#!/usr/bin/ruby
include('Turtle.sf')
class LSystem(
    angle  = 90,
    scale  = 1,
    xoff   = 0,
    yoff   = 0,
    len    = 5,
    color  = 'black',
    width  = 500,
    height = 500,
    turn   = 0,
) {
    method execute(string, repetitions, filename, rules) {
        var theta  = angle.deg2rad
        var turtle = Turtle(
            x:     width,
            y:     height,
            angle: turn,
            scale: scale,
            color: color,
            xoff:  xoff,
            yoff:  yoff,
        )
        var stack = []
        var table = Hash(
            '+' => { turtle.turn(theta) },
            '-' => { turtle.turn(-theta) },
            ':' => { turtle.mirror },
            '[' => { stack.push(turtle.state) },
            ']' => { turtle.setstate(stack.pop) },
        )
        repetitions.times {
            string.gsub!(/(.)/, {|c| rules{c} \\ c })
        }
        string.each_char { |c|
            if (table.contains(c)) {
                table{c}.run
            }
            elsif (c.is_uppercase) {
                turtle.forward(len)
            }
        }
        turtle.save_as(filename)
    }
}