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

   1 """Database management."""
   2 from __future__ import annotations
   3 from os.path import isfile
   4 from difflib import Differ
   5 from sqlite3 import connect as sql_connect, Cursor, Row
   6 from typing import Any, Self, TypeVar, Generic
   7 from plomtask.exceptions import HandledException, NotFoundException
   8
   9 PATH_DB_SCHEMA = 'scripts/init.sql'
  10 EXPECTED_DB_VERSION = 0
  11
  12
  13 class DatabaseFile:  # pylint: disable=too-few-public-methods
  14     """Represents the sqlite3 database's file."""
  15
  16     def __init__(self, path: str) -> None:
  17         self.path = path
  18         self._check()
  19
  20     def remake(self) -> None:
  21         """Create tables in self.path file as per PATH_DB_SCHEMA sql file."""
  22         with sql_connect(self.path) as conn:
  23             with open(PATH_DB_SCHEMA, 'r', encoding='utf-8') as f:
  24                 conn.executescript(f.read())
  25         self._check()
  26
  27     def _check(self) -> None:
  28         """Check file exists, and is of proper DB version and schema."""
  29         self.exists = isfile(self.path)
  30         if self.exists:
  31             self._validate_user_version()
  32             self._validate_schema()
  33
  34     def _validate_user_version(self) -> None:
  35         """Compare DB user_version with EXPECTED_DB_VERSION."""
  36         sql_for_db_version = 'PRAGMA user_version'
  37         with sql_connect(self.path) as conn:
  38             db_version = list(conn.execute(sql_for_db_version))[0][0]
  39             if db_version != EXPECTED_DB_VERSION:
  40                 msg = f'Wrong DB version, expected '\
  41                         f'{EXPECTED_DB_VERSION}, got {db_version}.'
  42                 raise HandledException(msg)
  43
  44     def _validate_schema(self) -> None:
  45         """Compare found schema with what's stored at PATH_DB_SCHEMA."""
  46         sql_for_schema = 'SELECT sql FROM sqlite_master ORDER BY sql'
  47         msg_err = 'Database has wrong tables schema. Diff:\n'
  48         with sql_connect(self.path) as conn:
  49             schema_rows = [r[0] for r in conn.execute(sql_for_schema) if r[0]]
  50             retrieved_schema = ';\n'.join(schema_rows) + ';'
  51             with open(PATH_DB_SCHEMA, 'r', encoding='utf-8') as f:
  52                 stored_schema = f.read().rstrip()
  53                 if stored_schema != retrieved_schema:
  54                     diff_msg = Differ().compare(retrieved_schema.splitlines(),
  55                                                 stored_schema.splitlines())
  56                     raise HandledException(msg_err + '\n'.join(diff_msg))
  57
  58
  59 class DatabaseConnection:
  60     """A single connection to the database."""
  61
  62     def __init__(self, db_file: DatabaseFile) -> None:
  63         self.file = db_file
  64         self.conn = sql_connect(self.file.path)
  65
  66     def commit(self) -> None:
  67         """Commit SQL transaction."""
  68         self.conn.commit()
  69
  70     def exec(self, code: str, inputs: tuple[Any, ...] = tuple()) -> Cursor:
  71         """Add commands to SQL transaction."""
  72         return self.conn.execute(code, inputs)
  73
  74     def close(self) -> None:
  75         """Close DB connection."""
  76         self.conn.close()
  77
  78     def rewrite_relations(self, table_name: str, key: str, target: int,
  79                           rows: list[list[Any]]) -> None:
  80         """Rewrite relations in table_name to target, with rows values."""
  81         self.delete_where(table_name, key, target)
  82         for row in rows:
  83             values = tuple([target] + row)
  84             q_marks = self.__class__.q_marks_from_values(values)
  85             self.exec(f'INSERT INTO {table_name} VALUES {q_marks}', values)
  86
  87     def row_where(self, table_name: str, key: str,
  88                   target: int | str) -> list[Row]:
  89         """Return list of Rows at table where key == target."""
  90         return list(self.exec(f'SELECT * FROM {table_name} WHERE {key} = ?',
  91                               (target,)))
  92
  93     def column_where(self, table_name: str, column: str, key: str,
  94                      target: int | str) -> list[Any]:
  95         """Return column of table where key == target."""
  96         return [row[0] for row in
  97                 self.exec(f'SELECT {column} FROM {table_name} '
  98                           f'WHERE {key} = ?', (target,))]
  99
 100     def column_all(self, table_name: str, column: str) -> list[Any]:
 101         """Return complete column of table."""
 102         return [row[0] for row in
 103                 self.exec(f'SELECT {column} FROM {table_name}')]
 104
 105     def delete_where(self, table_name: str, key: str,
 106                      target: int | str) -> None:
 107         """Delete from table where key == target."""
 108         self.exec(f'DELETE FROM {table_name} WHERE {key} = ?', (target,))
 109
 110     @staticmethod
 111     def q_marks_from_values(values: tuple[Any]) -> str:
 112         """Return placeholder to insert values into SQL code."""
 113         return '(' + ','.join(['?'] * len(values)) + ')'
 114
 115
 116 BaseModelId = TypeVar('BaseModelId', int, str)
 117 BaseModelInstance = TypeVar('BaseModelInstance', bound='BaseModel[Any]')
 118
 119
 120 class BaseModel(Generic[BaseModelId]):
 121     """Template for most of the models we use/derive from the DB."""
 122     table_name = ''
 123     to_save: list[str] = []
 124     id_: None | BaseModelId
 125     cache_: dict[BaseModelId, Self]
 126
 127     def __init__(self, id_: BaseModelId | None) -> None:
 128         if isinstance(id_, int) and id_ < 1:
 129             msg = f'illegal {self.__class__.__name__} ID, must be >=1: {id_}'
 130             raise HandledException(msg)
 131         self.id_ = id_
 132
 133     @classmethod
 134     def get_cached(cls: type[BaseModelInstance],
 135                    id_: BaseModelId) -> BaseModelInstance | None:
 136         """Get object of id_ from class's cache, or None if not found."""
 137         # pylint: disable=consider-iterating-dictionary
 138         cache = cls.get_cache()
 139         if id_ in cache.keys():
 140             obj = cache[id_]
 141             assert isinstance(obj, cls)
 142             return obj
 143         return None
 144
 145     @classmethod
 146     def empty_cache(cls) -> None:
 147         """Empty class's cache."""
 148         cls.cache_ = {}
 149
 150     @classmethod
 151     def get_cache(cls: type[BaseModelInstance]) -> dict[Any, BaseModel[Any]]:
 152         """Get cache dictionary, create it if not yet existing."""
 153         if not hasattr(cls, 'cache_'):
 154             d: dict[Any, BaseModel[Any]] = {}
 155             cls.cache_ = d
 156         return cls.cache_
 157
 158     def cache(self) -> None:
 159         """Update object in class's cache."""
 160         if self.id_ is None:
 161             raise HandledException('Cannot cache object without ID.')
 162         cache = self.__class__.get_cache()
 163         cache[self.id_] = self
 164
 165     def uncache(self) -> None:
 166         """Remove self from cache."""
 167         if self.id_ is None:
 168             raise HandledException('Cannot un-cache object without ID.')
 169         cache = self.__class__.get_cache()
 170         del cache[self.id_]
 171
 172     @classmethod
 173     def from_table_row(cls: type[BaseModelInstance],
 174                        # pylint: disable=unused-argument
 175                        db_conn: DatabaseConnection,
 176                        row: Row | list[Any]) -> BaseModelInstance:
 177         """Make from DB row, write to DB cache."""
 178         obj = cls(*row)
 179         obj.cache()
 180         return obj
 181
 182     @classmethod
 183     def by_id(cls, db_conn: DatabaseConnection,
 184               id_: BaseModelId | None,
 185               # pylint: disable=unused-argument
 186               create: bool = False) -> Self:
 187         """Retrieve by id_, on failure throw NotFoundException.
 188
 189         First try to get from cls.cache_, only then check DB; if found,
 190         put into cache.
 191
 192         If create=True, make anew (but do not cache yet).
 193         """
 194         obj = None
 195         if id_ is not None:
 196             obj = cls.get_cached(id_)
 197             if not obj:
 198                 for row in db_conn.row_where(cls.table_name, 'id', id_):
 199                     obj = cls.from_table_row(db_conn, row)
 200                     obj.cache()
 201                     break
 202         if obj:
 203             return obj
 204         if create:
 205             obj = cls(id_)
 206             return obj
 207         raise NotFoundException(f'found no object of ID {id_}')
 208
 209     @classmethod
 210     def all(cls: type[BaseModelInstance],
 211             db_conn: DatabaseConnection) -> list[BaseModelInstance]:
 212         """Collect all objects of class."""
 213         items: dict[BaseModelId, BaseModelInstance] = {}
 214         for k, v in cls.get_cache().items():
 215             assert isinstance(v, cls)
 216             items[k] = v
 217         already_recorded = items.keys()
 218         for id_ in db_conn.column_all(cls.table_name, 'id'):
 219             if id_ not in already_recorded:
 220                 item = cls.by_id(db_conn, id_)
 221                 assert item.id_ is not None
 222                 items[item.id_] = item
 223         return list(items.values())
 224
 225     def __eq__(self, other: object) -> bool:
 226         if not isinstance(other, self.__class__):
 227             msg = 'cannot compare to object of different class'
 228             raise HandledException(msg)
 229         to_hash_me = tuple([self.id_] +
 230                            [getattr(self, name) for name in self.to_save])
 231         to_hash_other = tuple([other.id_] +
 232                               [getattr(other, name) for name in other.to_save])
 233         return hash(to_hash_me) == hash(to_hash_other)
 234
 235     def save_core(self, db_conn: DatabaseConnection) -> None:
 236         """Write bare-bones self (sans connected items), ensuring self.id_.
 237
 238         Write both to DB, and to cache. To DB, write .id_ and attributes
 239         listed in cls.to_save.
 240
 241         Ensure self.id_ by setting it to what the DB command returns as the
 242         last saved row's ID (cursor.lastrowid), EXCEPT if self.id_ already
 243         exists as a 'str', which implies we do our own ID creation (so far
 244         only the case with the Day class, where it's to be a date string.
 245         """
 246         values = tuple([self.id_] + [getattr(self, key)
 247                                      for key in self.to_save])
 248         q_marks = DatabaseConnection.q_marks_from_values(values)
 249         table_name = self.table_name
 250         cursor = db_conn.exec(f'REPLACE INTO {table_name} VALUES {q_marks}',
 251                               values)
 252         if not isinstance(self.id_, str):
 253             self.id_ = cursor.lastrowid  # type: ignore[assignment]
 254         self.cache()
 255
 256     def remove(self, db_conn: DatabaseConnection) -> None:
 257         """Remove from DB."""
 258         assert isinstance(self.id_, int | str)
 259         self.uncache()
 260         db_conn.delete_where(self.table_name, 'id', self.id_)