#!/usr/bin/env python3
"""Group the demo CSV by camera and event type, ready to compare with a BI pivot."""
import argparse
import csv
from collections import Counter
from pathlib import Path


def summarize(source, output):
    with Path(source).open(encoding="utf-8-sig", newline="") as stream:
        reader = csv.DictReader(stream)
        if not {"Камера", "Тип"}.issubset(reader.fieldnames or []):
            raise ValueError("Ожидаются колонки Камера и Тип")
        counts = Counter((row["Камера"], row["Тип"]) for row in reader)
    with Path(output).open("w", encoding="utf-8", newline="") as stream:
        writer = csv.writer(stream, lineterminator="\n")
        writer.writerow(["Камера", "Тип", "Количество"])
        writer.writerows([camera, kind, count] for (camera, kind), count in sorted(counts.items()))


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("source")
    parser.add_argument("--output", default="summary.csv")
    args = parser.parse_args()
    summarize(args.source, args.output)