"""List every .pdf key under the configured bucket+prefix.

Output:
    {"keys": ["2026/04/a.pdf", ...], "count": N, "pages": N}

Used as the first state in the metadata-index pipeline. The "keys" array
feeds an SFN Map state that runs ExtractMetadata in parallel per key.
"""
import os

import boto3

_s3 = boto3.client("s3", endpoint_url=os.environ.get("S3_ENDPOINT_URL") or None)


def handler(event, context):
    bucket = event.get("bucket") or os.environ["BUCKET_NAME"]
    prefix = event.get("prefix") or os.environ["PREFIX"]

    keys = []
    pages = 0
    paginator = _s3.get_paginator("list_objects_v2")
    for page in paginator.paginate(
        Bucket=bucket, Prefix=prefix, PaginationConfig={"PageSize": 1000}
    ):
        pages += 1
        for obj in page.get("Contents", []) or []:
            key = obj["Key"]
            if key.lower().endswith(".pdf"):
                keys.append(key)

    return {"keys": keys, "count": len(keys), "pages": pages}