"""
 turtle.py

 Papert's turtle graphics, 
 with a 'turtle' that can turns and moves,
 drawing a line as it goes.
 
 Uses the graphics.py package from Zell's 'Python Programming' text.
 Colors are strings like 'black', 'red1', 'red3', '#ff0000'.

 Example of drawing a square :
   $ python
   >>> from turtle import Turtle
   >>> t = Turtle(width=200, height=200)
   >>> for i in range(4):
   ...     t.move(20)
   ...     t.turn(90)
 
"""

from graphics import GraphWin, Point, Line
from math import sin, cos, pi

class Turtle:
    """ Turtles can turn, move, and trace a line when their pen is down. """
    def __init__(self, width=400, height=400,
                 color="black", background="white" ):
        title = "Turtle_Graphics"
        self.window = GraphWin(title, width, height)
        self.window.setCoords(-width/2, -height/2, width/2, height/2)
        self.window.setBackground(background)
        self.color=color
        self.pi_over_180 = pi/180.0
        self.reset()
    def setColor(self, color):
        self.color=color
    def getPenDown(self):
        return self.penDown
    def setPenDown(self, state):
        self.penDown = state
    def penDown(self):
        self.penDown = True
    def penUp(self):
        self.penDown = False
    def reset(self):
        self.x = 0.0
        self.y = 0.0
        self.angle = 0.0     # in degress
        self.penDown = True
    def jump(x=0, y=0):
        self.x = x
        self.y = y
    def turn(self, angle):
        self.angle += float(angle)
    def move(self, distance):
        x = self.x
        y = self.y
        d = float(distance)
        self.x = x + d * cos( self.angle * self.pi_over_180 )
        self.y = y + d * sin( self.angle * self.pi_over_180 )
        if self.penDown:
            line = Line(Point(x, y), Point(self.x, self.y))
            line.setOutline(self.color)
            line.draw(self.window)