import Foundation

/// Wiring around `AdaptiveRefreshPolicy` for `UsageStore.startTimer()`: gathering live signals,
/// logging the resulting decision, and applying the DEBUG-only sleep-duration override used by
/// tests. Split out of UsageStore.swift to keep that file's class body under the lint line limit.
extension UsageStore {
    func effectiveTimerSleepDuration(_ computed: Duration) -> Duration {
        #if DEBUG
        self.refreshTimerSleepOverrideForTesting ?? computed
        #else
        computed
        #endif
    }

    /// Pure wiring helper: builds the `AdaptiveRefreshPolicy.Input` from explicit values and
    /// returns the resulting decision. `startTimer()` supplies live `ProcessInfo` state and
    /// `lastMenuOpenAt` at call time; this stays a plain, testable function of its arguments.
    nonisolated static func adaptiveRefreshDecision(
        now: Date,
        lastMenuOpenAt: Date?,
        lowPowerModeEnabled: Bool,
        thermalState: ProcessInfo.ThermalState,
        policy: AdaptiveRefreshPolicy = AdaptiveRefreshPolicy()) -> AdaptiveRefreshPolicy.Decision
    {
        policy.nextDelay(for: AdaptiveRefreshPolicy.Input(
            now: now,
            lastMenuOpenAt: lastMenuOpenAt,
            lowPowerModeEnabled: lowPowerModeEnabled,
            thermalState: thermalState))
    }

    nonisolated static func shouldAdvanceAdaptiveTimer(scheduledAt: Date?, candidate: Date) -> Bool {
        guard let scheduledAt else { return true }
        return candidate < scheduledAt
    }

    /// Advances a fixed timer from the last scheduled tick instead of the refresh completion time.
    /// Missed ticks are skipped so a refresh that runs longer than its interval does not create
    /// overlapping catch-up refreshes.
    nonisolated static func nextFixedTimerScheduledAt(
        previousScheduledAt: ContinuousClock.Instant,
        completedAt: ContinuousClock.Instant,
        interval: Duration) -> ContinuousClock.Instant
    {
        precondition(interval > .zero)
        var scheduledAt = previousScheduledAt + interval
        while scheduledAt <= completedAt {
            scheduledAt += interval
        }
        return scheduledAt
    }

    nonisolated static func runFixedRefreshTimer(
        interval: Duration,
        sleepOverride: Duration? = nil,
        now: @escaping @Sendable () async -> ContinuousClock.Instant = { ContinuousClock.now },
        sleep: @escaping @Sendable (Duration) async throws -> Void = { duration in
            try await Task.sleep(for: duration)
        },
        refresh: @escaping @Sendable () async -> Void) async
    {
        precondition(interval > .zero)
        var scheduledAt = await now() + interval
        while !Task.isCancelled {
            let current = await now()
            let computedSleep = current >= scheduledAt ? .zero : scheduledAt - current
            do {
                try await sleep(sleepOverride ?? computedSleep)
            } catch {
                return
            }
            guard !Task.isCancelled else { return }
            await refresh()
            scheduledAt = await self.nextFixedTimerScheduledAt(
                previousScheduledAt: scheduledAt,
                completedAt: now(),
                interval: interval)
        }
    }

    func logAdaptiveRefreshDecision(_ decision: AdaptiveRefreshPolicy.Decision) {
        // Reason and delay only; never provider/account/email/path/credential/response data.
        // No "adaptive refresh: " prefix — the adaptiveRefresh log category already identifies the source.
        self.adaptiveRefreshLogger.debug(
            "reason=\(decision.reason.rawValue) delay=\(decision.delay.components.seconds)s")
    }

    /// Computes this tick's adaptive sleep duration (and logs the decision) while briefly holding a
    /// strong reference to `store`; returns nil once the store has deallocated, ending the loop.
    /// Kept as a separate call so the strong reference doesn't extend into the caller's `Task.sleep`.
    static func nextAdaptiveTimerSleepDuration(for store: UsageStore?) async -> Duration? {
        guard let store else { return nil }
        let now = Date()
        let decision = Self.adaptiveRefreshDecision(
            now: now,
            lastMenuOpenAt: store.lastMenuOpenAt,
            lowPowerModeEnabled: ProcessInfo.processInfo.isLowPowerModeEnabled,
            thermalState: ProcessInfo.processInfo.thermalState)
        store.adaptiveRefreshScheduledAt = now.addingTimeInterval(TimeInterval(decision.delay.components.seconds))
        store.logAdaptiveRefreshDecision(decision)
        return store.effectiveTimerSleepDuration(decision.delay)
    }

    /// The refresh interval scheduling *heuristics* (reset-boundary refresh, OpenAI web staleness,
    /// persistent-CLI-session idle windows) should use as "how often does a normal refresh happen".
    /// This is deliberately distinct from `RefreshFrequency.seconds`, which is nil for both `.manual`
    /// (no timer at all — heuristics correctly get nil here too) and `.adaptive` (no *fixed*
    /// interval, but ticks are still happening on a real, computable cadence). For `.adaptive`, this
    /// resolves to what `AdaptiveRefreshPolicy` would decide right now from live signals, so those
    /// heuristics stay active and roughly proportionate instead of silently behaving like manual.
    func normalRefreshIntervalForHeuristics() -> TimeInterval? {
        switch self.settings.refreshFrequency {
        case .manual:
            nil
        case .adaptive:
            TimeInterval(Self.adaptiveRefreshDecision(
                now: Date(),
                lastMenuOpenAt: self.lastMenuOpenAt,
                lowPowerModeEnabled: ProcessInfo.processInfo.isLowPowerModeEnabled,
                thermalState: ProcessInfo.processInfo.thermalState).delay.components.seconds)
        default:
            self.settings.refreshFrequency.seconds
        }
    }
}