"""Read-only installation state used by the native launcher."""

from __future__ import annotations

from dataclasses import dataclass
from enum import Enum
import json
from pathlib import Path

from .paths import AppPaths


REQUIRED_GAME_FILES = (
	Path("Game.exe"),
	Path("game.dll"),
	Path("game.ini"),
	Path("game/maps/WhisperingVale.rovug"),
)


class PrimaryAction(str, Enum):
	"""Action presented by the launcher's large primary button."""

	INSTALL = "INSTALL"
	UPDATE = "UPDATE"
	PLAY = "PLAY"


@dataclass(frozen=True)
class GameInstallationStatus:
	"""Local game completeness and its relationship to the official depot."""

	action: PrimaryAction
	installed: bool
	local_build: int | None
	official_build: int | None
	missing_files: tuple[Path, ...]


def inspect_game_installation(
	paths: AppPaths,
	official_build: int | None = None,
) -> GameInstallationStatus:
	"""Select Install, Update, or Play without modifying the installation.

	A completed native sync is the verified source for the local depot build.
	When the official build cannot be checked, a complete local game remains
	playable so temporary network failures do not lock users out.
	"""

	if official_build is not None and (
		isinstance(official_build, bool)
		or not isinstance(official_build, int)
		or official_build < 0
	):
		raise ValueError("official build must be a non-negative integer")

	missing_files = tuple(
		relative
		for relative in REQUIRED_GAME_FILES
		if not (paths.source_game / relative).is_file()
	)
	installed = not missing_files
	local_build = _read_verified_local_build(paths.native_depot_state)
	if not installed:
		action = PrimaryAction.INSTALL
	elif official_build is not None and (
		local_build is None or local_build < official_build
	):
		action = PrimaryAction.UPDATE
	else:
		action = PrimaryAction.PLAY
	return GameInstallationStatus(
		action=action,
		installed=installed,
		local_build=local_build,
		official_build=official_build,
		missing_files=missing_files,
	)


def _read_verified_local_build(path: Path) -> int | None:
	try:
		value = json.loads(path.read_text(encoding="utf-8"))
	except (OSError, UnicodeError, json.JSONDecodeError):
		return None
	if not isinstance(value, dict) or value.get("dry_run") is not False:
		return None
	build = value.get("build")
	if isinstance(build, bool) or not isinstance(build, int) or build < 0:
		return None
	return build