using System.Runtime.InteropServices;
using Brutal.ImGuiApi;
using Brutal.Numerics;
using KSA;

using static Brutal.Logging.DefaultCategory;

namespace OemLoader;

public class MainWindow(string title)
{
    public bool Typing { get; private set; }
    public bool Open;
    public bool DrawRealTrajectory;
    
    private readonly ImInputString _filename = new(short.MaxValue);
    public EphemerisTrajectory? Ephemeris { get; private set; }
    private string? _errorMessage;
    private long _sliderTicks;

    // Assume the ephemeris is for the home body of the system (i.e. Earth), fall back to vehicle's current parent
    // if null
    public IParentBody? ParentBody => Universe.CurrentSystem?.HomeBody ?? Program.ControlledVehicle?.Parent;

    
    private void GoToTime(DateTime time)
    {
        if (Program.ControlledVehicle is null || Ephemeris is not EphemerisTrajectory oem) return;
        var body = ParentBody;
        if (body is null) return;
        
        var orb = oem.OrbitForTime(time, body, Program.ControlledVehicle.Orbit.OrbitLineColor);
        if (orb is null) return;
        var simTime = new SimTime((time - OemLoader.KsaEpoch).TotalSeconds);

        // If the position at the provided time is within the SOI of a child body, transform the orbit to
        // an orbit around the child body.
        // (Code mostly stolen from KSA.KinematicStates.CheckSoiTransitions)
        var posCci = orb.GetStateVectorsAt(simTime).PositionCci;
        foreach (var child in body.Children)
        {
            if (child is not Celestial childCelestial) continue;
            var soi = childCelestial.SphereOfInfluence;
            var childPos = child.GetPositionOrb(simTime).Transform(childCelestial.Orbit.GetOrb2ParentCci());
            var distance = (posCci - childPos).Length();
            
            if (distance > soi) continue;
            var rotation = doubleQuat.Concatenate(childCelestial.GetCci2Orb(), childCelestial.Orbit.Orb2ParentCci)
                .Inverse();
            var newPosition = (posCci - childPos).Transform(rotation);
            var newVelocity = (orb.GetVelocityCciAt(simTime) - childCelestial.GetVelocityCci(simTime)).Transform(rotation);
            orb = Orbit.CreateFromStateCci(childCelestial, simTime, newPosition, newVelocity, orb.OrbitLineColor);
        }
        
        // Go to the specified time (thanks to UniversePatch.ApplyVehicleSolversTranspiler this works
        // even for negative values of dt)
        var dt = simTime.Seconds() - Universe.GetElapsedSeconds();
        // This is similar to the implementation of the stock `simulate` console command, but we
        // reset the simulation speed to 1x to avoid the bug in that command where the time step
        // gets multiplied by the simulation speed
        var step = Universe.GetJobSimStep(dt);
        Universe.ApplyVehicleSolvers();
        Universe.ApplyOrbitSolvers();
        Universe.ResetSimulationSpeed();
        Universe.ExecuteNextOrbitSolvers(dt, step);
        Universe.ExecuteNextVehicleSolvers(dt, step);
        Universe.ApplyVehicleSolvers();
        Universe.ApplyOrbitSolvers();
        // Finally, teleport the vehicle onto the orbit calculated from the ephemeris
        Program.ControlledVehicle.Teleport(orb, null, null);
        Log.Debug($"OemLoader: Jumped to time {time} from ephemeris");
    }
    
    public void Render()
    {
        Typing = false;
        if (!Open || !Program.DrawUI) return;
        
        ImGui.SetNextWindowSize(new float2(500, 300), ImGuiCond.Once);
        ImGui.SetNextWindowSizeConstraints(new float2(200), new float2(2000));
        if (ImGui.Begin(title, ref Open))
        {
            var windows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
            ImGui.InputTextWithHint("OEM file path", windows ? @"C:\Users\User\OEM.asc" : "/home/user/OEM.asc", _filename);
            
            if (ImGui.Button("Load OEM file"))
            {
                try
                {
                    Log.Debug($"OemLoader: Attempting to load ephemeris from {_filename.ToString()}...");
                    Ephemeris = EphemerisTrajectory.ReadFile(_filename.ToString());
                    if (Ephemeris is EphemerisTrajectory oem)
                    {
                        _sliderTicks = oem.StartTime.Ticks;
                        _errorMessage = null;
                        Log.Info($"OemLoader: Loaded ephemeris from {_filename.ToString()}"
                                 + $" ({oem.Count} entries from {oem.StartTime} to {oem.EndTime})");
                    }
                    else
                    {
                        _errorMessage = "Could not find any ephemeris data in file";
                        Log.Warning($"OemLoader: Could not find any ephemeris data in {_filename.ToString()}");
                    }
                }
                catch (Exception e)
                {
                    _errorMessage = $"Failed to open file:\n{e}";
                    Log.Warning($"OemLoader: Failed to open ephemeris file {_filename.ToString()}:\n{e}");
                }
            }

            if (_errorMessage is not null)
            {
                ImGui.TextColored(new float4(0.863f, 0.196f, 0.184f, 1f), _errorMessage);
            }
            
            if (Ephemeris is EphemerisTrajectory traj && Program.ControlledVehicle is not null)
            {
                ImGui.Text($"Loaded ephemeris valid from {traj.StartTime} to {traj.EndTime}");

                ImGui.Checkbox("Draw trajectory", ref DrawRealTrajectory);
                
                var now = DateTime.UtcNow;
                if (traj.StartTime <= now && now <= traj.EndTime)
                {
                    if (ImGui.Button("Go to now"))
                        GoToTime(now);
                }

                var minTicks = traj.StartTime.Ticks;
                var maxTicks = traj.EndTime.Ticks;
                unsafe
                {
                    fixed (long* pTicks = &_sliderTicks)
                        ImGui.SliderScalar(
                            "Time",
                            ImGuiDataType.U64,
                            pTicks,
                            &minTicks,
                            &maxTicks,
                            "",
                            ImGuiSliderFlags.AlwaysClamp | ImGuiSliderFlags.NoRoundToFormat
                        );
                }
                
                var sliderTime = new DateTime(_sliderTicks);
                if (ImGui.Button($"Go to {sliderTime}"))
                    GoToTime(sliderTime);
            }
            
            Typing = ImGui.IsWindowFocused() && ImGui.GetIO().WantCaptureKeyboard;
        }
        ImGui.End();
    }
}