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
   9 TIMESTAMP_FMT = '%Y-%m-%d %H:%M:%S.%f'
  10
  11
  12 class VersionedAttribute:
  13     """Attributes whose values are recorded as a timestamped history."""
  14
  15     def __init__(self,
  16                  parent: Any, table_name: str, default: str | float) -> None:
  17         self.parent = parent
  18         self.table_name = table_name
  19         self.default = default
  20         self.history: dict[str, str | float] = {}
  21
  22     def __hash__(self) -> int:
  23         history_tuples = tuple((k, v) for k, v in self.history.items())
  24         hashable = (self.parent.id_, self.table_name, self.default,
  25                     history_tuples)
  26         return hash(hashable)
  27
  28     @property
  29     def _newest_timestamp(self) -> str:
  30         """Return most recent timestamp."""
  31         return sorted(self.history.keys())[-1]
  32
  33     @property
  34     def newest(self) -> str | float:
  35         """Return most recent value, or self.default if self.history empty."""
  36         if 0 == len(self.history):
  37             return self.default
  38         return self.history[self._newest_timestamp]
  39
  40     def reset_timestamp(self, old_str: str, new_str: str) -> None:
  41         """Rename self.history key (timestamp) old to new.
  42
  43         Chronological sequence of keys must be preserved, i.e. cannot move
  44         key before earlier or after later timestamp.
  45         """
  46         try:
  47             new = datetime.strptime(new_str, TIMESTAMP_FMT)
  48             old = datetime.strptime(old_str, TIMESTAMP_FMT)
  49         except ValueError as exc:
  50             raise BadFormatException('Timestamp of illegal format.') from exc
  51         timestamps = list(self.history.keys())
  52         if old_str not in timestamps:
  53             raise HandledException(f'Timestamp {old} not found in history.')
  54         sorted_timestamps = sorted([datetime.strptime(t, TIMESTAMP_FMT)
  55                                     for t in timestamps])
  56         expected_position = sorted_timestamps.index(old)
  57         sorted_timestamps.remove(old)
  58         sorted_timestamps += [new]
  59         sorted_timestamps.sort()
  60         if sorted_timestamps.index(new) != expected_position:
  61             raise HandledException('Timestamp not respecting chronology.')
  62         value = self.history[old_str]
  63         del self.history[old_str]
  64         self.history[new_str] = value
  65
  66     def set(self, value: str | float) -> None:
  67         """Add to self.history if and only if not same value as newest one.
  68
  69         Note that we wait one micro-second, as timestamp comparison to check
  70         most recent elements only goes up to that precision.
  71
  72         Also note that we don't check against .newest because that may make us
  73         compare value against .default even if not set. We want to be able to
  74         explicitly set .default as the first element.
  75         """
  76         sleep(0.00001)
  77         if 0 == len(self.history) \
  78                 or value != self.history[self._newest_timestamp]:
  79             self.history[datetime.now().strftime(TIMESTAMP_FMT)] = value
  80
  81     def history_from_row(self, row: Row) -> None:
  82         """Extend self.history from expected table row format."""
  83         self.history[row[1]] = row[2]
  84
  85     def at(self, queried_time: str) -> str | float:
  86         """Retrieve value of timestamp nearest queried_time from the past."""
  87         if len(queried_time) == 10:
  88             queried_time += ' 23:59:59.999'
  89         sorted_timestamps = sorted(self.history.keys())
  90         if 0 == len(sorted_timestamps):
  91             return self.default
  92         selected_timestamp = sorted_timestamps[0]
  93         for timestamp in sorted_timestamps[1:]:
  94             if timestamp > queried_time:
  95                 break
  96             selected_timestamp = timestamp
  97         return self.history[selected_timestamp]
  98
  99     def save(self, db_conn: DatabaseConnection) -> None:
 100         """Save as self.history entries, but first wipe old ones."""
 101         db_conn.rewrite_relations(self.table_name, 'parent', self.parent.id_,
 102                                   [[item[0], item[1]]
 103                                    for item in self.history.items()])
 104
 105     def remove(self, db_conn: DatabaseConnection) -> None:
 106         """Remove from DB."""
 107         db_conn.delete_where(self.table_name, 'parent', self.parent.id_)