import decimal
import json
import math
from typing import TYPE_CHECKING

import boto3
from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.utilities.batch import (
    BatchProcessor,
    EventType,
    process_partial_response,
)
from aws_lambda_powertools.utilities.data_classes.dynamo_db_stream_event import (
    DynamoDBRecord,
    DynamoDBRecordEventName,
)
from aws_lambda_powertools.utilities.typing import LambdaContext
from layercake.dateutils import now, ttl
from utils import diff, table_from_arn

if TYPE_CHECKING:
    from mypy_boto3_events.client import EventBridgeClient
else:
    EventBridgeClient = object

client: EventBridgeClient = boto3.client('events')
processor = BatchProcessor(event_type=EventType.DynamoDBStreams)
tracer = Tracer()
logger = Logger()


@tracer.capture_method
def record_handler(record: DynamoDBRecord):
    detail_type = record.raw_event['eventName']
    table_name: str = table_from_arn(record.event_source_arn)  # type: ignore
    new_image: dict = record.dynamodb.new_image  # type: ignore
    old_image: dict = record.dynamodb.old_image  # type: ignore
    record_ttl: int | None = old_image.get('ttl')
    changes = diff(new_image, old_image)
    now_ = now()

    # Should be EXPIRE if event is REMOVE and TTL has elapsed
    if (
        record.event_name is DynamoDBRecordEventName.REMOVE
        and record_ttl
        and ttl() >= record_ttl
    ):
        detail_type = 'EXPIRE'

    detail = {
        'keys': record.dynamodb.keys,  # type: ignore
        'new_image': new_image,
        'old_image': old_image,
        'changes': changes,
        # Post-migration: remove the following line
        'modified': changes,
    }

    result = client.put_events(
        Entries=[
            {
                'Source': record.event_source,  # type: ignore
                'DetailType': detail_type,
                'Resources': [table_name],
                'Detail': json.dumps(detail, cls=JSONEncoder),
                'Time': now_,
            }
        ]
    )

    logger.info('Event result', result=result)


@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext):
    return process_partial_response(
        event=event,
        record_handler=record_handler,
        processor=processor,
        context=context,
    )


class JSONEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, decimal.Decimal):
            if o.is_nan():
                return math.nan

            if o % 1 != 0:
                return float(o.quantize(decimal.Decimal('0.00')))

            return int(o)

        if isinstance(o, set):
            return list(o)

        return super().default(o)