X-Git-Url: https://plomlompom.com/repos/berlin_corona.txt?a=blobdiff_plain;f=plomtask%2Fdb.py;h=abd8f6181db946b357902a0ec851f51919f37344;hb=5a5d713ce0b223ab2f6ef34c15bb82b614bdda98;hp=f53a94c4f085f3664d66f0b0cc38863b217741e1;hpb=56b8aa166d51d139edb41f0ef250b1854a5e93e8;p=plomtask

diff --git a/plomtask/db.py b/plomtask/db.py
index f53a94c..abd8f61 100644
--- a/plomtask/db.py
+++ b/plomtask/db.py
@@ -1,7 +1,7 @@
 """Database management."""
 from os.path import isfile
 from difflib import Differ
-from sqlite3 import connect as sql_connect, Cursor
+from sqlite3 import connect as sql_connect, Cursor, Row
 from typing import Any, Dict
 from plomtask.exceptions import HandledException
 
@@ -66,3 +66,61 @@ class DatabaseConnection:
     def close(self) -> None:
         """Close DB connection."""
         self.conn.close()
+
+
+class BaseModel:
+    """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
+
+    @classmethod
+    def from_table_row(cls, db_conn: DatabaseConnection,
+                       row: Row | list[Any]) -> Any:
+        """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
+        return obj
+
+    @classmethod
+    def _by_id(cls,
+               db_conn: DatabaseConnection,
+               id_: int | str) -> tuple[Any, 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_]
+            from_cache = True
+        else:
+            for row in db_conn.exec(f'SELECT * FROM {cls.table_name} '
+                                    'WHERE id = ?', (id_,)):
+                obj = cls.from_table_row(db_conn, row)
+                cache[id_] = obj
+                break
+        return obj, from_cache
+
+    def set_int_id(self, id_: int | None) -> None:
+        """Set id_ if >= 1 or None, else fail."""
+        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_
+
+    def save_core(self, db_conn: DatabaseConnection,
+                  update_with_lastrowid: bool = True) -> None:
+        """Write bare-bones self (sans connected items), ensuring self.id_."""
+        q_marks = ','.join(['?'] * (len(self.to_save) + 1))
+        values = tuple([self.id_] + [getattr(self, key)
+                                     for key in self.to_save])
+        table_name = self.table_name
+        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