#
#  calculator.py : A calculator module for the deskbar applet.
#
#  Copyright (C) 2006 by Callum McKenzie
#
#  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.
# 
#  Authors: Callum McKenzie <callum@spooky-possum.org>
#

from gettext import gettext as _
import deskbar.Handler, deskbar.Match
import deskbar.Categories
import cgi

# This is evil since I strongly suspect this isn't meant to be public API.
# However, I can't see a better way.
deskbar.Categories.CATEGORIES["calculator"] = { "name" : _("Calculator") }

HANDLERS = {
    "CalculatorHandler" : {
    "name" : _("Calculator"),
    "description" : _("Calculate simple equations"),
    "version" : "1.0",
    }
}

class CalculatorMatch (deskbar.Match.Match):
    def get_name (self, text=None):
        # I really think that deskbar should be doing the
        # escaping for us.
        escapedtext = cgi.escape (text)
        return { "name" : self.name, "escapedtext" : escapedtext }

    def get_verb (self):
        """We print out the entire equation."""
        return "%(escapedtext)s = <b>%(name)s</b>"
    
    def get_category (self):
        return "calculator"
    
class CalculatorHandler (deskbar.Handler.Handler):
    # This white list includes all the python mathemetical operators which
    # aren't comparison operators. Unfortunately >> contains >, so some slip
    # through. In fact the only missing operator in =.
    # What you get is a set of simple arithmetic and bitwise operators. No
    # math functions like abs, sqrt, sin, cos, etc. because I couldn't
    # think of a convenient way to check for them.
    whitelist = ".0123456789+-*/%<>&|^~() "
    
    def __init__ (self):
        deskbar.Handler.Handler.__init__ (self, "gtk-add")

    def query (self, query):
        """We evaluate the equation by first checking if all
        the characters are in our white list and then passing the
        result to python for evaluation. Any errors are ignored."""
        try:
            for c in query:
                if c not in CalculatorHandler.whitelist:
                    return []
            answer = eval (query)
            return [ CalculatorMatch (self, name=answer)]
        except:
            return []