using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Client.Shared.Models;
using ZB.MOM.WW.OtOpcUa.Client.UI.Services;
using ZB.MOM.WW.OtOpcUa.Client.UI.Tests.Fakes;
using ZB.MOM.WW.OtOpcUa.Client.UI.ViewModels;

namespace ZB.MOM.WW.OtOpcUa.Client.UI.Tests;

public class AlarmsViewModelTests
{
    private readonly FakeOpcUaClientService _service;
    private readonly AlarmsViewModel _vm;

    /// <summary>Initializes a new test instance.</summary>
    public AlarmsViewModelTests()
    {
        _service = new FakeOpcUaClientService();
        var dispatcher = new SynchronousUiDispatcher();
        _vm = new AlarmsViewModel(_service, dispatcher);
    }

    /// <summary>Verifies that SubscribeCommand cannot execute when disconnected.</summary>
    [Fact]
    public void SubscribeCommand_CannotExecute_WhenDisconnected()
    {
        _vm.IsConnected = false;
        _vm.SubscribeCommand.CanExecute(null).ShouldBeFalse();
    }

    /// <summary>Verifies that SubscribeCommand cannot execute when already subscribed.</summary>
    [Fact]
    public void SubscribeCommand_CannotExecute_WhenAlreadySubscribed()
    {
        _vm.IsConnected = true;
        _vm.IsSubscribed = true;
        _vm.SubscribeCommand.CanExecute(null).ShouldBeFalse();
    }

    /// <summary>Verifies that SubscribeCommand can execute when connected and not subscribed.</summary>
    [Fact]
    public void SubscribeCommand_CanExecute_WhenConnectedAndNotSubscribed()
    {
        _vm.IsConnected = true;
        _vm.IsSubscribed = false;
        _vm.SubscribeCommand.CanExecute(null).ShouldBeTrue();
    }

    /// <summary>Verifies that SubscribeCommand sets IsSubscribed flag.</summary>
    [Fact]
    public async Task SubscribeCommand_SetsIsSubscribed()
    {
        _vm.IsConnected = true;

        await _vm.SubscribeCommand.ExecuteAsync(null);

        _vm.IsSubscribed.ShouldBeTrue();
        _service.SubscribeAlarmsCallCount.ShouldBe(1);
    }

    /// <summary>Verifies that UnsubscribeCommand cannot execute when not subscribed.</summary>
    [Fact]
    public void UnsubscribeCommand_CannotExecute_WhenNotSubscribed()
    {
        _vm.IsConnected = true;
        _vm.IsSubscribed = false;
        _vm.UnsubscribeCommand.CanExecute(null).ShouldBeFalse();
    }

    /// <summary>Verifies that UnsubscribeCommand clears IsSubscribed flag.</summary>
    [Fact]
    public async Task UnsubscribeCommand_ClearsIsSubscribed()
    {
        _vm.IsConnected = true;
        await _vm.SubscribeCommand.ExecuteAsync(null);

        await _vm.UnsubscribeCommand.ExecuteAsync(null);

        _vm.IsSubscribed.ShouldBeFalse();
        _service.UnsubscribeAlarmsCallCount.ShouldBe(1);
    }

    /// <summary>Verifies that RefreshCommand calls the service.</summary>
    [Fact]
    public async Task RefreshCommand_CallsService()
    {
        _vm.IsConnected = true;
        _vm.IsSubscribed = true;

        await _vm.RefreshCommand.ExecuteAsync(null);

        _service.RequestConditionRefreshCallCount.ShouldBe(1);
    }

    /// <summary>Verifies that RefreshCommand cannot execute when not subscribed.</summary>
    [Fact]
    public void RefreshCommand_CannotExecute_WhenNotSubscribed()
    {
        _vm.IsConnected = true;
        _vm.IsSubscribed = false;
        _vm.RefreshCommand.CanExecute(null).ShouldBeFalse();
    }

    /// <summary>Verifies that alarm events are added to the collection.</summary>
    [Fact]
    public void AlarmEvent_AddsToCollection()
    {
        var alarm = new AlarmEventArgs(
            "Source1", "HighAlarm", 500, "Temperature high",
            true, true, false, DateTime.UtcNow);

        _service.RaiseAlarmEvent(alarm);

        _vm.AlarmEvents.Count.ShouldBe(1);
        _vm.AlarmEvents[0].SourceName.ShouldBe("Source1");
        _vm.AlarmEvents[0].ConditionName.ShouldBe("HighAlarm");
        _vm.AlarmEvents[0].Severity.ShouldBe((ushort)500);
        _vm.AlarmEvents[0].Message.ShouldBe("Temperature high");
    }

    /// <summary>Verifies that Clear resets the view model state.</summary>
    [Fact]
    public void Clear_ResetsState()
    {
        _vm.IsSubscribed = true;
        _vm.AlarmEvents.Add(new AlarmEventViewModel("Src", "Cond", 100, "Msg", true, true, false, DateTime.UtcNow));

        _vm.Clear();

        _vm.AlarmEvents.ShouldBeEmpty();
        _vm.IsSubscribed.ShouldBeFalse();
    }

    /// <summary>Verifies that Teardown unregisters the event handler.</summary>
    [Fact]
    public void Teardown_UnhooksEventHandler()
    {
        _vm.Teardown();

        var alarm = new AlarmEventArgs(
            "Source1", "HighAlarm", 500, "Test",
            true, true, false, DateTime.UtcNow);
        _service.RaiseAlarmEvent(alarm);

        _vm.AlarmEvents.ShouldBeEmpty();
    }

    /// <summary>Verifies that the default polling interval is 1000ms.</summary>
    [Fact]
    public void DefaultInterval_Is1000()
    {
        _vm.Interval.ShouldBe(1000);
    }

    /// <summary>
    /// Regression test for Client.UI-006 — when SubscribeAlarmsAsync throws, the failure must be
    /// surfaced to the operator via the view model's StatusMessage rather than silently swallowed.
    /// </summary>
    [Fact]
    public async Task Subscribe_OnFailure_SurfacesStatusMessage()
    {
        _vm.IsConnected = true;
        _service.SubscribeAlarmsException = new Exception("Server returned BadSubscriptionIdInvalid");

        await _vm.SubscribeCommand.ExecuteAsync(null);

        _vm.IsSubscribed.ShouldBeFalse();
        _vm.StatusMessage.ShouldNotBeNullOrWhiteSpace();
        _vm.StatusMessage.ShouldContain("BadSubscriptionIdInvalid");
    }
}