"""DynamoDB client for storing and retrieving offboarding snapshots."""

import logging
from datetime import datetime, timezone
from typing import TYPE_CHECKING

import boto3
from shared.schemas.dynamo import Snapshot

if TYPE_CHECKING:
    from mypy_boto3_dynamodb import DynamoDBServiceResource
    from mypy_boto3_dynamodb.service_resource import Table

LOGGER = logging.getLogger(__name__)


class DynamoClient:
    """Stores and retrieves Phase 1 offboarding snapshots in DynamoDB.

    The table uses ``ticket_id`` as the partition key. Each item has a ``ttl``
    attribute (Unix epoch) that DynamoDB uses to automatically expire stale
    records after the configured number of days.
    """

    def __init__(self, table_name: str, region: str = 'us-east-1') -> None:
        """Initialise with the target table name and AWS region.

        :param table_name: DynamoDB table name.
        :param region: AWS region.
        """
        resource: 'DynamoDBServiceResource' = boto3.resource(
            'dynamodb', region_name=region
        )
        self._table: 'Table' = resource.Table(table_name)

    def put_snapshot(self, snapshot: Snapshot, ttl_days: int = 7) -> None:
        """Write a snapshot item to DynamoDB.

        Overwrites any existing item with the same ``ticket_id``.

        :param snapshot: The snapshot to store.
        :param ttl_days: Number of days until DynamoDB auto-expires the item.
        """
        now = datetime.now(tz=timezone.utc)
        ttl = int(now.timestamp()) + ttl_days * 86400
        item = snapshot.model_dump()
        item['ttl'] = ttl
        self._table.put_item(Item=item)
        LOGGER.info('Stored snapshot for ticket %s (ttl=%d).', snapshot.ticket_id, ttl)

    def get_snapshot(self, ticket_id: str) -> 'Snapshot | None':
        """Retrieve a snapshot by ticket ID.

        :param ticket_id: Jira ticket key (e.g. ``SYS-123``).
        :return: Snapshot if found, None otherwise.
        """
        response = self._table.get_item(Key={'ticket_id': ticket_id})
        item = response.get('Item')
        if item is None:
            LOGGER.info('No snapshot found for ticket %s.', ticket_id)
            return None
        # Remove DynamoDB-only field before validating
        item.pop('ttl', None)
        LOGGER.info('Retrieved snapshot for ticket %s.', ticket_id)
        return Snapshot.model_validate(item)

    def delete_snapshot(self, ticket_id: str) -> None:
        """Delete a snapshot by ticket ID.

        Idempotent — deleting a non-existent item is a no-op.

        :param ticket_id: Jira ticket key to delete.
        """
        self._table.delete_item(Key={'ticket_id': ticket_id})
        LOGGER.info('Deleted snapshot for ticket %s.', ticket_id)