import XCTest
@testable import LCFeatureControl

/// Test-only mutable clock box — a `var` captured directly by the cache's
/// escaping `@Sendable` closure would trip strict-concurrency capture checks;
/// this mirrors the `@unchecked Sendable` pattern `StubURLProtocol` already uses.
private final class MutableClock: @unchecked Sendable {
    var value: Date
    init(_ value: Date) { self.value = value }
}

final class FeatureControlCacheTests: XCTestCase {

    private func snapshot(configVersion: Int) -> FeatureControlSnapshot {
        FeatureControlSnapshot(evaluatedAt: Date(), configVersion: configVersion, flags: [:])
    }

    private func key(_ keys: [String] = ["a", "b"]) -> FeatureControlCacheKey {
        FeatureControlCacheKey(environment: "production", subjectId: "cust_1",
                               sortedKeys: keys.sorted(), platform: "ios", appVersion: "1.0")
    }

    func testHitWithinTTLReturnsSameSnapshot() async {
        let cache = FeatureControlCache(now: { Date() })
        await cache.set(key(), snapshot: snapshot(configVersion: 1), ttl: 45)
        let hit = await cache.get(key(), allowStale: false)
        XCTAssertEqual(hit?.configVersion, 1)
    }

    func testMissAfterTTLExpiryReturnsNilWhenStaleNotAllowed() async {
        let clock = MutableClock(Date())
        let cache = FeatureControlCache(now: { clock.value })
        await cache.set(key(), snapshot: snapshot(configVersion: 1), ttl: 1)
        clock.value = clock.value.addingTimeInterval(2)
        let hit = await cache.get(key(), allowStale: false)
        XCTAssertNil(hit)
    }

    func testStaleAllowedReturnsExpiredEntry() async {
        let clock = MutableClock(Date())
        let cache = FeatureControlCache(now: { clock.value })
        await cache.set(key(), snapshot: snapshot(configVersion: 1), ttl: 1)
        clock.value = clock.value.addingTimeInterval(2)
        let hit = await cache.get(key(), allowStale: true)
        XCTAssertEqual(hit?.configVersion, 1)
    }

    func testKeyDiffersBySortedKeysNotInputOrder() async {
        let cache = FeatureControlCache(now: { Date() })
        await cache.set(key(["a", "b"]), snapshot: snapshot(configVersion: 1), ttl: 45)
        let hit = await cache.get(key(["b", "a"]), allowStale: false)
        XCTAssertEqual(hit?.configVersion, 1)
    }

    func testSetOverwritesPriorConfigVersion() async {
        let cache = FeatureControlCache(now: { Date() })
        await cache.set(key(), snapshot: snapshot(configVersion: 7), ttl: 45)
        await cache.set(key(), snapshot: snapshot(configVersion: 8), ttl: 45)
        let hit = await cache.get(key(), allowStale: false)
        XCTAssertEqual(hit?.configVersion, 8)
    }

    func testInvalidateAllClearsEntries() async {
        let cache = FeatureControlCache(now: { Date() })
        await cache.set(key(), snapshot: snapshot(configVersion: 1), ttl: 45)
        await cache.invalidateAll()
        let hit = await cache.get(key(), allowStale: true)
        XCTAssertNil(hit)
    }
}