import turtle


def points(tup):
	"""
	Given a tuple ((x_1, y_1), (x_2, y_2), (x_n, y_n),...)
	return a function f(x_n): y=y_n.
	"""
	return lambda x: dict(tup)[float(x)]


class Tools():
	"""Miscellanous functions for turtle"""
	def go(self, x, y):
		"""Move cursor to point (x, y) without drawing a line"""
		self.pu()
		self.goto(x, y)
		self.pd()


class Arrow(turtle.Pen, Tools):
	"""Custom turtle cursor"""
	def __init__(self):
		super(Arrow, self).__init__()
		self.speed(0)
		self.shape("triangle")
		self.shapesize(0.5)


class Graph(turtle.Pen, Tools):

	def __init__(self, canvas, X=10, Y=10):
		"""
		Initialization of the graph.
		Providing the size of the axes if necessary.
		"""
		super(Graph, self).__init__()
		turtle.title("Plot")
		self.X = X
		self.Y = Y
		self.canvas = canvas
		self.frame = turtle._Screen._root
		self.axes()
		self.arrows()

	def axes(self):
		"""Draw the axes of the coordinate plane"""
		turtle.setworldcoordinates(
			-(self.X + 2), -(self.Y + 2),
			self.X + 2, self.Y + 2)
		self.hideturtle()
		self.speed(0)
		self.go(-self.X, 0)
		self.fd(self.X * 2)
		self.go(0, -self.Y)
		self.lt(90)
		self.fd(self.Y * 2)

	def arrows(self):
		"""Draw arrows and labels"""
		a = Arrow()
		a.go(self.X, 0)
		a.write("   x", font=("helvetiva", 16))
		b = Arrow()
		b.lt(90)
		b.go(0, self.Y)
		b.write("   y", font=("helvetiva", 16))

	def plot(self, function, start, stop, color="blue"):
		"""Plot a function"""
		medium = 2 / self.X
		self.color(color)
		try:
			self.go(start, function(start))
		except ZeroDivisionError:
			self.go(start, function(start + 1 * medium))
		for x in range(int(start / medium), int(stop / medium) + 1):
			x *= medium
			try:
				self.goto(x, function(x))
			except ZeroDivisionError:
				self.go(x, function(x + 1 * medium))

	def clean(self):
		"""Clean the canvas redraw axes"""
		self.reset()
		self.axes()