fix(steam_backlog_enforcer): prevent enforce daemon from deleting assigned game

- Guard enforce_allowed_game() and _guard_installed_games() against
  current_app_id=None so they never treat all games as unauthorized
- Add early return in _enforce_loop_iteration when no game is assigned
- Wrap State.load() in enforce loop with error handling for corrupt files
- Switch all config/cache file writes to atomic (tmpfile + rename)
- Add robust error handling to State.load() for corrupt JSON
- Update tests for new behavior and add coverage for atomic writes

steam_backlog_enforcer/_enforce_loop.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import json
 import logging
 import time
 
@@ -64,6 +65,8 @@ def _guard_installed_games(allowed_app_id: int | None) -> int:
 
     Returns number of games removed this pass.
     """
+    if allowed_app_id is None:
+        return 0
     installed = get_installed_games()
     count = 0
     for app_id, name in installed:
@@ -165,6 +168,9 @@ def _enforce_loop_iteration(config: Config, state: State) -> None:
         config: Enforcer configuration.
         state: Current enforcer state.
     """
+    if state.current_app_id is None:
+        return
+
     # A) Kill unauthorized game processes.
     if config.kill_unauthorized_games:
         violations = enforce_allowed_game(
@@ -223,7 +229,12 @@ def do_enforce(config: Config, state: State) -> None:
             # Reload state from disk so CLI changes (e.g. new game
             # assignment via ``done`` / ``scan``) take effect immediately
             # without needing to restart the daemon.
+            try:
                 fresh = State.load()
+            except (json.JSONDecodeError, OSError, ValueError) as exc:
+                logger.warning("Failed to reload state: %s", exc)
+                time.sleep(ENFORCE_INTERVAL)
+                continue
             state.current_app_id = fresh.current_app_id
             state.current_game_name = fresh.current_game_name
             state.finished_app_ids = fresh.finished_app_ids

steam_backlog_enforcer/config.py

@@ -2,10 +2,14 @@
 
 from __future__ import annotations
 
+import contextlib
 from dataclasses import dataclass, field
 import json
+import logging
+import os
 from pathlib import Path
 import sys
+import tempfile
 from typing import Any
 
 CONFIG_DIR = Path.home() / ".config" / "steam_backlog_enforcer"
@@ -25,6 +29,25 @@ BLOCKED_DOMAINS = [
 
 HOSTS_FILE = Path("/etc/hosts")
 
+logger = logging.getLogger(__name__)
+
+
+def _atomic_write(path: Path, data: str) -> None:
+    """Write data to a file atomically via a temporary file + rename."""
+    path.parent.mkdir(parents=True, exist_ok=True)
+    fd, tmp = tempfile.mkstemp(dir=path.parent, suffix=".tmp")
+    tmp_path = Path(tmp)
+    try:
+        os.write(fd, data.encode("utf-8"))
+        os.close(fd)
+        tmp_path.replace(path)
+    except BaseException:
+        with contextlib.suppress(OSError):
+            os.close(fd)
+        with contextlib.suppress(OSError):
+            tmp_path.unlink()
+        raise
+
 
 @dataclass
 class Config:
@@ -40,9 +63,9 @@ class Config:
 
     def save(self) -> None:
         """Persist config to disk."""
-        CONFIG_DIR.mkdir(parents=True, exist_ok=True)
+        _atomic_write(
-        CONFIG_FILE.write_text(
+            CONFIG_FILE,
-            json.dumps(self.__dict__, indent=2) + "\n", encoding="utf-8"
+            json.dumps(self.__dict__, indent=2) + "\n",
         )
 
     @classmethod
@@ -66,16 +89,20 @@ class State:
 
     def save(self) -> None:
         """Persist state to disk."""
-        CONFIG_DIR.mkdir(parents=True, exist_ok=True)
+        _atomic_write(
-        STATE_FILE.write_text(
+            STATE_FILE,
-            json.dumps(self.__dict__, indent=2) + "\n", encoding="utf-8"
+            json.dumps(self.__dict__, indent=2) + "\n",
         )
 
     @classmethod
     def load(cls) -> State:
         """Load state from disk, or return defaults."""
         if STATE_FILE.exists():
+            try:
                 data = json.loads(STATE_FILE.read_text(encoding="utf-8"))
+            except (json.JSONDecodeError, OSError, ValueError):
+                logger.warning("Corrupt state file, using defaults.")
+                return cls()
             return cls(
                 **{k: v for k, v in data.items() if k in cls.__dataclass_fields__}
             )
@@ -84,8 +111,10 @@ class State:
 
 def save_snapshot(data: list[dict[str, Any]]) -> None:
     """Save an achievement snapshot to disk."""
-    CONFIG_DIR.mkdir(parents=True, exist_ok=True)
+    _atomic_write(
-    SNAPSHOT_FILE.write_text(json.dumps(data, indent=2) + "\n", encoding="utf-8")
+        SNAPSHOT_FILE,
+        json.dumps(data, indent=2) + "\n",
+    )
 
 
 def load_snapshot() -> list[dict[str, Any]] | None:

steam_backlog_enforcer/enforcer.py

@@ -47,6 +47,8 @@ def enforce_allowed_game(
 
     Returns list of (pid, app_id) that were killed or detected.
     """
+    if allowed_app_id is None:
+        return []
     running = get_running_steam_game_pids()
     violations: list[tuple[int, int]] = []
 

steam_backlog_enforcer/hltb.py

@@ -23,7 +23,7 @@ from typing import Any
 import aiohttp
 from howlongtobeatpy.HTMLRequests import HTMLRequests
 
-from python_pkg.steam_backlog_enforcer.config import CONFIG_DIR
+from python_pkg.steam_backlog_enforcer.config import CONFIG_DIR, _atomic_write
 
 logger = logging.getLogger(__name__)
 
@@ -71,11 +71,10 @@ def load_hltb_cache() -> dict[int, float]:
 
 def save_hltb_cache(cache: dict[int, float]) -> None:
     """Save the HLTB cache to disk."""
-    CONFIG_DIR.mkdir(parents=True, exist_ok=True)
     try:
-        HLTB_CACHE_FILE.write_text(
+        _atomic_write(
+            HLTB_CACHE_FILE,
             json.dumps({str(k): v for k, v in cache.items()}, indent=2) + "\n",
-            encoding="utf-8",
         )
     except OSError:
         logger.exception("Failed to save HLTB cache")

steam_backlog_enforcer/protondb.py

@@ -17,7 +17,7 @@ from typing import Any
 
 import aiohttp
 
-from python_pkg.steam_backlog_enforcer.config import CONFIG_DIR
+from python_pkg.steam_backlog_enforcer.config import CONFIG_DIR, _atomic_write
 
 logger = logging.getLogger(__name__)
 
@@ -92,8 +92,10 @@ def _load_cache() -> dict[str, Any]:
 
 def _save_cache(cache: dict[str, Any]) -> None:
     """Persist the ProtonDB cache."""
-    CONFIG_DIR.mkdir(parents=True, exist_ok=True)
+    _atomic_write(
-    PROTONDB_CACHE_FILE.write_text(json.dumps(cache, indent=2) + "\n", encoding="utf-8")
+        PROTONDB_CACHE_FILE,
+        json.dumps(cache, indent=2) + "\n",
+    )
 
 
 async def _fetch_one(

steam_backlog_enforcer/tests/test_config.py

@@ -11,6 +11,7 @@ import pytest
 from python_pkg.steam_backlog_enforcer.config import (
     Config,
     State,
+    _atomic_write,
     interactive_setup,
     load_snapshot,
     save_snapshot,
@@ -20,6 +21,49 @@ if TYPE_CHECKING:
     from pathlib import Path
 
 
+class TestAtomicWrite:
+    """Tests for _atomic_write."""
+
+    def test_writes_file(self, tmp_path: Path) -> None:
+        target = tmp_path / "out.json"
+        _atomic_write(target, '{"key": "value"}\n')
+        assert target.read_text(encoding="utf-8") == '{"key": "value"}\n'
+
+    def test_creates_parent_dirs(self, tmp_path: Path) -> None:
+        target = tmp_path / "sub" / "deep" / "out.json"
+        _atomic_write(target, "data")
+        assert target.read_text(encoding="utf-8") == "data"
+
+    def test_cleanup_on_write_error(self, tmp_path: Path) -> None:
+        target = tmp_path / "out.json"
+        with (
+            patch(
+                "python_pkg.steam_backlog_enforcer.config.os.write",
+                side_effect=OSError("disk full"),
+            ),
+            pytest.raises(OSError, match="disk full"),
+        ):
+            _atomic_write(target, "data")
+        assert not target.exists()
+        tmp_files = list(tmp_path.glob("*.tmp"))
+        assert tmp_files == []
+
+    def test_cleanup_on_replace_error(self, tmp_path: Path) -> None:
+        target = tmp_path / "out.json"
+        with (
+            patch.object(
+                type(target),
+                "replace",
+                side_effect=OSError("no perm"),
+            ),
+            pytest.raises(OSError, match="no perm"),
+        ):
+            _atomic_write(target, "data")
+        assert not target.exists()
+        tmp_files = list(tmp_path.glob("*.tmp"))
+        assert tmp_files == []
+
+
 class TestConfig:
     """Tests for Config dataclass."""
 
@@ -120,6 +164,14 @@ class TestState:
             st = State.load()
             assert st.current_app_id is None
 
+    def test_load_corrupt(self, tmp_path: Path) -> None:
+        state_file = tmp_path / "state.json"
+        state_file.write_text("not valid json{{", encoding="utf-8")
+        with patch("python_pkg.steam_backlog_enforcer.config.STATE_FILE", state_file):
+            st = State.load()
+            assert st.current_app_id is None
+            assert st.current_game_name == ""
+
 
 class TestSnapshot:
     """Tests for snapshot save/load."""

steam_backlog_enforcer/tests/test_enforce_loop.py

@@ -102,6 +102,9 @@ class TestGuardInstalledGames:
         ):
             assert _guard_installed_games(440) == 0
 
+    def test_allowed_none_skips(self) -> None:
+        assert _guard_installed_games(None) == 0
+
 
 class TestEnforceSetup:
     """Tests for _enforce_setup."""
@@ -297,8 +300,14 @@ class TestEnforceLoopIteration:
             uninstall_other_games=False,
         )
         state = State(current_app_id=None)
-        with patch(f"{PKG}.is_game_installed") as mock_installed:
+        with (
+            patch(f"{PKG}.enforce_allowed_game") as mock_enforce,
+            patch(f"{PKG}._guard_installed_games") as mock_guard,
+            patch(f"{PKG}.is_game_installed") as mock_installed,
+        ):
             _enforce_loop_iteration(config, state)
+            mock_enforce.assert_not_called()
+            mock_guard.assert_not_called()
             mock_installed.assert_not_called()
 
 
@@ -350,3 +359,31 @@ class TestDoEnforce:
         ):
             do_enforce(config, state)
             assert call_count == 2
+
+    def test_state_load_failure_continues(self) -> None:
+        """Corrupt state file should not crash the daemon."""
+        import json as json_mod
+
+        state = State(current_app_id=1, current_game_name="G")
+        config = Config()
+        call_count = 0
+
+        def load_side_effect() -> State:
+            nonlocal call_count
+            call_count += 1
+            if call_count == 1:
+                msg = "bad"
+                raise json_mod.JSONDecodeError(msg, "", 0)
+            if call_count == 2:
+                raise KeyboardInterrupt
+            return State(current_app_id=1)  # pragma: no cover
+
+        with (
+            patch(f"{PKG}._enforce_setup"),
+            patch(f"{PKG}._echo"),
+            patch.object(State, "load", side_effect=load_side_effect),
+            patch(f"{PKG}._enforce_loop_iteration") as mock_iter,
+            patch(f"{PKG}.time.sleep"),
+        ):
+            do_enforce(config, state)
+            mock_iter.assert_not_called()

steam_backlog_enforcer/tests/test_enforcer.py

@@ -130,18 +130,8 @@ class TestEnforceAllowedGame:
             assert result == [(100, 570)]
 
     def test_allowed_none(self) -> None:
-        with (
-            patch(
-                "python_pkg.steam_backlog_enforcer.enforcer.get_running_steam_game_pids",
-                return_value={100: 570},
-            ),
-            patch(
-                "python_pkg.steam_backlog_enforcer.enforcer.kill_process"
-            ) as mock_kill,
-        ):
         result = enforce_allowed_game(None, kill_unauthorized=True)
-            assert result == [(100, 570)]
+        assert result == []
-            mock_kill.assert_called_once_with(100, 570)
 
 
 class TestKillProcess:

steam_backlog_enforcer/tests/test_hltb.py

@@ -66,14 +66,9 @@ class TestHltbCache:
             assert cache_file.exists()
 
     def test_save_cache_os_error(self, tmp_path: Path) -> None:
-        cache_file = MagicMock()
+        with patch(
-        cache_file.write_text = MagicMock(side_effect=OSError)
+            "python_pkg.steam_backlog_enforcer.hltb._atomic_write",
-        with (
+            side_effect=OSError("disk full"),
-            patch("python_pkg.steam_backlog_enforcer.hltb.HLTB_CACHE_FILE", cache_file),
-            patch(
-                "python_pkg.steam_backlog_enforcer.hltb.CONFIG_DIR",
-                MagicMock(mkdir=MagicMock()),
-            ),
         ):
             save_hltb_cache({440: 10.5})  # Should not raise