using Akka.Actor;
using Akka.Cluster;
using Akka.Configuration;
using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.Secrets.Abstractions;
using ZB.MOM.WW.Secrets.Replication;
using ZB.MOM.WW.Secrets.Replicator.AkkaDotNet.Tests.Fakes;
using ZB.MOM.WW.Secrets.Sqlite;

namespace ZB.MOM.WW.Secrets.Replicator.AkkaDotNet.Tests;

/// <summary>
/// Two real cluster nodes, two real SQLite stores, real remoting over loopback — the gate the G-7
/// design called for, run in-process so it belongs to the ordinary offline suite instead of needing
/// a deployed rig.
/// </summary>
/// <remarks>
/// Nothing here is faked: each node runs its own <see cref="ActorSystem"/> with Akka.Remote on its
/// own port, they form a cluster, and rows travel through the actual serializer and the actual
/// distributed pub/sub mediator. A mock-based test of this behaviour would prove almost nothing —
/// the failure modes worth catching (self-echo, sender loss across the mediator, tombstones that do
/// not propagate, a partition that never re-converges) only appear when messages really cross nodes.
/// </remarks>
public sealed class TwoNodeClusterReplicationTests : IAsyncLifetime
{
    private readonly List<string> _dbPaths = [];
    private ActorSystem _systemA = null!;
    private ActorSystem _systemB = null!;
    private SqliteSecretStore _storeA = null!;
    private SqliteSecretStore _storeB = null!;
    private ISecretStore _writableA = null!;
    private IActorRef _replicatorB = null!;

    // Short so anti-entropy assertions do not dominate the suite's runtime.
    private static readonly TimeSpan AnnounceInterval = TimeSpan.FromMilliseconds(300);
    private static readonly TimeSpan Patience = TimeSpan.FromSeconds(20);

    public async Task InitializeAsync()
    {
        _storeA = CreateStore();
        _storeB = CreateStore();

        // Port 0 lets the OS assign free ports, so parallel test runs cannot collide.
        _systemA = ActorSystem.Create("zb-secrets-cluster", ClusterConfig(port: 0));
        int portA = ClusterPort(_systemA);

        // Node A seeds itself; node B joins it.
        _systemA.Dispose();
        _systemA = ActorSystem.Create("zb-secrets-cluster", ClusterConfig(portA, seedPort: portA));
        _systemB = ActorSystem.Create("zb-secrets-cluster", ClusterConfig(port: 0, seedPort: portA));

        await AwaitClusterUpAsync(_systemA, expectedMembers: 2);
        await AwaitClusterUpAsync(_systemB, expectedMembers: 2);

        IActorRef replicatorA = _systemA.ActorOf(
            SecretReplicationActor.Props(_storeA, null, AnnounceInterval), "zb-secret-replication");
        _replicatorB = _systemB.ActorOf(
            SecretReplicationActor.Props(_storeB, null, AnnounceInterval), "zb-secret-replication");

        _writableA = new ReplicatingSecretStore(
            _storeA, new AkkaSecretReplicator(replicatorA), NullLogger<ReplicatingSecretStore>.Instance);

        // The mediator gossips subscriptions between nodes; publishing before both sides are
        // registered would silently drop the message.
        await AwaitBothSubscribedAsync();
    }

    private SqliteSecretStore CreateStore()
    {
        string path = Path.Combine(Path.GetTempPath(), $"zb-akka-{Guid.NewGuid():N}.db");
        _dbPaths.Add(path);
        var factory = new SecretsSqliteConnectionFactory(path);
        new SqliteSecretsStoreMigrator(factory).MigrateAsync(CancellationToken.None).GetAwaiter().GetResult();
        return new SqliteSecretStore(factory);
    }

    private static Config ClusterConfig(int port, int? seedPort = null)
    {
        string seeds = seedPort is null
            ? "[]"
            : $"[\"akka.tcp://zb-secrets-cluster@127.0.0.1:{seedPort}\"]";

        return ConfigurationFactory.ParseString($$"""
            akka {
              loglevel = WARNING
              actor.provider = cluster
              remote.dot-netty.tcp {
                hostname = "127.0.0.1"
                public-hostname = "127.0.0.1"
                port = {{port}}
              }
              cluster {
                seed-nodes = {{seeds}}
                downing-provider-class = "Akka.Cluster.SBR.SplitBrainResolverProvider"
              }
            }
            """).WithFallback(AkkaSecretsReplication.SerializationConfig);
    }

    private static int ClusterPort(ActorSystem system) =>
        Cluster.Get(system).SelfAddress.Port
        ?? throw new InvalidOperationException("Cluster address has no port.");

    private static async Task AwaitClusterUpAsync(ActorSystem system, int expectedMembers)
    {
        Cluster cluster = Cluster.Get(system);
        DateTime deadline = DateTime.UtcNow + Patience;

        while (DateTime.UtcNow < deadline)
        {
            if (cluster.State.Members.Count(m => m.Status == MemberStatus.Up) >= expectedMembers)
            {
                return;
            }

            await Task.Delay(100);
        }

        throw new TimeoutException(
            $"Cluster did not reach {expectedMembers} Up members within {Patience}.");
    }

    // Writes a throwaway secret on A and waits for it to land on B. That round trip is the only
    // reliable signal that pub/sub subscriptions have gossiped across both nodes.
    private async Task AwaitBothSubscribedAsync()
    {
        var probe = new SecretName("warmup/probe");
        DateTime deadline = DateTime.UtcNow + Patience;

        while (DateTime.UtcNow < deadline)
        {
            await _writableA.UpsertAsync(Row("warmup/probe", 0x01), CancellationToken.None);

            if (await WaitForAsync(_storeB, probe, _ => true, TimeSpan.FromMilliseconds(500)))
            {
                await _storeA.DeleteAsync(probe, "warmup", CancellationToken.None);
                await _storeB.DeleteAsync(probe, "warmup", CancellationToken.None);
                return;
            }
        }

        throw new TimeoutException("Nodes did not establish pub/sub subscriptions in time.");
    }

    private static StoredSecret Row(string name, byte marker) => new()
    {
        Name = new SecretName(name),
        ContentType = SecretContentType.Text,
        Ciphertext = [marker],
        Nonce = [1],
        Tag = [2],
        WrappedDek = [3],
        WrapNonce = [4],
        WrapTag = [5],
        KekId = "sha256:shared-kek",
        Revision = 0,
        CreatedUtc = DateTimeOffset.UtcNow,
        UpdatedUtc = DateTimeOffset.UtcNow,
    };

    private static async Task<bool> WaitForAsync(
        ISecretStore store, SecretName name, Func<StoredSecret, bool> predicate, TimeSpan? timeout = null)
    {
        DateTime deadline = DateTime.UtcNow + (timeout ?? Patience);

        while (DateTime.UtcNow < deadline)
        {
            StoredSecret? row = await store.GetAsync(name, CancellationToken.None);

            if (row is not null && predicate(row))
            {
                return true;
            }

            await Task.Delay(50);
        }

        return false;
    }

    [Fact]
    public async Task A_secret_written_on_node_A_becomes_resolvable_on_node_B()
    {
        var name = new SecretName("db/password");
        await _writableA.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeB, name, r => r.Ciphertext[0] == 0xAA),
            "Node B never received the secret written on node A.");
    }

    [Fact]
    public async Task The_ciphertext_arrives_byte_identical()
    {
        var name = new SecretName("app/exact");
        await _writableA.UpsertAsync(Row("app/exact", 0x7F), CancellationToken.None);

        Assert.True(await WaitForAsync(_storeB, name, _ => true));

        StoredSecret onA = (await _storeA.GetAsync(name, CancellationToken.None))!;
        StoredSecret onB = (await _storeB.GetAsync(name, CancellationToken.None))!;

        Assert.Equal(onA.Ciphertext, onB.Ciphertext);
        Assert.Equal(onA.WrappedDek, onB.WrappedDek);
        Assert.Equal(onA.KekId, onB.KekId);
        // Verbatim: the peer keeps the originating node's revision and timestamp, or the row would
        // look newer on B than on A and bounce back.
        Assert.Equal(onA.Revision, onB.Revision);
        Assert.Equal(onA.UpdatedUtc, onB.UpdatedUtc);
    }

    [Fact]
    public async Task A_delete_on_node_A_tombstones_the_row_on_node_B()
    {
        var name = new SecretName("app/doomed");
        await _writableA.UpsertAsync(Row("app/doomed", 0xBB), CancellationToken.None);
        Assert.True(await WaitForAsync(_storeB, name, _ => true));

        await _writableA.DeleteAsync(name, "operator", CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeB, name, r => r.IsDeleted),
            "The delete never propagated to node B.");
    }

    [Fact]
    public async Task An_update_overwrites_the_earlier_value_on_the_peer()
    {
        var name = new SecretName("app/rotating");
        await _writableA.UpsertAsync(Row("app/rotating", 0x01), CancellationToken.None);
        Assert.True(await WaitForAsync(_storeB, name, r => r.Ciphertext[0] == 0x01));

        await _writableA.UpsertAsync(Row("app/rotating", 0x02), CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeB, name, r => r.Ciphertext[0] == 0x02 && r.Revision == 1),
            "Node B did not converge on the updated value.");
    }

    [Fact]
    public async Task Anti_entropy_repairs_a_write_that_never_got_broadcast()
    {
        // Simulates a dropped publish — the write goes straight to node A's store, bypassing the
        // replicator entirely, so the ONLY route to node B is the periodic manifest exchange. This is
        // the case that makes best-effort publishing safe.
        var name = new SecretName("app/missed-broadcast");
        await _storeA.UpsertAsync(Row("app/missed-broadcast", 0xCC), CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeB, name, r => r.Ciphertext[0] == 0xCC),
            "Anti-entropy failed to repair a write that was never broadcast.");
    }

    [Fact]
    public async Task Anti_entropy_pulls_in_the_other_direction_too()
    {
        // The mirror case: node B holds a row node A has never heard of. A cannot request a name it
        // does not know exists, so this only converges if the exchange pushes as well as pulls.
        var name = new SecretName("app/born-on-b");
        await _storeB.UpsertAsync(Row("app/born-on-b", 0xDD), CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeA, name, r => r.Ciphertext[0] == 0xDD),
            "Node A never learned about a secret that originated on node B.");
    }

    [Fact]
    public async Task Anti_entropy_still_works_when_the_store_is_genuinely_asynchronous()
    {
        // Regression guard for a bug the rest of this suite could not see. A local SQLite store
        // usually completes `await` synchronously, so continuations stayed on the actor's mailbox
        // thread and code that touched actor context after an await worked by accident. Wrapping the
        // store so every call really yields makes that illegal access deterministic — this test
        // fails outright if anti-entropy touches actor context across an await.
        SqliteSecretStore backing = CreateStore();
        var slowStore = new GenuinelyAsyncSecretStore(backing);

        _systemB.ActorOf(
            SecretReplicationActor.Props(slowStore, null, AnnounceInterval), "slow-node");

        await _writableA.UpsertAsync(Row("slow/inbound", 0x42), CancellationToken.None);

        Assert.True(
            await WaitForAsync(slowStore, new SecretName("slow/inbound"), r => r.Ciphertext[0] == 0x42),
            "A node whose store is genuinely async never received the secret.");

        // And the other direction, which can ONLY converge through the anti-entropy exchange.
        await backing.UpsertAsync(Row("slow/outbound", 0x43), CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeA, new SecretName("slow/outbound"), r => r.Ciphertext[0] == 0x43),
            "Node A never learned about a secret held by a node whose store is genuinely async.");
    }

    [Fact]
    public async Task A_node_that_joins_late_catches_up_on_everything()
    {
        // Partition-heal / cold-start: the whole reason to choose this transport over a shared store.
        await _writableA.UpsertAsync(Row("bulk/one", 0x11), CancellationToken.None);
        await _writableA.UpsertAsync(Row("bulk/two", 0x22), CancellationToken.None);
        await _writableA.UpsertAsync(Row("bulk/three", 0x33), CancellationToken.None);

        SqliteSecretStore lateStore = CreateStore();
        _systemB.ActorOf(
            SecretReplicationActor.Props(lateStore, null, AnnounceInterval), "late-joiner");

        Assert.True(await WaitForAsync(lateStore, new SecretName("bulk/one"), r => r.Ciphertext[0] == 0x11));
        Assert.True(await WaitForAsync(lateStore, new SecretName("bulk/two"), r => r.Ciphertext[0] == 0x22));
        Assert.True(await WaitForAsync(lateStore, new SecretName("bulk/three"), r => r.Ciphertext[0] == 0x33));
    }

    [Fact]
    public async Task A_broadcast_round_trip_does_not_drift_the_originating_nodes_revision()
    {
        // Note on what this does and does NOT prove: the revision would also stay put if the self-echo
        // filter were removed, because re-applying an identical row ties on (updated_utc, revision)
        // and last-writer-wins rejects a tie. So this covers the drift symptom via defence in depth,
        // not the filter itself. The filter is what stops the echo being forwarded onward, which
        // needs three nodes to observe — worth adding if a third node ever joins this rig.
        var name = new SecretName("app/no-echo");
        await _writableA.UpsertAsync(Row("app/no-echo", 0xEE), CancellationToken.None);
        Assert.True(await WaitForAsync(_storeB, name, _ => true));

        await Task.Delay(AnnounceInterval * 4);

        StoredSecret onA = (await _storeA.GetAsync(name, CancellationToken.None))!;
        Assert.Equal(0, onA.Revision);
    }

    [Fact]
    public async Task A_malformed_row_from_a_peer_is_discarded_without_stalling_replication()
    {
        // Peer input is untrusted: a path-traversing name must be dropped, and — critically — the
        // actor must keep serving everything else afterwards.
        _replicatorB.Tell(new Protocol.SecretRowsMessage(
        [
            new Protocol.SecretRowDto
            {
                Name = "../../etc/passwd",
                ContentType = "Text",
                Ciphertext = [1], Nonce = [1], Tag = [1],
                WrappedDek = [1], WrapNonce = [1], WrapTag = [1],
                KekId = "sha256:x",
                Revision = 0,
                CreatedUtc = DateTimeOffset.UtcNow.ToString("O"),
                UpdatedUtc = DateTimeOffset.UtcNow.ToString("O"),
            },
        ]));

        var name = new SecretName("app/after-malformed");
        await _writableA.UpsertAsync(Row("app/after-malformed", 0x5A), CancellationToken.None);

        Assert.True(
            await WaitForAsync(_storeB, name, r => r.Ciphertext[0] == 0x5A),
            "Replication stalled after a malformed row was received.");
    }

    public async Task DisposeAsync()
    {
        await CoordinatedShutdown.Get(_systemA).Run(CoordinatedShutdown.ClrExitReason.Instance);
        await CoordinatedShutdown.Get(_systemB).Run(CoordinatedShutdown.ClrExitReason.Instance);

        Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();

        foreach (string db in _dbPaths)
        {
            foreach (string path in new[] { db, db + "-wal", db + "-shm" })
            {
                try
                {
                    if (File.Exists(path))
                    {
                        File.Delete(path);
                    }
                }
                catch (IOException)
                {
                    // Best-effort temp cleanup.
                }
            }
        }
    }
}