using QVPN.Core;

internal static class SubscriptionRefreshPolicyTests
{
    public static async Task RunAsync(Func<string, Action, Task> test)
    {
        var now = DateTimeOffset.Parse("2026-10-06T21:00:00Z");
        await test("Service startup refreshes stale or undated subscription before health succeeds", () =>
        {
            var policy = new SubscriptionRefreshPolicy();
            Check(policy.ShouldRefreshOnConnect(now.AddHours(-2), now));
            Check(policy.ShouldRefreshOnConnect(null, now));
            Check(policy.ShouldRefreshOnConnect(now.AddMinutes(-15), now));
            Check(!policy.ShouldRefreshOnConnect(now.AddMinutes(-14), now));
        });
        await test("A new explicit connect checks current endpoint even with recently cached subscription", () =>
        {
            var policy = new SubscriptionRefreshPolicy();
            Check(policy.ShouldRefreshOnConnect(now, now, explicitConnect: true));
            policy.Attempted(now);
            Check(!policy.ShouldRefreshOnConnect(now, now.AddSeconds(59), explicitConnect: true));
            Check(policy.ShouldRefreshOnConnect(now, now.AddSeconds(60), explicitConnect: true));
        });
        await test("Endpoint outage refresh is allowed without a connected engine and limited to once per minute", () =>
        {
            var policy = new SubscriptionRefreshPolicy();
            Check(policy.ShouldRefreshAfterEndpointFailure(now));
            policy.Attempted(now);
            for (int seconds = 0; seconds < 60; seconds++) Check(!policy.ShouldRefreshAfterEndpointFailure(now.AddSeconds(seconds)));
            Check(policy.ShouldRefreshAfterEndpointFailure(now.AddSeconds(60)));
        });
        await test("Manual or routine subscription attempts also suppress immediate outage refresh loops", () =>
        {
            var policy = new SubscriptionRefreshPolicy();
            policy.Attempted(now);
            Check(!policy.ShouldRefreshAfterEndpointFailure(now.AddSeconds(1)));
            Check(!policy.ShouldRefreshOnConnect(now.AddHours(-2), now.AddSeconds(1)));
            policy.Attempted(now.AddSeconds(60));
            Check(!policy.ShouldRefreshAfterEndpointFailure(now.AddSeconds(61)));
        });
        await test("A fresh successful subscription prevents automatic startup refresh after the retry cooldown", () =>
        {
            var policy = new SubscriptionRefreshPolicy();
            policy.Attempted(now);
            Check(!policy.ShouldRefreshOnConnect(now, now.AddMinutes(2)));
            Check(policy.ShouldRefreshOnConnect(now, now.AddMinutes(15)));
        });
        await test("Clock rollback does not cause repeated automatic subscription refresh", () =>
        {
            var policy = new SubscriptionRefreshPolicy();
            policy.Attempted(now);
            Check(!policy.ShouldRefreshAfterEndpointFailure(now.AddMinutes(-5)));
            Check(!policy.ShouldRefreshOnConnect(now.AddHours(-2), now.AddMinutes(-5), explicitConnect: true));
        });
    }

    private static void Check(bool condition)
    {
        if (!condition) throw new InvalidOperationException("Subscription refresh policy regression.");
    }
}