"""Pack a Modelling Run's resolved properties into SQS-message-sized batches.

Batches stay postcode-grouped — properties sharing a postcode ride the same
message so the workers' prediction cohort cache keeps paying (ADR-0055), the
same packing the trigger script has been running.
"""

from backend.app.modelling.property_filters import FilteredProperty
from utilities.grouped_batching import iter_grouped_batches

BATCH_SIZE = 50


def pack_postcode_batches(
    properties: list[FilteredProperty], batch_size: int = BATCH_SIZE
) -> list[list[FilteredProperty]]:
    """Pack *properties* into batches of ~*batch_size*, never splitting a
    postcode across batches. A single postcode larger than *batch_size*
    becomes its own oversized batch."""
    return list(
        iter_grouped_batches(
            properties, key=lambda p: p.postcode or "", max_batch_size=batch_size
        )
    )