# Source code for plugins.turtle

    # $Id$
    ##
    ##  This file is part of pyFormex 1.0.5  (Sat Feb 16 10:40:32 CET 2019)
    ##  pyFormex is a tool for generating, manipulating and transforming 3D
    ##  geometrical models by sequences of mathematical operations.
    ##  Home page: http://pyformex.org
    ##  Project page:  http://savannah.nongnu.org/projects/pyformex/
    ##  Copyright 2004-2018 (C) Benedict Verhegghe (benedict.verhegghe@ugent.be)
    ##  Distributed under the GNU General Public License version 3 or later.
    ##
    ##  This program is free software: you can redistribute it and/or modify
    ##  it under the terms of the GNU General Public License as published by
    ##  the Free Software Foundation, either version 3 of the License, or
    ##  (at your option) any later version.
    ##
    ##  This program is distributed in the hope that it will be useful,
    ##  but WITHOUT ANY WARRANTY; without even the implied warranty of
    ##  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ##  GNU General Public License for more details.
    ##
    ##  You should have received a copy of the GNU General Public License
    ##  along with this program.  If not, see http://www.gnu.org/licenses/.
    ##
    """Turtle graphics for pyFormex

    This module was mainly aimed at the drawing of Lindenmayer products
    (see :mod:`plugins.lima` and the Lima example).

    The idea is that a turtle can be moved in 2D from one position to another,
    thereby creating a line between start and endpoint or not.

    The current state of the turtle is defined by

    - ``pos``: the position as a 2D coordinate pair (x,y),
    - ``angle``: the moving direction as an angle (in degrees) with the x-axis,
    - ``step``: the speed, as a discrete step size.

    The start conditions are: ``pos=(0,0), step=1., angle=0.``

    The followin example turtle script creates a unit square::

      fd();ro(90);fd();ro(90);fd();ro(90);fd()
    """
    from __future__ import absolute_import, division, print_function

    import math
    deg = math.pi/180.

    def sind(arg):
        """Return the sine of an angle in degrees."""
        return math.sin(arg*deg)

    def cosd(arg):
        """Return the cosine of an angle in degrees."""
        return math.cos(arg*deg)

    def reset():
        """Reset the turtle graphics engine to start conditions.

        This resets the turtle's state to the starting conditions
        ``pos=(0,0), step=1., angle=0.``, removes everything from the state save
        stack and empties the resulting path.
        """
        global pos, step, angle, list, save
        pos = [0., 0.]
        step = 1.
        angle = 0.
        list=[]
        save=[]

    def push():
        """Save the current state of the turtle.

        The turtle state includes its position, step and angle.
        """
        global save
        save.append([pos, step, angle])

    def pop():
        """Restore the turtle state to the last saved state."""
        global pos, step, angle, list, save
        pos, step, angle = save.pop(-1)

    def fd(d=None,connect=True):
        """Move forward over a step `d`, with or without drawing.

        The direction is the current direction.
        If `d` is not given, the step size is the current step.

        By default, the new position is connected to the previous with a
        straight line segment.
        """
        global pos, step, angle, list
        if d:
            step = d
        p = [ pos[0] + step * cosd(angle), pos[1] + step * sind(angle) ]
        if connect:
            list.append([pos, p])
        pos = p

    def mv(d=None):
        """Move over step `d` without drawing."""
        fd(d, False)

    def ro(a):
        """Rotate over angle `a`. The new direction is incremented with `a`"""
        global pos, step, angle, list
        angle += a

    def go(p):
        """Go to position `p` (without drawing).

        While the `mv` method performs a relative move, this is an absolute move.
        `p` is a tuple of (x,y) values.
        """
        global pos, step, angle, list
        pos = p

    def st(d):
        """Set the step size."""
        global pos, step, angle, list
        step = d

    def an(a):
        """Set the angle"""
        global pos, step, angle, list
        angle = a

    def play(scr,glob=None):
        """Play all the commands in the script `scr`

        The script is a string of turtle commands, where each command
        is ended with a semicolon (';').

        If a dict `glob` is specified, it will be update with the turtle
        module's globals() after each turtle command.
        """
        for line in scr.split(';'):
            if line:
                if glob:
                    glob.update(globals())
                    eval(line, glob)
                else:
                    eval(line)
        return list

    reset()

    if __name__ == '__main__':
        def test(txt):
            l = play(txt)
            print("%s line segments" % len(l))
            print(l)

        test("fd();ro(90);fd();ro(90);fd();ro(90);fd()")
        test("fd();ro(90);fd();ro(90);fd();ro(90);fd()")
        test("reset();fd();ro(90);fd();ro(90);fd();ro(90);fd()")

    # End