using Age.Engine.Diagnostics;
using Age.Engine.Sys4;
using Age.Engine.Vm;
using Xunit;

public class NaturalBootIntegrationTests
{
    private sealed class ReachedSc0000Exception : Exception { }

    private sealed class StopAtSc0000Sink : ITraceSink
    {
        public readonly List<string> Entered = new();
        public Action<string>? OnEnter;
        public bool TracingSteps => false;

        public void Emit(in TraceEvent e)
        {
            if (e.Kind == TraceEventKind.FrameEnter && e.Name != null)
            {
                Entered.Add(e.Name);
                OnEnter?.Invoke(e.Name);
                if (e.Name.Equals("SC0000.BIN", StringComparison.OrdinalIgnoreCase))
                    throw new ReachedSc0000Exception();
            }
        }
    }

    private sealed class NewGameInputHost : RecordingHost
    {
        public VirtualMachine Vm = null!;
        private long _now;
        public int TitlePollSleeps;
        private bool _inGameStart;
        private int _gameStartPollSleeps;
        public override long InputClockMilliseconds => _now;

        public void BeginGameStart()
        {
            _inGameStart = true;
            _gameStartPollSleeps = 0;
            Vm.UpdateMouseButtonState(0x1, false);
            Vm.UpdateInputCallbackState(4, false);
            Vm.QueueInputCallback(10);
        }

        public override void Sleep(long duration)
        {
            base.Sleep(duration);
            _now += Math.Max(1, duration);
            if (duration > 1) return;

            // TITLE's first menu entry is Game Start. Hold the pointer over its native 800x600
            // rectangle, then provide one complete primary-button edge to its raw input callback.
            int polls = _inGameStart ? ++_gameStartPollSleeps : ++TitlePollSleeps;
            int cycle = polls % 200;
            if (_inGameStart && polls <= 200) return;
            if (cycle == 1)
            {
                int input = _inGameStart && polls <= 400 ? 0 : 4;
                if (!_inGameStart)
                {
                    Vm.UpdatePointer(400, 300);
                    Vm.UpdateMouseButtonState(0x1, true);
                }
                Vm.UpdateInputCallbackState(input, true);
            }
            // TITLE polls its registered mouse callback every 50 ms and activates on the release edge.
            // Keep the button down through one callback, then release it before the next.
            else if (cycle == 120)
            {
                int input = _inGameStart && polls <= 400 ? 0 : 4;
                if (!_inGameStart) Vm.UpdateMouseButtonState(0x1, false);
                Vm.UpdateInputCallbackState(input, false);
                Vm.QueueInputCallback(10); // native/main-thread release callback unlocks the menu input gate
            }
        }
    }

    [Fact]
    public void System4Root_NewGameSelectionNaturallyCallsSc0000()
    {
        var table = OpcodeTableJson.Load(Paths.OpcodesJson);
        var scripts = Sys4ScriptProvider.Load(table);
        var host = new NewGameInputHost();
        var sink = new StopAtSc0000Sink();
        var vm = new VirtualMachine(scripts.RequireByName("SYSTEM4.BIN"), table, host,
            new VmOptions(MaxSteps: 5_000_000), scripts, sink);
        host.Vm = vm;
        sink.OnEnter = name =>
        {
            if (name.Equals("GAMESTART.BIN", StringComparison.OrdinalIgnoreCase)) host.BeginGameStart();
        };

        var exception = Record.Exception(() => vm.Run());
        Assert.True(exception is ReachedSc0000Exception,
            $"halt={vm.HaltReason}; title_sleeps={host.TitlePollSleeps}; entered={string.Join(",", sink.Entered)}");

        Assert.Equal(new[]
        {
            "SYSTEM4.BIN", "INITCONFIG.BIN", "INIT2.BIN",
        }, sink.Entered.Take(3));
        Assert.Contains("TITLE.BIN", sink.Entered);
        Assert.Contains("GAMESTART.BIN", sink.Entered);
        Assert.Contains("UNITECH.BIN", sink.Entered);
        Assert.Contains("CALCARR.BIN", sink.Entered);
        Assert.Equal("SC0000.BIN", sink.Entered[^1]);
        Assert.Equal(1, vm.Globals.GetValueOrDefault(0));
        Assert.Equal(0x22, vm.Globals.GetValueOrDefault(0x699));
        Assert.Equal(1, vm.Globals.GetValueOrDefault(0x6c1));
    }
}