Merge pull request #812 from corona-warn-app/hotfix/pruning-2

Hotfix/pruning 2

src/xcode/ENA/ENA/Source/Workers/TracingStatusHistory.swift

@@ -57,18 +57,20 @@ extension Array where Element == TracingStatusEntry {
 		return copy
 	}
 
+	struct PrunedEntries {
+		let relevant: [TracingStatusEntry]
+		let lastIrrelevant: TracingStatusEntry?
+	}
+
 	// MARK: - Prune stale elements older than 14 days
 	/// Clean up `[TracingStatusEntry]` so we do not store entries past the threshold (14 days)
 	///
 	/// - parameter threshold: Max seconds entries can be in the past for. Defaults to 14 days
-	private func pruned(with threshold: TimeInterval = Self.maxStoredSeconds) -> TracingStatusHistory {
+	private func pruned(with threshold: TimeInterval = Self.maxStoredSeconds) -> PrunedEntries {
 		let maxPast = Date().addingTimeInterval(-threshold)
 		let relevantEntries = filter { $0.date > maxPast }
 		let irrelevantEntries = filter { $0.date <= maxPast }
-		if let lastIrrelevantEntry = irrelevantEntries.last {
-			return [lastIrrelevantEntry] + relevantEntries
-		}
-		return relevantEntries
+		return .init(relevant: relevantEntries, lastIrrelevant: irrelevantEntries.last)
 	}
 
 	// MARK: - Check Tracing History for Risk Calculation
@@ -106,27 +108,37 @@ extension Array where Element == TracingStatusEntry {
 		// In order to have a minimal set of changes for hotfix #1 we hard-code
 		// the precondition (self is pruned) here and have the old, tested code
 		// stay the same in _getContinuousEnabledInterval.
-		pruned()._getContinuousEnabledInterval(since: since)
+		let prunedEntries = pruned()
+
+		let intervalForRelevantEntries = prunedEntries.relevant._getContinuousEnabledInterval(since: since)
+
+		let oldestRelevantDate = prunedEntries.relevant.first?.date ?? since
+		if prunedEntries.lastIrrelevant?.on == true {
+			let now = since
+			let earliestPotentialDate = now.addingTimeInterval(-Self.maxStoredSeconds)
+			let delta = oldestRelevantDate.timeIntervalSince(earliestPotentialDate)
+			return intervalForRelevantEntries + delta
+		}
+
+		return intervalForRelevantEntries
 	}
 
 	private func _getContinuousEnabledInterval(since: Date = Date()) -> TimeInterval {
 		// self is pruned
 		guard !isEmpty else {
 			return .zero
 		}
-
 		var prevDate = since
 		// Assume pruned array
-		let sum = reversed().reduce(.zero) { acc, next -> TimeInterval in
+		return reversed().reduce(.zero) { acc, next -> TimeInterval in
 			if next.on {
 				let sum = acc + prevDate.timeIntervalSince(next.date)
+				prevDate = next.date
 				return sum
 			}
 			prevDate = next.date
 			return acc
 		}
-
-		return sum
 	}
 
 	// MARK: - Constants for Tracing
@@ -139,5 +151,4 @@ extension Array where Element == TracingStatusEntry {
 	static let maxStoredDays = 14
 	/// The maximum count of seconds to keep tracing history for
 	static var maxStoredSeconds: TimeInterval { TimeInterval(maxStoredDays * 24 * 60 * 60) }
-
 }

src/xcode/ENA/ENA/Source/Workers/__tests__/TracingStatusHistoryTests.swift

@@ -121,7 +121,7 @@ final class TracingStatusHistoryTests: XCTestCase {
 
 		history = history.consumingState(goodState, date)
 
-		XCTAssertEqual(history.countEnabledDays(), 15)
+		XCTAssertEqual(history.countEnabledDays(), 14)
 	}
 
 	func testIfTracingActiveForThresholdDuration_EnabledClosePast() throws {
@@ -197,17 +197,88 @@ final class TracingStatusHistoryTests: XCTestCase {
 		XCTAssertEqual(history.countEnabledHours(), 1)
 	}
 
-	func testEnabledHoursCount_Complex() throws {
+	func testEnabledHoursCount_WithTheFirstEntryBeingInDistantPast() throws {
 		var history = TracingStatusHistory()
 		let goodState = ExposureManagerState(authorized: true, enabled: true, status: .active)
 		let badState = ExposureManagerState(authorized: true, enabled: false, status: .active)
 
-		history = history.consumingState(goodState, Date().addingTimeInterval(.init(days: -15)))
-		history = history.consumingState(badState, Date().addingTimeInterval(.init(days: -10)))	// active for 5 days
-		history = history.consumingState(goodState, Date().addingTimeInterval(.init(days: -1))) // inactive for 9 days
-		history = history.consumingState(badState, Date().addingTimeInterval(.init(hours: -1)))	// active for 23 hours
+		let now = Date()
+
+		history = history.consumingState(goodState, now.addingTimeInterval(.init(days: -100)))
+		history = history.consumingState(badState, now.addingTimeInterval(.init(days: -10)))	// stop being active after 4 days
+
+		XCTAssertEqual(history.countEnabledHours(since: now), 96)
+		XCTAssertEqual(history.countEnabledDays(since: now), 4)
+	}
+
+
+	func testEnabledHoursCount_Complex() {
+		var history = TracingStatusHistory()
+		let goodState = ExposureManagerState(authorized: true, enabled: true, status: .active)
+		let badState = ExposureManagerState(authorized: true, enabled: false, status: .active)
+
+		let now = Date()
+
+		history = history.consumingState(goodState, now.addingTimeInterval(.init(days: -15)))
+		history = history.consumingState(badState, now.addingTimeInterval(.init(days: -10)))	// active for 5 days (where one day is 'irrelevant'
+		history = history.consumingState(goodState, now.addingTimeInterval(.init(days: -1))) // inactive for 9 days
+		history = history.consumingState(badState, now.addingTimeInterval(.init(hours: -1)))	// active for 23 hours
+
+		XCTAssertEqual(history.countEnabledHours(since: now), 24 * 4 + 23)
+		XCTAssertEqual(history.countEnabledDays(since: now), 4)
+	}
+
+	func testGetEnabledInterval_Accumulator_Good() {
+		let now = Date()
+
+		let history: TracingStatusHistory = [
+			.init(on: true, date: now.addingTimeInterval(.init(days: -10))),
+			.init(on: true, date: now.addingTimeInterval(.init(days: -5)))
+		]
+
+		XCTAssertEqual(history.countEnabledHours(since: now), 24 * 10)
+		XCTAssertEqual(history.countEnabledDays(since: now), 10)
+	}
+
+	func testGetEnabledInterval_Accumulator_Good_2() {
+		let now = Date()
+
+		let history: TracingStatusHistory = [
+			.init(on: true, date: now.addingTimeInterval(.init(days: -10))),
+			.init(on: true, date: now.addingTimeInterval(.init(days: -5))),
+			.init(on: true, date: now.addingTimeInterval(.init(days: -3))),
+			.init(on: true, date: now.addingTimeInterval(.init(days: -1)))
+		]
+
+		XCTAssertEqual(history.countEnabledHours(since: now), 24 * 10)
+		XCTAssertEqual(history.countEnabledDays(since: now), 10)
+	}
+
+	func testGetEnabledInterval_Accumulator_Good_3() {
+		let now = Date()
+
+		let history: TracingStatusHistory = [
+			.init(on: true, date: now.addingTimeInterval(.init(days: -10))),
+			.init(on: false, date: now.addingTimeInterval(.init(days: -5))),	// Active for 5 days
+			.init(on: true, date: now.addingTimeInterval(.init(days: -2)))		// Inactive for 3 days
+			// Active for 2 more days
+		]
+
+		XCTAssertEqual(history.countEnabledHours(since: now), 24 * 7)
+		XCTAssertEqual(history.countEnabledDays(since: now), 7)
+	}
+
+	func testGetEnabledInterval_Accumulator_Bad() {
+		let now = Date()
+
+		let history: TracingStatusHistory = [
+			.init(on: false, date: now.addingTimeInterval(.init(days: -10))),
+			.init(on: false, date: now.addingTimeInterval(.init(days: -5))),
+			.init(on: true, date: now.addingTimeInterval(.init(days: -2)))
+		]
 
-		XCTAssertEqual(history.countEnabledHours(), 24 * 5 + 23)
+		XCTAssertEqual(history.countEnabledHours(since: now), 24 * 2)
+		XCTAssertEqual(history.countEnabledDays(since: now), 2)
 	}
 }