from dataclasses import dataclass
from pathlib import Path
from typing import Self
import argparse
import sys
import json


@dataclass
class Config:
    source_lock: Path = Path.home() / ".hive/flake.lock"
    source_nixpkgs: str = "nixpkgs-unstable"
    target_lock: Path = Path.cwd() / "flake.lock"
    dry: bool = False

    @classmethod
    def load(cls, paths: list[Path]) -> Self:
        c = cls()

        args = cls.argparse()

        c.dry = args.dry

        # Target lock can only be set via args
        if args.target_lock:
            c.target_lock = Path(args.target_lock)

        # We do not need to read config files.
        if args.source_lock:
            c.source_lock = Path(args.source_lock)
            return c

        # Check if source_lock is set somewhere
        for p in paths:
            if not p.exists():
                continue

            with p.open(mode="r") as f:
                cfg = json.load(f)
                c.source_lock = Path(cfg["source_lock"])
                c.source_nixpkgs = cfg["source_nixpkgs"]
                break

        return c

    @staticmethod
    def argparse() -> argparse.Namespace:
        args = argparse.ArgumentParser()
        args.add_argument(
            "--source_lock",
            type=Path,
            default=None,
            required=False,
            help="The flake.lock file to read nixpkgs from.",
        )
        args.add_argument(
            "--source_nixpkgs",
            type=Path,
            default=None,
            required=False,
            help="The nixpkgs in flake.lock to use.",
        )
        args.add_argument(
            "--target_lock",
            type=Path,
            default=None,
            required=False,
            help="The flake.lock file to write nixpkgs to. Use CWD/flake.lock if unset",
        )
        args.add_argument(
            "--dry",
            action="store_true",
            help="Only show what would be done.",
        )

        return args.parse_args(sys.argv[1:])