refactor(services): one ConfigStore for the JSON-file config mechanics

Five services shipped byte-identical save_config copies and as many the
same get_config skeleton — the next fix (an atomic write, a better
error) would have had to land in every one. load_json_config /
save_json_config own the mechanics; the path, the default, and any
behaviour around the write stay per-service.

Byte-compatible with the copies: plain open(..., 'w'), no locking, no
atomic rename — adding those here would be a behaviour change smuggled
in with a consolidation; if they're ever wanted they now land once.
Divergent services (template cache invalidation, storage secret
merging, email_relay's DB backing, build_service's leaner return dict)
keep their own methods. monitoring_service converts separately — it is
mid-edit on another branch of this plan.

backend/app/services/backup_service.py

@@ -15,6 +15,7 @@ import schedule
 
 from app import paths
 from app.utils import backup_crypto
+from app.utils.config_store import load_json_config, save_json_config
 from app.utils.formatting import format_bytes
 from app.utils.system import is_command_available
 from app.services.telemetry_service import TelemetryService, generate_correlation_id
@@ -53,14 +54,7 @@ class BackupService:
     @classmethod
     def get_config(cls) -> Dict:
         """Get backup configuration."""
-        if os.path.exists(cls.BACKUP_CONFIG):
-            try:
-                with open(cls.BACKUP_CONFIG, 'r') as f:
-                    return json.load(f)
-            except Exception:
-                pass
-
-        return {
+        return load_json_config(cls.BACKUP_CONFIG, {
             'enabled': False,
             'retention_days': 30,
             'encrypt_backups': False,
@@ -70,18 +64,12 @@ class BackupService:
                 'on_failure': True,
                 'email': ''
             }
-        }
+        })
 
     @classmethod
     def save_config(cls, config: Dict) -> Dict:
         """Save backup configuration."""
-        try:
-            os.makedirs(cls.CONFIG_DIR, exist_ok=True)
-            with open(cls.BACKUP_CONFIG, 'w') as f:
-                json.dump(config, f, indent=2)
-            return {'success': True, 'message': 'Configuration saved'}
-        except Exception as e:
-            return {'success': False, 'error': str(e)}
+        return save_json_config(cls.BACKUP_CONFIG, config)
 
     @classmethod
     def backup_application(cls, app_name: str, app_path: str,

backend/app/services/build_service.py

@@ -22,6 +22,7 @@ from typing import Dict, List, Optional, Callable, Generator
 from pathlib import Path
 
 from app import paths
+from app.utils.config_store import load_json_config
 
 
 class BuildService:
@@ -68,13 +69,7 @@ class BuildService:
     @classmethod
     def get_config(cls) -> Dict:
         """Get build configuration."""
-        if os.path.exists(cls.BUILD_CONFIG):
-            try:
-                with open(cls.BUILD_CONFIG, 'r') as f:
-                    return json.load(f)
-            except Exception:
-                pass
-        return {'apps': {}}
+        return load_json_config(cls.BUILD_CONFIG, {'apps': {}})
 
     @classmethod
     def save_config(cls, config: Dict) -> Dict:

backend/app/services/git_service.py

@@ -9,6 +9,7 @@ from typing import Dict, List, Optional
 from pathlib import Path
 
 from app import paths
+from app.utils.config_store import load_json_config, save_json_config
 from app.utils.git_security import (
     git_argv,
     git_env,
@@ -28,28 +29,15 @@ class GitService:
     @classmethod
     def get_config(cls) -> Dict:
         """Get deployment configuration."""
-        if os.path.exists(cls.DEPLOY_CONFIG):
-            try:
-                with open(cls.DEPLOY_CONFIG, 'r') as f:
-                    return json.load(f)
-            except Exception:
-                pass
-
-        return {
+        return load_json_config(cls.DEPLOY_CONFIG, {
             'apps': {},  # app_id -> deployment config
             'webhook_secret': cls._generate_secret()
-        }
+        })
 
     @classmethod
     def save_config(cls, config: Dict) -> Dict:
         """Save deployment configuration."""
-        try:
-            os.makedirs(cls.CONFIG_DIR, exist_ok=True)
-            with open(cls.DEPLOY_CONFIG, 'w') as f:
-                json.dump(config, f, indent=2)
-            return {'success': True, 'message': 'Configuration saved'}
-        except Exception as e:
-            return {'success': False, 'error': str(e)}
+        return save_json_config(cls.DEPLOY_CONFIG, config)
 
     @staticmethod
     def _generate_secret() -> str:

backend/app/services/notification_service.py

@@ -20,6 +20,7 @@ from typing import Dict, List, Optional
 from pathlib import Path
 
 from app import paths
+from app.utils.config_store import load_json_config, save_json_config
 
 
 class NotificationService:
@@ -40,14 +41,7 @@ class NotificationService:
     @classmethod
     def get_config(cls) -> Dict:
         """Get notification configuration."""
-        if os.path.exists(cls.NOTIFICATIONS_CONFIG):
-            try:
-                with open(cls.NOTIFICATIONS_CONFIG, 'r') as f:
-                    return json.load(f)
-            except Exception:
-                pass
-
-        return {
+        return load_json_config(cls.NOTIFICATIONS_CONFIG, {
             'discord': {
                 'enabled': False,
                 'webhook_url': '',
@@ -87,18 +81,12 @@ class NotificationService:
                 'headers': {},
                 'notify_on': ['critical', 'warning']
             }
-        }
+        })
 
     @classmethod
     def save_config(cls, config: Dict) -> Dict:
         """Save notification configuration."""
-        try:
-            os.makedirs(cls.CONFIG_DIR, exist_ok=True)
-            with open(cls.NOTIFICATIONS_CONFIG, 'w') as f:
-                json.dump(config, f, indent=2)
-            return {'success': True, 'message': 'Configuration saved'}
-        except Exception as e:
-            return {'success': False, 'error': str(e)}
+        return save_json_config(cls.NOTIFICATIONS_CONFIG, config)
 
     @classmethod
     def update_channel_config(cls, channel: str, settings: Dict) -> Dict:

backend/app/services/security_service.py

@@ -20,6 +20,7 @@ from pathlib import Path
 
 from .notification_service import NotificationService
 from app import paths
+from app.utils.config_store import load_json_config, save_json_config
 from app.utils.system import (
     PackageManager,
     ServiceControl,
@@ -44,14 +45,7 @@ class SecurityService:
     @classmethod
     def get_config(cls) -> Dict:
         """Get security configuration."""
-        if os.path.exists(cls.SECURITY_CONFIG):
-            try:
-                with open(cls.SECURITY_CONFIG, 'r') as f:
-                    return json.load(f)
-            except Exception:
-                pass
-
-        return {
+        return load_json_config(cls.SECURITY_CONFIG, {
             'clamav': {
                 'enabled': True,
                 'scan_paths': ['/var/www', '/home'],
@@ -84,18 +78,12 @@ class SecurityService:
                 'on_suspicious_activity': True,
                 'severity': 'critical'
             }
-        }
+        })
 
     @classmethod
     def save_config(cls, config: Dict) -> Dict:
         """Save security configuration."""
-        try:
-            os.makedirs(cls.CONFIG_DIR, exist_ok=True)
-            with open(cls.SECURITY_CONFIG, 'w') as f:
-                json.dump(config, f, indent=2)
-            return {'success': True, 'message': 'Configuration saved'}
-        except Exception as e:
-            return {'success': False, 'error': str(e)}
+        return save_json_config(cls.SECURITY_CONFIG, config)
 
     # ==========================================
     # CLAMAV INTEGRATION

backend/app/utils/config_store.py

@@ -0,0 +1,44 @@
+"""JSON-file config persistence — one door for the load-or-default /
+dump-or-error mechanics (plan 75 §F4).
+
+Five services shipped byte-identical ``save_config`` copies and seven more the
+same ``get_config`` skeleton, each a place a fix (an atomic write, a better
+error) would have had to land N times. These two helpers own the mechanics;
+the per-service parts stay per-service: the path, the default, and any extra
+behaviour around the write (cache invalidation, secret merging — those keep
+their own methods and may call these helpers inside).
+
+Deliberate parity with the copies they replace: plain ``open(..., 'w')``, no
+locking, no atomic rename — none of the originals had them, and adding them
+here would be a behaviour change smuggled in with a consolidation. If atomic
+writes are ever wanted, they land here, once.
+"""
+import json
+import os
+
+
+def load_json_config(path, default):
+    """JSON file → dict; *default* on missing or corrupt.
+
+    A corrupt config reads as the default, never raises — the same contract
+    the hand-rolled copies had, and the one callers rely on at boot.
+    """
+    if os.path.exists(path):
+        try:
+            with open(path, 'r') as f:
+                return json.load(f)
+        except Exception:  # noqa: BLE001
+            pass
+    return default
+
+
+def save_json_config(path, config):
+    """dict → JSON file (indented), creating the parent dir. Returns the
+    service-dict shape every caller already returns."""
+    try:
+        os.makedirs(os.path.dirname(path) or '.', exist_ok=True)
+        with open(path, 'w') as f:
+            json.dump(config, f, indent=2)
+        return {'success': True, 'message': 'Configuration saved'}
+    except Exception as e:  # noqa: BLE001
+        return {'success': False, 'error': str(e)}

backend/tests/test_config_store.py

@@ -0,0 +1,79 @@
+"""The ConfigStore contract (plan 75 §F4).
+
+Five services shipped byte-identical save_config copies; the helpers in
+``app.utils.config_store`` are now the one place those mechanics live. These
+tests pin the behaviour the copies had — byte-for-byte compatibility is the
+point of the consolidation: indented JSON, parent dir created, corrupt file
+reads as the default, and the service-dict return shape.
+"""
+import json
+import os
+
+from app.utils.config_store import load_json_config, save_json_config
+
+
+def test_missing_file_reads_as_the_default(tmp_path):
+    default = {'enabled': False}
+    assert load_json_config(str(tmp_path / 'cfg.json'), default) == default
+
+
+def test_the_default_is_not_shared_between_calls(tmp_path):
+    """Callers mutate what they get back; a shared default would leak."""
+    default = {'items': []}
+    first = load_json_config(str(tmp_path / 'cfg.json'), default)
+    first['items'].append('x')
+    assert load_json_config(str(tmp_path / 'cfg.json'), default) == default
+
+
+def test_corrupt_file_reads_as_the_default_never_raises(tmp_path):
+    path = tmp_path / 'cfg.json'
+    path.write_text('{"truncated":')
+    assert load_json_config(str(path), {'a': 1}) == {'a': 1}
+
+
+def test_save_creates_the_parent_dir_and_writes_indented_json(tmp_path):
+    path = tmp_path / 'nested' / 'cfg.json'
+    result = save_json_config(str(path), {'b': 2})
+
+    assert result == {'success': True, 'message': 'Configuration saved'}
+    assert json.loads(path.read_text()) == {'b': 2}
+    assert path.read_text() == json.dumps({'b': 2}, indent=2)
+
+
+def test_save_failure_returns_the_error_shape(tmp_path):
+    blocked = tmp_path / 'a-file'
+    blocked.write_text('x')
+    result = save_json_config(str(blocked / 'cfg.json'), {'b': 2})
+
+    assert result['success'] is False
+    assert result['error']
+
+
+def test_round_trip(tmp_path):
+    path = str(tmp_path / 'cfg.json')
+    save_json_config(path, {'retention_days': 30})
+    assert load_json_config(path, {}) == {'retention_days': 30}
+
+
+# --------------------------------------------------------------------------- #
+# The converted services actually go through the one door
+# --------------------------------------------------------------------------- #
+
+def test_converted_services_use_the_store(tmp_path, monkeypatch):
+    """Spot-check two of the converted services end to end: their get/save
+    config must round-trip through the store with unchanged semantics."""
+    from app.services.backup_service import BackupService
+    from app.services.git_service import GitService
+
+    backup_path = str(tmp_path / 'backup.json')
+    monkeypatch.setattr(BackupService, 'BACKUP_CONFIG', backup_path)
+    assert BackupService.get_config()['retention_days'] == 30
+    assert BackupService.save_config({'retention_days': 7})['success'] is True
+    assert BackupService.get_config() == {'retention_days': 7}
+
+    git_path = str(tmp_path / 'deployments.json')
+    monkeypatch.setattr(GitService, 'DEPLOY_CONFIG', git_path)
+    default = GitService.get_config()
+    assert 'webhook_secret' in default and default['apps'] == {}
+    assert GitService.save_config({'apps': {'1': {}}})['success'] is True
+    assert GitService.get_config() == {'apps': {'1': {}}}