#!/usr/bin/env python3
"""Fill missing ROW integers within each (PATH, DATE) group of a satellite imagery CSV."""

import csv
import sys
from collections import defaultdict
from pathlib import Path


def fill_csv(input_path: Path, output_path: Path) -> None:
    with open(input_path, newline="", encoding="utf-8") as f:
        reader = csv.reader(f)
        header = next(reader)
        rows = list(reader)

    num_cols = len(header)

    # Group data rows by (PATH, DATE) — columns 3 and 9
    groups: dict[tuple, list] = defaultdict(list)
    for row in rows:
        path_val = row[3]
        date_val = row[9]
        groups[(path_val, date_val)].append(row)

    synthetic_rows: list[list[str]] = []

    for (path_val, date_val), group in groups.items():
        row_numbers = {int(r[4]) for r in group}
        min_row = min(row_numbers)
        max_row = max(row_numbers)
        missing = set(range(min_row, max_row + 1)) - row_numbers

        template = group[0]
        for r in sorted(missing):
            new_row = (
                template[:4]                       # cols 0–3: RECORD_TYP, MISSION, SENSOR, PATH
                + [str(r)]                         # col 4: ROW
                + template[5:8]                    # cols 5–7: SCENE, SUB, SHIFT
                + [f"{template[3]}/{r}"]           # col 8: LABEL
                + [template[9]]                    # col 9: DATE
                + [""] * (num_cols - 10)           # cols 10–end: blank
            )
            synthetic_rows.append(new_row)

    all_rows = rows + synthetic_rows
    all_rows.sort(key=lambda r: (r[3], r[9], int(r[4])))

    with open(output_path, "w", newline="", encoding="utf-8") as f:
        writer = csv.writer(f, quoting=csv.QUOTE_ALL)
        writer.writerow(header)
        writer.writerows(all_rows)

    print(f"Original rows : {len(rows)}")
    print(f"Synthetic rows: {len(synthetic_rows)}")
    print(f"Total rows    : {len(all_rows)}")
    print(f"Output written: {output_path}")


def main() -> None:
    if len(sys.argv) < 2:
        print(f"Usage: {sys.argv[0]} <input.csv> [output.csv]", file=sys.stderr)
        sys.exit(1)

    input_path = Path(sys.argv[1])
    if len(sys.argv) >= 3:
        output_path = Path(sys.argv[2])
    else:
        output_path = input_path.with_stem(input_path.stem + "_filled")

    fill_csv(input_path, output_path)


if __name__ == "__main__":
    main()