Re-write caching.

[plomtask] / plomtask / db.py

diff --git a/plomtask/db.py b/plomtask/db.py
index dd2ee2452a7480878c47b38f2669c08cee229ca6..e8a542e6176937a7c205a9a5909a5c776bdbd7db 100644 (file)
--- a/plomtask/db.py
+++ b/plomtask/db.py
@@ -1,8 +1,9 @@
 """Database management."""
+from __future__ import annotations
 from os.path import isfile
 from difflib import Differ
 from sqlite3 import connect as sql_connect, Cursor, Row
-from typing import Any, Dict
+from typing import Any, Self, TypeVar, Generic
 from plomtask.exceptions import HandledException
 
 PATH_DB_SCHEMA = 'scripts/init.sql'
@@ -61,11 +62,6 @@ class DatabaseConnection:
     def __init__(self, db_file: DatabaseFile) -> None:
         self.file = db_file
         self.conn = sql_connect(self.file.path)
-        self.cached_todos: Dict[int, Any] = {}
-        self.cached_days: Dict[str, Any] = {}
-        self.cached_process_steps: Dict[int, Any] = {}
-        self.cached_processes: Dict[int, Any] = {}
-        self.cached_conditions: Dict[int, Any] = {}
 
     def commit(self) -> None:
         """Commit SQL transaction."""
@@ -116,38 +112,41 @@ class DatabaseConnection:
         return '(' + ','.join(['?'] * len(values)) + ')'
 
 
-class BaseModel:
+X = TypeVar('X', int, str)
+T = TypeVar('T', bound='BaseModel[Any]')
+
+
+class BaseModel(Generic[X]):
     """Template for most of the models we use/derive from the DB."""
     table_name = ''
     to_save: list[str] = []
-    id_: None | int | str
-    id_type: type[Any] = int
+    id_: None | X
+    cache_: dict[X, Self] = {}
 
     @classmethod
-    def from_table_row(cls, db_conn: DatabaseConnection,
-                       row: Row | list[Any]) -> Any:
+    def from_table_row(cls: type[T],
+                       # pylint: disable=unused-argument
+                       db_conn: DatabaseConnection,
+                       row: Row | list[Any]) -> T:
         """Make from DB row, write to DB cache."""
         obj = cls(*row)
-        assert isinstance(obj.id_, cls.id_type)
-        cache = getattr(db_conn, f'cached_{cls.table_name}')
-        cache[obj.id_] = obj
+        obj.cache()
         return obj
 
     @classmethod
     def _by_id(cls,
                db_conn: DatabaseConnection,
-               id_: int | str) -> tuple[Any, bool]:
+               id_: X) -> tuple[Self | None, bool]:
         """Return instance found by ID, or None, and if from cache or not."""
         from_cache = False
-        obj = None
-        cache = getattr(db_conn, f'cached_{cls.table_name}')
-        if id_ in cache.keys():
-            obj = cache[id_]
+        obj = cls.get_cached(id_)
+        if obj:
             from_cache = True
         else:
             for row in db_conn.row_where(cls.table_name, 'id', id_):
                 obj = cls.from_table_row(db_conn, row)
-                cache[id_] = obj
+                assert isinstance(obj, cls)
+                obj.cache()
                 break
         return obj, from_cache
 
@@ -156,7 +155,7 @@ class BaseModel:
         if (id_ is not None) and id_ < 1:
             msg = f'illegal {self.__class__.__name__} ID, must be >=1: {id_}'
             raise HandledException(msg)
-        self.id_ = id_
+        self.id_ = id_  # type: ignore[assignment]
 
     def save_core(self, db_conn: DatabaseConnection,
                   update_with_lastrowid: bool = True) -> None:
@@ -168,6 +167,32 @@ class BaseModel:
         cursor = db_conn.exec(f'REPLACE INTO {table_name} VALUES {q_marks}',
                               values)
         if update_with_lastrowid:
-            self.id_ = cursor.lastrowid
-        cache = getattr(db_conn, f'cached_{table_name}')
-        cache[self.id_] = self
+            self.id_ = cursor.lastrowid  # type: ignore[assignment]
+        self.cache()
+
+    @classmethod
+    def get_cached(cls: type[T], id_: X) -> T | None:
+        """Get object of id_ from class's cache, or None if not found."""
+        # pylint: disable=consider-iterating-dictionary
+        if id_ in cls.cache_.keys():
+            obj = cls.cache_[id_]
+            assert isinstance(obj, cls)
+            return obj
+        return None
+
+    def cache(self) -> None:
+        """Update object in class's cache."""
+        if self.id_ is None:
+            raise HandledException('Cannot cache object without ID.')
+        self.__class__.cache_[self.id_] = self
+
+    def uncache(self) -> None:
+        """Remove self from cache."""
+        if self.id_ is None:
+            raise HandledException('Cannot un-cache object without ID.')
+        del self.__class__.cache_[self.id_]
+
+    @classmethod
+    def empty_cache(cls) -> None:
+        """Empty class's cache."""
+        cls.cache_ = {}