using System.Linq;
using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Numerics;
using MoonTools.Core.Structs;
using MoreLinq;
namespace MoonTools.Core.Bonk
{
///
/// A Shape defined by an arbitrary collection of vertices.
/// NOTE: A Polygon must have more than 2 vertices, be convex, and should not have duplicate vertices.
///
public struct Polygon : IShape2D, IEquatable
{
private ImmutableArray vertices;
public IEnumerable Vertices { get { return vertices == null ? Enumerable.Empty() : vertices; } }
// vertices are local to the origin
public Polygon(params Position2D[] vertices) // TODO: remove this, params is bad because it allocates an array
{
this.vertices = ImmutableArray.Create(vertices);
}
public Polygon(ImmutableArray vertices)
{
this.vertices = vertices;
}
public Vector2 Support(Vector2 direction, Transform2D transform)
{
return Vertices.Select(vertex => Vector2.Transform(vertex, transform.TransformMatrix)).MaxBy(transformed => Vector2.Dot(transformed, direction)).First();
}
public AABB AABB(Transform2D Transform2D)
{
return Bonk.AABB.FromTransformedVertices(Vertices, Transform2D);
}
public override bool Equals(object obj)
{
if (obj is IShape2D other)
{
return Equals(other);
}
return false;
}
public bool Equals(IShape2D other)
{
if (other is Polygon otherPolygon)
{
var q = from a in vertices
join b in otherPolygon.vertices on a equals b
select a;
return vertices.Length == otherPolygon.vertices.Length && q.Count() == vertices.Length;
}
else if (other is Rectangle rectangle)
{
var q = from a in vertices
join b in rectangle.Vertices on a equals b
select a;
return vertices.Length == 4 && q.Count() == vertices.Length;
}
return false;
}
public override int GetHashCode()
{
return HashCode.Combine(vertices, Vertices);
}
public static bool operator ==(Polygon a, Polygon b)
{
return a.Equals(b);
}
public static bool operator !=(Polygon a, Polygon b)
{
return !(a == b);
}
public static bool operator ==(Polygon a, Rectangle b)
{
return a.Equals(b);
}
public static bool operator !=(Polygon a, Rectangle b)
{
return !(a == b);
}
}
}