# Langton ant (Rule 2) moving in a Truchet-tiled torus world
# rule: enter cell, follow grey border, change cell, repeat
# Wolfgang.Urban@schule.at

from xturtle import *

SPEED = 3

# build 'truchet tile' turtleshapes 
def buildtiles(dd):
    d = dd/2
    e = d/2**0.5
    i = 1

    s = Shape("compound")
    poly0 = ((-d,-d),(d,-d),(d,d),(-d,d),(-d,-d))
    s.addComponent(poly0,"grey","black")
    poly = ((d-i,-d+i),(i,-d+i),(d-e,-d+e),(d-i,i),(d-i,-d+i))
    s.addComponent(poly,"white",None)
    poly = ((-d+i,d-i),(i,d-i),(-d+e,d-e),(-d+i,i),(-d+i,d-i))
    s.addComponent(poly,"white",None)
    addshape("VR",s)

    s = Shape("compound")
    s.addComponent(poly0,"white","black")
    poly = ((d-i,d-i),(i,d-i),(d-e,d-e),(d-i,i),(d-i,d-i))
    s.addComponent(poly,"grey",None)
    poly = ((-d+i,-d+i),(i,-d+i),(-d+e,-d+e),(-d+i,i),(-d+i,-d+i))
    s.addComponent(poly,"grey",None)
    addshape("VL",s)

    s = Shape("compound")
    s.addComponent(poly0,"white","black")
    poly = ((d-i,-d+i),(i,-d+i),(d-e,-d+e),(d-i,i),(d-i,-d+i))
    s.addComponent(poly,"grey",None)
    poly = ((-d+i,d-i),(i,d-i),(-d+e,d-e),(-d+i,i),(-d+i,d-i))
    s.addComponent(poly,"grey",None)
    addshape("HL",s)

    s = Shape("compound")
    s.addComponent(poly0,"grey","black")
    poly = ((d-i,d-i),(i,d-i),(d-e,d-e),(d-i,i),(d-i,d-i))
    s.addComponent(poly,"white",None)
    poly = ((-d+i,-d+i),(i,-d+i),(-d+e,-d+e),(-d+i,i),(-d+i,-d+i))
    s.addComponent(poly,"white",None)
    addshape("HR",s)


class World:
    # n = side length of world, D = size of single tile
    def __init__(self,n=6,D=50):
        self.x0 = self.y0 = -D*n/2                  # left bottom 
        self.n,self.D = n,D
        self.MIN,self.MAX = self.x0+2,self.x0+n*D-2 # boundaries

        winsize(n*D+D,n*D+D)            # screen without scrolls
        screensize(n*D+D-50,n*D+D-50)
        reset()
        mode("logo")
        buildtiles(D)

        tracer(100,0)
        # tile floor with left tiles
        self.world = {}
        for y in range(n):
            for x in range(n):
                if (x+y)%2==0:
                    self.world[(x,y)] = Tile("HL",-1,self.x0+x*D+D/2,self.y0+y*D+D/2)
                else:
                    self.world[(x,y)] = Tile("VL",-1,self.x0+x*D+D/2,self.y0+y*D+D/2)
        
        # ants starting position 
        self.xx,self.yy = n//2,n//2   # Cell coordinates
        self.x,self.y = self.x0+self.xx*D+D/2,self.y0+self.yy*D # Screen coordinates

        tracer(1,50)
        width(2)
        color("red")
        shape("turtle")
        penup()
        setpos(self.x,self.y)
        self.direction = 0  # up
        speed(SPEED)
        delay(20)
        
    def walk(self):
        # cell to enter
        t = self.world[self.xx,self.yy]
        
        self.direction = (self.direction+t.typ)%4
        if self.direction == 0: self.yy = (self.yy+1)%self.n
        elif self.direction == 2: self.yy = (self.yy-1)%self.n            
        elif self.direction == 1: self.xx = (self.xx+1)%self.n
        elif self.direction == 3: self.xx = (self.xx-1)%self.n

        r = -t.typ*self.D/2
        circle(r,90,3)
        # connect boundaries
        if not ((self.MIN<=xcor()<self.MAX) and (self.MIN<=ycor()<self.MAX)):
            speed(0)
            bk(self.n*self.D)
            speed(SPEED)
        t.switch()

    def run(self):
        while True:
            self.walk()

class Tile(Pen):
    # type -1,1 for Left, Right
    def __init__(self,pattern,typ,x,y):
        Pen.__init__(self)
        self.penup()
        self.speed(0)
        self.setpos(x,y)
        self.pattern,self.typ = pattern,typ
        self.shape(pattern)
        self.next = {"VL":"VR","VR":"VL","HL":"HR","HR":"HL"}

    def switch(self):
        self.typ = -self.typ
        self.pattern = self.next[self.pattern]
        self.shape(self.pattern)


w = World(8,60)
w.run()