using Microsoft.Extensions.Logging.Abstractions;
using Opc.Ua;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;

/// <summary>
///     Write-outcome self-correction — the BEHAVIOURAL half of the failed-device-write surfacing
///     (the pure decision tables live in <see cref="EquipmentWriteGateTests"/>). Boots a real
///     <see cref="OtOpcUaSdkServer"/> through <see cref="OpcUaApplicationHost"/> (the same harness
///     <see cref="NodeManagerHistorizeTests"/> uses) so the continuation runs against a live node
///     manager (real <c>Lock</c> + <c>SystemContext</c> + <c>Server</c>), and drives
///     <see cref="OtOpcUaNodeManager.RevertOptimisticWriteIfNeeded"/> +
///     <see cref="OtOpcUaNodeManager.BuildWriteFailureAuditEvent"/> directly:
///     <list type="bullet">
///         <item>Item B (Bad-quality blip + settle): a FAILED outcome on a node still holding the
///         optimistic value settles the node back to its prior value/status; SUCCESS / a moved-on poll
///         leave the node untouched.</item>
///         <item>Item C (AuditWriteUpdateEvent): the built audit event-state carries SourceNode=node,
///         AttributeId=Value, OldValue=prior, NewValue=attempted, ClientUserId=writer, Status=false, and
///         the device Reason in its Message. (The end-to-end <c>Server.ReportEvent</c> dispatch needs a
///         subscribed event monitored-item to observe — the nearest deterministic seam is the builder.)</item>
///     </list>
///     <para>
///         Coverage boundary (deliberate): Item C asserts the audit-event <i>builder</i> in isolation,
///         not its single call-site wiring inside <see cref="OtOpcUaNodeManager.RevertOptimisticWriteIfNeeded"/>
///         (line ~1107). Observing that wiring end-to-end would require a subscribed event monitored-item;
///         the one in-lock builder call is covered by inspection + the production-proven path (shipped
///         <c>bb59fd4e</c>). If a second audit call-site is ever added, promote this to an observed-event test.
///     </para>
/// </summary>
public sealed class NodeManagerWriteRevertTests : IDisposable
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    private readonly string _pkiRoot = Path.Combine(
        Path.GetTempPath(),
        $"otopcua-write-revert-{Guid.NewGuid():N}");

    // ───────────────────────────── Item B — Bad-quality blip + settle ─────────────────────────────

    /// <summary>(B1) A FAILED device-write outcome on a node that still holds the optimistic value SETTLES the
    /// node back to its captured prior value + prior status (the transient Bad blip coalesces within one
    /// publishing interval — see the method remarks — so we assert the observable settled state).</summary>
    [Fact]
    public async Task Failed_outcome_settles_node_back_to_prior_value_and_status()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        nm.EnsureVariable("eq-1/sp", parentFolderNodeId: null, displayName: "Sp", dataType: "Int32", writable: true);
        // Prior state = Good 7; the SDK then optimistically applied 42 (the write the device will reject).
        nm.WriteValue("eq-1/sp", 7, OpcUaQuality.Good, DateTime.UtcNow);
        var node = nm.TryGetVariable("eq-1/sp")!;
        node.Value = 42; // simulate the SDK's optimistic apply of the rejected write

        nm.RevertOptimisticWriteIfNeeded(
            "eq-1/sp",
            outcome: new NodeWriteOutcome(false, "device rejected register 42"),
            optimisticValue: 42,
            priorValue: 7,
            priorStatus: StatusCodes.Good,
            clientUserId: "op");

        node.Value.ShouldBe(7);                              // settled back to prior value
        node.StatusCode.ShouldBe((StatusCode)StatusCodes.Good); // settled back to prior status (NOT stuck Bad)

        await host.DisposeAsync();
    }

    /// <summary>(B2) A SUCCESS outcome NEVER reverts — the optimistic value stands (the next poll re-confirms
    /// it via the normal WriteValue path).</summary>
    [Fact]
    public async Task Successful_outcome_leaves_optimistic_value()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        nm.EnsureVariable("eq-1/sp", parentFolderNodeId: null, displayName: "Sp", dataType: "Int32", writable: true);
        nm.WriteValue("eq-1/sp", 7, OpcUaQuality.Good, DateTime.UtcNow);
        var node = nm.TryGetVariable("eq-1/sp")!;
        node.Value = 42;

        nm.RevertOptimisticWriteIfNeeded(
            "eq-1/sp",
            outcome: new NodeWriteOutcome(true, null),
            optimisticValue: 42, priorValue: 7, priorStatus: StatusCodes.Good, clientUserId: "op");

        node.Value.ShouldBe(42); // success ⇒ optimistic value stands

        await host.DisposeAsync();
    }

    /// <summary>(B3) A failed outcome where a fresh driver poll already moved the node OFF the optimistic value
    /// does NOT clobber the poll — the node keeps the fresh polled value (the still-holds-optimistic guard).</summary>
    [Fact]
    public async Task Failed_outcome_does_not_clobber_a_fresh_poll()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        nm.EnsureVariable("eq-1/sp", parentFolderNodeId: null, displayName: "Sp", dataType: "Int32", writable: true);
        nm.WriteValue("eq-1/sp", 7, OpcUaQuality.Good, DateTime.UtcNow);
        var node = nm.TryGetVariable("eq-1/sp")!;
        node.Value = 99; // a fresh poll already republished the confirmed register value (NOT the optimistic 42)

        nm.RevertOptimisticWriteIfNeeded(
            "eq-1/sp",
            outcome: new NodeWriteOutcome(false, "device rejected"),
            optimisticValue: 42, priorValue: 7, priorStatus: StatusCodes.Good, clientUserId: "op");

        node.Value.ShouldBe(99); // poll value preserved — not reverted to 7

        await host.DisposeAsync();
    }

    /// <summary>(B4) An unknown node id (rebuilt/removed in the interim) is a no-op — the continuation must not
    /// throw out of its fire-and-forget body.</summary>
    [Fact]
    public async Task Failed_outcome_on_missing_node_is_a_noop()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        Should.NotThrow(() => nm.RevertOptimisticWriteIfNeeded(
            "eq-1/gone",
            outcome: new NodeWriteOutcome(false, "device rejected"),
            optimisticValue: 42, priorValue: 7, priorStatus: StatusCodes.Good, clientUserId: "op"));

        await host.DisposeAsync();
    }

    // ───────────────────────────── Item C — AuditWriteUpdateEvent builder ─────────────────────────────

    /// <summary>(C1) The built audit event reflects the rejected write: SourceNode = the node, AttributeId =
    /// Value, OldValue = prior, NewValue = attempted, ClientUserId = the writer, the AuditEvent Status boolean
    /// = false (failed), and the device Reason is carried in the Message.</summary>
    [Fact]
    public async Task Built_audit_event_reflects_the_failed_write()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        nm.EnsureVariable("eq-1/sp", parentFolderNodeId: null, displayName: "Sp", dataType: "Int32", writable: true);
        nm.WriteValue("eq-1/sp", 7, OpcUaQuality.Good, DateTime.UtcNow);
        var node = nm.TryGetVariable("eq-1/sp")!;

        var audit = nm.BuildWriteFailureAuditEvent(
            node,
            outcome: new NodeWriteOutcome(false, "FC06 rejected"),
            optimisticValue: 42,
            priorValue: 7,
            clientUserId: "op");

        audit.ShouldNotBeNull();
        audit.SourceNode.Value.ShouldBe(node.NodeId);
        audit.AttributeId.Value.ShouldBe((uint)Attributes.Value);
        audit.OldValue.Value.ShouldBe(7);
        audit.NewValue.Value.ShouldBe(42);
        audit.ClientUserId.Value.ShouldBe("op");
        audit.Status.Value.ShouldBeFalse();           // AuditEvent Status = false ⇒ the write failed
        audit.Message.Value.Text.ShouldContain("FC06 rejected"); // device Reason carried in the Message

        await host.DisposeAsync();
    }

    /// <summary>(C2) When the device gives no Reason, the audit Message still carries a sensible default
    /// ("device write rejected") rather than an empty/null message.</summary>
    [Fact]
    public async Task Built_audit_event_uses_default_reason_when_none_supplied()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        nm.EnsureVariable("eq-1/sp", parentFolderNodeId: null, displayName: "Sp", dataType: "Int32", writable: true);
        nm.WriteValue("eq-1/sp", 7, OpcUaQuality.Good, DateTime.UtcNow);
        var node = nm.TryGetVariable("eq-1/sp")!;

        var audit = nm.BuildWriteFailureAuditEvent(
            node,
            outcome: new NodeWriteOutcome(false, null),
            optimisticValue: 42, priorValue: 7, clientUserId: "op");

        audit.Message.Value.Text.ShouldContain("device write rejected");

        await host.DisposeAsync();
    }

    private async Task<(OpcUaApplicationHost Host, OtOpcUaSdkServer Server)> BootAsync()
    {
        var host = new OpcUaApplicationHost(
            new OpcUaApplicationHostOptions
            {
                ApplicationName = "OtOpcUa.WriteRevertTest",
                ApplicationUri = $"urn:OtOpcUa.WriteRevertTest:{Guid.NewGuid():N}",
                OpcUaPort = AllocateFreePort(),
                PublicHostname = "localhost",
                PkiStoreRoot = _pkiRoot,
            },
            NullLogger<OpcUaApplicationHost>.Instance);

        var server = new OtOpcUaSdkServer();
        await host.StartAsync(server, Ct);
        return (host, server);
    }

    private static int AllocateFreePort()
    {
        using var listener = new System.Net.Sockets.TcpListener(System.Net.IPAddress.Loopback, 0);
        listener.Start();
        var port = ((System.Net.IPEndPoint)listener.LocalEndpoint).Port;
        listener.Stop();
        return port;
    }

    /// <summary>Cleans up the PKI root directory.</summary>
    public void Dispose()
    {
        if (Directory.Exists(_pkiRoot))
        {
            try { Directory.Delete(_pkiRoot, recursive: true); }
            catch { /* best-effort cleanup */ }
        }
    }
}