using UnityEngine;
using System.Collections;
using System;
using System.Collections.Generic;

[Serializable]
public class IdleThrolleController
{
    public double IdleSpeed;
    public double SpeedThreshold = 1.0;
    public double LagConstant = 1.0;
    public double IdleThrolle = 0.0;

    public void Integrate(double dt, double speed)
    {
        var throlleDerivative = ((0.5f*(1.0 - Math.Tanh(4.0*(speed - IdleSpeed)/SpeedThreshold))) - IdleThrolle)/LagConstant;
        IdleThrolle += throlleDerivative * dt;
    }
}

public class CarEngine : MonoBehaviour {
    public Flywheel flywheel;
	public int cylinderCount = 4;
	public float startRpm = 50;

    public double inertia = 0.3f;
    public double inputInertia = 0.0;
    public double inputTorque = 0.0;

    /*public abstract Curve TorqueCurve { get;}
	public abstract Curve FrictionCurve { get;}*/
    public float Weight = 100;

	public Starter starter;

    public double inputThrolle = 0.0f;
    public double engineThrolle = 0.0f;
    public IdleThrolleController idleThrolleController;
    public double crankshaftAngle = 0.0; //radians
    public double angularSpeed;
    public double angularSpeedRPM;
    public double k_Friction = 0.000003;

    public Curve powerCurve;

    public double k_FrictionTorque = 0.75f;
    public double kinematicFrictionTorque = 0;

    public double Rpm
    {
        get { return angularSpeed * MathEx.RadSToRpm; }
    }


   /* private static KeyValuePair<int, float>[] _starterTable = new KeyValuePair<int, float>[]{
		new KeyValuePair<int, float>(2, 12.5f),
		new KeyValuePair<int, float>(4, 8.0f),
		new KeyValuePair<int, float>(6, 6.5f),
		new KeyValuePair<int, float>(8, 6.0f),
		new KeyValuePair<int, float>(12, 5.5f)
	};*/


    void FixedUpdate()
    {
        Integrate(Time.fixedDeltaTime);
    }

    public void Integrate(double dt) {
        //do idle throlle
        idleThrolleController.Integrate(dt, Rpm);
        engineThrolle = Math.Max(inputThrolle, idleThrolleController.IdleThrolle);

        //integrate angular acceleration and speed
        var angularDerivative = (GetTorque(engineThrolle, Rpm) - inputTorque) / (inertia + inputInertia);
        angularSpeed += angularDerivative * dt;

        angularSpeedRPM = MathEx.RadSToRpm * angularSpeed;

        //integrate angle
        crankshaftAngle += angularSpeed * dt;

        kinematicFrictionTorque = (angularSpeedRPM/60.0)*k_FrictionTorque;
    }

    public double GetTorque(double throlle, double rpm)
    {
        var t = GetTorque(rpm);
        t = t * throlle - k_Friction * rpm * rpm * (1.0 - throlle);
        return t; 
    }

    public double GetTorque(double rpm){
        if (powerCurve == null)
        {
            return 0;
        }
        return powerCurve.Sample((float)rpm);
    }

	public static float GetWatts(float torque, float rpm){
		return torque * rpm / 9549.0f;
	}

	public static float GetHp(float torque, float rpm){
		return GetWatts(torque, rpm) * 1.36f;
	}

	public bool Started = false;
}