using System.Collections.Concurrent;
using Akka.Actor;
using Akka.TestKit.Xunit2;
using Microsoft.Extensions.Logging;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Deployment;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Actors;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Deployment;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Persistence;

namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Actors;

/// <summary>
/// Tests for <see cref="SiteReconciliationActor"/>: the per-node startup self-heal that
/// reports the node's local deployed inventory to central (over the SiteCommunicationActor
/// Ask), fetches the gap (missing/stale configs) over HTTP, guarded-writes them, and only
/// LOGS orphans (never deletes). Best-effort throughout — a central-unreachable Ask or a
/// per-item fetch failure must never crash the actor.
/// </summary>
public class SiteReconciliationActorTests : TestKit, IDisposable
{
    private const string SiteIdentifier = "site-1";
    private const string NodeId = "node-a";

    private readonly SiteStorageService _storage;
    private readonly string _dbFile;

    public SiteReconciliationActorTests()
    {
        _dbFile = Path.Combine(Path.GetTempPath(), $"site-reconcile-test-{Guid.NewGuid():N}.db");
        _storage = new SiteStorageService(
            $"Data Source={_dbFile}", Microsoft.Extensions.Logging.Abstractions.NullLogger<SiteStorageService>.Instance);
        _storage.InitializeAsync().GetAwaiter().GetResult();
    }

    void IDisposable.Dispose()
    {
        Shutdown();
        try { File.Delete(_dbFile); } catch { /* cleanup */ }
    }

    private IActorRef CreateReconciliationActor(
        IActorRef siteCommunicationActor,
        IDeploymentConfigFetcher fetcher,
        ILogger<SiteReconciliationActor>? logger = null,
        TimeSpan? askTimeout = null) =>
        ActorOf(Props.Create(() => new SiteReconciliationActor(
            _storage,
            fetcher,
            siteCommunicationActor,
            SiteIdentifier,
            NodeId,
            logger ?? Microsoft.Extensions.Logging.Abstractions.NullLogger<SiteReconciliationActor>.Instance,
            TimeSpan.FromMilliseconds(50),                 // initial delay — fast for tests
            askTimeout ?? TimeSpan.FromSeconds(5))));       // ask timeout

    [Fact]
    public async Task MissingInstance_IsFetchedAndStored()
    {
        // Local inventory has A@rev1; central reports B is missing → fetch + store B.
        await _storage.StoreDeployedConfigAsync("A", "{\"instanceUniqueName\":\"A\"}", "depA", "rev1", true);

        const string configB = "{\"instanceUniqueName\":\"B\"}";
        var fetcher = new FakeConfigFetcher(_ => Task.FromResult(configB));
        var commProbe = CreateTestProbe();

        CreateReconciliationActor(commProbe, fetcher);

        var req = commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        Assert.Equal(SiteIdentifier, req.SiteIdentifier);
        Assert.Equal(NodeId, req.NodeId);
        Assert.True(req.LocalNameToRevisionHash.TryGetValue("A", out var hashA));
        Assert.Equal("rev1", hashA);

        commProbe.Reply(new ReconcileSiteResponse(
            [new ReconcileGapItem("B", "depB", "rev2", true, "tok-b")],
            [],
            "http://central:9000"));

        await AwaitAssertAsync(async () =>
        {
            var configs = await _storage.GetAllDeployedConfigsAsync();
            var row = Assert.Single(configs, c => c.InstanceUniqueName == "B");
            Assert.Equal(configB, row.ConfigJson);
            Assert.Equal("depB", row.DeploymentId);
            Assert.Equal("rev2", row.RevisionHash);
            Assert.True(row.IsEnabled);
        }, TimeSpan.FromSeconds(5));

        var call = Assert.Single(fetcher.Calls);
        Assert.Equal("http://central:9000", call.BaseUrl);
        Assert.Equal("depB", call.DeploymentId);
        Assert.Equal("tok-b", call.Token);
    }

    [Fact]
    public async Task StaleInstance_IsRefreshed()
    {
        // Local A@rev1; central reports A is stale (now depA2/rev2) → fetch + guarded-write A.
        await _storage.StoreDeployedConfigAsync("A", "{\"old\":true}", "depA", "rev1", true);

        const string configA2 = "{\"instanceUniqueName\":\"A\",\"v\":2}";
        var fetcher = new FakeConfigFetcher(_ => Task.FromResult(configA2));
        var commProbe = CreateTestProbe();

        CreateReconciliationActor(commProbe, fetcher);

        commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        commProbe.Reply(new ReconcileSiteResponse(
            [new ReconcileGapItem("A", "depA2", "rev2", false, "tok-a")],
            [],
            "http://central:9000"));

        await AwaitAssertAsync(async () =>
        {
            var configs = await _storage.GetAllDeployedConfigsAsync();
            var row = Assert.Single(configs, c => c.InstanceUniqueName == "A");
            Assert.Equal(configA2, row.ConfigJson);
            Assert.Equal("depA2", row.DeploymentId);
            Assert.Equal("rev2", row.RevisionHash);
            Assert.False(row.IsEnabled);
        }, TimeSpan.FromSeconds(5));

        var call = Assert.Single(fetcher.Calls);
        Assert.Equal("depA2", call.DeploymentId);
        Assert.Equal("tok-a", call.Token);
    }

    [Fact]
    public async Task Orphan_IsLoggedNotDeleted()
    {
        // Local Z exists; central reports Z as an orphan → log a warning, leave Z in place.
        await _storage.StoreDeployedConfigAsync("Z", "{\"instanceUniqueName\":\"Z\"}", "depZ", "revZ", true);

        var fetcher = new FakeConfigFetcher(_ => Task.FromResult("never"));
        var logger = new CapturingLogger<SiteReconciliationActor>();
        var commProbe = CreateTestProbe();

        CreateReconciliationActor(commProbe, fetcher, logger);

        commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        commProbe.Reply(new ReconcileSiteResponse([], ["Z"], "http://central:9000"));

        // A warning mentioning the orphan name must be logged.
        await AwaitAssertAsync(() =>
        {
            Assert.Contains(logger.Entries, e =>
                e.Level == LogLevel.Warning && e.Message.Contains("Z"));
            return Task.CompletedTask;
        }, TimeSpan.FromSeconds(5));

        // ...and Z is still present (never deleted) and no fetch happened.
        var configs = await _storage.GetAllDeployedConfigsAsync();
        Assert.Contains(configs, c => c.InstanceUniqueName == "Z");
        Assert.Empty(fetcher.Calls);
    }

    [Fact]
    public async Task NoGap_DoesNotFetch()
    {
        // Empty gap and no orphans → the fetcher is never called.
        var fetcher = new FakeConfigFetcher(_ => Task.FromResult("never"));
        var commProbe = CreateTestProbe();

        var actor = CreateReconciliationActor(commProbe, fetcher);

        commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        commProbe.Reply(new ReconcileSiteResponse([], [], "http://central:9000"));

        // Give any (erroneous) continuation time to run, then prove no fetch happened.
        Watch(actor);
        ExpectNoMsg(TimeSpan.FromMilliseconds(500));
        Assert.Empty(fetcher.Calls);
    }

    [Fact]
    public async Task PerItemFetchFailure_DoesNotAbortTheRest()
    {
        // Gap = [Bad, Good]; the Bad fetch throws but Good must still be fetched + stored.
        const string configGood = "{\"instanceUniqueName\":\"Good\"}";
        var fetcher = new FakeConfigFetcher(depId => depId == "depBad"
            ? Task.FromException<string>(new DeploymentConfigFetchException("boom", isSuperseded: false))
            : Task.FromResult(configGood));
        var commProbe = CreateTestProbe();

        var actor = CreateReconciliationActor(commProbe, fetcher);
        Watch(actor);

        commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        commProbe.Reply(new ReconcileSiteResponse(
            [
                new ReconcileGapItem("Bad", "depBad", "revBad", true, "tok-bad"),
                new ReconcileGapItem("Good", "depGood", "revGood", true, "tok-good")
            ],
            [],
            "http://central:9000"));

        await AwaitAssertAsync(async () =>
        {
            var configs = await _storage.GetAllDeployedConfigsAsync();
            var row = Assert.Single(configs, c => c.InstanceUniqueName == "Good");
            Assert.Equal(configGood, row.ConfigJson);
        }, TimeSpan.FromSeconds(5));

        // Bad was attempted but never stored; the actor survived the per-item failure.
        var all = await _storage.GetAllDeployedConfigsAsync();
        Assert.DoesNotContain(all, c => c.InstanceUniqueName == "Bad");
        ExpectNoMsg(TimeSpan.FromMilliseconds(300));
    }

    [Fact]
    public async Task SupersededItem_IsSkippedQuietly_OthersStillApply()
    {
        // Gap = [Gone, Good]; the Gone fetch throws a 404 (superseded/expired). That branch is
        // a quiet skip (logged Info, NOT counted as a failure) — the Good item must still apply
        // and the actor must not crash.
        const string configGood = "{\"instanceUniqueName\":\"Good\"}";
        var fetcher = new FakeConfigFetcher(depId => depId == "depGone"
            ? Task.FromException<string>(new DeploymentConfigFetchException("expired", isSuperseded: true))
            : Task.FromResult(configGood));
        var logger = new CapturingLogger<SiteReconciliationActor>();
        var commProbe = CreateTestProbe();

        var actor = CreateReconciliationActor(commProbe, fetcher, logger);
        Watch(actor);

        commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        commProbe.Reply(new ReconcileSiteResponse(
            [
                new ReconcileGapItem("Gone", "depGone", "revGone", true, "tok-gone"),
                new ReconcileGapItem("Good", "depGood", "revGood", true, "tok-good")
            ],
            [],
            "http://central:9000"));

        await AwaitAssertAsync(async () =>
        {
            var configs = await _storage.GetAllDeployedConfigsAsync();
            var row = Assert.Single(configs, c => c.InstanceUniqueName == "Good");
            Assert.Equal(configGood, row.ConfigJson);
        }, TimeSpan.FromSeconds(5));

        // The superseded item was attempted but never stored, and was logged at Info as a skip
        // (not Error) — and the actor survived.
        var all = await _storage.GetAllDeployedConfigsAsync();
        Assert.DoesNotContain(all, c => c.InstanceUniqueName == "Gone");
        Assert.Contains(logger.Entries, e =>
            e.Level == LogLevel.Information && e.Message.Contains("Gone"));
        Assert.DoesNotContain(logger.Entries, e =>
            e.Level == LogLevel.Error && e.Message.Contains("Gone"));
        ExpectNoMsg(TimeSpan.FromMilliseconds(300));
    }

    [Fact]
    public void CentralAskFails_ActorSurvives()
    {
        // The SiteCommunicationActor probe never replies → the Ask times out. The actor must
        // log + survive (reconcile re-runs on the next startup), not crash.
        var fetcher = new FakeConfigFetcher(_ => Task.FromResult("never"));
        var logger = new CapturingLogger<SiteReconciliationActor>();
        var commProbe = CreateTestProbe();

        var actor = CreateReconciliationActor(
            commProbe, fetcher, logger, askTimeout: TimeSpan.FromMilliseconds(300));
        Watch(actor);

        // The request is sent...
        commProbe.ExpectMsg<ReconcileSiteRequest>(TimeSpan.FromSeconds(5));
        // ...but the probe does NOT reply, forcing an Ask timeout.

        // The actor does not die (no Terminated within the window) and never fetched.
        ExpectNoMsg(TimeSpan.FromSeconds(1));
        Assert.Empty(fetcher.Calls);
    }

    /// <summary>
    /// In-test fake <see cref="IDeploymentConfigFetcher"/>: runs a per-deploymentId behavior
    /// (return config JSON or throw, as a Task) and records every call's coords thread-safely
    /// (the fetch runs on a pool thread).
    /// </summary>
    private sealed class FakeConfigFetcher : IDeploymentConfigFetcher
    {
        private readonly Func<string, Task<string>> _behavior;
        public ConcurrentQueue<(string BaseUrl, string DeploymentId, string Token)> Calls { get; } = new();

        public FakeConfigFetcher(Func<string, Task<string>> behavior) => _behavior = behavior;

        public async Task<string> FetchAsync(
            string centralFetchBaseUrl, string deploymentId, string token, CancellationToken ct)
        {
            Calls.Enqueue((centralFetchBaseUrl, deploymentId, token));
            await Task.Yield();
            return await _behavior(deploymentId);
        }
    }

    /// <summary>Thread-safe capturing logger so tests can assert on emitted warnings.</summary>
    private sealed class CapturingLogger<T> : ILogger<T>
    {
        public ConcurrentQueue<(LogLevel Level, string Message)> Entries { get; } = new();

        IDisposable? ILogger.BeginScope<TState>(TState state) => null;
        public bool IsEnabled(LogLevel logLevel) => true;

        public void Log<TState>(
            LogLevel logLevel, EventId eventId, TState state, Exception? exception,
            Func<TState, Exception?, string> formatter)
            => Entries.Enqueue((logLevel, formatter(state, exception)));
    }
}