#!/usr/bin/env python3
"""Read bump-my-version's current_version from a local file or Git ref."""

from __future__ import annotations

import argparse
import re
import subprocess
import sys
import tomllib


def parse_args() -> argparse.Namespace:
	parser = argparse.ArgumentParser()
	parser.add_argument("config_file")
	parser.add_argument("--ref")
	parser.add_argument("--fallback-version-file")
	return parser.parse_args()


def read_bootstrap_version(args: argparse.Namespace, config_error: KeyError) -> str:
	if not args.ref or not args.fallback_version_file:
		raise SystemExit(
			f"Could not read tool.bumpversion.current_version from {args.config_file}: {config_error}"
		) from config_error

	try:
		version_content = subprocess.check_output(
			["git", "show", f"{args.ref}:{args.fallback_version_file}"],
			text=True,
		)
	except (OSError, subprocess.CalledProcessError) as error:
		raise SystemExit(
			f"Could not load bootstrap version file {args.fallback_version_file}: {error}"
		) from error

	match = re.search(r'^__version__ = "(\d+\.\d+\.\d+)"$', version_content, re.MULTILINE)
	if not match:
		raise SystemExit(f"Could not read __version__ from bootstrap file {args.fallback_version_file}")

	version = match.group(1)
	print(f"Using bootstrap version {version} from {args.fallback_version_file}", file=sys.stderr)
	return version


def main() -> None:
	args = parse_args()
	try:
		if args.ref:
			content = subprocess.check_output(
				["git", "show", f"{args.ref}:{args.config_file}"],
			)
		else:
			with open(args.config_file, "rb") as config_file:
				content = config_file.read()
	except (OSError, subprocess.CalledProcessError) as error:
		raise SystemExit(f"Could not load {args.config_file}: {error}") from error

	try:
		version = tomllib.loads(content.decode())["tool"]["bumpversion"]["current_version"]
	except KeyError as error:
		version = read_bootstrap_version(args, error)
	except (TypeError, UnicodeDecodeError, tomllib.TOMLDecodeError) as error:
		raise SystemExit(
			f"Could not read tool.bumpversion.current_version from {args.config_file}: {error}"
		) from error

	if not isinstance(version, str):
		raise SystemExit("tool.bumpversion.current_version must be a string")
	print(version)


if __name__ == "__main__":
	main()