"""
Declarative objects for FormEncode.

Declarative objects have a simple protocol: you can use classes in
lieu of instances and they are equivalent, and any keyword arguments
you give to the constructor will override those instance variables.
(So if a class is received, we'll simply instantiate an instance with
no arguments).

You can provide a variable __unpackargs__ (a list of strings), and if
the constructor is called with non-keyword arguments they will be
interpreted as the given keyword arguments.

If __unpackargs__ is ('*', name), then all the arguments will be put
in a variable by that name.
"""

import copy
try:
    from cStringIO import StringIO
except ImportError:
    from StringIO import StringIO

_declarativeCount = 0

def _getCount():
    global _declarativeCount
    last, _declarativeCount = _declarativeCount, _declarativeCount+1
    return last


class classinstancemethod(object):
    """
    Acts like a class method when called from a class, like an
    instance method when called by an instance.  The method should
    take two arguments, 'self' and 'cls'; one of these will be None
    depending on how the method was called.
    """

    def __init__(self, func):
        self.func = func

    def __get__(self, obj, type=None):
        return _methodwrapper(self.func, obj=obj, type=type)

class _methodwrapper(object):

    def __init__(self, func, obj, type):
        self.func = func
        self.obj = obj
        self.type = type

    def __call__(self, *args, **kw):
        assert not kw.has_key('self') and not kw.has_key('cls'), "You cannot use 'self' or 'cls' arguments to a classinstancemethod"
        #kw['self'] = self.obj
        #kw['cls'] = self.type
        #print self.func, args, kw
        return self.func(*((self.obj, self.type) + args), **kw)

    def __repr__(self):
        if self.obj is None:
            return '<bound class method %s.%s>' % (self.type.__name__, self.func.func_name)
        else:
            return '<bound method %s.%s of %r>' % (self.type.__name__, self.func.func_name, self.obj)


class DeclarativeMeta(type):

    def __new__(meta, className, bases, d):
        global _declarativeCount
        cls = type.__new__(meta, className, bases, d)
        #if d.has_key('__classinit__'):
        #    cls.__classinit__ = staticmethod(cls.__classinit__)
        cls.declarativeCount = _getCount()
        cls.__classinit__.im_func(cls)
        return cls

class Declarative(object):

    __unpackargs__ = ()

    __mutableattributes__ = ()

    __metaclass__ = DeclarativeMeta

    def __classinit__(cls):
        pass

    def __init__(self, *args, **kw):
        if self.__unpackargs__ and self.__unpackargs__[0] == '*':
            assert len(self.__unpackargs__) == 2, \
                   "When using __unpackargs__ = ('*', varname), you must only provide a single variable name (you gave %r)" % self.__unpackargs__
            name = self.__unpackargs__[1]
            if kw.has_key(name):
                raise TypeError(
                    "keyword parameter '%s' was given by position and name"
                    % name)
            kw[name] = args
        else:
            if len(args) > len(self.__unpackargs__):
                raise TypeError(
                    '%s() takes at most %i arguments (%i given)'
                    % (self.__class__.__name__,
                       len(self.__unpackargs__),
                       len(args)))
            for name, arg in zip(self.__unpackargs__, args):
                if kw.has_key(name):
                    raise TypeError(
                        "keyword parameter '%s' was given by position and name"
                        % name)
                kw[name] = arg
        if kw.has_key('__alsocopy'):
            for name, value in kw['__alsocopy'].items():
                if not kw.has_key(name):
                    if name in self.__mutableattributes__:
                        value = copy.copy(value)
                    kw[name] = value
            del kw['__alsocopy']
        for name, value in kw.items():
            setattr(self, name, value)
        if not kw.has_key('declarativeCount'):
            self.declarativeCount = _getCount()

    def __call__(self, *args, **kw):
        kw['__alsocopy'] = self.__dict__
        return self.__class__(*args, **kw)

    def singleton(cls):
        name = '_%s__singleton' % cls.__name__
        if not hasattr(cls, name):
            setattr(cls, name, cls(declarativeCount=cls.declarativeCount))
        return getattr(cls, name)
    singleton = classmethod(singleton)

    def __sourcerepr__(self, source, binding=None):
        if binding and len(self.__dict__) > 3:
            return self._sourceReprClass(source, binding=binding)
        else:
            vals = self.__dict__.copy()
            if vals.has_key('declarativeCount'):
                del vals['declarativeCount']
            args = []
            if (self.__unpackargs__ and self.__unpackargs__[0] == '*'
                and vals.has_key(self.__unpackargs__[1])):
                v = vals[self.__unpackargs__[1]]
                if isinstance(v, (list, int)):
                    args.extend(map(source.makeRepr, v))
                    del v[self.__unpackargs__[1]]
            for name in self.__unpackargs__:
                if vals.has_key(name):
                    args.append(source.makeRepr(vals[name]))
                    del vals[name]
                else:
                    break
            args.extend(['%s=%s' % (name, source.makeRepr(value))
                         for (name, value) in vals.items()])
            return '%s(%s)' % (self.__class__.__name__,
                               ', '.join(args))

    def _sourceReprClass(self, source, binding=None):
        d = self.__dict__.copy()
        if d.has_key('declarativeCount'):
            del d['declarativeCount']
        return source.makeClass(self, binding, d,
                                (self.__class__,))

    def __classsourcerepr__(cls, source, binding=None):
        d = cls.__dict__.copy()
        del d['declarativeCount']
        return source.makeClass(cls, binding or cls.__name__, d,
                                cls.__bases__)
    __classsourcerepr__ = classmethod(__classsourcerepr__)

    def __repr__(self, cls):
        if self:
            name = '%s object' % self.__class__.__name__
            v = self.__dict__.copy()
        else:
            name = '%s class' % cls.__name__
            v = cls.__dict__.copy()
        if v.has_key('declarativeCount'):
            name = '%s %i' % (name, v['declarativeCount'])
            del v['declarativeCount']
        names = v.keys()
        args = []
        for n in self._reprVars(names):
            args.append('%s=%r' % (n, v[n]))
        if not args:
            return '<%s>' % name
        else:
            return '<%s %s>' % (name, ' '.join(args))

    def _reprVars(dictNames):
        names = [n for n in dictNames
                 if not n.startswith('_')
                 and n != 'declarativeCount']
        names.sort()
        return names
    _reprVars = staticmethod(_reprVars)

    __repr__ = classinstancemethod(__repr__)

def getinstance(v):
    """
    Returns an instance of v is v is a class, else v.
    """
    if isinstance(v, type):
        return v()
    else:
        return v