[plomtask] / plomtask / db.py

"""Database management."""
from os.path import isfile
from difflib import Differ
from sqlite3 import connect as sql_connect, Cursor, Row
from typing import Any, Dict
from plomtask.exceptions import HandledException

PATH_DB_SCHEMA = 'scripts/init.sql'
EXPECTED_DB_VERSION = 0


class DatabaseFile:  # pylint: disable=too-few-public-methods
    """Represents the sqlite3 database's file."""

    def __init__(self, path: str) -> None:
        self.path = path
        self._check()

    def remake(self) -> None:
        """Create tables in self.path file as per PATH_DB_SCHEMA sql file."""
        with sql_connect(self.path) as conn:
            with open(PATH_DB_SCHEMA, 'r', encoding='utf-8') as f:
                conn.executescript(f.read())
        self._check()

    def _check(self) -> None:
        """Check file exists, and is of proper DB version and schema."""
        self.exists = isfile(self.path)
        if self.exists:
            self._validate_user_version()
            self._validate_schema()

    def _validate_user_version(self) -> None:
        """Compare DB user_version with EXPECTED_DB_VERSION."""
        sql_for_db_version = 'PRAGMA user_version'
        with sql_connect(self.path) as conn:
            db_version = list(conn.execute(sql_for_db_version))[0][0]
            if db_version != EXPECTED_DB_VERSION:
                msg = f'Wrong DB version, expected '\
                        f'{EXPECTED_DB_VERSION}, got {db_version}.'
                raise HandledException(msg)

    def _validate_schema(self) -> None:
        """Compare found schema with what's stored at PATH_DB_SCHEMA."""
        sql_for_schema = 'SELECT sql FROM sqlite_master ORDER BY sql'
        msg_err = 'Database has wrong tables schema. Diff:\n'
        with sql_connect(self.path) as conn:
            schema_rows = [r[0] for r in conn.execute(sql_for_schema) if r[0]]
            retrieved_schema = ';\n'.join(schema_rows) + ';'
            with open(PATH_DB_SCHEMA, 'r', encoding='utf-8') as f:
                stored_schema = f.read().rstrip()
                if stored_schema != retrieved_schema:
                    diff_msg = Differ().compare(retrieved_schema.splitlines(),
                                                stored_schema.splitlines())
                    raise HandledException(msg_err + '\n'.join(diff_msg))


class DatabaseConnection:
    """A single connection to the database."""

    def __init__(self, db_file: DatabaseFile) -> None:
        self.file = db_file
        self.conn = sql_connect(self.file.path)
        self.cached_todos: Dict[int, Any] = {}
        self.cached_days: Dict[str, Any] = {}
        self.cached_process_steps: Dict[int, Any] = {}
        self.cached_processes: Dict[int, Any] = {}
        self.cached_conditions: Dict[int, Any] = {}

    def commit(self) -> None:
        """Commit SQL transaction."""
        self.conn.commit()

    def exec(self, code: str, inputs: tuple[Any, ...] = tuple()) -> Cursor:
        """Add commands to SQL transaction."""
        return self.conn.execute(code, inputs)

    def close(self) -> None:
        """Close DB connection."""
        self.conn.close()

    def rewrite_relations(self, table_name: str, key: str, target: int,
                          rows: list[list[Any]]) -> None:
        """Rewrite relations in table_name to target, with rows values."""
        self.delete_where(table_name, key, target)
        for row in rows:
            values = tuple([target] + row)
            q_marks = self.__class__.q_marks_from_values(values)
            self.exec(f'INSERT INTO {table_name} VALUES {q_marks}', values)

    def row_where(self, table_name: str, key: str,
                  target: int | str) -> list[Row]:
        """Return list of Rows at table where key == target."""
        return list(self.exec(f'SELECT * FROM {table_name} WHERE {key} = ?',
                              (target,)))

    def column_where(self, table_name: str, column: str, key: str,
                     target: int | str) -> list[Any]:
        """Return column of table where key == target."""
        return [row[0] for row in
                self.exec(f'SELECT {column} FROM {table_name} '
                          f'WHERE {key} = ?', (target,))]

    def column_all(self, table_name: str, column: str) -> list[Any]:
        """Return complete column of table."""
        return [row[0] for row in
                self.exec(f'SELECT {column} FROM {table_name}')]

    def delete_where(self, table_name: str, key: str, target: int) -> None:
        """Delete from table where key == target."""
        self.exec(f'DELETE FROM {table_name} WHERE {key} = ?', (target,))

    @staticmethod
    def q_marks_from_values(values: tuple[Any]) -> str:
        """Return placeholder to insert values into SQL code."""
        return '(' + ','.join(['?'] * len(values)) + ')'


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.row_where(cls.table_name, '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_."""
        values = tuple([self.id_] + [getattr(self, key)
                                     for key in self.to_save])
        q_marks = DatabaseConnection.q_marks_from_values(values)
        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