import csv
import json
from pathlib import Path
from typing import cast


def packages_csv(input_dir: Path, output_dir: Path) -> None:
    output_file = output_dir / "packages.csv"
    with output_file.open("w") as fw:
        writer = csv.writer(fw)
        writer.writerow(["date", "package", "version", "count"])

        for j in input_dir.glob("*.json"):
            with open(j) as fr:
                date = j.stem
                data: dict[str, object] = {}
                try:
                    data = json.load(fr)
                except json.JSONDecodeError:
                    print(f"WARN: Could not decode JSON data for file {j}")
                    continue

                if "Versions" not in data or not isinstance(data["Versions"], dict):
                    print(
                        f"WARN: No correct json structure containing 'Versions' field in file {j}"
                    )
                    continue

                data_versions = cast(dict[str, dict[str, int]], data["Versions"])
                for package_name, package_versions in data_versions.items():
                    if not isinstance(package_versions, dict):
                        print(
                            f"WARN: No correct json version structure containing versions in the Version field in file {j}"
                        )
                        continue
                    for version, count in package_versions.items():
                        p_name = package_name
                        p_version = version
                        v_count = count
                        p_date = date
                        writer.writerow([p_date, p_name, p_version, v_count])


def ensure_dirs(input_dir: Path, output_dir: Path):
    if not input_dir.is_dir():
        raise ValueError
    output_dir.mkdir(exist_ok=True, parents=True)


def main(input: str, output: str) -> None:
    input_dir = Path(input)
    output_dir = Path(output)
    ensure_dirs(input_dir, output_dir)
    packages_csv(input_dir, output_dir)


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)