using Microsoft.Extensions.Logging.Abstractions;
using Opc.Ua;
using Opc.Ua.Server;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
using ZB.MOM.WW.OtOpcUa.Core.Authorization;
using ZB.MOM.WW.OtOpcUa.OpcUaServer.Security;

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

/// <summary>
///     Gitea #563 (arch-review 03/S19 residual R2) — with <c>Security:Acl:Enabled</c> <b>off</b>, the two
///     server-wide role gates (<c>WriteOperate</c> on Value writes, <c>AlarmAck</c> on the Part 9 methods)
///     re-check that the session's API key is still usable on every call.
/// </summary>
/// <remarks>
///     <para>
///         A session's roles are resolved once, at activation, from the key's grants. Before #563 nothing
///         with the flag off ever looked at the key again, so a key whose <c>ExpiresUtc</c> passed — or that
///         a deployment disabled — kept <c>WriteOperate</c> / <c>AlarmAck</c> until the client chose to
///         disconnect, which on a machine-to-machine data plane can be never.
///     </para>
///     <para>
///         Every test here is an <b>allow-then-deny</b> on the same session: the first call proves the
///         session genuinely holds the role, so the later denial can only have come from the key check. A
///         deny-only test would pass against a gate that denied everything.
///     </para>
/// </remarks>
public sealed class NodeManagerKeyUsabilityGateTests : IDisposable
{
    private const string Cluster = "SITE-A";
    private const string Principal = "scadabridge";
    private const string KeyId = "k-563";

    private static readonly DateTime Start = new(2026, 10, 7, 12, 0, 0, DateTimeKind.Utc);

    private static CancellationToken Ct => TestContext.Current.CancellationToken;

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

    /// <summary>
    ///     THE #563 test for the write gate: ACL off, a key-carrying session holding <c>WriteOperate</c>
    ///     writes; only the clock moves past <c>ExpiresUtc</c>; the next write is refused and never reaches
    ///     the device.
    /// </summary>
    [Fact]
    public async Task An_expired_key_loses_its_write_role_on_the_clock_with_acl_off()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            var gateway = new RecordingWriteGateway();
            nm.NodeWriteGateway = gateway;
            var clock = new FakeClock(Start);
            var (state, authorizer) = Wire(nm, clock, Key(expiresUtc: Start.AddMinutes(10)));
            authorizer.Enabled.ShouldBeFalse();
            var nodeId = Writable(nm, "Plant/Modbus/dev1/Setpoint");
            var identity = KeyIdentity(OpcUaDataPlaneRoles.WriteOperate);

            Write(nm, identity, nodeId, 1f)[0].StatusCode.Code.ShouldBe(StatusCodes.Good);

            clock.Advance(TimeSpan.FromMinutes(20));

            Write(nm, identity, nodeId, 2f)[0].StatusCode.Code.ShouldBe(StatusCodes.BadUserAccessDenied);
            gateway.Writes.Count.ShouldBe(1);
            state.Current.GenerationId.ShouldBe(1); // no deployment moved anything — only the clock did
        }
        finally { await host.DisposeAsync(); }
    }

    /// <summary>
    ///     The deployment axis of the same gate: a deployment that disables the key strips the write role
    ///     from the session that is already open.
    /// </summary>
    [Fact]
    public async Task A_key_disabled_by_a_deployment_loses_its_write_role_with_acl_off()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            var gateway = new RecordingWriteGateway();
            nm.NodeWriteGateway = gateway;
            var (state, _) = Wire(nm, new FakeClock(Start), Key(expiresUtc: null));
            var nodeId = Writable(nm, "Plant/Modbus/dev1/Setpoint");
            var identity = KeyIdentity(OpcUaDataPlaneRoles.WriteOperate);

            Write(nm, identity, nodeId, 1f)[0].StatusCode.Code.ShouldBe(StatusCodes.Good);

            var disabled = Key(expiresUtc: null);
            disabled.Enabled = false;
            state.Apply(Cluster, "rev-2", [disabled], [], NoScopes);

            Write(nm, identity, nodeId, 2f)[0].StatusCode.Code.ShouldBe(StatusCodes.BadUserAccessDenied);
            gateway.Writes.Count.ShouldBe(1);
        }
        finally { await host.DisposeAsync(); }
    }

    /// <summary>
    ///     Anonymous carries no key, so nothing can expire: an anonymous session granted
    ///     <c>WriteOperate</c> keeps writing however far the clock moves, against a snapshot holding no keys
    ///     at all. Pins that the new check keys on the presence of a key id, not on "is this session in the
    ///     key table".
    /// </summary>
    [Fact]
    public async Task An_anonymous_session_is_unaffected_by_the_key_check()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            var gateway = new RecordingWriteGateway();
            nm.NodeWriteGateway = gateway;
            var clock = new FakeClock(Start);
            Wire(nm, clock);
            var nodeId = Writable(nm, "Plant/Modbus/dev1/Setpoint");
            var anonymous = new RoleCarryingUserIdentity(
                new AnonymousIdentityToken(), [OpcUaDataPlaneRoles.WriteOperate],
                OpcUaPrincipals.Anonymous, apiKeyId: null);

            Write(nm, anonymous, nodeId, 1f)[0].StatusCode.Code.ShouldBe(StatusCodes.Good);
            clock.Advance(TimeSpan.FromDays(400));
            Write(nm, anonymous, nodeId, 2f)[0].StatusCode.Code.ShouldBe(StatusCodes.Good);

            gateway.Writes.Count.ShouldBe(2);
        }
        finally { await host.DisposeAsync(); }
    }

    /// <summary>
    ///     The alarm half: ACL off, a key-carrying session holding <c>AlarmAck</c> acknowledges; the key
    ///     expires by the clock; the next acknowledge is refused and routes nothing.
    /// </summary>
    [Fact]
    public async Task An_expired_key_loses_its_alarm_ack_role_on_the_clock_with_acl_off()
    {
        var (host, server) = await BootAsync();
        try
        {
            var nm = server.NodeManager!;
            var routed = new List<AlarmCommand>();
            nm.AlarmCommandRouter = routed.Add;
            var clock = new FakeClock(Start);
            Wire(nm, clock, Key(expiresUtc: Start.AddMinutes(10)));

            nm.EnsureFolder("eq-1", parentNodeId: null, displayName: "Equipment 1", realm: AddressSpaceRealm.Uns);
            nm.MaterialiseAlarmCondition(
                "alm-1", "eq-1", "HighTemp", "OffNormalAlarm", severity: 700, realm: AddressSpaceRealm.Uns);
            var condition = nm.TryGetAlarmCondition("alm-1")!;
            var ctx = new ServerSystemContext(server.CurrentInstance)
            {
                UserIdentity = KeyIdentity(OpcUaDataPlaneRoles.AlarmAck),
            };

            condition.OnAcknowledge!(ctx, condition, Guid.NewGuid().ToByteArray(), new LocalizedText("1"))
                .ShouldBe(ServiceResult.Good);

            clock.Advance(TimeSpan.FromMinutes(20));

            condition.OnAcknowledge!(ctx, condition, Guid.NewGuid().ToByteArray(), new LocalizedText("2"))
                .StatusCode.Code.ShouldBe(StatusCodes.BadUserAccessDenied);
            routed.Count.ShouldBe(1);
        }
        finally { await host.DisposeAsync(); }
    }

    // ───────────────────────────── helpers ─────────────────────────────

    private static readonly IReadOnlyDictionary<AclScopeRef, IReadOnlyList<NodeAclPath>> NoScopes =
        new Dictionary<AclScopeRef, IReadOnlyList<NodeAclPath>>();

    private static ApiKey Key(DateTime? expiresUtc) => new()
    {
        ApiKeyId = KeyId,
        Name = KeyId,
        SecretHash = "hash",
        Principal = Principal,
        Enabled = true,
        CreatedUtc = Start.AddDays(-1),
        ExpiresUtc = expiresUtc,
    };

    /// <summary>A key-carrying session whose activation-time roles are <paramref name="roles"/>.</summary>
    private static RoleCarryingUserIdentity KeyIdentity(params string[] roles) =>
        new(new UserNameIdentityToken { UserName = "apikey" }, roles, Principal, KeyId);

    /// <summary>
    ///     Wires a production-shaped, flag-OFF authorizer over one applied snapshot. The node manager's
    ///     authority source and the authorizer's are the same instance, as the host wires them.
    /// </summary>
    private static (DataPlaneAuthorityState State, DataPlaneAuthorizer Authorizer) Wire(
        OtOpcUaNodeManager nm, TimeProvider clock, params ApiKey[] keys)
    {
        var state = new DataPlaneAuthorityState();
        state.Apply(Cluster, "rev-1", keys, [], NoScopes);
        var authorizer = new DataPlaneAuthorizer(
            state, new TriePermissionEvaluator(state.Tries), enabled: false, NullLogger.Instance, clock);
        nm.DataPlaneAuthority = state;
        nm.Authorizer = authorizer;
        return (state, authorizer);
    }

    private static NodeId Writable(OtOpcUaNodeManager nm, string rawPath)
    {
        nm.EnsureVariable(rawPath, parentFolderNodeId: null, displayName: rawPath, dataType: "Float",
            writable: true, historianTagname: null, realm: AddressSpaceRealm.Raw);
        return nm.TryGetVariable(rawPath, AddressSpaceRealm.Raw)!.NodeId;
    }

    private static List<ServiceResult> Write(
        OtOpcUaNodeManager nm, IUserIdentity identity, NodeId nodeId, object value)
    {
        var context = new OperationContext(
            new RequestHeader(), secureChannelContext: null, RequestType.Write, identity);
        var writes = new List<WriteValue>
        {
            new()
            {
                NodeId = nodeId,
                AttributeId = Attributes.Value,
                Value = new DataValue(new Variant(value)) { StatusCode = StatusCodes.Good },
            },
        };
        var errors = Enumerable.Repeat<ServiceResult>(null!, writes.Count).ToList();
        nm.Write(context, writes, errors);
        return errors;
    }

    /// <summary>Records what actually reached the device.</summary>
    private sealed class RecordingWriteGateway : IOpcUaNodeWriteGateway
    {
        public List<string> Writes { get; } = [];

        public Task<NodeWriteOutcome> WriteAsync(
            string nodeId, object? value, AddressSpaceRealm realm, CancellationToken ct)
        {
            lock (Writes) Writes.Add(nodeId);
            return Task.FromResult(new NodeWriteOutcome(true, null));
        }
    }

    /// <summary>A hand-advanced clock; the authorizer reads it on every decision.</summary>
    private sealed class FakeClock(DateTime utcNow) : TimeProvider
    {
        private DateTimeOffset _now = new(utcNow, TimeSpan.Zero);

        /// <inheritdoc />
        public override DateTimeOffset GetUtcNow() => _now;

        /// <summary>Moves the clock forward.</summary>
        /// <param name="by">How far forward.</param>
        public void Advance(TimeSpan by) => _now = _now.Add(by);
    }

    private async Task<(OpcUaApplicationHost Host, OtOpcUaSdkServer Server)> BootAsync()
    {
        var applicationUri = $"urn:OtOpcUa.KeyGateTest:{Guid.NewGuid():N}";
        var started = await OpcUaHostStart.StartAsync(
            port => new OpcUaApplicationHost(
                new OpcUaApplicationHostOptions
                {
                    ApplicationName = "OtOpcUa.KeyGateTest",
                    ApplicationUri = applicationUri,
                    OpcUaPort = port,
                    PublicHostname = "localhost",
                    PkiStoreRoot = _pkiRoot,
                },
                NullLogger<OpcUaApplicationHost>.Instance),
            () => new OtOpcUaSdkServer(), Ct);
        var host = started.Host;
        var server = started.Server;
        return (host, server);
    }

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