"""
Validators for applying validations in sequence.
"""

from api import *

# @@ ianb 2005-05: should CompoundValidator be included?
__all__ = ['Any', 'All', 'Pipe']

############################################################
## Compound Validators
############################################################

def to_python(validator, value, state):
    return validator.to_python(value, state)


def from_python(validator, value, state):
    return validator.from_python(value, state)


class CompoundValidator(FancyValidator):

    if_invalid = NoDefault
    accept_iterator = False

    validators = []

    __unpackargs__ = ('*', 'validatorArgs')

    __mutableattributes__ = ('validators',)

    def __classinit__(cls, new_attrs):
        toAdd = []
        for name, value in new_attrs.items():
            if is_validator(value) and value is not Identity:
                toAdd.append((name, value))
                # @@: Should we really delete too?
                delattr(cls, name)
        toAdd.sort()
        cls.validators.extend([v for n, v in toAdd])

    def __init__(self, *args, **kw):
        Validator.__init__(self, *args, **kw)
        self.validators = self.validators[:]
        self.validators.extend(self.validatorArgs)

    def _reprVars(names):
        return [n for n in Validator._reprVars(names)
                if n != 'validatorArgs']
    _reprVars = staticmethod(_reprVars)

    def attempt_convert(self, value, state, convertFunc):
        raise NotImplementedError, "Subclasses must implement attempt_convert"

    def _to_python(self, value, state=None):
        return self.attempt_convert(value, state,
                                    to_python)
    
    def _from_python(self, value, state=None):
        return self.attempt_convert(value, state,
                                    from_python)

    def subvalidators(self):
        return self.validators


class Any(CompoundValidator):
    """
    This class is like an 'or' operator for validators.  The first 
    validator/converter in the order of evaluation that validates the value
    will be used.

    The order of evaluation differs depending on if you are validating to
    python or from python as follows:

    The validators are evaluated right to left when validating to python.

    The validators are evaluated left to right when validating from python.
    """

    def attempt_convert(self, value, state, validate):
        lastException = None
        if validate is to_python:
            validators = self.validators[::-1]
        else:
            validators = self.validators
        for validator in validators:
            try:
                return validate(validator, value, state)
            except Invalid, e:
                lastException = e
        if self.if_invalid is NoDefault:
            raise lastException
        else:
            return self.if_invalid

    def not_empty__get(self):
        not_empty = True
        for validator in self.validators:
            not_empty = not_empty and getattr(validator, 'not_empty', False)
        return not_empty
    not_empty = property(not_empty__get)

    def is_empty(self, value):
        # sub-validators should handle emptiness.
        return False

    def accept_iterator__get(self):
        accept_iterator = False
        for validator in self.validators:
            accept_iterator = accept_iterator or getattr(validator, 'accept_iterator', False)
        return accept_iterator
    accept_iterator = property(accept_iterator__get)


class All(CompoundValidator):
    """
    This class is like an 'and' operator for validators.  All
    validators must work, and the results are passed in turn through
    all validators for conversion in the order of evaluation. All
    is the same as `Pipe` but operates in the reverse order.

    The order of evaluation differs depending on if you are validating to
    python or from python as follows:

    The validators are evaluated right to left when validating to python.

    The validators are evaluated left to right when validating from python.

    `Pipe` is more intuitive when predominatenly validating to python.

    Examples::

        >>> from formencode.validators import DictConverter
        >>> av = All(validators=[DictConverter({2: 1}), DictConverter({3: 2}), DictConverter({4: 3})])
        >>> av.to_python(4)
        1
        >>> av.from_python(1)
        4

    """

    def __repr__(self):
        return '<All %s>' % self.validators

    def attempt_convert(self, value, state, validate):
        # To preserve the order of the transformations, we do them
        # differently when we are converting to and from python.
        if validate is to_python:
            validators = list(self.validators)
            validators.reverse()
        else:
            validators = self.validators
        try:
            for validator in validators:
                value = validate(validator, value, state)
            return value
        except Invalid:
            if self.if_invalid is NoDefault:
                raise
            return self.if_invalid

    def with_validator(self, validator):
        """
        Adds the validator (or list of validators) to a copy of
        this validator.
        """
        new = self.validators[:]
        if isinstance(validator, list) or isinstance(validator, tuple):
            new.extend(validator)
        else:
            new.append(validator)
        return self.__class__(*new, **dict(if_invalid=self.if_invalid))

    def join(cls, *validators):
        """
        Joins several validators together as a single validator,
        filtering out None and trying to keep `All` validators from
        being nested (which isn't needed).
        """
        validators = filter(lambda v: v and v is not Identity, validators)
        if not validators:
            return Identity
        if len(validators) == 1:
            return validators[0]
        elif isinstance(validators[0], All):
            return validators[0].with_validator(validators[1:])
        else:
            return cls(*validators)
    join = classmethod(join)

    def if_missing__get(self):
        for validator in self.validators:
            v = validator.if_missing
            if v is not NoDefault:
                return v
        return NoDefault
    if_missing = property(if_missing__get)

    def not_empty__get(self):
        not_empty = False
        for validator in self.validators:
            not_empty = not_empty or getattr(validator, 'not_empty', False)
        return not_empty
    not_empty = property(not_empty__get)

    def is_empty(self, value):
        # sub-validators should handle emptiness.
        return False

    def accept_iterator__get(self):
        accept_iterator = True
        for validator in self.validators:
            accept_iterator = accept_iterator and getattr(validator, 'accept_iterator', False)
        return accept_iterator
    accept_iterator = property(accept_iterator__get)


class Pipe(All):
    """
    This class works like `All` but the order of evaluation is opposite. All
    validators must work, and the results are passed in turn through
    each validator for conversion in the order of evaluation.  A behaviour
    known to Unix and GNU users as 'pipe'.

    The order of evaluation differs depending on if you are validating to
    python or from python as follows:

    The validators are evaluated left to right when validating to python.

    The validators are evaluated right to left when validating from python.

    Examples::

        >>> from formencode.validators import DictConverter
        >>> pv = Pipe(validators=[DictConverter({1: 2}), DictConverter({2: 3}), DictConverter({3: 4})])
        >>> pv.to_python(1)
        4
        >>> pv.from_python(4)
        1

    """

    def __repr__(self):
        return '<Pipe %s>' % self.validators

    def attempt_convert(self, value, state, validate):
        # To preserve the order of the transformations, we do them
        # differently when we are converting to and from Python.
        if validate is from_python:
            validators = list(self.validators)
            validators.reverse()
        else:
            validators = self.validators
        try:
            for validator in validators:
                value = validate(validator, value, state)
            return value
        except Invalid:
            if self.if_invalid is NoDefault:
                raise
            return self.if_invalid