Improve consistency of DB column names.

[plomtask] / plomtask / misc.py

diff --git a/plomtask/misc.py b/plomtask/misc.py
index 1b780e29d90af5c17820f642fc445e27b9e8cc25..dcaad175874c3d21041bd77fe0240f9060324cdd 100644 (file)
--- a/plomtask/misc.py
+++ b/plomtask/misc.py
@@ -1,8 +1,53 @@
-"""
-Whatever fits nowhere else, and/or is too small/trivial
-to merit its own module at this point.
-"""
+"""Attributes whose values are recorded as a timestamped history."""
+from datetime import datetime
+from typing import Any
+from plomtask.db import DatabaseConnection
 
 
-class HandledException(Exception):
-    """To identify Exceptions based on expected (if faulty) user behavior."""
+class VersionedAttribute:
+    """Attributes whose values are recorded as a timestamped history."""
+
+    def __init__(self,
+                 parent: Any, table_name: str, default: str | float) -> None:
+        self.parent = parent
+        self.table_name = table_name
+        self.default = default
+        self.history: dict[str, str | float] = {}
+
+    @property
+    def _newest_timestamp(self) -> str:
+        """Return most recent timestamp."""
+        return sorted(self.history.keys())[-1]
+
+    @property
+    def newest(self) -> str | float:
+        """Return most recent value, or self.default if self.history empty."""
+        if 0 == len(self.history):
+            return self.default
+        return self.history[self._newest_timestamp]
+
+    def set(self, value: str | float) -> None:
+        """Add to self.history if and only if not same value as newest one."""
+        if 0 == len(self.history) \
+                or value != self.history[self._newest_timestamp]:
+            self.history[datetime.now().strftime('%Y-%m-%d %H:%M:%S')] = value
+
+    def at(self, queried_time: str) -> str | float:
+        """Retrieve value of timestamp nearest queried_time from the past."""
+        sorted_timestamps = sorted(self.history.keys())
+        if 0 == len(sorted_timestamps):
+            return self.default
+        selected_timestamp = sorted_timestamps[0]
+        for timestamp in sorted_timestamps[1:]:
+            if timestamp > queried_time:
+                break
+            selected_timestamp = timestamp
+        return self.history[selected_timestamp]
+
+    def save(self, db_conn: DatabaseConnection) -> None:
+        """Save as self.history entries, but first wipe old ones."""
+        db_conn.exec(f'DELETE FROM {self.table_name} WHERE parent = ?',
+                     (self.parent.id_,))
+        for timestamp, value in self.history.items():
+            db_conn.exec(f'INSERT INTO {self.table_name} VALUES (?, ?, ?)',
+                         (self.parent.id_, timestamp, value))