# inter - Robot simulation interface. {{{
#
# Copyright (C) 2008 Nicolas Schodet
#
# APBTeam:
#        Web: http://apbteam.org/
#      Email: team AT apbteam DOT org
#
# 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 2 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, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#
# }}}
"""Distance sensor."""
from math import pi, cos, sin, sqrt

from Tkinter import *
from simu.inter.drawable import *
from utils.observable import Observable

class DistSensor (Drawable, Observable):
    """A distance sensor."""

    def __init__ (self, onto, pos, angle, range):
        Drawable.__init__ (self, onto)
        Observable.__init__ (self)
        self.onto = onto
        self.pos = pos
        self.angle = angle
        self.range = range
        self.target = (pos[0] + cos (angle) * range,
                pos[1] + sin (angle) * range)
        self.obstacles = [ ]
        self.distance = None
        self.hide = False

    def compute (self):
        # Could do better by trans_applying until on the same drawable as the
        # obstacle.
        pos = self.onto.trans_apply (self.pos)
        target = self.onto.trans_apply (self.target)
        n = ((target[0] - pos[0]) / self.range,
                (target[1] - pos[1]) / self.range)
        self.distance = None
        for o in self.obstacles:
            # Does the line intersect with the obstacle?
            ao = (o.pos[0] - pos[0], o.pos[1] - pos[1])
            doc = abs (ao[0] * -n[1] + ao[1] * n[0])
            if doc < o.radius:
                # Does the segment intersect?
                m = ao[0] * n[0] + ao[1] * n[1]
                f = sqrt (o.radius ** 2 - doc ** 2)
                if m - f > 0 and m - f < self.range:
                    d = m - f
                    if self.distance is None or self.distance > d:
                        self.distance = d
                elif m + f > 0 and m + f < self.range:
                    d = m + f
                    if self.distance is None or self.distance > d:
                        self.distance = d
        self.notify ()
        return self.distance

    def draw (self):
        self.compute ()
        self.reset ()
        if self.hide:
            return
        if self.distance is None:
            self.draw_line (self.pos, self.target, fill = 'blue', arrow = LAST)
        else:
            inter = (self.pos[0] + cos (self.angle) * self.distance,
                    self.pos[1] + sin (self.angle) * self.distance)
            self.draw_line (self.pos, inter, fill = 'red', arrow = LAST)
            self.draw_line (inter, self.target, fill = 'blue', arrow = LAST)
