# Chronogram drawing by Michael Goldwasser

import turtle
#turtle.screensize(400,1000)

def draw(tree, xScale, yScale, parentTime):
    reset()
    drawRecurse(tree, xScale, yScale, parentTime)

def drawRecurse(tree, xScale, yScale, parentTime):
    """Draw the tree centered to the right of the current position,
    such that leaves end up separated vertically by yScale,
    and levels separated horizontally by xScale.

    The evolutionary time of the parent is the final parameter.
    """
    # name the three pieces of the tuple
    label,first,second = tree
    isInternal = (first != ())  # by convention

    myTime = label if isInternal else 0
    distance = (parentTime-myTime) * xScale

    # advance to node and draw label
    advance(distance)

    if isInternal:
        # if there are subtrees, draw those
        a = leafCount(first)
        b = leafCount(second)
        n = a + b

        lateral(-b/2 * yScale)
        drawRecurse(first, xScale, yScale, label)   # recurse
        lateral(n/2 * yScale)
        drawRecurse(second, xScale, yScale, label)  # recurse
        lateral(-a/2 * yScale)

    drawLabel(yScale, label)

    # remember to retreat from the node
    advance(-distance)

#==============================================================

def advance(distance):
    """Move forward given distance in current direction."""
    turtle.forward(distance)

def lateral(distance):
    """Assuming turtle starts (and ends) with rightward orientation,
    implement a vertical move of given distance.

    Positive value should be upward.
    """
    turtle.right(90)
    turtle.forward(distance)
    turtle.left(90)


#=========== some utility functions we've written =============
def drawLabel(yScale,label):
    fontSize = min(20,round(0.9*yScale))
    if isinstance(label, float):
        label = '%5.2f' % label
        fontSize //= 2

    turtle.penup()
    turtle.right(90)
    turtle.forward(fontSize/2)
    turtle.left(90)
    turtle.write( ' '+str(label), font=("Arial", fontSize, "normal"))
    turtle.right(90)
    turtle.backward(fontSize/2)
    turtle.left(90)
    turtle.pendown()
    
def leafCount(tree):
    """Return number of leaves of the tree."""
    root,first,second = tree    # unpack the tuple
    if first == second == ():
        return 1              # tree with one node
    else:
        return leafCount(first) + leafCount(second)

def savePostscript(filename):
    turtle.getscreen().getcanvas().postscript(file=filename)

def reset():
    """Reset the state of the turtle canvas and position."""
    turtle.speed(0)
    turtle.clear()
    turtle.up()
    turtle.goto(-0.5*turtle.window_width(), 0)
    turtle.down()
    turtle.setheading(0)

#==============================================================