"""
 tsp.py

 Playing around with the traveling salesman problem.

"""

from random import random
from turtle import (setup, setworldcoordinates, degrees, speed,
                    colormode, pencolor, bgcolor, width, hideturtle,
                    setposition, setheading, mode, clear,
                    pendown, penup, pensize,
                    forward, backward, left, right)

def initialize_turtle_window(width=600, height=600,
                             xmin=0.0, xmax=1.0, ymin=0.0, ymax=1.0,
                             bg_color=(10,10,10),
                             color=(220,220,220)):
    """ initialize turtle graphics window and settings """
    # (0,0) is bottom left; (x,y) euclidian coords
    # pen will be up by default
    setup(width, height)   # Set window width & height (pixels)
    mode('standard')       # Set heading angles to be euclidian
    degrees(360)           # Set turtle orientation units to degrees.
    setworldcoordinates(xmin, ymin, xmax, ymax)
    colormode(255)         # Set color (r,g,b) units to (0 .. 255).
    speed(0)               # No animation. (1=slow,10=fast; 0=fastest)
    hideturtle()           # Don't show a shape for the turtle itself.
    bgcolor(bg_color)      # Set background color.
    setposition(xmax/2, ymax/2) # Put turtle at window center.
    pencolor(color)
    penup()

def box(x, y, size=0.02):
    setposition(x-size/2, y+size/2)
    setheading(0)
    pendown()
    for i in range(4):
        forward(size)
        right(90)
    penup()

def pythagorean(x1, y1, x2, y2):
    """ square of pythagorean distance between two points """
    return (x1 - x2)**2 + (y1 - y2)**2

def draw_line(x1, y1, x2, y2):
    """ draw a line between two points """
    setposition(x1, y1)
    pendown()
    setposition(x2, y2)
    penup()

def main():
    initialize_turtle_window()

    # Create (x,y) points for Traveling Salesman problem.
    n = 10                                # number of points
    xs = [random() for i in range(n)]     # x coords, xs[i]
    ys = [random() for i in range(n)]     # y coords, ys[i]
    
    for i in range(n):       # draw boxes at points
        box(xs[i], ys[i])

    for i in range(n):       # draw lines between all pairs of points
        for j in range(i+1, n):
            draw_line(xs[i], ys[i], xs[j], ys[j])
        
    wait = input("Done?")

main()