import csv
import io
import json
from functools import cache

import boto3
from botocore.config import Config


@cache
def get_s3_client():
    """Get a cached S3 client."""
    return boto3.client("s3", config=Config())


def list_s3_objects(bucket, prefix):
    """List objects in an S3 bucket under a given prefix."""
    client = get_s3_client()
    paginator = client.get_paginator("list_objects_v2")
    page_iterator = paginator.paginate(Bucket=bucket, Prefix=prefix)

    objects = []
    for page in page_iterator:
        if "Contents" in page:
            for obj in page["Contents"]:
                objects.append(obj["Key"])
    return objects


def create_presigned_url(bucket, key):
    """Generate a presigned URL to share an S3 object."""
    client = get_s3_client()
    return client.generate_presigned_url(
        "get_object",
        Params={"Bucket": bucket, "Key": key},
        ExpiresIn=3600
    )


def write_json_to_s3(data, bucket, key):
    """Write a dictionary to S3 as a JSON file."""
    client = get_s3_client()
    client.put_object(
        Bucket=bucket,
        Key=key,
        Body=json.dumps(data),
        ContentType="application/json"
    )

def write_csv_to_s3(header, rows, bucket, key):
    """Write headers and rows to S3 as a CSV file."""
    client = get_s3_client()
    output = io.StringIO()
    writer = csv.writer(output)
    writer.writerow(header)
    writer.writerows(rows)
    client.put_object(
        Bucket=bucket,
        Key=key,
        Body=output.getvalue(),
        ContentType="text/csv"
    )