"""Exact-profile selection for the post-login V21 world-transition helper."""

from __future__ import annotations

import hashlib
from pathlib import Path


V21_BINARY_HASHES = {
	"Game.exe": "2bc3edd26c5f6d7ae9bbdc23967c5aefd374bdf934fcdfa2ed42c6442e550837",
	"game.dll": "4b4e5c28e2bfdaa8d36c8341fad27becfd03faf63aa8ea874f5d43c5b1961868",
}
WORLD_FIX_HELPER_FILENAME = "pt-world-fix.exe"
# Filled from the reproducible stripped PE after the native helper is built.
WORLD_FIX_HELPER_SHA256 = (
	"d5bdf655f62dae429eff627cf8960f670ec59c12a9759dcd14342786f53e4019"
)


class WorldFixError(RuntimeError):
	"""Raised when an exact client needs a missing or untrusted helper."""


def packaged_world_fix_helper() -> Path:
	return Path(__file__).resolve().parent / "native" / WORLD_FIX_HELPER_FILENAME


def resolve_world_fix_helper(
	game_directory: Path,
	*,
	helper: Path | None = None,
) -> Path | None:
	"""Return the verified helper only for the exact publisher V21 pair."""

	game = game_directory.expanduser().resolve(strict=False)
	hashes = {
		name: _sha256(game / name)
		for name in V21_BINARY_HASHES
		if (game / name).is_file()
	}
	if hashes != V21_BINARY_HASHES:
		return None
	requested = packaged_world_fix_helper() if helper is None else helper.expanduser()
	if requested.is_symlink():
		raise WorldFixError(
			"the post-login world-fix helper must not be a symbolic link"
		)
	candidate = requested.resolve()
	if not candidate.is_file():
		raise WorldFixError(
			"the verified post-login world-fix helper is missing; reinstall the launcher"
		)
	digest = _sha256(candidate)
	if digest != WORLD_FIX_HELPER_SHA256:
		raise WorldFixError(
			"the post-login world-fix helper failed its launcher integrity check"
		)
	return candidate


def _sha256(path: Path) -> str:
	digest = hashlib.sha256()
	with path.open("rb") as handle:
		for chunk in iter(lambda: handle.read(1024 * 1024), b""):
			digest.update(chunk)
	return digest.hexdigest()