import re
from decimal import Decimal
from functools import reduce
from http import HTTPStatus
from typing import Any, Literal
from uuid import uuid4

from aws_lambda_powertools.event_handler.api_gateway import Router
from aws_lambda_powertools.event_handler.exceptions import (
    NotFoundError,
)
from layercake.dateutils import now, ttl
from layercake.dynamodb import DynamoDBPersistenceLayer, KeyPair
from layercake.extra_types import CnpjStr, CpfStr, CreditCard, NameStr
from pydantic import (
    UUID4,
    BaseModel,
    ConfigDict,
    EmailStr,
    Field,
    field_validator,
    model_validator,
)

from api_gateway import JSONResponse
from boto3clients import dynamodb_client
from config import ORDER_TABLE
from routes.enrollments.enroll import Enrollment

router = Router()
dyn = DynamoDBPersistenceLayer(ORDER_TABLE, dynamodb_client)


class CouponNotFoundError(NotFoundError): ...


class User(BaseModel):
    id: UUID4 | str
    name: NameStr


class Address(BaseModel):
    model_config = ConfigDict(str_strip_whitespace=True)

    postcode: str
    address1: str
    address2: str | None = None
    neighborhood: str
    city: str
    state: str

    @field_validator('postcode')
    @classmethod
    def ensure_numbers(cls, v: str) -> str:
        return re.sub(r'\D', '', v)


class Item(BaseModel):
    id: UUID4
    name: str
    unit_price: Decimal
    quantity: int = 1


class Coupon(BaseModel):
    code: str
    type: Literal['PERCENT', 'FIXED']
    amount: Decimal


class Checkout(BaseModel):
    model_config = ConfigDict(str_strip_whitespace=True)

    id: UUID4 = Field(default_factory=uuid4)
    name: str
    email: EmailStr
    address: Address
    payment_method: Literal['PIX', 'CREDIT_CARD', 'BANK_SLIP', 'MANUAL']
    items: tuple[Item, ...]
    enrollments: tuple[Enrollment, ...] = tuple()
    coupon: Coupon | None = None
    org_id: UUID4 | str | None = None
    user_id: UUID4 | str | None = None
    cnpj: CnpjStr | None = None
    cpf: CpfStr | None = None
    created_by: User | None = None
    credit_card: CreditCard | None = None
    installments: int | None = Field(None, ge=1, le=12)

    @model_validator(mode='after')
    def verify_fields(self):
        if not any([self.cnpj, self.cpf]):
            raise ValueError('cnpj or cpf is required')

        if self.cnpj is not None:
            if self.org_id is None:
                raise ValueError('org_id is missing')

            if self.created_by is None:
                raise ValueError('created_by is missing')

        if self.cpf is not None and self.user_id is None:
            raise ValueError('user_id is missing')

        return self

    def model_dump(self, **kwargs) -> dict[str, Any]:
        return super().model_dump(
            exclude_none=True,
            exclude={
                'items',
                'address',
                'created_by',
                'coupon',
                'credit_card',
                'enrollments',
            },
            **kwargs,
        )


@router.post('/')
def checkout(payload: Checkout):
    now_ = now()
    order_id = payload.id
    address = payload.address
    credit_card = payload.credit_card
    items = payload.items
    enrollments = payload.enrollments
    coupon = payload.coupon
    subtotal = _sum_items(items)
    discount = (
        _apply_discount(subtotal, coupon.amount, coupon.type) * -1
        if coupon
        else Decimal('0')
    )
    total = subtotal + discount if subtotal > Decimal('0') else Decimal('0')

    with dyn.transact_writer() as transact:
        transact.put(
            item={
                'id': order_id,
                'sk': '0',
                'status': 'PENDING',
                'subtotal': subtotal,
                'total': total,
                'discount': discount,
                # Post-migration (orders): rename `create_date` to `created_at`
                'create_date': now_,
                'due_date': '',
            }
            | ({'coupon': coupon.code} if coupon else {})
            | ({'installments': payload.installments} if payload.installments else {})
            | payload.model_dump()
        )

        transact.put(
            item={
                'id': order_id,
                'sk': 'ITEMS',
                'items': [item.model_dump() for item in items],
                'created_at': now_,
            }
        )
        transact.put(
            item={
                'id': order_id,
                'sk': 'ADDRESS',
                'created_at': now_,
            }
            | address.model_dump()
        )

        if credit_card:
            transact.put(
                item={
                    'id': order_id,
                    'sk': 'CREDIT_CARD',
                    'ttl': ttl(start_dt=now_, minutes=5),
                    'created_at': now_,
                }
                | credit_card.model_dump(),
            )

        if coupon:
            transact.put(
                item={
                    'id': order_id,
                    'sk': 'METADATA#COUPON',
                    'created_at': now_,
                }
                | coupon.model_dump()
            )
            transact.condition(
                key=KeyPair('COUPON', coupon.code),
                cond_expr='attribute_exists(sk) \
                           AND discount_type = :type \
                           AND discount_amount = :amount',
                expr_attr_values={
                    ':type': coupon.type,
                    ':amount': coupon.amount,
                },
                exc_cls=CouponNotFoundError,
            )

        for enrollment in enrollments:
            transact.put(
                item={
                    'id': order_id,
                    'sk': f'ENROLLMENT#{enrollment.id}',
                    'status': 'UNPROCESSED',
                    'created_at': now_,
                }
                | enrollment.model_dump(exclude={'id'})
            )

    return JSONResponse(body={'id': order_id}, status_code=HTTPStatus.CREATED)


def _sum_items(items: tuple[Item, ...]):
    def sum(total: Decimal, item: Item) -> Decimal:
        return total + item.unit_price * item.quantity

    return reduce(sum, items, Decimal(0))


def _calc_interest(total, installments: int) -> Decimal:
    rate2to6 = 0.055
    rate7to12 = 0.0608
    rate = rate7to12 if installments >= 7 else rate2to6
    return total * Decimal((1 - 0.0382) / (1 - rate))


def _apply_discount(
    subtotal: Decimal,
    discount_amount: Decimal,
    discount_type: Literal['FIXED', 'PERCENT'],
) -> Decimal:
    if subtotal <= Decimal('0'):
        return Decimal('0')

    amount = (
        (subtotal * discount_amount) / Decimal('100')
        if discount_type == 'PERCENT'
        else discount_amount
    )

    return min(amount, subtotal)