"""Resume state loading from previously-written success CSV."""

import csv
import logging
import os

from schemas.columns import CsvColumn

logger = logging.getLogger(__name__)


def load_processed_identifiers(
    success_csv: str | None,
) -> set[tuple[str, str]]:
    """Load (account_id, contract_name) pairs from an existing success CSV.

    Returns an empty set if the file doesn't exist, is empty, or can't be read.
    """
    if (
        not success_csv
        or not os.path.exists(success_csv)
        or os.path.getsize(success_csv) == 0
    ):
        return set()

    processed: set[tuple[str, str]] = set()
    try:
        with open(success_csv, 'r', encoding='utf-8') as f:
            reader = csv.DictReader(f)
            for row in reader:
                account_id = row.get(CsvColumn.ACCOUNT_ID.value, '')
                contract_name = row.get(CsvColumn.CONTRACT_NAME.value, '')
                if account_id and contract_name:
                    processed.add((account_id, contract_name))
        logger.info(
            f'[RESUME] Found {len(processed)} existing contracts — will skip these'
        )
    except Exception as e:
        logger.warning(f'Could not load existing success CSV: {e}')

    return processed