using System.Net;
using System.Text;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using Opc.Ua;
using Opc.Ua.Client;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Core.Authorization;
using ZB.MOM.WW.OtOpcUa.Host.OpcUa;
using ZB.MOM.WW.OtOpcUa.OpcUaServer.Security;

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

/// <summary>
///     lmxopcua#751 over the wire — session activation hands the authenticator the client's remote endpoint,
///     and the per-client API-key miss budget therefore applies to a real client.
/// </summary>
/// <remarks>
///     The SDK exposes no client address on any public surface; <see cref="SecureChannelRemoteEndpoint"/>
///     reads it from the TCP listener by reflection and degrades to null when that path breaks. These tests are
///     what turn an SDK upgrade that breaks it into a failure instead of a silent fall-back to process-wide
///     accounting.
/// </remarks>
public sealed class ApiKeyMissBudgetPerEndpointTests
{
    [Fact]
    public async Task Session_activation_hands_the_authenticator_the_clients_address()
    {
        var ct = TestContext.Current.CancellationToken;
        var recorder = new RecordingAuthenticator();
        await using var rig = await Rig.StartAsync("RemoteEndpoint", recorder, ct);

        using var session = await rig.ConnectAsync("otua_k-probe_secret", ct);

        recorder.Seen.ShouldNotBeNull("the server must resolve the activating client's endpoint");
        IPAddress.IsLoopback(recorder.Seen!.Address).ShouldBeTrue($"connected from loopback, got {recorder.Seen}");
        recorder.Seen.Port.ShouldBeGreaterThan(0);
    }

    /// <summary>
    ///     The production authenticator over the bounded store: with a per-client burst of 2 and the known-id
    ///     set unavailable, a client's third and fourth unknown keys are refused without reaching the store.
    /// </summary>
    [Fact]
    public async Task A_client_past_its_miss_budget_is_refused_without_a_store_read()
    {
        var ct = TestContext.Current.CancellationToken;
        var inner = new UnlistingStore();
        var options = Options.Create(new ApiKeyOptions
        {
            Username = "apikey", Pepper = "integration-pepper-xxxx", StoreTimeoutMs = 0, StoreCacheSeconds = 0,
        });
        var bounded = new BoundedApiKeyStore(
            inner, options, NullLogger<BoundedApiKeyStore>.Instance, TimeProvider.System,
            new ApiKeyStoreGuardOptions
            {
                MissBurst = 100, MissRefillPerSecond = 0, MissBurstPerEndpoint = 2, MissRefillPerSecondPerEndpoint = 0,
            });
        var authenticator = new ApiKeyOpcUaUserAuthenticator(
            bounded, options, NullLogger<ApiKeyOpcUaUserAuthenticator>.Instance);
        await using var rig = await Rig.StartAsync("MissBudget", authenticator, ct);

        for (var i = 0; i < 4; i++)
        {
            var rejected = await Should.ThrowAsync<ServiceResultException>(
                () => rig.ConnectAsync($"otua_k-guess-{i}_secret", ct));
            rejected.StatusCode.ShouldBe(StatusCodes.BadIdentityTokenRejected);
        }

        inner.FindCalls.ShouldBe(2, "only the client's first two misses may reach the store");
    }

    private sealed class Rig : IAsyncDisposable
    {
        private readonly string _pkiRoot;
        private OpcUaApplicationHost _host = null!;
        private int _port;

        private Rig(string pkiRoot) => _pkiRoot = pkiRoot;

        public static async Task<Rig> StartAsync(string name, IOpcUaUserAuthenticator authenticator, CancellationToken ct)
        {
            var rig = new Rig(Path.Combine(Path.GetTempPath(), $"otopcua-{name}-{Guid.NewGuid():N}"));
            var applicationUri = $"urn:OtOpcUa.{name}.{Guid.NewGuid():N}";
            (rig._host, _) = await OpcUaHostStart.StartAsync(
                port =>
                {
                    rig._port = port;
                    return new OpcUaApplicationHost(
                        new OpcUaApplicationHostOptions
                        {
                            ApplicationName = $"OtOpcUa.{name}",
                            ApplicationUri = applicationUri,
                            OpcUaPort = port,
                            PublicHostname = "127.0.0.1",
                            PkiStoreRoot = rig._pkiRoot,
                            EnabledSecurityProfiles = [OpcUaSecurityProfile.None],
                            AutoAcceptUntrustedClientCertificates = true,
                        },
                        NullLogger<OpcUaApplicationHost>.Instance,
                        authenticator);
                },
                () => new OtOpcUaSdkServer(), ct);
            return rig;
        }

        public async Task<ISession> ConnectAsync(string credential, CancellationToken ct)
        {
            var appConfig = new ApplicationConfiguration
            {
                ApplicationName = "OtOpcUa.MissBudgetClient",
                ApplicationUri = $"urn:OtOpcUa.MissBudgetClient.{Guid.NewGuid():N}",
                ApplicationType = ApplicationType.Client,
                SecurityConfiguration = TestClientSecurity.Build(TestClientSecurity.AllocatePkiRoot()),
                ClientConfiguration = new ClientConfiguration { DefaultSessionTimeout = 60_000 },
            };
            await appConfig.ValidateAsync(ApplicationType.Client, ct);
            appConfig.CertificateValidator.CertificateValidation += (_, e) => e.Accept = true;

            var endpoint = await CoreClientUtils.SelectEndpointAsync(
                appConfig, $"opc.tcp://127.0.0.1:{_port}/OtOpcUa", false, DefaultTelemetry.Create(_ => { }), ct);

            return await new DefaultSessionFactory(DefaultTelemetry.Create(_ => { })).CreateAsync(
                appConfig,
                new ConfiguredEndpoint(null, endpoint, EndpointConfiguration.Create(appConfig)),
                updateBeforeConnect: false,
                checkDomain: false,
                sessionName: "ApiKeyMissBudgetPerEndpointTests",
                sessionTimeout: 60_000,
                identity: new UserIdentity(new UserNameIdentityToken
                {
                    UserName = "apikey",
                    DecryptedPassword = Encoding.UTF8.GetBytes(credential),
                }),
                preferredLocales: null,
                ct: ct);
        }

        public async ValueTask DisposeAsync()
        {
            await _host.DisposeAsync();
            if (Directory.Exists(_pkiRoot))
            {
                try { Directory.Delete(_pkiRoot, recursive: true); }
                catch (IOException) { /* best effort */ }
            }
        }
    }

    /// <summary>Admits every UserName token and records the endpoint the server handed it.</summary>
    private sealed class RecordingAuthenticator : IOpcUaUserAuthenticator
    {
        public IPEndPoint? Seen { get; private set; }

        public Task<OpcUaUserAuthResult> AuthenticateUserNameAsync(string username, string password, CancellationToken ct) =>
            throw new InvalidOperationException("the server must call the endpoint-carrying overload");

        public Task<OpcUaUserAuthResult> AuthenticateUserNameAsync(
            string username, string password, IPEndPoint? remoteEndpoint, CancellationToken ct)
        {
            Seen = remoteEndpoint;
            return Task.FromResult(OpcUaUserAuthResult.AllowKey("probe", [], "k-probe"));
        }
    }

    /// <summary>Holds no keys and cannot list ids, so every lookup is a miss under the budget.</summary>
    private sealed class UnlistingStore : IApiKeyStore
    {
        private int _findCalls;

        public int FindCalls => Volatile.Read(ref _findCalls);

        public Task<ApiKeyLookup?> FindAsync(string apiKeyId, DateTime utcNow, CancellationToken ct)
        {
            Interlocked.Increment(ref _findCalls);
            return Task.FromResult<ApiKeyLookup?>(null);
        }

        public Task<IReadOnlyList<NodeAcl>> FindGrantsAsync(string principal, CancellationToken ct) =>
            Task.FromResult<IReadOnlyList<NodeAcl>>([]);
    }
}