kafka_event.py

import base64
from functools import cached_property
from typing import Any, Dict, Iterator, List, Optional, overload

from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
from aws_lambda_powertools.utilities.data_classes.shared_functions import (
    get_header_value,
)


class KafkaEventRecord(DictWrapper):
    @property
    def topic(self) -> str:
        """The Kafka topic."""
        return self["topic"]

    @property
    def partition(self) -> int:
        """The Kafka record parition."""
        return self["partition"]

    @property
    def offset(self) -> int:
        """The Kafka record offset."""
        return self["offset"]

    @property
    def timestamp(self) -> int:
        """The Kafka record timestamp."""
        return self["timestamp"]

    @property
    def timestamp_type(self) -> str:
        """The Kafka record timestamp type."""
        return self["timestampType"]

    @property
    def key(self) -> str:
        """The raw (base64 encoded) Kafka record key."""
        return self["key"]

    @property
    def decoded_key(self) -> bytes:
        """Decode the base64 encoded key as bytes."""
        return base64.b64decode(self.key)

    @property
    def value(self) -> str:
        """The raw (base64 encoded) Kafka record value."""
        return self["value"]

    @property
    def decoded_value(self) -> bytes:
        """Decodes the base64 encoded value as bytes."""
        return base64.b64decode(self.value)

    @cached_property
    def json_value(self) -> Any:
        """Decodes the text encoded data as JSON."""
        return self._json_deserializer(self.decoded_value.decode("utf-8"))

    @property
    def headers(self) -> List[Dict[str, List[int]]]:
        """The raw Kafka record headers."""
        return self["headers"]

    @property
    def decoded_headers(self) -> Dict[str, bytes]:
        """Decodes the headers as a single dictionary."""
        return {k: bytes(v) for chunk in self.headers for k, v in chunk.items()}

    @overload
    def get_header_value(
        self,
        name: str,
        default_value: str,
        case_sensitive: bool = True,
    ) -> str:
        ...

    @overload
    def get_header_value(
        self,
        name: str,
        default_value: Optional[str] = None,
        case_sensitive: bool = True,
    ) -> Optional[str]:
        ...

    def get_header_value(
        self,
        name: str,
        default_value: Optional[str] = None,
        case_sensitive: bool = True,
    ) -> Optional[str]:
        """Get a decoded header value by name."""
        return get_header_value(
            headers=self.decoded_headers,
            name=name,
            default_value=default_value,
            case_sensitive=case_sensitive,
        )


class KafkaEvent(DictWrapper):
    """Self-managed or MSK Apache Kafka event trigger
    Documentation:
    --------------
    - https://docs.aws.amazon.com/lambda/latest/dg/with-kafka.html
    - https://docs.aws.amazon.com/lambda/latest/dg/with-msk.html
    """

    def __init__(self, data: Dict[str, Any]):
        super().__init__(data)
        self._records: Optional[Iterator[KafkaEventRecord]] = None

    @property
    def event_source(self) -> str:
        """The AWS service from which the Kafka event record originated."""
        return self["eventSource"]

    @property
    def event_source_arn(self) -> Optional[str]:
        """The AWS service ARN from which the Kafka event record originated, mandatory for AWS MSK."""
        return self.get("eventSourceArn")

    @property
    def bootstrap_servers(self) -> str:
        """The Kafka bootstrap URL."""
        return self["bootstrapServers"]

    @property
    def decoded_bootstrap_servers(self) -> List[str]:
        """The decoded Kafka bootstrap URL."""
        return self.bootstrap_servers.split(",")

    @property
    def records(self) -> Iterator[KafkaEventRecord]:
        """The Kafka records."""
        for chunk in self["records"].values():
            for record in chunk:
                yield KafkaEventRecord(data=record, json_deserializer=self._json_deserializer)

    @property
    def record(self) -> KafkaEventRecord:
        """
        Returns the next Kafka record using an iterator.

        Returns
        -------
        KafkaEventRecord
            The next Kafka record.

        Raises
        ------
        StopIteration
            If there are no more records available.

        """
        if self._records is None:
            self._records = self.records
        return next(self._records)