From f84449d4e6f1d2db99c9b78627435308d71dfe91 Mon Sep 17 00:00:00 2001
From: Cat Flynn <me@ktyl.dev>
Date: Mon, 5 Sep 2022 22:13:53 +0100
Subject: [PATCH] WIP - RESET THIS

---
 scripts/orbits/IMassiveExtensions.cs         |  4 ++
 scripts/orbits/IOrbit.cs                     |  7 +++
 scripts/orbits/IOrbitalElementsExtensions.cs | 13 ++++++
 scripts/orbits/Orbit.cs                      |  2 +-
 scripts/orbits/OrbitalElements.cs            | 46 ++++++++++++++++++++
 5 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 scripts/orbits/IMassiveExtensions.cs
 create mode 100644 scripts/orbits/IOrbit.cs
 create mode 100644 scripts/orbits/IOrbitalElementsExtensions.cs
 create mode 100644 scripts/orbits/OrbitalElements.cs

diff --git a/scripts/orbits/IMassiveExtensions.cs b/scripts/orbits/IMassiveExtensions.cs
new file mode 100644
index 0000000..6f4cf1a
--- /dev/null
+++ b/scripts/orbits/IMassiveExtensions.cs
@@ -0,0 +1,4 @@
+public static class IMassiveExtensions
+{
+    public static double U(this IMassive m) => Kepler.U(m.Mass);
+}
\ No newline at end of file
diff --git a/scripts/orbits/IOrbit.cs b/scripts/orbits/IOrbit.cs
new file mode 100644
index 0000000..6bbbb05
--- /dev/null
+++ b/scripts/orbits/IOrbit.cs
@@ -0,0 +1,7 @@
+using Vim.Math3d;
+
+public interface IOrbit
+{
+    Ellipse Ellipse { get; }
+    DVector3 GetPosition(float t);
+}
\ No newline at end of file
diff --git a/scripts/orbits/IOrbitalElementsExtensions.cs b/scripts/orbits/IOrbitalElementsExtensions.cs
new file mode 100644
index 0000000..f8dbda1
--- /dev/null
+++ b/scripts/orbits/IOrbitalElementsExtensions.cs
@@ -0,0 +1,13 @@
+using Vim.Math3d;
+using static System.Math;
+
+public static class IOrbitalElementsExtensions
+{
+    /// <summary>
+    /// Get the Cartesian position on the orbit for a given mean anomaly.
+    /// </summary>
+    /// <param name="M">Mean anomaly</param>
+    /// <returns>Position</returns>
+    public static DVector2 GetEccentricPosition2D(this OrbitalElements elements, double M) =>
+        Kepler.GetEccentricPosition2D(elements.e, elements.a, M);
+}
\ No newline at end of file
diff --git a/scripts/orbits/Orbit.cs b/scripts/orbits/Orbit.cs
index 3ebab6c..147aa8f 100644
--- a/scripts/orbits/Orbit.cs
+++ b/scripts/orbits/Orbit.cs
@@ -2,7 +2,7 @@ using Godot;
 using System;
 using Vim.Math3d;
 
-public class Orbit
+public class Orbit : IOrbit
 {
     // The position of the primary body relative to the ellipse - the 
     // orbit itself is presented as being centred on the primary, but
diff --git a/scripts/orbits/OrbitalElements.cs b/scripts/orbits/OrbitalElements.cs
new file mode 100644
index 0000000..c501dc8
--- /dev/null
+++ b/scripts/orbits/OrbitalElements.cs
@@ -0,0 +1,46 @@
+public struct OrbitalElements
+{
+    private Ellipse _ellipse;
+    /// <summary>
+    /// Semi-major axis in AU
+    /// </summary>
+    public double a => _ellipse.a;
+    /// <summary>
+    /// Eccentricity
+    /// </summary>
+    public double e => _ellipse.e;
+    /// <summary>
+    /// Inclination in degrees
+    /// </summary>
+    public double i { get; private set; }
+    /// <summary>
+    /// Argument of ascending node in degrees
+    /// </summary>
+    public double W { get; private set; }
+    /// <summary>
+    /// Argument of periapsis in degrees
+    /// </summary>
+    public double p { get; private set; }
+    /// <summary>
+    /// Mean anomaly at epoch
+    /// </summary>
+    public double M0 { get; private set; }
+
+    /// <summary>
+    ///
+    /// </summary>
+    /// <param name="a">Semi-major axis in AU</param>
+    /// <param name="e">eccentricity</param>
+    /// <param name="i">Inclination in degrees</param>
+    /// <param name="W">Argument of ascending node in degrees</param>
+    /// <param name="p">Argument of periapsis in degrees</param>
+    /// <param name="M0">Mean anomaly at epoch</param>
+    public OrbitalElements(double a, double e, double i, double W, double p, double M0)
+    {
+        _ellipse = new Ellipse(a, e);
+        this.i = i;
+        this.W = W;
+        this.p = p;
+        this.M0 = M0;
+    }
+}
\ No newline at end of file