using FluentAssertions;
using StellaOps.AirGap.Importer.Versioning;

namespace StellaOps.AirGap.Importer.Tests.Versioning;

public sealed class VersionMonotonicityCheckerTests
{
    [Fact]
    public async Task CheckAsync_WhenNoCurrent_ShouldBeFirstActivation()
    {
        var store = new InMemoryBundleVersionStore();
        var checker = new VersionMonotonicityChecker(store, new FixedTimeProvider(DateTimeOffset.Parse("2025-12-14T00:00:00Z")));

        var incoming = BundleVersion.Parse("1.0.0", DateTimeOffset.Parse("2025-12-14T00:00:00Z"));
        var result = await checker.CheckAsync("tenant-a", "offline-kit", incoming);

        result.IsMonotonic.Should().BeTrue();
        result.ReasonCode.Should().Be("FIRST_ACTIVATION");
        result.CurrentVersion.Should().BeNull();
        result.CurrentBundleDigest.Should().BeNull();
    }

    [Fact]
    public async Task CheckAsync_WhenOlder_ShouldBeNonMonotonic()
    {
        var store = new InMemoryBundleVersionStore();
        await store.UpsertAsync(new BundleVersionRecord(
            TenantId: "tenant-a",
            BundleType: "offline-kit",
            VersionString: "2.0.0",
            Major: 2,
            Minor: 0,
            Patch: 0,
            Prerelease: null,
            BundleCreatedAt: DateTimeOffset.Parse("2025-12-14T00:00:00Z"),
            BundleDigest: "sha256:current",
            ActivatedAt: DateTimeOffset.Parse("2025-12-14T00:00:00Z"),
            WasForceActivated: false,
            ForceActivateReason: null));

        var checker = new VersionMonotonicityChecker(store, new FixedTimeProvider(DateTimeOffset.Parse("2025-12-14T00:00:00Z")));
        var incoming = BundleVersion.Parse("1.0.0", DateTimeOffset.Parse("2025-12-14T00:00:00Z"));

        var result = await checker.CheckAsync("tenant-a", "offline-kit", incoming);

        result.IsMonotonic.Should().BeFalse();
        result.ReasonCode.Should().Be("VERSION_NON_MONOTONIC");
        result.CurrentVersion.Should().NotBeNull();
        result.CurrentVersion!.SemVer.Should().Be("2.0.0");
    }

    [Fact]
    public async Task RecordActivationAsync_WhenNonMonotonicWithoutForce_ShouldThrow()
    {
        var store = new InMemoryBundleVersionStore();
        await store.UpsertAsync(new BundleVersionRecord(
            TenantId: "tenant-a",
            BundleType: "offline-kit",
            VersionString: "2.0.0",
            Major: 2,
            Minor: 0,
            Patch: 0,
            Prerelease: null,
            BundleCreatedAt: DateTimeOffset.Parse("2025-12-14T00:00:00Z"),
            BundleDigest: "sha256:current",
            ActivatedAt: DateTimeOffset.Parse("2025-12-14T00:00:00Z"),
            WasForceActivated: false,
            ForceActivateReason: null));

        var checker = new VersionMonotonicityChecker(store, new FixedTimeProvider(DateTimeOffset.Parse("2025-12-15T00:00:00Z")));
        var incoming = BundleVersion.Parse("1.0.0", DateTimeOffset.Parse("2025-12-15T00:00:00Z"));

        var act = () => checker.RecordActivationAsync("tenant-a", "offline-kit", incoming, "sha256:new");
        await act.Should().ThrowAsync<InvalidOperationException>();
    }

    [Fact]
    public async Task RecordActivationAsync_WhenForced_ShouldWriteForceFields()
    {
        var store = new InMemoryBundleVersionStore();
        await store.UpsertAsync(new BundleVersionRecord(
            TenantId: "tenant-a",
            BundleType: "offline-kit",
            VersionString: "2.0.0",
            Major: 2,
            Minor: 0,
            Patch: 0,
            Prerelease: null,
            BundleCreatedAt: DateTimeOffset.Parse("2025-12-14T00:00:00Z"),
            BundleDigest: "sha256:current",
            ActivatedAt: DateTimeOffset.Parse("2025-12-14T00:00:00Z"),
            WasForceActivated: false,
            ForceActivateReason: null));

        var checker = new VersionMonotonicityChecker(store, new FixedTimeProvider(DateTimeOffset.Parse("2025-12-15T00:00:00Z")));
        var incoming = BundleVersion.Parse("1.0.0", DateTimeOffset.Parse("2025-12-15T00:00:00Z"));

        await checker.RecordActivationAsync(
            "tenant-a",
            "offline-kit",
            incoming,
            "sha256:new",
            wasForceActivated: true,
            forceActivateReason: "manual rollback permitted");

        var current = await store.GetCurrentAsync("tenant-a", "offline-kit");
        current.Should().NotBeNull();
        current!.WasForceActivated.Should().BeTrue();
        current.ForceActivateReason.Should().Be("manual rollback permitted");
        current.BundleDigest.Should().Be("sha256:new");
    }

    private sealed class InMemoryBundleVersionStore : IBundleVersionStore
    {
        private BundleVersionRecord? _current;
        private readonly List<BundleVersionRecord> _history = new();

        public Task<BundleVersionRecord?> GetCurrentAsync(string tenantId, string bundleType, CancellationToken ct = default)
        {
            return Task.FromResult(_current is not null &&
                    _current.TenantId.Equals(tenantId, StringComparison.Ordinal) &&
                    _current.BundleType.Equals(bundleType, StringComparison.Ordinal)
                ? _current
                : null);
        }

        public Task UpsertAsync(BundleVersionRecord record, CancellationToken ct = default)
        {
            _current = record;
            _history.Insert(0, record);
            return Task.CompletedTask;
        }

        public Task<IReadOnlyList<BundleVersionRecord>> GetHistoryAsync(string tenantId, string bundleType, int limit = 10, CancellationToken ct = default)
        {
            var items = _history
                .Where(r => r.TenantId.Equals(tenantId, StringComparison.Ordinal) && r.BundleType.Equals(bundleType, StringComparison.Ordinal))
                .Take(limit)
                .ToArray();

            return Task.FromResult<IReadOnlyList<BundleVersionRecord>>(items);
        }
    }

    private sealed class FixedTimeProvider : TimeProvider
    {
        private readonly DateTimeOffset _utcNow;

        public FixedTimeProvider(DateTimeOffset utcNow)
        {
            _utcNow = utcNow;
        }

        public override DateTimeOffset GetUtcNow() => _utcNow;
    }
}