import csv
from io import StringIO

import boto3
from aws_lambda_powertools.utilities.data_classes import (
    EventBridgeEvent,
    event_source,
)
from aws_lambda_powertools.utilities.typing import LambdaContext

from csv_utils import byte_ranges

CHUNK_SIZE = 50
s3_client = boto3.client('s3')


@event_source(data_class=EventBridgeEvent)
def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool:
    new_image = event.detail['new_image']
    csvfile = new_image['csv_s3uri']
    *_, pair = byte_ranges(csvfile, CHUNK_SIZE)

    data = get_object_range(csvfile, pair[0], pair[1], s3_client=s3_client)
    reader = csv.reader(data)

    for x in reader:
        print(x)
    return True


def get_object_range(
    s3_uri: str,
    start_byte: int,
    end_byte: int = -1,
    *,
    s3_client,
) -> StringIO:
    bucket, key = s3_uri.replace('s3://', '').split('/', 1)
    range_ = f'bytes={start_byte}-{end_byte}' if end_byte else f'bytes={start_byte}-'

    response = s3_client.get_object(
        Bucket=bucket,
        Key=key,
        Range=range_,
    )

    return StringIO(response['Body'].read().decode('utf-8'))