"""
PynamoDB attributes
"""
import six
import json
from base64 import b64encode, b64decode
from delorean import Delorean, parse
from pynamodb.constants import (
    STRING, NUMBER, BINARY, UTC, DATETIME_FORMAT, BINARY_SET, STRING_SET, NUMBER_SET,
    DEFAULT_ENCODING
)


class Attribute(object):
    """
    An attribute of a model
    """
    attr_name = None
    attr_type = None
    null = False

    def __init__(self,
                 hash_key=False,
                 range_key=False,
                 null=None,
                 default=None,
                 attr_name=None
                 ):
        self.default = default
        if null is not None:
            self.null = null
        self.is_hash_key = hash_key
        self.is_range_key = range_key
        if attr_name is not None:
            self.attr_name = attr_name

    def __set__(self, instance, value):
        if isinstance(value, Attribute):
            return self
        if instance:
            instance.attribute_values[self.attr_name] = value

    def __get__(self, instance, owner):
        if instance:
            return instance.attribute_values.get(self.attr_name, None)
        else:
            return self

    def serialize(self, value):
        """
        This method should return a dynamodb compatible value
        """
        return value

    def deserialize(self, value):
        """
        Performs any needed deserialization on the value
        """
        return value


class SetMixin(object):
    """
    Adds (de)serialization methods for sets
    """
    def serialize(self, value):
        """
        Serializes a set

        Because dynamodb doesn't store empty attributes,
        empty sets return None
        """
        if value is not None:
            try:
                iter(value)
            except TypeError:
                value = [value]
            if len(value):
                return [json.dumps(val) for val in sorted(value)]
        return None

    def deserialize(self, value):
        """
        Deserializes a set
        """
        if value and len(value):
            return set([json.loads(val) for val in value])


class BinaryAttribute(Attribute):
    """
    A binary attribute
    """
    attr_type = BINARY

    def serialize(self, value):
        """
        Returns a base64 encoded binary string
        """
        return b64encode(value).decode(DEFAULT_ENCODING)

    def deserialize(self, value):
        """
        Returns a decoded string from base64
        """
        try:
            return b64decode(value.decode(DEFAULT_ENCODING))
        except AttributeError:
            return b64decode(value)


class BinarySetAttribute(SetMixin, Attribute):
    """
    A binary set
    """
    attr_type = BINARY_SET
    null = True

    def serialize(self, value):
        """
        Returns a base64 encoded binary string
        """
        if value and len(value):
            return [b64encode(val).decode(DEFAULT_ENCODING) for val in sorted(value)]
        else:
            return None

    def deserialize(self, value):
        """
        Returns a decoded string from base64
        """
        if value and len(value):
            return set([b64decode(val.encode(DEFAULT_ENCODING)) for val in value])


class UnicodeSetAttribute(SetMixin, Attribute):
    """
    A unicode set
    """
    attr_type = STRING_SET
    null = True


class UnicodeAttribute(Attribute):
    """
    A unicode attribute
    """
    attr_type = STRING

    def serialize(self, value):
        """
        Returns a unicode string
        """
        if value is None or not len(value):
            return None
        return unicode(value)


class JSONAttribute(Attribute):
    """
    A JSON Attribute

    Encodes JSON to unicode internally
    """
    attr_type = STRING

    def serialize(self, value):
        """
        Serializes JSON to unicode
        """
        if value is None:
            return None
        encoded = json.dumps(value)

        try:
            return unicode(encoded)
        except NameError:
            return encoded

    def deserialize(self, value):
        """
        Deserializes JSON
        """
        return json.loads(value, strict=False)


class BooleanAttribute(Attribute):
    """
    A class for boolean attributes

    This attribute type uses a number attribute to save space
    """
    attr_type = NUMBER

    def serialize(self, value):
        """
        Encodes True as 1, False as 0
        """
        if value is None:
            return None
        elif value:
            return json.dumps(1)
        else:
            return json.dumps(0)

    def deserialize(self, value):
        """
        Encode
        """
        return bool(json.loads(value))


class NumberSetAttribute(SetMixin, Attribute):
    """
    A number set attribute
    """
    attr_type = NUMBER_SET
    null = True


class NumberAttribute(Attribute):
    """
    A number attribute
    """
    attr_type = NUMBER

    def serialize(self, value):
        """
        Encode numbers as JSON
        """
        return json.dumps(value)

    def deserialize(self, value):
        """
        Decode numbers from JSON
        """
        return json.loads(value)


class UTCDateTimeAttribute(Attribute):
    """
    An attribute for storing a UTC Datetime
    """
    attr_type = STRING

    def serialize(self, value):
        """
        Takes a datetime object and returns a string
        """
        fmt = Delorean(value, timezone=UTC).datetime.strftime(DATETIME_FORMAT)
        return unicode(fmt)

    def deserialize(self, value):
        """
        Takes a UTC datetime string and returns a datetime object
        """
        return parse(value).datetime
