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

public class SolarSystem : MonoBehaviour
{
    [SerializeField] private float G = 100f;
    private GameObject[] celestials;
    void Start()
    {
        celestials = GameObject.FindGameObjectsWithTag("Celestial");
        InitialVelocity();
    }
    private void FixedUpdate()
    {
        Gravity();
    }
    void Gravity()
    {
        foreach (GameObject a in celestials)
        {
            foreach (GameObject b in celestials)
            {
                if (!a.Equals(b))
                {
                    float m1 = a.GetComponent<Rigidbody>().mass;
                    float m2 = b.GetComponent<Rigidbody>().mass;
                    float r = Vector3.Distance(a.transform.position, b.transform.position);
                    a.GetComponent<Rigidbody>().AddForce(
                        (b.transform.position - a.transform.position).normalized *
                        (G * (m1 * m2) / (r * r))
                    );
                }
            }
        }
    }
    void InitialVelocity()
    {
        foreach (GameObject a in celestials)
        {
            foreach (GameObject b in celestials)
            {
                if (!a.Equals(b))
                {
                    float m2 = b.GetComponent<Rigidbody>().mass;
                    float r = Vector3.Distance(a.transform.position, b.transform.position);
                    a.transform.LookAt(b.transform);
                    a.GetComponent<Rigidbody>().velocity +=
                        a.transform.right * Mathf.Sqrt((G * m2) / r);
                }
            }
        }
    }
}