from datetime import datetime, time, timedelta

from aws_lambda_powertools import Logger
from aws_lambda_powertools.utilities.data_classes import (
    EventBridgeEvent,
    event_source,
)
from aws_lambda_powertools.utilities.typing import LambdaContext
from layercake.dateutils import now, ttl
from layercake.dynamodb import (
    DynamoDBPersistenceLayer,
    KeyPair,
    SortKey,
    TransactKey,
)
from layercake.funcs import pick

from boto3clients import dynamodb_client
from config import COURSE_TABLE, ENROLLMENT_TABLE, ORDER_TABLE
from utils import get_billing_period

logger = Logger(__name__)
order_layer = DynamoDBPersistenceLayer(ORDER_TABLE, dynamodb_client)
enrollment_layer = DynamoDBPersistenceLayer(ENROLLMENT_TABLE, dynamodb_client)
course_layer = DynamoDBPersistenceLayer(COURSE_TABLE, dynamodb_client)


@event_source(data_class=EventBridgeEvent)
@logger.inject_lambda_context
def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool:
    new_image = event.detail['new_image']
    now_ = now()
    enrollment_id = new_image['id']
    org_id = new_image['org_id']
    data = enrollment_layer.collection.get_items(
        TransactKey(enrollment_id) + SortKey('0') + SortKey('author')
    )

    if not data:
        logger.debug('Enrollment not found')
        return False

    start_date, end_date = get_billing_period(new_image['billing_day'])
    pk = 'BILLING#ORG#{org_id}'.format(org_id=org_id)
    sk = 'START#{start}#END#{end}'.format(
        start=start_date.isoformat(),
        end=end_date.isoformat(),
    )

    try:
        with order_layer.transact_writer() as transact:
            transact.put(
                item={
                    'id': pk,
                    'sk': sk,
                    'status': 'PENDING',
                    'created_at': now_,
                },
                cond_expr='attribute_not_exists(sk)',
                exc_cls=ExistingBillingConflictError,
            )
            transact.put(
                item={
                    'id': pk,
                    'sk': f'{sk}#SCHEDULE#AUTO_CLOSE',
                    'ttl': ttl(
                        start_dt=datetime.combine(end_date, time()) + timedelta(days=1)
                    ),
                    'created_at': now_,
                }
            )
    except ExistingBillingConflictError:
        pass

    try:
        with order_layer.transact_writer() as transact:
            author = data['author']
            course_id = data['course']['id']
            course = course_layer.collection.get_items(
                KeyPair(
                    pk=course_id,
                    sk=SortKey('0', path_spec='metadata__unit_price'),
                    rename_key='unit_price',
                )
                + KeyPair(
                    pk=f'CUSTOM_PRICING#ORG#{org_id}',
                    sk=SortKey(f'COURSE#{course_id}', path_spec='unit_price'),
                    rename_key='unit_price',
                ),
                flatten_top=False,
            )

            transact.condition(
                key=KeyPair(pk, sk),
                cond_expr='attribute_exists(sk)',
                exc_cls=BillingNotFoundError,
            )
            transact.put(
                item={
                    'id': pk,
                    'sk': f'{sk}#ENROLLMENT#{enrollment_id}',
                    'user': pick(('id', 'name'), data['user']),
                    'course': pick(('id', 'name'), data['course']),
                    'unit_price': course['unit_price'],
                    'author': {
                        'id': author['user_id'],
                        'name': author['name'],
                    },
                    # Post-migration: uncomment the following line
                    # 'enrolled_at': data['created_at'],
                    'enrolled_at': data['create_date'],
                    'created_at': now_,
                },
                cond_expr='attribute_not_exists(sk)',
            )
    except Exception:
        return False
    else:
        return True


class ExistingBillingConflictError(Exception): ...


class BillingNotFoundError(Exception): ...