mc-mesh/src/main/java/com/aaaaahhhhhhh/bananapuncher714/tess4j/HalfWing.java

package com.aaaaahhhhhhh.bananapuncher714.tess4j;

import com.aaaaahhhhhhh.bananapuncher714.mesh.Vector2d;

public class HalfWing {
    protected HalfWing sym;
    protected HalfWing prev;
    protected HalfWing next;
    
    protected Vertex origin;
    
    public HalfWing() {
        init();
        
        new HalfWing( this );
    }
    
    private HalfWing( HalfWing o ) {
        init();
        
        sym = o;
        o.sym = this;
        
        next = o;
        o.next = this;
    }
    
    private void init() {
        origin = new Vertex( this );
        prev = this;
    }
    
    public Vertex getOrigin() {
        return origin;
    }
    
    public HalfWing setOrigin( Vertex vert ) {
        origin = vert;
        return this;
    }
    
    public HalfWing getSym() {
        return sym;
    }
    
    public HalfWing getPrev() {
        return prev;
    }
    
    public HalfWing setPrev( HalfWing wing ) {
        this.prev = wing;
        return this;
    }
    
    public HalfWing getNext() {
        return next;
    }
    
    public HalfWing setNext( HalfWing wing ) {
        this.next = wing;
        return this;
    }
    
    public Vertex getDest() {
        return sym.origin;
    }
    
    public Vector2d toVector2d() {
        return getDest().getPosition().subtracted( getOrigin().getPosition() );
    }
    
    public boolean isZero() {
        return getOrigin().equals( getDest() );
    }
    
    // Split this edge in half, and return the new edge
    public HalfWing split() {
        HalfWing wing = new HalfWing();
        
        splice( wing, getNext() );
        
        splice( getSym(), getNext() );
        splice( getSym(), wing.getSym() );
        
        wing.setOrigin( getDest() );
        wing.getOrigin().setWing( wing );
        
        getSym().setOrigin( wing.getDest() );
        getDest().setWing( getSym() );
        
        wing.getOrigin().update();
        wing.getDest().update();
        
        return wing.getSym();
    }
    
    public static void splice( HalfWing a, HalfWing b ) {
        HalfWing ap = a.prev;
        HalfWing bp = b.prev;
        
        a.prev = bp;
        b.prev = ap;
        
        ap.sym.next = b;
        bp.sym.next = a;
    }
}