: now)!
+    calculation.update("100 USD to DKK")
+    #expect(calculation.result?.copyValue == "400 DKK")
+    #expect(calculation.result?.detail.contains("Stale cache; refreshing") == true)
+    try await waitForRates { requests.pending.count == 2 }
+    calculation.update("50 USD to DKK")
+    requests.pending[1].resume(throwing: URLError(.notConnectedToInternet))
+    try await waitForRates { completions == 2 }
+    #expect(calculation.result?.copyValue == nil)
+    #expect(calculation.result?.displayValue == "Currency rates unavailable")
+    calculation.update("50 USD to DKK")
+    #expect(calculation.result?.copyValue == nil)
+    #expect(requests.pending.count == 2)
+
+    calculation.update("25 USD to DKK")
+    try await waitForRates { requests.pending.count == 3 }
+    calculation.update("Safari") // Leaving currency does not cancel shared work.
+    #expect(!calculation.isCurrency)
+    #expect(calculation.result == nil)
+    requests.pending[2].resume(returning: snapshot)
+    try await waitForRates { completions == 3 }
+    #expect(calculation.result == nil)
+    calculation.update("25 USD to DKK")
+    #expect(calculation.result?.copyValue == "100 DKK")
+    #expect(requests.pending.count == 3) // Fetch day, not snapshot metadata, controls freshness.
+    calculation.update("1 km to mi")
+    #expect(!calculation.isCurrency)
+    #expect(calculation.result?.copyValue == "0.621371192237 mi")
+}