import datetime
import decimal
from typing import Optional, List, Type, TYPE_CHECKING

import sqlalchemy
from pydantic import Json
from pydantic.fields import ModelField

import orm
from orm.exceptions import ModelDefinitionError, RelationshipInstanceError

if TYPE_CHECKING:  # pragma no cover
    from orm.models import Model


class BaseField:
    __type__ = None

    def __init__(self, *args, **kwargs) -> None:
        name = kwargs.pop('name', None)
        args = list(args)
        if args:
            if isinstance(args[0], str):
                if name is not None:
                    raise ModelDefinitionError(
                        'Column name cannot be passed positionally and as a keyword.'
                    )
                name = args.pop(0)

        self.name = name
        self.primary_key = kwargs.pop('primary_key', False)
        self.autoincrement = kwargs.pop('autoincrement', self.primary_key and self.__type__ == int)

        self.nullable = kwargs.pop('nullable', not self.primary_key)
        self.default = kwargs.pop('default', None)
        self.server_default = kwargs.pop('server_default', None)

        self.index = kwargs.pop('index', None)
        self.unique = kwargs.pop('unique', None)

        self.pydantic_only = kwargs.pop('pydantic_only', False)
        if self.pydantic_only and self.primary_key:
            raise ModelDefinitionError('Primary key column cannot be pydantic only.')

    @property
    def is_required(self):
        return not self.nullable and not self.has_default and not self.is_auto_primary_key

    @property
    def default_value(self):
        default = self.default if self.default is not None else self.server_default
        return default() if callable(default) else default

    @property
    def has_default(self):
        return self.default is not None or self.server_default is not None

    @property
    def is_auto_primary_key(self):
        if self.primary_key:
            return self.autoincrement
        return False

    def get_column(self, name: str = None) -> sqlalchemy.Column:
        self.name = self.name or name
        constraints = self.get_constraints()
        return sqlalchemy.Column(
            self.name,
            self.get_column_type(),
            *constraints,
            primary_key=self.primary_key,
            autoincrement=self.autoincrement,
            nullable=self.nullable,
            index=self.index,
            unique=self.unique,
            default=self.default,
            server_default=self.server_default
        )

    def get_column_type(self) -> sqlalchemy.types.TypeEngine:
        raise NotImplementedError()  # pragma: no cover

    def get_constraints(self) -> Optional[List]:
        return []

    def expand_relationship(self, value, child):
        return value


class String(BaseField):
    __type__ = str

    def __init__(self, *args, **kwargs):
        assert 'length' in kwargs, 'length is required'
        self.length = kwargs.pop('length')
        super().__init__(*args, **kwargs)

    def get_column_type(self):
        return sqlalchemy.String(self.length)


class Integer(BaseField):
    __type__ = int

    def get_column_type(self):
        return sqlalchemy.Integer()


class Text(BaseField):
    __type__ = str

    def get_column_type(self):
        return sqlalchemy.Text()


class Float(BaseField):
    __type__ = float

    def get_column_type(self):
        return sqlalchemy.Float()


class Boolean(BaseField):
    __type__ = bool

    def get_column_type(self):
        return sqlalchemy.Boolean()


class DateTime(BaseField):
    __type__ = datetime.datetime

    def get_column_type(self):
        return sqlalchemy.DateTime()


class Date(BaseField):
    __type__ = datetime.date

    def get_column_type(self):
        return sqlalchemy.Date()


class Time(BaseField):
    __type__ = datetime.time

    def get_column_type(self):
        return sqlalchemy.Time()


class JSON(BaseField):
    __type__ = Json

    def get_column_type(self):
        return sqlalchemy.JSON()


class BigInteger(BaseField):
    __type__ = int

    def get_column_type(self):
        return sqlalchemy.BigInteger()


class Decimal(BaseField):
    __type__ = decimal.Decimal

    def __init__(self, *args, **kwargs):
        assert 'precision' in kwargs, 'precision is required'
        assert 'length' in kwargs, 'length is required'
        self.length = kwargs.pop('length')
        self.precision = kwargs.pop('precision')
        super().__init__(*args, **kwargs)

    def get_column_type(self):
        return sqlalchemy.DECIMAL(self.length, self.precision)


def create_dummy_instance(fk: Type['Model'], pk: int = None):
    init_dict = {fk.__pkname__: pk or -1}
    init_dict = {**init_dict, **{k: create_dummy_instance(v.to)
                                 for k, v in fk.__model_fields__.items()
                                 if isinstance(v, ForeignKey) and not v.nullable and not v.virtual}}
    return fk(**init_dict)


class ForeignKey(BaseField):
    def __init__(self, to, name: str = None, related_name: str = None, nullable: bool = True, virtual: bool = False):
        super().__init__(nullable=nullable, name=name)
        self.virtual = virtual
        self.related_name = related_name
        self.to = to

    @property
    def __type__(self):
        return self.to.__pydantic_model__

    def get_constraints(self):
        fk_string = self.to.__tablename__ + "." + self.to.__pkname__
        return [sqlalchemy.schema.ForeignKey(fk_string)]

    def get_column_type(self):
        to_column = self.to.__model_fields__[self.to.__pkname__]
        return to_column.get_column_type()

    def expand_relationship(self, value, child):
        if not isinstance(value, (self.to, dict, int, str, list)) or (
                isinstance(value, orm.models.Model) and not isinstance(value, self.to)):
            raise RelationshipInstanceError(
                'Relationship model can be build only from orm.Model, dict and integer or string (pk).')
        if isinstance(value, list) and not isinstance(value, self.to):
            model = [self.expand_relationship(val, child) for val in value]
            return model

        if isinstance(value, self.to):
            model = value
        elif isinstance(value, dict):
            model = self.to(**value)
        else:
            model = create_dummy_instance(fk=self.to, pk=value)

        child_model_name = self.related_name or child.__class__.__name__.lower() + 's'
        model._orm_relationship_manager.add_relation(model.__class__.__name__.lower(),
                                                     child.__class__.__name__.lower(),
                                                     model, child, virtual=self.virtual)

        if child_model_name not in model.__fields__ \
                and child.__class__.__name__.lower() not in model.__fields__:
            model.__fields__[child_model_name] = ModelField(name=child_model_name,
                                                            type_=Optional[child.__pydantic_model__],
                                                            model_config=child.__pydantic_model__.__config__,
                                                            class_validators=child.__pydantic_model__.__validators__)
            model.__model_fields__[child_model_name] = ForeignKey(child.__class__,
                                                                  name=child_model_name,
                                                                  virtual=True)

        return model