using UnityEngine;
using System.Collections;
using System.Collections.Generic;
 
public class CarController : MonoBehaviour {
    //四个车轮碰撞器---前两个，后两个
    public WheelCollider flWheelCollider;
    public WheelCollider frWheelCollider;
    public WheelCollider rlWheelCollider;
    public WheelCollider rrWheelCollider;
 
    /// <summary>
    /// 刹车的力矩
    /// </summary>
    public float maxTorque = 150.0f;
    /// <summary>
    /// 最大刹车力矩
    /// </summary>
    public float maxBrakeTorque = 500.0f;
    /// <summary>
    /// 车轮转向角
    /// </summary>
    public float maxSteerAngle = 30.0f;
    public float maxSpeedSteerAngle = 10.0f;
    /// <summary>
    /// 前进最大速度
    /// </summary>
    public float maxSpeed = 200.0f;
    /// <summary>
    /// 后退最大速度
    /// </summary>
    public float maxBackwardSpeed = 40.0f;
    /// <summary>
    /// 当前速度
    /// </summary>
    public float currentSpeed = 0.0f;
    /// <summary>
    /// 是否刹车
    /// </summary>
    private bool isBraking = false;
 
    public float centerOfMassY = 0;
 
    void Awake()
    {
        //设置小车重心
        rigidbody.centerOfMass = new Vector3(0, centerOfMassY, 0);
 
    }
 
    void FixedUpdate()
    {
        //速度
        currentSpeed = (Mathf.PI * 2 * flWheelCollider.radius) * flWheelCollider.rpm * 60 / 1000;
        currentSpeed = Mathf.Round(currentSpeed);
 
        //速度大于0并且按下后退键<S>,或者速度小于0并且按下前进键<W>
        if (((currentSpeed > 0) && (Input.GetAxis("Vertical") < 0)) || ((currentSpeed < 0) && (Input.GetAxis("Vertical") > 0)))
        {
            isBraking = true;
        }
        else
        {
            isBraking = false;
            //设置刹车力为0
            flWheelCollider.brakeTorque = 0;
            frWheelCollider.brakeTorque = 0;
        }
 
        if (isBraking == false)
        {
            //速度小于最大速度
            if ((currentSpeed < maxSpeed) && (currentSpeed > (maxBackwardSpeed * -1)))
            {
                //让车辆向前滚动
                flWheelCollider.motorTorque = maxTorque * Input.GetAxis("Vertical");
                frWheelCollider.motorTorque = maxTorque * Input.GetAxis("Vertical");
            }
            else
            {
                //不继续增加滚动力
                flWheelCollider.motorTorque = 0;
                frWheelCollider.motorTorque = 0;
            }
        }
        else
        {
            //刹车
            flWheelCollider.brakeTorque = maxBrakeTorque;
            frWheelCollider.brakeTorque = maxBrakeTorque;
            flWheelCollider.motorTorque = 0;
            frWheelCollider.motorTorque = 0;
        }
 
        float speedProcent = currentSpeed / maxSpeed;
        speedProcent = Mathf.Clamp(speedProcent, 0, 1);
        float speedControlledMaxSteerAngle;
        speedControlledMaxSteerAngle = maxSteerAngle - ((maxSteerAngle - maxSpeedSteerAngle) * speedProcent);
        flWheelCollider.steerAngle = speedControlledMaxSteerAngle * Input.GetAxis("Horizontal");
        frWheelCollider.steerAngle = speedControlledMaxSteerAngle * Input.GetAxis("Horizontal");
 
    }
   
    private void OnGUI()
    {
        GUILayout.Label(currentSpeed.ToString());
    }
}