using System.Reflection;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.RenderTree;
using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.Web.Infrastructure;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Raw;

/// <summary>
///     Issue #604 / review R3-M1: the error boundary must live INSIDE the interactive scope. These tests
///     drive the real <see cref="PageErrorBoundary"/> through a real <see cref="Renderer"/> (no bUnit in this
///     project): a child that throws while rendering is contained (nothing reaches the renderer's unhandled
///     path, i.e. the circuit survives), "Try again" and a location change both recover, and disposing the
///     boundary unsubscribes from the navigation manager. A structural guard also pins that every
///     interactive page actually wraps its body.
/// </summary>
#pragma warning disable BL0006
// Renderer lives in Microsoft.AspNetCore.Components.RenderTree; subclassing it is the only way to host a
// component without a bUnit dependency (same approach as RawBrowseModalStaleOpenTests).
public sealed class PageErrorBoundaryTests : IDisposable
{
    private readonly FakeNav _nav = new();
    private readonly TestRenderer _renderer;

    public PageErrorBoundaryTests()
    {
        var sp = new ServiceCollection()
            .AddSingleton<NavigationManager>(_nav)
            .AddSingleton<IErrorBoundaryLogger, NullBoundaryLogger>()
            .BuildServiceProvider();
        _renderer = new TestRenderer(sp);
    }

    [Fact]
    public async Task A_throw_in_the_page_body_is_contained_and_Try_again_recovers()
    {
        Thrower.ShouldThrow = false;
        await _renderer.RenderRootAsync();
        _renderer.Text.ShouldContain("page body ok");   // positive control: the healthy body renders

        Thrower.ShouldThrow = true;
        await _renderer.Dispatcher.InvokeAsync(() => _renderer.RerenderThrower());

        _renderer.Unhandled.ShouldBeEmpty();             // contained: the circuit would have survived
        _renderer.Text.ShouldContain("This page hit an unexpected error.");
        _renderer.Text.ShouldContain("boom");
        _renderer.Text.ShouldNotContain("page body ok");

        // "Try again" is a live handler, not dead static markup.
        Thrower.ShouldThrow = false;
        _renderer.LastOnClickHandlerId.ShouldNotBe(0UL);
        await _renderer.Dispatcher.InvokeAsync(() =>
            _renderer.DispatchEventAsync(_renderer.LastOnClickHandlerId, null, new EventArgs()));

        _renderer.Text.ShouldContain("page body ok");
        _renderer.Unhandled.ShouldBeEmpty();
    }

    [Fact]
    public async Task A_location_change_recovers_a_tripped_boundary()
    {
        Thrower.ShouldThrow = false;
        await _renderer.RenderRootAsync();
        Thrower.ShouldThrow = true;
        await _renderer.Dispatcher.InvokeAsync(() => _renderer.RerenderThrower());
        _renderer.Text.ShouldContain("This page hit an unexpected error.");

        Thrower.ShouldThrow = false;
        await _renderer.Dispatcher.InvokeAsync(() => _nav.NavigateTo("http://localhost/other"));
        await _renderer.Dispatcher.InvokeAsync(() => Task.CompletedTask); // let the queued Recover run

        _renderer.Text.ShouldContain("page body ok");
    }

    [Fact]
    public async Task Disposing_the_boundary_unsubscribes_from_navigation()
    {
        Thrower.ShouldThrow = false;
        await _renderer.RenderRootAsync();
        FakeNav.HandlerCount(_nav).ShouldBe(1);          // positive control: it did subscribe

        _renderer.Dispose();
        FakeNav.HandlerCount(_nav).ShouldBe(0);
    }

    [Fact]
    public void Every_interactive_page_wraps_its_body_in_PageErrorBoundary_and_the_layout_does_not_pretend_to()
    {
        var components = ComponentsDir();
        var offenders = new List<string>();
        foreach (var file in Directory.EnumerateFiles(Path.Combine(components, "Pages"), "*.razor", SearchOption.AllDirectories))
        {
            var text = File.ReadAllText(file);
            if (!text.Contains("@rendermode")) { continue; }
            // Same text the router compiles: the wrapper must open before, and close after, the markup.
            var open = text.IndexOf("<PageErrorBoundary>", StringComparison.Ordinal);
            var close = text.LastIndexOf("</PageErrorBoundary>", StringComparison.Ordinal);
            var code = text.IndexOf("\n@code", StringComparison.Ordinal);
            var ok = open > -1 && close > open && (code < 0 || close < code);
            if (!ok) { offenders.Add(Path.GetRelativePath(components, file).Replace('\\', '/')); }
        }

        offenders.ShouldBeEmpty("interactive pages without a PageErrorBoundary wrapper: " + string.Join(", ", offenders));

        // The static layout is not an ancestor of interactive pages: a boundary there is inert.
        File.ReadAllText(Path.Combine(components, "Layout", "MainLayout.razor")).ShouldNotContain("<ErrorBoundary");
    }

    public void Dispose() => _renderer.Dispose();

    private static string ComponentsDir()
    {
        var dir = new DirectoryInfo(AppContext.BaseDirectory);
        while (dir is not null)
        {
            var candidate = Path.Combine(dir.FullName, "src", "Server", "ZB.MOM.WW.OtOpcUa.AdminUI", "Components");
            if (Directory.Exists(candidate)) { return candidate; }
            dir = dir.Parent;
        }
        throw new DirectoryNotFoundException("AdminUI Components directory not found above the test binaries.");
    }

    /// <summary>Throws from its render when <see cref="ShouldThrow"/> is set.</summary>
    private sealed class Thrower : ComponentBase
    {
        public static volatile bool ShouldThrow;

        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder builder)
        {
            if (ShouldThrow) { throw new InvalidOperationException("boom"); }
            builder.AddMarkupContent(0, "page body ok");
        }

        public void Poke() => StateHasChanged();
    }

    private sealed class Host : ComponentBase
    {
        internal Thrower? Child;

        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder builder)
        {
            builder.OpenComponent<PageErrorBoundary>(0);
            builder.AddAttribute(1, nameof(PageErrorBoundary.ChildContent), (RenderFragment)(b =>
            {
                b.OpenComponent<Thrower>(0);
                b.AddComponentReferenceCapture(1, o => Child = (Thrower)o);
                b.CloseComponent();
            }));
            builder.CloseComponent();
        }
    }

    private sealed class FakeNav : NavigationManager
    {
        public FakeNav() => Initialize("http://localhost/", "http://localhost/");

        protected override void NavigateToCore(string uri, NavigationOptions options)
        {
            Uri = uri;
            NotifyLocationChanged(isInterceptedLink: false);
        }

        public static int HandlerCount(NavigationManager nav)
        {
            var field = typeof(NavigationManager).GetField("_locationChanged", BindingFlags.Instance | BindingFlags.NonPublic);
            field.ShouldNotBeNull("NavigationManager's LocationChanged backing field was renamed; update this probe");
            return (field.GetValue(nav) as Delegate)?.GetInvocationList().Length ?? 0;
        }
    }

    private sealed class NullBoundaryLogger : IErrorBoundaryLogger
    {
        public ValueTask LogErrorAsync(Exception exception) => ValueTask.CompletedTask;
    }

    private sealed class TestRenderer(IServiceProvider sp) : Renderer(sp, NullLoggerFactory.Instance)
    {
        private Host? _host;
        private readonly List<string> _text = new();

        public List<Exception> Unhandled { get; } = new();

        public ulong LastOnClickHandlerId { get; private set; }

        public string Text => string.Concat(_text);

        public override Dispatcher Dispatcher { get; } = Dispatcher.CreateDefault();

        public async Task RenderRootAsync()
        {
            await Dispatcher.InvokeAsync(async () =>
            {
                _host = (Host)InstantiateComponent(typeof(Host));
                var id = AssignRootComponentId(_host);
                await RenderRootComponentAsync(id);
            });
        }

        public Task RerenderThrower()
        {
            _host!.Child!.Poke();
            return Task.CompletedTask;
        }

        protected override void HandleException(Exception exception) => Unhandled.Add(exception);

        protected override Task UpdateDisplayAsync(in RenderBatch renderBatch)
        {
            // Each batch replaces the visible text when it carries any: the swap between ChildContent and
            // ErrorContent is a whole-subtree change, so its frames are all in that batch.
            var batchText = new List<string>();
            var frames = renderBatch.ReferenceFrames;
            for (var i = 0; i < frames.Count; i++)
            {
                ref readonly var f = ref frames.Array[i];
                switch (f.FrameType)
                {
                    case RenderTreeFrameType.Text:
                        batchText.Add(f.TextContent);
                        break;
                    case RenderTreeFrameType.Markup:
                        batchText.Add(f.MarkupContent);
                        break;
                    case RenderTreeFrameType.Attribute when f.AttributeEventHandlerId != 0:
                        LastOnClickHandlerId = f.AttributeEventHandlerId;
                        break;
                }
            }
            if (batchText.Count > 0) { _text.Clear(); _text.AddRange(batchText); }
            return Task.CompletedTask;
        }
    }
}