using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.PlcFamilies;
using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport;
using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Tests.Fakes;

namespace ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests;

/// <summary>
///     Gitea #593 follow-up: a native write the runtime would refuse (a T/C/R status-bit sub-element such as
///     <c>T4:0.DN</c>, or any PLC-5 write) is refused by the DRIVER before a runtime is created — so the
///     refusal holds on a FIRST-TOUCH write too, with zero PCCC requests on the wire.
/// </summary>
/// <remarks>
///     Before the fix the write path created and initialised the tag's runtime first, and a native init is one
///     READ. Against a device whose T/C/R file is missing — the <c>ab_server</c> fixture has none — that read
///     failed, so the write surfaced as <c>BadCommunicationError</c>, evicted the handle and degraded health
///     (the comms-loss watchdog's input) instead of the documented <c>BadNotSupported</c>. These tests run the
///     PRODUCTION <see cref="NativeAbLegacyTagFactory"/> over a real socket to a <see cref="FakeEipServer"/>
///     that, like <c>ab_server</c>, only has an N7 file, and count the PCCC requests it receives.
/// </remarks>
[Trait("Category", "Unit")]
public sealed class NativeAbLegacyRefusedWriteTests
{
    private static readonly byte[] FixedId = [0x07, 0x3D, 0xF3, 0x45, 0x43, 0x50, 0x21];

    /// <summary>A PCCC-only fake: N7 exists (reads answer one zero word, writes succeed); every other file answers
    /// "file does not exist" (STS F0 / EXT 06 → NotFound), as a device without that file would.</summary>
    private sealed class N7OnlyServer : IAsyncDisposable
    {
        private int _pccc;

        public FakeEipServer Server { get; } = new() { ZeroReplyContext = true };

        /// <summary>Execute PCCC requests received (reads AND writes).</summary>
        public int PcccRequests => Volatile.Read(ref _pccc);

        public N7OnlyServer()
        {
            Server.Handler = req =>
            {
                if (FakeEipServer.Command(req) != Ab.Transport.Eip.EncapCommand.SendRRData) return null;
                var cip = FakeEipServer.RequestCip(req);
                Interlocked.Increment(ref _pccc);
                // cip: 4B 02 20 67 24 01 | id(7) | cmd 0F, sts, tns(2), fnc, byteCount, file#, fileType, element, sub
                var fileNumber = cip[19];
                byte[] head = [0xCB, 0x00, 0x00, 0x00, .. FixedId, 0x4F];
                return fileNumber == 7
                    ? FakeEipServer.RRReply(req, [.. head, 0x00, cip[15], cip[16], .. cip[17] == 0xA2 ? new byte[] { 0, 0 } : []])
                    : FakeEipServer.RRReply(req, [.. head, 0xF0, cip[15], cip[16], 0x06]); // EXT 06: file does not exist
            };
        }

        public ValueTask DisposeAsync() => Server.DisposeAsync();
    }

    // These tests call the driver's WriteAsync/ReadAsync directly to pin its OWN status mapping; resilience
    // wrapping (CapabilityInvoker) is out of scope and would retry/mask the very status under test.
#pragma warning disable OTOPCUA0001
    private static async Task<AbLegacyDriver> DriverAsync(
        N7OnlyServer s, AbLegacyPlcFamily family, params AbLegacyTagDefinition[] tags)
    {
        var host = $"ab://127.0.0.1:{s.Server.Port}/1,0";
        var driver = new AbLegacyDriver(new AbLegacyDriverOptions
        {
            Devices = [new AbLegacyDeviceOptions(host, family)],
            RawTags = AbLegacyRawTags.Entries(tags.Select(t => t with { DeviceHostAddress = host }).ToArray()),
            Timeout = TimeSpan.FromSeconds(5),
            Probe = new AbLegacyProbeOptions { Enabled = false },
        }, "drv-refused-write", new NativeAbLegacyTagFactory(new DeviceSessionPool()));
        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
        return driver;
    }

    private static AbLegacyTagDefinition Tag(string name, string address, AbLegacyDataType type, bool writable = false) =>
        new(name, "", address, type, Writable: writable);

    /// <summary>
    ///     A first-touch status-bit write is BadNotSupported with nothing on the wire and health unchanged, even
    ///     though the device has no such file. The positive control (an N7 read on the same driver afterwards) is
    ///     what proves the fake counts requests — and that the refusal left the connection usable.
    /// </summary>
    [Theory]
    [InlineData("T4:0.DN", AbLegacyDataType.Bit)]
    [InlineData("C5:0.CU", AbLegacyDataType.Bit)]
    [InlineData("R6:0.EN", AbLegacyDataType.Bit)]
    [InlineData("T4:0.TT", AbLegacyDataType.Int)] // the refusal follows the ADDRESS, not the authored type
    [InlineData("C5:0.DN", AbLegacyDataType.TimerElement)]
    public async Task A_first_touch_status_bit_write_is_BadNotSupported_with_nothing_on_the_wire(
        string address, AbLegacyDataType type)
    {
        var ct = TestContext.Current.CancellationToken;
        await using var s = new N7OnlyServer();
        var driver = await DriverAsync(s, AbLegacyPlcFamily.Slc500,
            Tag("Scratch", "N7:5", AbLegacyDataType.Int),
            Tag("Bit", address, type, writable: true));
        var health = driver.GetHealth();

        var results = await driver.WriteAsync([new WriteRequest("Bit", true)], ct);

        results.Single().StatusCode.ShouldBe(AbLegacyStatusMapper.BadNotSupported);
        s.PcccRequests.ShouldBe(0);
        driver.GetHealth().ShouldBe(health);

        // Positive control: the same driver does reach this server, and the refusal did not poison anything.
        (await driver.ReadAsync(["Scratch"], ct)).Single().StatusCode.ShouldBe(AbLegacyStatusMapper.Good);
        s.PcccRequests.ShouldBeGreaterThan(0); // init read + read
        driver.GetHealth().State.ShouldBe(DriverState.Healthy);
        await driver.ShutdownAsync(ct);
        s.Server.HandlerErrors.ShouldBeEmpty();
    }

    /// <summary>A PLC-5 write (including a bit-within-word RMW, which would otherwise READ the parent word
    /// first) is refused with nothing on the wire.</summary>
    [Theory]
    [InlineData("N7:5", AbLegacyDataType.Int, (short)7)]
    [InlineData("N7:5/3", AbLegacyDataType.Bit, true)]
    public async Task A_first_touch_PLC5_write_is_BadNotSupported_with_nothing_on_the_wire(
        string address, AbLegacyDataType type, object value)
    {
        var ct = TestContext.Current.CancellationToken;
        await using var s = new N7OnlyServer();
        var driver = await DriverAsync(s, AbLegacyPlcFamily.Plc5, Tag("W", address, type, writable: true));
        var health = driver.GetHealth();

        (await driver.WriteAsync([new WriteRequest("W", value)], ct)).Single().StatusCode
            .ShouldBe(AbLegacyStatusMapper.BadNotSupported);

        s.PcccRequests.ShouldBe(0);
        driver.GetHealth().ShouldBe(health);
        await driver.ShutdownAsync(ct);
    }

    /// <summary>Positive control for the refusal's scope: an ordinary SLC write still reaches the wire, so the
    /// pre-check is not swallowing every write (the T/C/R word sub-element case is
    /// <c>NativeAbLegacyTagRuntimeTests.A_word_sub_element_write_through_the_driver_sends_a_typed_write</c>).</summary>
    [Fact]
    public async Task An_SLC_word_write_still_reaches_the_wire()
    {
        var ct = TestContext.Current.CancellationToken;
        await using var s = new N7OnlyServer();
        var driver = await DriverAsync(s, AbLegacyPlcFamily.Slc500, Tag("W", "N7:5", AbLegacyDataType.Int, writable: true));

        (await driver.WriteAsync([new WriteRequest("W", (short)7)], ct)).Single().StatusCode
            .ShouldBe(AbLegacyStatusMapper.Good);

        s.PcccRequests.ShouldBeGreaterThanOrEqualTo(1);
        await driver.ShutdownAsync(ct);
    }
#pragma warning restore OTOPCUA0001

    [Theory]
    [InlineData("slc500", "T4:0.DN", true)]
    [InlineData("slc500", "C5:0.UA", true)]
    [InlineData("micrologix", "R6:0.FD", true)]
    [InlineData("slc500", "T4:0.PRE", false)]
    [InlineData("slc500", "T4:0.ACC", false)]
    [InlineData("slc500", "R6:0.POS", false)]
    [InlineData("slc500", "N7:0/3", false)]
    [InlineData("slc500", "B3:0/0", false)]
    [InlineData("slc500", "N7:0", false)]
    [InlineData("plc5", "N7:0", true)]
    [InlineData("plc5", "T4:0.PRE", true)]
    [InlineData("slc500", "T4:0.NOPE", false)] // unknown sub-element: refused by the runtime's own address check
    [InlineData("slc500", "garbage", false)]
    public void The_write_refusal_predicate_covers_status_bits_and_PLC5_only(string plc, string tag, bool refused)
    {
        var p = new AbLegacyTagCreateParams("h", 44818, "1,0", plc, tag, TimeSpan.FromSeconds(1));
        (NativeAbLegacyTagRuntime.WriteRefusal(p) is not null).ShouldBe(refused);
        (new NativeAbLegacyTagFactory().WriteRefusal(p) is not null).ShouldBe(refused);
    }
}