frappy/secop/properties.py

#  -*- coding: utf-8 -*-
# *****************************************************************************
#
# 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
#
# Module authors:
#   Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
#
# *****************************************************************************
"""Define validated data types."""


from collections import OrderedDict

from secop.errors import ProgrammingError, ConfigError


# storage for 'properties of a property'
class Property:
    '''base class holding info about a property

    properties are only sent to the ECS if export is True, or an extname is set
    if mandatory is True, they MUST have a value in the cfg file assigned to them.
    otherwise, this is optional in which case the default value is applied.
    All values MUST pass the datatype.
    '''
    # note: this is inteded to be used on base classes.
    #       the VALUES of the properties are on the instances!
    def __init__(self, description, datatype, default=None, extname='', export=False, mandatory=None, settable=True):
        if not callable(datatype):
            raise ValueError('datatype MUST be a valid DataType or a basic_validator')
        self.description = description
        self.default = datatype.default if default is None else datatype(default)
        self.datatype = datatype
        self.extname = extname
        self.export = export or bool(extname)
        if mandatory is None:
            mandatory = default is None
        self.mandatory = mandatory
        self.settable = settable or mandatory  # settable means settable from the cfg file

    def __repr__(self):
        return 'Property(%r, %s, default=%r, extname=%r, export=%r, mandatory=%r)' % (
            self.description, self.datatype, self.default, self.extname, self.export, self.mandatory)


class Properties(OrderedDict):
    """a collection of `Property` objects

    checks values upon assignment.
    You can either assign a Property object, or a value
    (which must pass the validator of the already existing Property)
    """
    def __setitem__(self, key, value):
        if not isinstance(value, Property):
            raise ProgrammingError('setting property %r on classes is not supported!' % key)
        # make sure, extname is valid if export is True
        if not value.extname and value.export:
            value.extname = '_%s' % key  # generate custom key
        elif value.extname and not value.export:
            value.export = True
        OrderedDict.__setitem__(self, key, value)

    def __delitem__(self, key):
        raise ProgrammingError('deleting Properties is not supported!')


class PropertyMeta(type):
    """Metaclass for HasProperties

    joining the class's properties with those of base classes.
    """

    def __new__(cls, name, bases, attrs):
        newtype = type.__new__(cls, name, bases, attrs)
        if '__constructed__' in attrs:
            return newtype

        newtype = cls.__join_properties__(newtype, name, bases, attrs)

        attrs['__constructed__'] = True
        return newtype

    @classmethod
    def __join_properties__(cls, newtype, name, bases, attrs):
        # merge properties from all sub-classes
        properties = Properties()
        for base in reversed(bases):
            properties.update(getattr(base, "properties", {}))
        # update with properties from new class
        properties.update(attrs.get('properties', {}))
        newtype.properties = properties

        # generate getters
        for k in properties:
            def getter(self, pname=k):
                val = self.__class__.properties[pname].default
                return self.properties.get(pname, val)
            if k in attrs:
                if not isinstance(attrs[k], property):
                    raise ProgrammingError('Name collision with property %r' % k)
            setattr(newtype, k, property(getter))
        return newtype


class HasProperties(metaclass=PropertyMeta):
    properties = {}

    def __init__(self):
        super(HasProperties, self).__init__()
        self.initProperties()

    def initProperties(self):
        # store property values in the instance, keep descriptors on the class
        self.properties = {}
        # pre-init with properties default value (if any)
        for pn, po in self.__class__.properties.items():
            if not po.mandatory:
                self.properties[pn] = po.default

    def checkProperties(self):
        """validates properties and checks for min... <= max..."""
        for pn, po in self.__class__.properties.items():
            if po.export and po.mandatory:
                if pn not in self.properties:
                    name = getattr(self, 'name', repr(self))
                    raise ConfigError('Property %r of %s needs a value of type %r!' % (pn, name, po.datatype))
                # apply validator (which may complain further)
                self.properties[pn] = po.datatype(self.properties[pn])
        for pn, po in self.__class__.properties.items():
            if pn.startswith('min'):
                maxname = 'max' + pn[3:]
                minval = self.properties[pn]
                maxval = self.properties.get(maxname, minval)
                if minval > maxval:
                    raise ConfigError('%s=%r must be <= %s=%r for %r' % (pn, minval, maxname, maxval, self))


    def getProperties(self):
        return self.__class__.properties

    def exportProperties(self):
        # export properties which have
        # export=True and
        # mandatory=True or non_default=True
        res = {}
        for pn, po in self.__class__.properties.items():
            val = self.properties.get(pn, None)
            if po.export and (po.mandatory or val != po.default):
                try:
                    val = po.datatype.export_value(val)
                except AttributeError:
                    pass # for properties, accept simple datatypes without export_value
                res[po.extname] = val
        return res

    def setProperty(self, key, value):
        self.properties[key] = self.__class__.properties[key].datatype(value)