"""Utility Function(s) for performers."""
from collections import defaultdict

from backend.models.performer_persister import PerformerPersister


def copy_tracks_performers(source_dest_tuid_list):
    """Copy performers from source tracks to destination tracks.

    Args:
        source_dest_tuid_list (list): List of tuples with source to dest tuid.
    """
    source_tuids = [
        source_tuid for source_tuid, dest_tuid in source_dest_tuid_list
    ]
    source_performers = PerformerPersister.get_performers_by_tuids(
        source_tuids).message['items']

    # Group performers by source tuid.
    source_tuid_performers_map = defaultdict(list)
    for performer in source_performers:
        tuid = performer.pop('tuid')
        source_tuid_performers_map[tuid].append(performer)

    for source_tuid, dest_tuid in source_dest_tuid_list:
        source_performers = source_tuid_performers_map[source_tuid]
        PerformerPersister.sync_track_performers(dest_tuid, source_performers)