import os
from datetime import datetime, timedelta

import pytz
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 glom import glom
from layercake.dateutils import fromisoformat, now, ttl
from layercake.dynamodb import DynamoDBPersistenceLayer
from layercake.funcs import pick

from boto3clients import dynamodb_client
from config import ENROLLMENT_TABLE

logger = Logger(__name__)
dyn = DynamoDBPersistenceLayer(ENROLLMENT_TABLE, dynamodb_client)
tz = os.getenv('TZ', 'UTC')


@event_source(data_class=EventBridgeEvent)
@logger.inject_lambda_context
def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool | None:
    new_image = event.detail['new_image']
    expires_at = glom(new_image, 'cert.expires_at', default=None)

    if not expires_at:
        return None

    enrollment_id = new_image['id']
    org_id = new_image['org_id']
    expires_at: datetime = fromisoformat(expires_at).replace(tzinfo=pytz.timezone(tz))  # type: ignore
    # The reporting month is the month before the certificate expires
    month_start = (expires_at.replace(day=1) - timedelta(days=1)).replace(day=1)
    now_ = now()
    pk = f'CERT#REPORTING#ORG#{org_id}'
    sk = 'MONTH#{}'.format(expires_at.strftime('%Y-%m'))

    if now_ > expires_at:
        return None

    try:
        with dyn.transact_writer() as transact:
            transact.put(
                item={
                    'id': pk,
                    'sk': 'MONTH#{}#SCHEDULE#SEND_REPORT_EMAIL'.format(
                        month_start.strftime('%Y-%m')
                    ),
                    'target_month': expires_at.strftime('%Y-%m'),
                    'ttl': ttl(start_dt=month_start),
                }
            )

            transact.put(
                item={
                    'id': pk,
                    'sk': f'{sk}#ENROLLMENT#{enrollment_id}',
                    'enrollment_id': new_image['id'],
                    'user': pick(('id', 'name'), new_image['user']),
                    'course': pick(('id', 'name'), new_image['course']),
                    'enrolled_at': new_image['created_at'],
                    'expires_at': expires_at,  # type: ignore
                    'completed_at': new_image['completed_at'],
                    'created_at': now_,
                },
                cond_expr='attribute_not_exists(sk)',
                exc_cls=EnrollmentConflictError,
            )
    except EnrollmentConflictError:
        return False

    return True


class EnrollmentConflictError(Exception): ...