"""Abstracted debezium message."""

from kafka_utils.consumer.deserializer.simple_json import JSONDeserializer
from kafka_utils.consumer.message.base import BaseEventMessage
from kafka_utils.exceptions import DebeziumMessageException
from kafka_utils.exceptions import IneligibleEventException


class DebeziumMessage(BaseEventMessage):
    """Debezium mysql replication message.

    Message structure:
    {
        schema: schema information
        payload: {
            op: "c|u|d",
            before: affected table row as a dictionary, null when op is c
            after: affected table row as a dictionary, null when op is d
            source: message metadata
        }
    }
    """

    def __init__(self, message, topic, allowed_event_ops=None):
        """Parse message.

        Args:
            message (dict): the string for JSON representing the message
            topic (str): The topic for the message.
            allowed_event_ops (list): a list of allowable operations (eg: c|u|d)
        """
        super().__init__(message, topic)
        self.value_deserializer = JSONDeserializer()
        self.message = self.value_deserializer.deserialize(self.message)
        if 'payload' not in self.message or not self.message.get('payload'):
            raise DebeziumMessageException('Missing data: payload')
        payload = self.message.get('payload')
        if 'op' not in payload or not payload.get('op'):
            raise DebeziumMessageException('Missing data: op')
        self.operation = payload.get('op')

        if allowed_event_ops and self.operation not in allowed_event_ops:
            raise IneligibleEventException(f'Event table operation ignored: {self.operation}')

        if self.operation != 'c':
            if 'before' not in payload or payload.get('before') is None:
                raise DebeziumMessageException('Missing data: before')
        self.before = payload.get('before')

        if self.operation != 'd':
            if 'after' not in payload or payload.get('after') is None:
                raise DebeziumMessageException('Missing data: after')
        self.after = payload.get('after')

    def get_field_values(self, field_name):
        """Get the before/after values for a field by name."""
        values = {'before': None, 'after': None}
        if self.operation != 'c':
            values.update({'before': self.before.get(field_name)})
        if self.operation != 'd':
            values.update({'after': self.after.get(field_name)})
        return values