feat: Configuration Storage

Change-Id: I39b975e4b9d43ac701805f796bd0316867eea87e
diff --git a/dcs/__init__.py b/dcs/__init__.py
new file mode 100644
index 0000000..f80504b
--- /dev/null
+++ b/dcs/__init__.py
@@ -0,0 +1,5 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
diff --git a/dcs/config/__init__.py b/dcs/config/__init__.py
new file mode 100644
index 0000000..78d7149
--- /dev/null
+++ b/dcs/config/__init__.py
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+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from .store import Store, TomlStore, default_store, ConfigObject
diff --git a/dcs/config/store.py b/dcs/config/store.py
new file mode 100644
index 0000000..84801ba
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+++ b/dcs/config/store.py
@@ -0,0 +1,121 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from __future__ import annotations
+
+import toml
+import json
+from typing import Dict, AnyStr, Callable, Type, Any, Optional
+from pydantic import BaseModel, PrivateAttr
+import appdirs
+import os
+import logging
+
+
+class ConfigObject(BaseModel):
+    _KEY: AnyStr = PrivateAttr()
+
+    @classmethod
+    def get_key(cls) -> AnyStr:
+        return cls._KEY
+
+
+class Store:
+    __instances: Dict[str, Store] = {}
+
+    def __init__(self, raw_objs: Dict[AnyStr, Any], save_cb: Optional[Callable[[Store], None]] = None):
+        self._raw_objs: Dict[AnyStr, Any] = raw_objs
+        self._cfg_objs: Dict[AnyStr, ConfigObject] = {}
+        self._save_cb: Optional[Callable[[Store], None]] = save_cb
+
+    @staticmethod
+    def get_instance(name: str = 'default') -> Store:
+        if name in Store.__instances:
+            return Store.__instances[name]
+        else:
+            raise KeyError(f'The Store instance {name} does not exist.')
+
+    @classmethod
+    def load_obj(cls, obj: Dict[AnyStr, Any], name: str = 'default', *args, **kwargs) -> Store:
+        if name not in Store.__instances:
+            Store.__instances[name] = cls(obj, *args, **kwargs)
+            return Store.__instances[name]
+        else:
+            raise KeyError(f'The Store instance {name} already exists.')
+
+    @classmethod
+    def new(cls, name: str = 'default', *args, **kwargs) -> Store:
+        if name not in Store.__instances:
+            Store.__instances[name] = cls({}, *args, **kwargs)
+            return Store.__instances[name]
+        else:
+            raise KeyError(f'The Store instance {name} already exists.')
+
+    def dump_obj(self) -> Dict[AnyStr, Any]:
+        obj: Dict[AnyStr, Any] = self._raw_objs
+        for key, item in self._cfg_objs.items():
+            obj[key] = json.loads(item.json())
+        return obj
+
+    def get_config(self, tp: Type[ConfigObject]):
+        key = tp.get_key()
+        if key not in self._cfg_objs:
+            if key in self._raw_objs:
+                self._cfg_objs[key] = tp.parse_obj(self._raw_objs[key])
+            else:
+                self._cfg_objs[key] = tp()
+        return self._cfg_objs[key]
+
+    def save(self) -> None:
+        if self._save_cb is not None:
+            self._save_cb(self)
+
+
+class TomlStore(Store):
+    def __init__(self, raw_objs: Dict[AnyStr, Any], toml_file: str):
+        super().__init__(raw_objs, save_cb=self._do_save)
+        self.toml_file: str = toml_file
+
+    @classmethod
+    def load_or_create_toml(cls, toml_file: str, name: str = 'default') -> TomlStore:
+        try:
+            s = Store.get_instance(name)
+        except KeyError:
+            try:
+                s = TomlStore.load_toml(toml_file, name)
+                logging.info(f'Loaded config from {toml_file}')
+            except FileNotFoundError:
+                s = TomlStore.new(name, toml_file=toml_file)
+                logging.info(f'New config at {toml_file}')
+        return s
+
+    @classmethod
+    def load_toml(cls, toml_file: str, name: str = 'default') -> TomlStore:
+        obj = toml.load(toml_file)
+        return TomlStore.load_obj(obj, name, toml_file=toml_file)
+
+    def dump_toml(self) -> None:
+        base_dir = os.path.dirname(self.toml_file)
+        if not os.path.exists(base_dir):
+            logging.info(f'Creating directory {base_dir}')
+            os.mkdir(base_dir)
+        with open(self.toml_file, 'w', encoding='utf-8') as f:
+            toml.dump(self.dump_obj(), f)
+
+    def _do_save(self, s: Store) -> None:
+        assert id(self) == id(s)
+        self.dump_toml()
+
+
+DEFAULT_PATH = os.path.join(
+    appdirs.user_config_dir('dcs_interactive', 'Philipp Le'),
+    'config.toml'
+)
+
+
+def default_store() -> TomlStore:
+    return TomlStore.load_or_create_toml(DEFAULT_PATH, 'default')
+