using System;

public class EngineControlUnit
{
    public double Throttle;
    public bool IsInNeutral = true;

    private const double _revLimit = 7000;
    private const double _idleRpm = 800;
    private const double _idleSensitivity = 1e-2;
    private const double _throttleSensitivity = 20;
    private const double _neutralThrottleLimit = 0.2;
    
    private double _idlePosition = 0;
    private double _targetThrottle = 0;
    private double _currentThrottle = 0;

    public EngineControlUnit()
    {

    }

    public void Update(double dt, Engine engine)
    {
        if (engine.RPM > _revLimit)
        {
            engine.ThrottlePosition = 0; return;
        }

        _targetThrottle = Math.Clamp(GetIdleThrottle(dt, engine.RPM) + Throttle, 0, 1);
        _currentThrottle = Util.Lerp(_currentThrottle, _targetThrottle, dt * _throttleSensitivity);

        if (IsInNeutral) _currentThrottle = Math.Min(_currentThrottle, _neutralThrottleLimit);

        engine.ThrottlePosition = _currentThrottle;
    }

    public double GetIdleThrottle(double dt, double rpm)
    {
        if (rpm > _idleRpm) return 0;

        double diff = rpm - _idleRpm;

        _idlePosition = Math.Clamp(_idlePosition - (diff * _idleSensitivity * dt), 0, 1.0);

        return _idlePosition;
    }
}