using AcDream.Plugin.Abstractions;
using System.Runtime.Loader;

namespace AcDream.Plugin.Tests.Fixtures.HostPlugin;

/// <summary>
/// Cross-host LA5 fixture. It deliberately takes the same path on graphical
/// and no-window hosts: observe the capability, register UI, and subscribe to
/// gameplay events. A headless registry must make the UI call harmless without
/// retaining this instance in the default load context.
/// </summary>
public sealed class HostPlugin : IAcDreamPlugin
{
    private IPluginHost? _host;
    private string? _assemblyDirectory;
    private bool _throwAfterRegistration;
    private bool _throwDuringInitialize;
    private int _entitiesSeen;

    public void Initialize(IPluginHost host)
    {
        _host = host ?? throw new ArgumentNullException(nameof(host));
        _assemblyDirectory = Path.GetDirectoryName(
            typeof(HostPlugin).Assembly.Location);
        _throwAfterRegistration = File.Exists(
            Path.Combine(_assemblyDirectory!, "throw-after-register"));
        _throwDuringInitialize = File.Exists(
            Path.Combine(_assemblyDirectory!, "throw-during-initialize"));
        host.Log.Info($"fixture-initialized:hasUi={host.HasUi}");
        if (_throwDuringInitialize)
        {
            RegisterHostCallbacks(host);
            AssemblyLoadContext.GetLoadContext(typeof(HostPlugin).Assembly)!
                .Unloading += OnUnloading;
            throw new InvalidOperationException(
                "fixture initialize failed after registering UI, entity, and selection callbacks");
        }
    }

    public void Enable()
    {
        IPluginHost host = _host
            ?? throw new InvalidOperationException("The fixture was not initialized.");
        RegisterHostCallbacks(host);
        if (_throwAfterRegistration)
        {
            throw new InvalidOperationException(
                "fixture enable failed after registering UI and events");
        }
        host.Log.Info(
            $"fixture-enabled:hasUi={host.HasUi}:entities={host.State.Entities.Count}");
    }

    public void Disable()
    {
        IPluginHost? host = _host;
        if (host is null)
            return;
        if (_throwAfterRegistration || _throwDuringInitialize)
        {
            throw new InvalidOperationException(
                "fixture disable intentionally refuses cleanup");
        }
        host.Events.EntitySpawned -= OnEntitySpawned;
        host.Selection.Changed -= OnSelectionChanged;
        host.Log.Info($"fixture-disabled:entitiesSeen={_entitiesSeen}");
        _host = null;
    }

    private void RegisterHostCallbacks(IPluginHost host)
    {
        host.Ui.AddMarkupPanel(
            Path.Combine(AppContext.BaseDirectory, "fixture-panel.xml"),
            this);
        host.Events.EntitySpawned += OnEntitySpawned;
        host.Selection.Changed += OnSelectionChanged;
    }

    private void OnEntitySpawned(WorldEntitySnapshot snapshot)
    {
        _entitiesSeen++;
        RecordUnexpectedCallback(snapshot.Id);
    }

    private void OnSelectionChanged(SelectionChangedEvent change) =>
        RecordUnexpectedCallback(change.SelectedObjectId ?? 0u);

    private void RecordUnexpectedCallback(uint objectId)
    {
        if ((_throwAfterRegistration || _throwDuringInitialize)
            && _assemblyDirectory is not null)
        {
            File.AppendAllText(
                Path.Combine(_assemblyDirectory, "unexpected-callback"),
                $"{objectId}{Environment.NewLine}");
        }
    }

    private void OnUnloading(AssemblyLoadContext context)
    {
        IPluginHost host = _host!;
        bool uiClosed = Rejects(() => host.Ui.AddMarkupPanel(
            Path.Combine(AppContext.BaseDirectory, "unloading-panel.xml"),
            this));
        bool eventsClosed = Rejects(() =>
        {
            host.Events.EntitySpawned += OnEntitySpawned;
        });
        bool selectionClosed = Rejects(() =>
        {
            host.Selection.Changed += OnSelectionChanged;
        });
        File.WriteAllText(
            Path.Combine(_assemblyDirectory!, "unload-observation"),
            $"ui={uiClosed};events={eventsClosed};selection={selectionClosed}");
    }

    private static bool Rejects(Action action)
    {
        try
        {
            action();
            return false;
        }
        catch (ObjectDisposedException)
        {
            return true;
        }
    }
}