using Microsoft.Extensions.Options;
using ScadaLink.Commons.Types.Transport;
using ScadaLink.Transport;
using ScadaLink.Transport.Import;

namespace ScadaLink.Transport.Tests.Import;

public sealed class BundleSessionStoreTests
{
    private static IOptions<TransportOptions> Options() => Microsoft.Extensions.Options.Options.Create(new TransportOptions());

    private static BundleSession SessionExpiringAt(DateTimeOffset expiresAt) => new()
    {
        SessionId = Guid.NewGuid(),
        Manifest = StubManifest(),
        DecryptedContent = Array.Empty<byte>(),
        ExpiresAt = expiresAt,
    };

    private static BundleManifest StubManifest() => new(
        BundleFormatVersion: 1,
        SchemaVersion: "1.0",
        CreatedAtUtc: DateTimeOffset.UnixEpoch,
        SourceEnvironment: "test",
        ExportedBy: "t",
        ScadaLinkVersion: "1",
        ContentHash: "0",
        Encryption: null,
        Summary: new BundleSummary(0, 0, 0, 0, 0, 0, 0, 0, 0),
        Contents: Array.Empty<ManifestContentEntry>());

    [Fact]
    public void Open_then_Get_returns_session()
    {
        var clock = new TestTimeProvider(DateTimeOffset.UtcNow);
        var sut = new BundleSessionStore(Options(), clock);
        var session = SessionExpiringAt(clock.GetUtcNow().AddMinutes(30));

        sut.Open(session);

        var fetched = sut.Get(session.SessionId);
        Assert.NotNull(fetched);
        Assert.Same(session, fetched);
    }

    [Fact]
    public void Get_after_TTL_returns_null_and_evicts()
    {
        var start = DateTimeOffset.UtcNow;
        var clock = new TestTimeProvider(start);
        var sut = new BundleSessionStore(Options(), clock);
        var session = SessionExpiringAt(start.AddMinutes(1));
        sut.Open(session);

        clock.Advance(TimeSpan.FromMinutes(2));

        Assert.Null(sut.Get(session.SessionId));
        // Lookup with no time advancement now returns null again — proves the
        // entry was evicted, not merely filtered.
        Assert.Null(sut.Get(session.SessionId));
    }

    [Fact]
    public void Remove_evicts_session()
    {
        var clock = new TestTimeProvider(DateTimeOffset.UtcNow);
        var sut = new BundleSessionStore(Options(), clock);
        var session = SessionExpiringAt(clock.GetUtcNow().AddHours(1));
        sut.Open(session);

        sut.Remove(session.SessionId);

        Assert.Null(sut.Get(session.SessionId));
    }

    [Fact]
    public void EvictExpired_removes_all_past_ttl()
    {
        var start = DateTimeOffset.UtcNow;
        var clock = new TestTimeProvider(start);
        var sut = new BundleSessionStore(Options(), clock);

        var keep = SessionExpiringAt(start.AddMinutes(30));
        var dropA = SessionExpiringAt(start.AddSeconds(10));
        var dropB = SessionExpiringAt(start.AddMinutes(1));
        sut.Open(keep);
        sut.Open(dropA);
        sut.Open(dropB);

        clock.Advance(TimeSpan.FromMinutes(2));
        sut.EvictExpired();

        Assert.NotNull(sut.Get(keep.SessionId));
        Assert.Null(sut.Get(dropA.SessionId));
        Assert.Null(sut.Get(dropB.SessionId));
    }

    [Fact]
    public void Three_failed_unlock_attempts_locks_session()
    {
        var clock = new TestTimeProvider(DateTimeOffset.UtcNow);
        var sut = new BundleSessionStore(Options(), clock);
        var session = SessionExpiringAt(clock.GetUtcNow().AddMinutes(30));
        sut.Open(session);

        var live = sut.Get(session.SessionId);
        Assert.NotNull(live);

        live!.FailedUnlockAttempts++;
        Assert.False(live.Locked);
        live.FailedUnlockAttempts++;
        Assert.False(live.Locked);
        live.FailedUnlockAttempts++;
        Assert.True(live.Locked);

        // Mutations are observable via re-fetch — confirms the store hands out
        // the shared reference (not a snapshot).
        var refetch = sut.Get(session.SessionId);
        Assert.NotNull(refetch);
        Assert.True(refetch!.Locked);
    }

    /// <summary>
    /// Minimal in-test <see cref="TimeProvider"/> with a mutable clock. Used in
    /// place of <c>Microsoft.Extensions.TimeProvider.Testing</c> (not in the
    /// central package list). Only <see cref="GetUtcNow"/> is overridden; the
    /// store does not use timers, so the base implementations suffice elsewhere.
    /// </summary>
    private sealed class TestTimeProvider : TimeProvider
    {
        private DateTimeOffset _now;
        public TestTimeProvider(DateTimeOffset start) { _now = start; }
        public override DateTimeOffset GetUtcNow() => _now;
        public void Advance(TimeSpan by) => _now = _now.Add(by);
    }
}