plomlompom.com Git - plomtask/blob - plomtask/versioned_attributes.py

   1 """Attributes whose values are recorded as a timestamped history."""
   2 from datetime import datetime
   3 from typing import Any
   4 from sqlite3 import Row
   5 from time import sleep
   6 from plomtask.db import DatabaseConnection
   7 from plomtask.exceptions import (HandledException, BadFormatException,
   8                                  NotFoundException)
   9
  10 TIMESTAMP_FMT = '%Y-%m-%d %H:%M:%S.%f'
  11
  12
  13 class VersionedAttribute:
  14     """Attributes whose values are recorded as a timestamped history."""
  15
  16     def __init__(self,
  17                  parent: Any, table_name: str, default: str | float) -> None:
  18         self.parent = parent
  19         self.table_name = table_name
  20         self.default = default
  21         self.history: dict[str, str | float] = {}
  22
  23     def __hash__(self) -> int:
  24         history_tuples = tuple((k, v) for k, v in self.history.items())
  25         hashable = (self.parent.id_, self.table_name, self.default,
  26                     history_tuples)
  27         return hash(hashable)
  28
  29     @property
  30     def _newest_timestamp(self) -> str:
  31         """Return most recent timestamp."""
  32         return sorted(self.history.keys())[-1]
  33
  34     @property
  35     def newest(self) -> str | float:
  36         """Return most recent value, or self.default if self.history empty."""
  37         if 0 == len(self.history):
  38             return self.default
  39         return self.history[self._newest_timestamp]
  40
  41     def reset_timestamp(self, old_str: str, new_str: str) -> None:
  42         """Rename self.history key (timestamp) old to new.
  43
  44         Chronological sequence of keys must be preserved, i.e. cannot move
  45         key before earlier or after later timestamp.
  46         """
  47         try:
  48             new = datetime.strptime(new_str, TIMESTAMP_FMT)
  49             old = datetime.strptime(old_str, TIMESTAMP_FMT)
  50         except ValueError as exc:
  51             raise BadFormatException('Timestamp of illegal format.') from exc
  52         timestamps = list(self.history.keys())
  53         if old_str not in timestamps:
  54             raise HandledException(f'Timestamp {old} not found in history.')
  55         sorted_timestamps = sorted([datetime.strptime(t, TIMESTAMP_FMT)
  56                                     for t in timestamps])
  57         expected_position = sorted_timestamps.index(old)
  58         sorted_timestamps.remove(old)
  59         sorted_timestamps += [new]
  60         sorted_timestamps.sort()
  61         if sorted_timestamps.index(new) != expected_position:
  62             raise HandledException('Timestamp not respecting chronology.')
  63         value = self.history[old_str]
  64         del self.history[old_str]
  65         self.history[new_str] = value
  66
  67     def set(self, value: str | float) -> None:
  68         """Add to self.history if and only if not same value as newest one.
  69
  70         Note that we wait one micro-second, as timestamp comparison to check
  71         most recent elements only goes up to that precision.
  72
  73         Also note that we don't check against .newest because that may make us
  74         compare value against .default even if not set. We want to be able to
  75         explicitly set .default as the first element.
  76         """
  77         sleep(0.00001)
  78         if 0 == len(self.history) \
  79                 or value != self.history[self._newest_timestamp]:
  80             self.history[datetime.now().strftime(TIMESTAMP_FMT)] = value
  81
  82     def history_from_row(self, row: Row) -> None:
  83         """Extend self.history from expected table row format."""
  84         self.history[row[1]] = row[2]
  85
  86     def at(self, queried_time: str) -> str | float:
  87         """Retrieve value of timestamp nearest queried_time from the past."""
  88         if len(queried_time) == 10:
  89             queried_time += ' 23:59:59.999'
  90         sorted_timestamps = sorted(self.history.keys())
  91         if 0 == len(sorted_timestamps):
  92             return self.default
  93         selected_timestamp = sorted_timestamps[0]
  94         for timestamp in sorted_timestamps[1:]:
  95             if timestamp > queried_time:
  96                 break
  97             selected_timestamp = timestamp
  98         return self.history[selected_timestamp]
  99
 100     def save(self, db_conn: DatabaseConnection) -> None:
 101         """Save as self.history entries, but first wipe old ones."""
 102         if self.parent.id_ is None:
 103             raise NotFoundException('cannot save attribute to parent if no ID')
 104         db_conn.rewrite_relations(self.table_name, 'parent', self.parent.id_,
 105                                   [[item[0], item[1]]
 106                                    for item in self.history.items()])
 107
 108     def remove(self, db_conn: DatabaseConnection) -> None:
 109         """Remove from DB."""
 110         db_conn.delete_where(self.table_name, 'parent', self.parent.id_)