using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.FOCAS;

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

[Trait("Category", "Unit")]
public sealed class FocasMessagesBlockTextFixedTreeTests
{
    private const string Host = "focas://10.0.0.7:8193";

    /// <summary>
    ///     Variant of <see cref="FakeFocasClient"/> that returns configurable
    ///     <see cref="FocasOperatorMessagesInfo"/> + <see cref="FocasCurrentBlockInfo"/>
    ///     snapshots for the F1-e Messages/External/Latest + Program/CurrentBlock
    ///     fixed-tree (issue #261).
    /// </summary>
    private sealed class MessagesAwareFakeFocasClient : FakeFocasClient, IFocasClient
    {
        public FocasOperatorMessagesInfo? Messages { get; set; }
        public FocasCurrentBlockInfo? CurrentBlock { get; set; }

        Task<FocasOperatorMessagesInfo?> IFocasClient.GetOperatorMessagesAsync(CancellationToken ct) =>
            Task.FromResult(Messages);

        Task<FocasCurrentBlockInfo?> IFocasClient.GetCurrentBlockAsync(CancellationToken ct) =>
            Task.FromResult(CurrentBlock);
    }

    [Fact]
    public async Task DiscoverAsync_emits_Messages_External_Latest_and_Program_CurrentBlock_nodes()
    {
        var builder = new RecordingBuilder();
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions(Host, DeviceName: "Mill-1")],
            Tags = [],
            Probe = new FocasProbeOptions { Enabled = false },
        }, "drv-msg", new FakeFocasClientFactory());
        await drv.InitializeAsync("{}", CancellationToken.None);

        await drv.DiscoverAsync(builder, CancellationToken.None);

        builder.Folders.ShouldContain(f => f.BrowseName == "Messages" && f.DisplayName == "Messages");
        builder.Folders.ShouldContain(f => f.BrowseName == "External" && f.DisplayName == "External");
        builder.Folders.ShouldContain(f => f.BrowseName == "Program" && f.DisplayName == "Program");

        var latest = builder.Variables.SingleOrDefault(v =>
            v.Info.FullName == $"{Host}::Messages/External/Latest");
        latest.BrowseName.ShouldBe("Latest");
        latest.Info.DriverDataType.ShouldBe(DriverDataType.String);
        latest.Info.SecurityClass.ShouldBe(SecurityClassification.ViewOnly);

        var block = builder.Variables.SingleOrDefault(v =>
            v.Info.FullName == $"{Host}::Program/CurrentBlock");
        block.BrowseName.ShouldBe("CurrentBlock");
        block.Info.DriverDataType.ShouldBe(DriverDataType.String);
        block.Info.SecurityClass.ShouldBe(SecurityClassification.ViewOnly);
    }

    [Fact]
    public async Task ReadAsync_serves_Messages_Latest_and_CurrentBlock_from_cached_snapshot()
    {
        var fake = new MessagesAwareFakeFocasClient
        {
            Messages = new FocasOperatorMessagesInfo(
            [
                new FocasOperatorMessage(2001, "OPMSG", "TOOL CHANGE READY"),
                new FocasOperatorMessage(3010, "EXTERN", "DOOR OPEN"),
            ]),
            CurrentBlock = new FocasCurrentBlockInfo("G01 X100. Y200. F500."),
        };
        var factory = new FakeFocasClientFactory { Customise = () => fake };
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions(Host)],
            Tags = [],
            Probe = new FocasProbeOptions { Enabled = true, Interval = TimeSpan.FromMilliseconds(50) },
        }, "drv-msg-read", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        await WaitForAsync(async () =>
        {
            var snap = (await drv.ReadAsync(
                [$"{Host}::Program/CurrentBlock"], CancellationToken.None)).Single();
            return snap.StatusCode == FocasStatusMapper.Good;
        }, TimeSpan.FromSeconds(3));

        var refs = new[]
        {
            $"{Host}::Messages/External/Latest",
            $"{Host}::Program/CurrentBlock",
        };
        var snaps = await drv.ReadAsync(refs, CancellationToken.None);

        // "Latest" surfaces the last entry in the message snapshot — issue #261 permits
        // this minimal "latest message" surface in lieu of full ring-buffer coverage.
        snaps[0].Value.ShouldBe("DOOR OPEN");
        snaps[1].Value.ShouldBe("G01 X100. Y200. F500.");
        foreach (var s in snaps) s.StatusCode.ShouldBe(FocasStatusMapper.Good);

        await drv.ShutdownAsync(CancellationToken.None);
    }

    [Fact]
    public async Task ReadAsync_returns_BadCommunicationError_when_caches_are_empty()
    {
        // Probe disabled — neither cache populates; the nodes still resolve as known
        // references but report Bad until the first poll. Mirrors the f1a/f1b/f1c/f1d
        // policy.
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions(Host)],
            Tags = [],
            Probe = new FocasProbeOptions { Enabled = false },
        }, "drv-msg-empty", new FakeFocasClientFactory());
        await drv.InitializeAsync("{}", CancellationToken.None);

        var snaps = await drv.ReadAsync(
            [$"{Host}::Messages/External/Latest", $"{Host}::Program/CurrentBlock"],
            CancellationToken.None);
        snaps[0].StatusCode.ShouldBe(FocasStatusMapper.BadCommunicationError);
        snaps[1].StatusCode.ShouldBe(FocasStatusMapper.BadCommunicationError);
    }

    [Fact]
    public async Task ReadAsync_publishes_empty_string_when_message_snapshot_is_empty()
    {
        // Empty snapshot (CNC reported no active messages) still publishes Good +
        // empty string — operators distinguish "no messages" from "Bad" without
        // having to read separate availability nodes.
        var fake = new MessagesAwareFakeFocasClient
        {
            Messages = new FocasOperatorMessagesInfo([]),
            CurrentBlock = new FocasCurrentBlockInfo(""),
        };
        var factory = new FakeFocasClientFactory { Customise = () => fake };
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions(Host)],
            Tags = [],
            Probe = new FocasProbeOptions { Enabled = true, Interval = TimeSpan.FromMilliseconds(50) },
        }, "drv-msg-empty-snap", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        await WaitForAsync(async () =>
        {
            var snap = (await drv.ReadAsync(
                [$"{Host}::Messages/External/Latest"], CancellationToken.None)).Single();
            return snap.StatusCode == FocasStatusMapper.Good;
        }, TimeSpan.FromSeconds(3));

        var snaps = await drv.ReadAsync(
            [$"{Host}::Messages/External/Latest", $"{Host}::Program/CurrentBlock"],
            CancellationToken.None);
        snaps[0].Value.ShouldBe(string.Empty);
        snaps[0].StatusCode.ShouldBe(FocasStatusMapper.Good);
        snaps[1].Value.ShouldBe(string.Empty);
        snaps[1].StatusCode.ShouldBe(FocasStatusMapper.Good);

        await drv.ShutdownAsync(CancellationToken.None);
    }

    [Fact]
    public async Task FwlibFocasClient_GetOperatorMessages_and_GetCurrentBlock_return_null_when_disconnected()
    {
        // Construction is licence-safe (no DLL load); the unconnected client must
        // short-circuit before P/Invoke. Returns null → driver leaves the cache
        // untouched, matching the policy in f1a/f1b/f1c/f1d.
        var client = new FwlibFocasClient();
        (await client.GetOperatorMessagesAsync(CancellationToken.None)).ShouldBeNull();
        (await client.GetCurrentBlockAsync(CancellationToken.None)).ShouldBeNull();
    }

    [Fact]
    public void TrimAnsiPadding_strips_trailing_nulls_and_spaces_for_round_trip()
    {
        // The CNC right-pads block text + opmsg bodies with NULs or spaces; the
        // managed side trims them so the same message round-trips with stable text
        // (issue #261). Stops at the first NUL so reused buffers don't leak old bytes.
        var buf = new byte[16];
        var bytes = System.Text.Encoding.ASCII.GetBytes("G01 X10 ");
        Array.Copy(bytes, buf, bytes.Length);
        FwlibFocasClient.TrimAnsiPadding(buf).ShouldBe("G01 X10");

        // NUL-terminated mid-buffer with trailing spaces beyond the NUL — trim stops
        // at the NUL so leftover bytes in the rest of the buffer are ignored.
        var buf2 = new byte[32];
        var bytes2 = System.Text.Encoding.ASCII.GetBytes("OPMSG TEXT");
        Array.Copy(bytes2, buf2, bytes2.Length);
        // After NUL the buffer has zeros — already invisible — but explicit space
        // padding before the NUL should be trimmed.
        var buf3 = new byte[32];
        var bytes3 = System.Text.Encoding.ASCII.GetBytes("HELLO     ");
        Array.Copy(bytes3, buf3, bytes3.Length);
        FwlibFocasClient.TrimAnsiPadding(buf2).ShouldBe("OPMSG TEXT");
        FwlibFocasClient.TrimAnsiPadding(buf3).ShouldBe("HELLO");

        // Empty buffer → empty string (no exception).
        FwlibFocasClient.TrimAnsiPadding(new byte[8]).ShouldBe(string.Empty);
    }

    private static async Task WaitForAsync(Func<Task<bool>> condition, TimeSpan timeout)
    {
        var deadline = DateTime.UtcNow + timeout;
        while (!await condition() && DateTime.UtcNow < deadline)
            await Task.Delay(20);
    }

    private sealed class RecordingBuilder : IAddressSpaceBuilder
    {
        public List<(string BrowseName, string DisplayName)> Folders { get; } = new();
        public List<(string BrowseName, DriverAttributeInfo Info)> Variables { get; } = new();

        public IAddressSpaceBuilder Folder(string browseName, string displayName)
        { Folders.Add((browseName, displayName)); return this; }

        public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo info)
        { Variables.Add((browseName, info)); return new Handle(info.FullName); }

        public void AddProperty(string _, DriverDataType __, object? ___) { }

        private sealed class Handle(string fullRef) : IVariableHandle
        {
            public string FullReference => fullRef;
            public IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info) => new NullSink();
        }
        private sealed class NullSink : IAlarmConditionSink { public void OnTransition(AlarmEventArgs args) { } }
    }
}