fields.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

import re
import fnmatch
import inspect

from calendar import timegm
from datetime import date, datetime
from decimal import Decimal, ROUND_HALF_EVEN
from email.utils import formatdate

from six import iteritems, itervalues, text_type, string_types
from six.moves.urllib.parse import urlparse, urlunparse

from flask import url_for, request
from werkzeug.utils import cached_property

from .inputs import date_from_iso8601, datetime_from_iso8601, datetime_from_rfc822, boolean
from .errors import RestError
from .marshalling import marshal
from .utils import camel_to_dash, not_none


__all__ = ('Raw', 'String', 'FormattedString', 'Url', 'DateTime', 'Date',
           'Boolean', 'Integer', 'Float', 'Arbitrary', 'Fixed',
           'Nested', 'List', 'ClassName', 'Polymorph', 'Wildcard',
           'StringMixin', 'MinMaxMixin', 'NumberMixin', 'MarshallingError')


class MarshallingError(RestError):
    '''
    This is an encapsulating Exception in case of marshalling error.
    '''
    def __init__(self, underlying_exception):
        # just put the contextual representation of the error to hint on what
        # went wrong without exposing internals
        super(MarshallingError, self).__init__(text_type(underlying_exception))


def is_indexable_but_not_string(obj):
    return not hasattr(obj, "strip") and hasattr(obj, "__iter__")


def get_value(key, obj, default=None):
    '''Helper for pulling a keyed value off various types of objects'''
    if isinstance(key, int):
        return _get_value_for_key(key, obj, default)
    elif callable(key):
        return key(obj)
    else:
        return _get_value_for_keys(key.split('.'), obj, default)


def _get_value_for_keys(keys, obj, default):
    if len(keys) == 1:
        return _get_value_for_key(keys[0], obj, default)
    else:
        return _get_value_for_keys(
            keys[1:], _get_value_for_key(keys[0], obj, default), default)


def _get_value_for_key(key, obj, default):
    if is_indexable_but_not_string(obj):
        try:
            return obj[key]
        except (IndexError, TypeError, KeyError):
            pass
    return getattr(obj, key, default)


def to_marshallable_type(obj):
    '''
    Helper for converting an object to a dictionary only if it is not
    dictionary already or an indexable object nor a simple type
    '''
    if obj is None:
        return None  # make it idempotent for None

    if hasattr(obj, '__marshallable__'):
        return obj.__marshallable__()

    if hasattr(obj, '__getitem__'):
        return obj  # it is indexable it is ok

    return dict(obj.__dict__)


class Raw(object):
    '''
    Raw provides a base field class from which others should extend. It
    applies no formatting by default, and should only be used in cases where
    data does not need to be formatted before being serialized. Fields should
    throw a :class:`MarshallingError` in case of parsing problem.

    :param default: The default value for the field, if no value is
        specified.
    :param attribute: If the public facing value differs from the internal
        value, use this to retrieve a different attribute from the response
        than the publicly named value.
    :param str title: The field title (for documentation purpose)
    :param str description: The field description (for documentation purpose)
    :param bool required: Is the field required ?
    :param bool readonly: Is the field read only ? (for documentation purpose)
    :param example: An optional data example (for documentation purpose)
    :param callable mask: An optional mask function to be applied to output
    '''
    #: The JSON/Swagger schema type
    __schema_type__ = 'object'
    #: The JSON/Swagger schema format
    __schema_format__ = None
    #: An optional JSON/Swagger schema example
    __schema_example__ = None

    def __init__(self, default=None, attribute=None, title=None, description=None,
                 required=None, readonly=None, example=None, mask=None, **kwargs):
        self.attribute = attribute
        self.default = default
        self.title = title
        self.description = description
        self.required = required
        self.readonly = readonly
        self.example = example or self.__schema_example__
        self.mask = mask

    def format(self, value):
        '''
        Formats a field's value. No-op by default - field classes that
        modify how the value of existing object keys should be presented should
        override this and apply the appropriate formatting.

        :param value: The value to format
        :raises MarshallingError: In case of formatting problem

        Ex::

            class TitleCase(Raw):
                def format(self, value):
                    return unicode(value).title()
        '''
        return value

    def output(self, key, obj, **kwargs):
        '''
        Pulls the value for the given key from the object, applies the
        field's formatting and returns the result. If the key is not found
        in the object, returns the default value. Field classes that create
        values which do not require the existence of the key in the object
        should override this and return the desired value.

        :raises MarshallingError: In case of formatting problem
        '''

        value = get_value(key if self.attribute is None else self.attribute, obj)

        if value is None:
            default = self._v('default')
            return self.format(default) if default else default

        try:
            data = self.format(value)
        except MarshallingError as e:
            msg = 'Unable to marshal field "{0}" value "{1}": {2}'.format(key, value, str(e))
            raise MarshallingError(msg)
        return self.mask.apply(data) if self.mask else data

    def _v(self, key):
        '''Helper for getting a value from attribute allowing callable'''
        value = getattr(self, key)
        return value() if callable(value) else value

    @cached_property
    def __schema__(self):
        return not_none(self.schema())

    def schema(self):
        return {
            'type': self.__schema_type__,
            'format': self.__schema_format__,
            'title': self.title,
            'description': self.description,
            'readOnly': self.readonly,
            'default': self._v('default'),
            'example': self.example,
        }


class Nested(Raw):
    '''
    Allows you to nest one set of fields inside another.
    See :ref:`nested-field` for more information

    :param dict model: The model dictionary to nest
    :param bool allow_null: Whether to return None instead of a dictionary
        with null keys, if a nested dictionary has all-null keys
    :param bool skip_none: Optional key will be used to eliminate inner fields
                           which value is None or the inner field's key not
                           exist in data
    :param kwargs: If ``default`` keyword argument is present, a nested
        dictionary will be marshaled as its value if nested dictionary is
        all-null keys (e.g. lets you return an empty JSON object instead of
        null)
    '''
    __schema_type__ = None

    def __init__(self, model, allow_null=False, skip_none=False, as_list=False, **kwargs):
        self.model = model
        self.as_list = as_list
        self.allow_null = allow_null
        self.skip_none = skip_none
        super(Nested, self).__init__(**kwargs)

    @property
    def nested(self):
        return getattr(self.model, 'resolved', self.model)

    def output(self, key, obj, ordered=False, **kwargs):
        value = get_value(key if self.attribute is None else self.attribute, obj)
        if value is None:
            if self.allow_null:
                return None
            elif self.default is not None:
                return self.default

        return marshal(value, self.nested, skip_none=self.skip_none, ordered=ordered)

    def schema(self):
        schema = super(Nested, self).schema()
        ref = '#/definitions/{0}'.format(self.nested.name)

        if self.as_list:
            schema['type'] = 'array'
            schema['items'] = {'$ref': ref}
        elif any(schema.values()):
            # There is already some properties in the schema
            allOf = schema.get('allOf', [])
            allOf.append({'$ref': ref})
            schema['allOf'] = allOf
        else:
            schema['$ref'] = ref
        return schema

    def clone(self, mask=None):
        kwargs = self.__dict__.copy()
        model = kwargs.pop('model')
        if mask:
            model = mask.apply(model.resolved if hasattr(model, 'resolved') else model)
        return self.__class__(model, **kwargs)


class List(Raw):
    '''
    Field for marshalling lists of other fields.

    See :ref:`list-field` for more information.

    :param cls_or_instance: The field type the list will contain.
    '''
    def __init__(self, cls_or_instance, **kwargs):
        self.min_items = kwargs.pop('min_items', None)
        self.max_items = kwargs.pop('max_items', None)
        self.unique = kwargs.pop('unique', None)
        super(List, self).__init__(**kwargs)
        error_msg = 'The type of the list elements must be a subclass of fields.Raw'
        if isinstance(cls_or_instance, type):
            if not issubclass(cls_or_instance, Raw):
                raise MarshallingError(error_msg)
            self.container = cls_or_instance()
        else:
            if not isinstance(cls_or_instance, Raw):
                raise MarshallingError(error_msg)
            self.container = cls_or_instance

    def format(self, value):
        # Convert all instances in typed list to container type
        if isinstance(value, set):
            value = list(value)

        is_nested = isinstance(self.container, Nested) or type(self.container) is Raw

        def is_attr(val):
            return self.container.attribute and hasattr(val, self.container.attribute)

        if value is None:
            return []
        return [
            self.container.output(idx,
                                  val if (isinstance(val, dict) or is_attr(val)) and not is_nested else value)
            for idx, val in enumerate(value)
        ]

    def output(self, key, data, ordered=False, **kwargs):
        value = get_value(key if self.attribute is None else self.attribute, data)
        # we cannot really test for external dict behavior
        if is_indexable_but_not_string(value) and not isinstance(value, dict):
            return self.format(value)

        if value is None:
            return self._v('default')

        return [marshal(value, self.container.nested)]

    def schema(self):
        schema = super(List, self).schema()
        schema.update(minItems=self._v('min_items'),
                      maxItems=self._v('max_items'),
                      uniqueItems=self._v('unique'))
        schema['type'] = 'array'
        schema['items'] = self.container.__schema__
        return schema

    def clone(self, mask=None):
        kwargs = self.__dict__.copy()
        model = kwargs.pop('container')
        if mask:
            model = mask.apply(model)
        return self.__class__(model, **kwargs)


class StringMixin(object):
    __schema_type__ = 'string'

    def __init__(self, *args, **kwargs):
        self.min_length = kwargs.pop('min_length', None)
        self.max_length = kwargs.pop('max_length', None)
        self.pattern = kwargs.pop('pattern', None)
        super(StringMixin, self).__init__(*args, **kwargs)

    def schema(self):
        schema = super(StringMixin, self).schema()
        schema.update(minLength=self._v('min_length'),
                      maxLength=self._v('max_length'),
                      pattern=self._v('pattern'))
        return schema


class MinMaxMixin(object):
    def __init__(self, *args, **kwargs):
        self.minimum = kwargs.pop('min', None)
        self.exclusiveMinimum = kwargs.pop('exclusiveMin', None)
        self.maximum = kwargs.pop('max', None)
        self.exclusiveMaximum = kwargs.pop('exclusiveMax', None)
        super(MinMaxMixin, self).__init__(*args, **kwargs)

    def schema(self):
        schema = super(MinMaxMixin, self).schema()
        schema.update(minimum=self._v('minimum'),
                      exclusiveMinimum=self._v('exclusiveMinimum'),
                      maximum=self._v('maximum'),
                      exclusiveMaximum=self._v('exclusiveMaximum'))
        return schema


class NumberMixin(MinMaxMixin):
    __schema_type__ = 'number'

    def __init__(self, *args, **kwargs):
        self.multiple = kwargs.pop('multiple', None)
        super(NumberMixin, self).__init__(*args, **kwargs)

    def schema(self):
        schema = super(NumberMixin, self).schema()
        schema.update(multipleOf=self._v('multiple'))
        return schema


class String(StringMixin, Raw):
    '''
    Marshal a value as a string. Uses ``six.text_type`` so values will
    be converted to :class:`unicode` in python2 and :class:`str` in
    python3.
    '''
    def __init__(self, *args, **kwargs):
        self.enum = kwargs.pop('enum', None)
        self.discriminator = kwargs.pop('discriminator', None)
        super(String, self).__init__(*args, **kwargs)
        self.required = self.discriminator or self.required

    def format(self, value):
        try:
            return text_type(value)
        except ValueError as ve:
            raise MarshallingError(ve)

    def schema(self):
        enum = self._v('enum')
        schema = super(String, self).schema()
        if enum:
            schema.update(enum=enum)
        if enum and schema['example'] is None:
            schema['example'] = enum[0]
        return schema


class Integer(NumberMixin, Raw):
    '''
    Field for outputting an integer value.

    :param int default: The default value for the field, if no value is specified.
    '''
    __schema_type__ = 'integer'

    def format(self, value):
        try:
            if value is None:
                return self.default
            return int(value)
        except ValueError as ve:
            raise MarshallingError(ve)


class Float(NumberMixin, Raw):
    '''
    A double as IEEE-754 double precision.

    ex : 3.141592653589793 3.1415926535897933e-06 3.141592653589793e+24 nan inf -inf
    '''

    def format(self, value):
        try:
            return float(value)
        except ValueError as ve:
            raise MarshallingError(ve)


class Arbitrary(NumberMixin, Raw):
    '''
    A floating point number with an arbitrary precision.

    ex: 634271127864378216478362784632784678324.23432
    '''

    def format(self, value):
        return text_type(Decimal(value))


ZERO = Decimal()


class Fixed(NumberMixin, Raw):
    '''
    A decimal number with a fixed precision.
    '''
    def __init__(self, decimals=5, **kwargs):
        super(Fixed, self).__init__(**kwargs)
        self.precision = Decimal('0.' + '0' * (decimals - 1) + '1')

    def format(self, value):
        dvalue = Decimal(value)
        if not dvalue.is_normal() and dvalue != ZERO:
            raise MarshallingError('Invalid Fixed precision number.')
        return text_type(dvalue.quantize(self.precision, rounding=ROUND_HALF_EVEN))


class Boolean(Raw):
    '''
    Field for outputting a boolean value.

    Empty collections such as ``""``, ``{}``, ``[]``, etc. will be converted to ``False``.
    '''
    __schema_type__ = 'boolean'

    def format(self, value):
        return boolean(value)


class DateTime(MinMaxMixin, Raw):
    '''
    Return a formatted datetime string in UTC. Supported formats are RFC 822 and ISO 8601.

    See :func:`email.utils.formatdate` for more info on the RFC 822 format.

    See :meth:`datetime.datetime.isoformat` for more info on the ISO 8601 format.

    :param str dt_format: ``rfc822`` or ``iso8601``
    '''
    __schema_type__ = 'string'
    __schema_format__ = 'date-time'

    def __init__(self, dt_format='iso8601', **kwargs):
        super(DateTime, self).__init__(**kwargs)
        self.dt_format = dt_format

    def parse(self, value):
        if value is None:
            return None
        elif isinstance(value, string_types):
            parser = datetime_from_iso8601 if self.dt_format == 'iso8601' else datetime_from_rfc822
            return parser(value)
        elif isinstance(value, datetime):
            return value
        elif isinstance(value, date):
            return datetime(value.year, value.month, value.day)
        else:
            raise ValueError('Unsupported DateTime format')

    def format(self, value):
        try:
            value = self.parse(value)
            if self.dt_format == 'iso8601':
                return self.format_iso8601(value)
            elif self.dt_format == 'rfc822':
                return self.format_rfc822(value)
            else:
                raise MarshallingError(
                    'Unsupported date format %s' % self.dt_format
                )
        except (AttributeError, ValueError) as e:
            raise MarshallingError(e)

    def format_rfc822(self, dt):
        '''
        Turn a datetime object into a formatted date.

        :param datetime dt: The datetime to transform
        :return: A RFC 822 formatted date string
        '''
        return formatdate(timegm(dt.utctimetuple()))

    def format_iso8601(self, dt):
        '''
        Turn a datetime object into an ISO8601 formatted date.

        :param datetime dt: The datetime to transform
        :return: A ISO 8601 formatted date string
        '''
        return dt.isoformat()

    def _for_schema(self, name):
        value = self.parse(self._v(name))
        return self.format(value) if value else None

    def schema(self):
        schema = super(DateTime, self).schema()
        schema['default'] = self._for_schema('default')
        schema['minimum'] = self._for_schema('minimum')
        schema['maximum'] = self._for_schema('maximum')
        return schema


class Date(DateTime):
    '''
    Return a formatted date string in UTC in ISO 8601.

    See :meth:`datetime.date.isoformat` for more info on the ISO 8601 format.
    '''
    __schema_format__ = 'date'

    def __init__(self, **kwargs):
        kwargs.pop('dt_format', None)
        super(Date, self).__init__(dt_format='iso8601', **kwargs)

    def parse(self, value):
        if value is None:
            return None
        elif isinstance(value, string_types):
            return date_from_iso8601(value)
        elif isinstance(value, datetime):
            return value.date()
        elif isinstance(value, date):
            return value
        else:
            raise ValueError('Unsupported Date format')


class Url(StringMixin, Raw):
    '''
    A string representation of a Url

    :param str endpoint: Endpoint name. If endpoint is ``None``, ``request.endpoint`` is used instead
    :param bool absolute: If ``True``, ensures that the generated urls will have the hostname included
    :param str scheme: URL scheme specifier (e.g. ``http``, ``https``)
    '''
    def __init__(self, endpoint=None, absolute=False, scheme=None, **kwargs):
        super(Url, self).__init__(**kwargs)
        self.endpoint = endpoint
        self.absolute = absolute
        self.scheme = scheme

    def output(self, key, obj, **kwargs):
        try:
            data = to_marshallable_type(obj)
            endpoint = self.endpoint if self.endpoint is not None else request.endpoint
            o = urlparse(url_for(endpoint, _external=self.absolute, **data))
            if self.absolute:
                scheme = self.scheme if self.scheme is not None else o.scheme
                return urlunparse((scheme, o.netloc, o.path, "", "", ""))
            return urlunparse(("", "", o.path, "", "", ""))
        except TypeError as te:
            raise MarshallingError(te)


class FormattedString(StringMixin, Raw):
    '''
    FormattedString is used to interpolate other values from
    the response into this field. The syntax for the source string is
    the same as the string :meth:`~str.format` method from the python
    stdlib.

    Ex::

        fields = {
            'name': fields.String,
            'greeting': fields.FormattedString("Hello {name}")
        }
        data = {
            'name': 'Doug',
        }
        marshal(data, fields)

    :param str src_str: the string to format with the other values from the response.
    '''
    def __init__(self, src_str, **kwargs):
        super(FormattedString, self).__init__(**kwargs)
        self.src_str = text_type(src_str)

    def output(self, key, obj, **kwargs):
        try:
            data = to_marshallable_type(obj)
            return self.src_str.format(**data)
        except (TypeError, IndexError) as error:
            raise MarshallingError(error)


class ClassName(String):
    '''
    Return the serialized object class name as string.

    :param bool dash: If `True`, transform CamelCase to kebab_case.
    '''
    def __init__(self, dash=False, **kwargs):
        super(ClassName, self).__init__(**kwargs)
        self.dash = dash

    def output(self, key, obj, **kwargs):
        classname = obj.__class__.__name__
        if classname == 'dict':
            return 'object'
        return camel_to_dash(classname) if self.dash else classname


class Polymorph(Nested):
    '''
    A Nested field handling inheritance.

    Allows you to specify a mapping between Python classes and fields specifications.

    .. code-block:: python

        mapping = {
            Child1: child1_fields,
            Child2: child2_fields,
        }

        fields = api.model('Thing', {
            owner: fields.Polymorph(mapping)
        })

    :param dict mapping: Maps classes to their model/fields representation
    '''
    def __init__(self, mapping, required=False, **kwargs):
        self.mapping = mapping
        parent = self.resolve_ancestor(list(itervalues(mapping)))
        super(Polymorph, self).__init__(parent, allow_null=not required, **kwargs)

    def output(self, key, obj, ordered=False, **kwargs):
        # Copied from upstream NestedField
        value = get_value(key if self.attribute is None else self.attribute, obj)
        if value is None:
            if self.allow_null:
                return None
            elif self.default is not None:
                return self.default

        # Handle mappings
        if not hasattr(value, '__class__'):
            raise ValueError('Polymorph field only accept class instances')

        candidates = [fields for cls, fields in iteritems(self.mapping) if type(value) == cls]

        if len(candidates) <= 0:
            raise ValueError('Unknown class: ' + value.__class__.__name__)
        elif len(candidates) > 1:
            raise ValueError('Unable to determine a candidate for: ' + value.__class__.__name__)
        else:
            return marshal(value, candidates[0].resolved, mask=self.mask, ordered=ordered)

    def resolve_ancestor(self, models):
        '''
        Resolve the common ancestor for all models.

        Assume there is only one common ancestor.
        '''
        ancestors = [m.ancestors for m in models]
        candidates = set.intersection(*ancestors)
        if len(candidates) != 1:
            field_names = [f.name for f in models]
            raise ValueError('Unable to determine the common ancestor for: ' + ', '.join(field_names))

        parent_name = candidates.pop()
        return models[0].get_parent(parent_name)

    def clone(self, mask=None):
        data = self.__dict__.copy()
        mapping = data.pop('mapping')
        for field in ('allow_null', 'model'):
            data.pop(field, None)

        data['mask'] = mask
        return Polymorph(mapping, **data)


class Wildcard(Raw):
    '''
    Field for marshalling list of "unkown" fields.

    :param cls_or_instance: The field type the list will contain.
    '''
    exclude = set()
    # cache the flat object
    _flat = None
    _obj = None
    _cache = set()
    _last = None

    def __init__(self, cls_or_instance, **kwargs):
        super(Wildcard, self).__init__(**kwargs)
        error_msg = 'The type of the wildcard elements must be a subclass of fields.Raw'
        if isinstance(cls_or_instance, type):
            if not issubclass(cls_or_instance, Raw):
                raise MarshallingError(error_msg)
            self.container = cls_or_instance()
        else:
            if not isinstance(cls_or_instance, Raw):
                raise MarshallingError(error_msg)
            self.container = cls_or_instance

    def _flatten(self, obj):
        if obj is None:
            return None
        if obj == self._obj and self._flat is not None:
            return self._flat
        if isinstance(obj, dict):
            self._flat = [x for x in iteritems(obj)]
        else:

            def __match_attributes(attribute):
                attr_name, attr_obj = attribute
                if inspect.isroutine(attr_obj) or \
                        (attr_name.startswith('__') and attr_name.endswith('__')):
                    return False
                return True

            attributes = inspect.getmembers(obj)
            self._flat = [x for x in attributes if __match_attributes(x)]

        self._cache = set()
        self._obj = obj
        return self._flat

    @property
    def key(self):
        return self._last

    def reset(self):
        self.exclude = set()
        self._flat = None
        self._obj = None
        self._cache = set()
        self._last = None

    def output(self, key, obj, ordered=False):
        value = None
        reg = fnmatch.translate(key)

        if self._flatten(obj):
            while True:
                try:
                    # we are using pop() so that we don't
                    # loop over the whole object every time dropping the
                    # complexity to O(n)
                    (objkey, val) = self._flat.pop()
                    if objkey not in self._cache and \
                            objkey not in self.exclude and \
                            re.match(reg, objkey, re.IGNORECASE):
                        value = val
                        self._cache.add(objkey)
                        self._last = objkey
                        break
                except IndexError:
                    break

        if value is None:
            if self.default is not None:
                return self.container.format(self.default)
            return None

        if isinstance(self.container, Nested):
            return marshal(value, self.container.nested, skip_none=self.container.skip_none, ordered=ordered)
        return self.container.format(value)

    def schema(self):
        schema = super(Wildcard, self).schema()
        schema['type'] = 'object'
        schema['additionalProperties'] = self.container.__schema__
        return schema

    def clone(self):
        kwargs = self.__dict__.copy()
        model = kwargs.pop('container')
        return self.__class__(model, **kwargs)