'''lecture_35_recursion_turtle_tree.py
Uses recursion and turtle to draw trees
Oliver W. Layton
CS 151: Computational Thinking: Visual Media
Spring 2021
'''

import turtle


class Tree:
    def __init__(self, start_x, start_y):
        '''
        Get turtle ready and in-position to draw an upright tree.
        Show animations (but fast ones) with speed of 7
        '''
        self.screen = turtle.Screen()
        self.turt = turtle.Turtle()

        # So we can see the tree being drawn, but not too slowly
        self.turt.speed(0)
        # Draw trees upward
        self.turt.setheading(90)

        self.turt.color('blue')

    def goto(self, x, y):
        self.turt.penup()
        self.turt.goto(x, y)
        self.turt.pendown()

    def hold(self):
        self.screen.exitonclick()

    def drawTree(self, distance):
        '''Draw a tree recursively with initial trunk/branch length `distance`.
        - Draw branches that look like "forks": straight part then left and right offshots
            +/-20 deg offset from straight.
        - Stop drawing branches when the branch distance is <= 5
        - After drawing left, right, and straight portions, always restore the turtle position
            to what it was before drawing the "fork".
        '''
        # What is the base case?
        # Stop drawing branches when the branch distance is <= 5
        if distance < 5:
            return

        # If we made it this far, the distance is > 5.
        # Draw the trunk of the tree
        self.turt.forward(distance)

        # Before we draw any branches, save turtle current position (x, y)
        # so we know where to get back to when we want to draw the right
        # branch
        x, y = self.turt.position()

        # Draw left branch (subtree). Branch angle = 20 from current heading
        self.turt.left(20)
        self.drawTree(distance/2)

        self.goto(x, y)

        # Draw right branch (subtree). Branch angle = 20 from current heading
        self.turt.right(40)
        self.drawTree(distance/2)

        self.turt.left(20)
        self.goto(x, y)


if __name__ == '__main__':
    tree = Tree(0, -700)
    # Draw the tree using recursion
    tree.drawTree(200)
    # Keep the screen up until we click
    tree.hold()