"""
Helper functions for the Mosaic library
"""

import csv
import codecs

def read_voterdata_csv_stream(input_stream, keys_needed=None) -> list:
    """
    read_voterdata_csv_stream: Read csv stream to list

    :param input_stream: Input stream to read from

    :return List of parsed csv rows
    """

    rows = []
    # note: using 'utf-8-sig' removes the annoying \ufeff BOM signature
    if keys_needed is None or len(keys_needed) > 0:
        key_list = keys_needed

    reader = csv.DictReader(codecs.getreader("utf-8-sig")(input_stream))
    for row in reader:
        if key_list is None:
            key_list = row.keys()
        new_row = {}
        for k in key_list:
            new_row[k] = row[k]
        rows.append(new_row)

    return rows


def write_csv_file(full_file_pathname, fieldnames, rows):
    """
    write_csv_file

    :param full_file_pathname:
    :param fieldnames:
    """
    with open(full_file_pathname, 'w', newline='', encoding='UTF-8') as csvfile:
        writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
        writer.writeheader()
        for row in rows:
            writer.writerow(row)