#!/usr/bin/env python
from dataclasses import * #dataclass, make_dataclass

def validate_positive(name, value):
    '''eine einfache Validierungsfunktion'''
    if value < 0:
        raise ValueError(
            f'The value for {name!r} must be positive, {value!r} is not.')


class YearBetweenValidator:
    '''komplexerer Validator, beachte die magische Methode __call__'''
    def __init__(self, mini, maxi):
        self.mini, self.maxi = mini, maxi

    def __call__(self, name, value):
        if value > self.mini and value < self.maxi:
            return True
        raise ValueError(f'The value for {name!r} must be between {self.mini!r} and {self.maxi!r}, {value!r} is not.')


class BaseDesc:
    '''ein Deskriptor'''
    def __init__(self, type, validators=[]):
        self.type = type
        self.validators = validators
        
    def __set_name__(self, owner, name):
        self.name = name
    
    def __get__(self, obj, objtype=None):
        return getattr(self, self.name)

    def __set__(self, obj, value):
        if not isinstance(value, self.type):
            raise TypeError(f'The value for {self.name!r} must be a {self.type!r}, {value!r} is not.')
        for validate in self.validators:
            validate(self.name, value)
        setattr(self, self.name, value)


class BaseData:
    class meta:
        '''docstrings are cool, too...'''
        s = '''This is just a metaclass whose attributes are not in BaseData...'''
        
    def getFields(self):
        return list(self.__dataclass_fields__.keys())

    def printme(self):
        rv = list()
        fields = self.getFields()
        for field in fields:
            rv.append('{}={}'.format(field, getattr(self, field, None)))
        print(' '.join(rv))
        return(rv)


def makePerson():
    rv = make_dataclass(
        'Person',
        bases=(BaseData,),
        fields=[
            ('vorname', str, field(default=BaseDesc(str))),
            ('nachname', str, field(default=BaseDesc(str))),
        ]
    )
    return rv


def makeStudent():
    rv = make_dataclass(
        'Student',
        bases=(BaseData,),
        fields=[
            ('vorname', str, field(default=BaseDesc(str))),
            ('nachname', str, field(default=BaseDesc(str))),
            ('matriculation', int, field(default=BaseDesc(int, [validate_positive]))),
        ]
    )
    return rv


def makeGraduate():
    rv = make_dataclass(
        'Graduate',
        bases=(BaseData,),
        fields=[
            ('vorname', str, field(default=BaseDesc(str))),
            ('nachname', str, field(default=BaseDesc(str))),
            ('matriculation', int, field(default=BaseDesc(int, [validate_positive]))),
            ('graduation', int, field(default=BaseDesc(int, [validate_positive, YearBetweenValidator(1990, 2020)]))),            
        ]
    )
    return rv


if __name__ == '__main__':
    Person = makePerson()
    Student = makeStudent()
    Graduate = makeGraduate()
    try:
        print(Person('Sheeva', 'Plug'))
    except Exception as e:
        print(str(e))

    try:
        print(Student('Sheeva', 'Plug', 1991))
    except Exception as e:
        print(str(e))
        
    try:
        print(Graduate('Sheeva', 'Plug', 1991, 1995))
    except Exception as e:
        print(str(e))
    
    try:
        print(Graduate('Sheeva', 'Plug', 1991, '1995'))
    except Exception as e:
        print(str(e))

    try:
        print(Graduate('Sheeva', 'Plug', 1991, -1995))
    except Exception as e:
        print(str(e))

    try:
        print(Graduate('Sheeva', 'Plug', 1989, 1989))
    except Exception as e:
        print(str(e))

    print('-------------------------------------------------------------')
    try:
        print(Graduate('Sheeva', 'Plug', 1991, 1995).getFields())
    except Exception as e:
        print(str(e))
      
    print('-------------------------------------------------------------')
    try:
        makeGraduate()('Sheeva', 'Plug', 1991, '1995').printme()
    except Exception as e:
        print(str(e))
    
    print('-------------------------------------------------------------')
    try:
        g = makeGraduate()('Sheeva', 'Plug', 1991, 1995)
        g.printme()
        print(g.meta.s)
        print(g.meta.__doc__)
        print(vars(g))
        print({i: getattr(g, i) for i in dir(g)})
    except Exception as e:
        print(str(e))