#!/usr/bin/env python
#
# $Id: _compat.py 1145 2011-10-11 10:30:02Z g.rodola $
#
# Copyright (c) 2009, Jay Loden, Giampaolo Rodola'. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Module which provides compatibility with older Python versions."""

__all__ = ["namedtuple", "property"]

from operator import itemgetter as _itemgetter
from keyword import iskeyword as _iskeyword
import sys as _sys
import __builtin__

try:
    from collections import namedtuple
except ImportError:
    def namedtuple(typename, field_names, verbose=False, rename=False):
        """A collections.namedtuple implementation written in Python
        to support Python versions < 2.6.

        Taken from: http://code.activestate.com/recipes/500261/
        """
        # Parse and validate the field names.  Validation serves two
        # purposes, generating informative error messages and preventing
        # template injection attacks.
        if isinstance(field_names, basestring):
             # names separated by whitespace and/or commas
            field_names = field_names.replace(',', ' ').split()
        field_names = tuple(map(str, field_names))
        if rename:
            names = list(field_names)
            seen = set()
            for i, name in enumerate(names):
                if (not min(c.isalnum() or c=='_' for c in name) or _iskeyword(name)
                    or not name or name[0].isdigit() or name.startswith('_')
                    or name in seen):
                        names[i] = '_%d' % i
                seen.add(name)
            field_names = tuple(names)
        for name in (typename,) + field_names:
            if not min(c.isalnum() or c=='_' for c in name):
                raise ValueError('Type names and field names can only contain ' \
                                 'alphanumeric characters and underscores: %r'
                                 % name)
            if _iskeyword(name):
                raise ValueError('Type names and field names cannot be a keyword: %r' \
                                 % name)
            if name[0].isdigit():
                raise ValueError('Type names and field names cannot start with a ' \
                                 'number: %r' % name)
        seen_names = set()
        for name in field_names:
            if name.startswith('_') and not rename:
                raise ValueError('Field names cannot start with an underscore: %r'
                                 % name)
            if name in seen_names:
                raise ValueError('Encountered duplicate field name: %r' % name)
            seen_names.add(name)

        # Create and fill-in the class template
        numfields = len(field_names)
        # tuple repr without parens or quotes
        argtxt = repr(field_names).replace("'", "")[1:-1]
        reprtxt = ', '.join('%s=%%r' % name for name in field_names)
        template = '''class %(typename)s(tuple):
        '%(typename)s(%(argtxt)s)' \n
        __slots__ = () \n
        _fields = %(field_names)r \n
        def __new__(_cls, %(argtxt)s):
            return _tuple.__new__(_cls, (%(argtxt)s)) \n
        @classmethod
        def _make(cls, iterable, new=tuple.__new__, len=len):
            'Make a new %(typename)s object from a sequence or iterable'
            result = new(cls, iterable)
            if len(result) != %(numfields)d:
                raise TypeError('Expected %(numfields)d arguments, got %%d' %% len(result))
            return result \n
        def __repr__(self):
            return '%(typename)s(%(reprtxt)s)' %% self \n
        def _asdict(self):
            'Return a new dict which maps field names to their values'
            return dict(zip(self._fields, self)) \n
        def _replace(_self, **kwds):
            'Return a new %(typename)s object replacing specified fields with new values'
            result = _self._make(map(kwds.pop, %(field_names)r, _self))
            if kwds:
                raise ValueError('Got unexpected field names: %%r' %% kwds.keys())
            return result \n
        def __getnewargs__(self):
            return tuple(self) \n\n''' % locals()
        for i, name in enumerate(field_names):
            template += '        %s = _property(_itemgetter(%d))\n' % (name, i)
        if verbose:
            print template

        # Execute the template string in a temporary namespace
        namespace = dict(_itemgetter=_itemgetter, __name__='namedtuple_%s' % typename,
                         _property=property, _tuple=tuple)
        try:
            exec template in namespace
        except SyntaxError, e:
            raise SyntaxError(e.message + ':\n' + template)
        result = namespace[typename]

        # For pickling to work, the __module__ variable needs to be set
        # to the frame where the named tuple is created.  Bypass this
        # step in enviroments where sys._getframe is not defined (Jython
        # for example) or sys._getframe is not defined for arguments
        # greater than 0 (IronPython).
        try:
            result.__module__ = _sys._getframe(1).f_globals.get('__name__', '__main__')
        except (AttributeError, ValueError):
            pass

        return result


# hack to support property.setter/deleter on python < 2.6
# http://docs.python.org/library/functions.html?highlight=property#property
if hasattr(property, 'setter'):
    property = property
else:
    class property(__builtin__.property):
        __metaclass__ = type

        def __init__(self, fget, *args, **kwargs):
            super(property, self).__init__(fget, *args, **kwargs)
            self.__doc__ = fget.__doc__

        def getter(self, method):
            return property(method, self.fset, self.fdel)

        def setter(self, method):
            return property(self.fget, method, self.fdel)

        def deleter(self, method):
            return property(self.fget, self.fset, method)
