using System;

using System.Collections.Generic;

using KSP.UI;

using UnityEngine;

using Random = UnityEngine.Random;

namespace ModuleManager.Cats

{

class CatOrbiter : MonoBehaviour

{

private static List<CatOrbiter> orbiters = new List<CatOrbiter>();

private static CatOrbiter sun;

private double _mass;

public Rigidbody2D rb;

private Vector2d pos;

private Vector2d vel;

private Vector2d force;

private float scale = 1;

private double G = 6.67408E-11;

public double Mass

{

get { return _mass; }

set

{

_mass = value;

if (rb!=null)

rb.mass = (float)_mass;

}

}

public void Init(CatOrbiter parent, float soi)

{

TimingManager.FixedUpdateAdd(TimingManager.TimingStage.Earlyish, DoForces);

orbiters.Add(this);

rb = gameObject.AddComponent<Rigidbody2D>();

rb.isKinematic = true;

if (orbiters.Count == 1)

{

sun = this;

Vector3 spos = new Vector3(Screen.width * 0.5f, Screen.height * 0.5f, -1);

transform.position = KSP.UI.UIMainCamera.Camera.ScreenToWorldPoint(spos);

Mass = 2E17;

pos.x = transform.position.x;

pos.y = transform.position.y;

}

else

{

Vector2 relativePos = Random.insideUnitCircle;

if (relativePos.magnitude < 0.2)

relativePos = relativePos.normalized * 0.3f;

Vector3 spos = UIMainCamera.Camera.WorldToScreenPoint(parent.transform.position) + (Vector3)(relativePos * soi);

spos.z = -1;

transform.position = UIMainCamera.Camera.ScreenToWorldPoint(spos);

pos.x = transform.position.x;

pos.y = transform.position.y;

//int scaleRange = 10;

//

//float factor = (1 + (scaleRange - 1) * Random.value);

//

//scale = parent.scale * factor / scaleRange;

scale = parent.scale * 0.6f;

transform.localScale *= scale;

TrailRenderer trail = gameObject.GetComponent<TrailRenderer>();

trail.colorGradient = new Gradient() {alphaKeys = new GradientAlphaKey[3] { new GradientAlphaKey(1, 0), new GradientAlphaKey(1, 0.7f), new GradientAlphaKey(0, 1) }};

trail.startWidth *= scale;

//trail.endWidth *= scale;

trail.widthCurve = new AnimationCurve(new Keyframe(0, trail.startWidth ), new Keyframe(0.7f, trail.startWidth), new Keyframe(1, trail.startWidth * 0.9f));

//Mass = factor * 2E16;

Mass = parent.Mass * 0.025;

Vector2d dist = parent.pos - pos;

double circularVel = Math.Sqrt(G * (Mass + parent.Mass) / dist.magnitude);

if (parent == sun)

circularVel *= Random.Range(0.9f, 1.1f);

Debug.Log("CatOrbiter " + circularVel.ToString("F3") + " " + Mass.ToString("F2") + " " + orbiters[0].Mass.ToString("F2") + " " +

dist.magnitude.ToString("F2"));

Vector3d normal = (Random.value >= 0.3) ? Vector3d.back : Vector3d.forward;

Vector3d vel3d = Vector3d.Cross(dist, normal).normalized * circularVel;

vel.x = parent.vel.x + vel3d.x;

vel.y = parent.vel.y + vel3d.y;

}

rb.MovePosition(new Vector2((float)pos.x, (float)pos.y));

}

private void DoForces()

{

force = Vector2d.zero;

foreach (CatOrbiter cat in orbiters)

{

if (cat == this)

continue;

// F = G * (m1 * m2) / r^2

Vector2d dir = cat.pos - pos;

double f = G * (cat.Mass * Mass) / (dir.sqrMagnitude + 10); // +10 to avoid div/0

force += (float)f * dir.normalized;

}

}

void OnDestroy()

{

orbiters.Remove(this);

TimingManager.FixedUpdateRemove(TimingManager.TimingStage.Earlyish, DoForces);

}

void FixedUpdate()

{

//if (this == sun)

// return;

vel += Time.fixedDeltaTime * force / Mass;

pos += Time.fixedDeltaTime * vel;

rb.MovePosition(new Vector2((float)pos.x, (float)pos.y));

double angle = Math.Atan2(vel.y, vel.x) * Mathf.Rad2Deg;

rb.MoveRotation((float)angle);

}

}

}