import csv
import json
from datetime import datetime
from pathlib import Path
from typing import Generator


def json_to_daily_pkg(input_dir: Path, output_dir: Path, force: bool = False) -> None:
    if not input_dir.is_dir():
        raise ValueError
    output_dir.mkdir(exist_ok=True, parents=True)

    # only clean if raw files have been updated since last time
    if not force and not newer_than_last_clean(
        input_dir.glob("*.json"), output_dir.glob("*.csv"), desc="daily packages"
    ):
        return

    for j in input_dir.glob("*.json"):
        with open(j) as fr:
            date = j.stem
            output_file = output_dir / f"{date}.csv"
            try:
                data = json.load(fr)
            except json.JSONDecodeError:
                print(f"WARN: Could not decode JSON data for file {j}")

            if "Packages" not in data:
                print(
                    f"WARN: No correct json structure containing 'Packages' field in file {j}"
                )

            with open(output_file, "w") as fw:
                writer = csv.writer(fw)
                writer.writerow(["date", "package", "downloads"])
                for entry in data["Packages"]:
                    p_name = entry
                    p_count = data["Packages"][entry]
                    p_date = date
                    writer.writerow([p_date, p_name, p_count])
                    # print(output_file, p_date, p_name, p_count)


def newer_than_last_clean(
    input_glob: Generator, output_glob: Generator, desc: str | None = None
) -> bool:
    last_raw_update: datetime = datetime(1, 1, 1)
    oldest_clean: datetime = datetime.now()
    for file in input_glob:
        mdate = datetime.fromtimestamp(file.stat().st_mtime)
        if mdate > last_raw_update:
            last_raw_update = mdate
    for file in output_glob:
        mdate = datetime.fromtimestamp(file.stat().st_mtime)
        if mdate < oldest_clean:
            oldest_clean = mdate
    if oldest_clean > last_raw_update:
        print(
            "INFO: Skip creating cleaned data"
            f"{f' for {desc}' if desc else ''}"
            f", last processing {oldest_clean} newer than {last_raw_update}"
        )
        return False
    return True


def main(input: str, output: str) -> None:
    json_to_daily_pkg(Path(input) / "daily", Path(output) / "daily", force=True)


if __name__ == "__main__":
    import sys

    if not len(sys.argv) == 3:
        print("Please provide exactly one input directory and one output directory.")
        sys.exit(1)
    inp = sys.argv[1]
    out = sys.argv[2]
    main(inp, out)