from typing import ClassVar
from dataclasses import Field

from serenitas.utils.db2 import dbconn


class Report:
    _sql_insert: ClassVar[str]
    _insert_queue: ClassVar[list]
    _insert_fields: ClassVar[list]
    _conn: ClassVar = dbconn("dawndb")

    def __init_subclass__(cls, table_name: str):
        cls._insert_fields = list(filter(cls.is_insert_field, cls.__annotations__))
        place_holders = ",".join(["%s"] * len(cls._insert_fields))
        cls._sql_insert = f"INSERT INTO {table_name}({','.join(cls._insert_fields)}) VALUES({place_holders}) ON CONFLICT DO NOTHING RETURNING *"
        cls._insert_queue = []

    @classmethod
    def is_insert_field(cls, attr):
        """fields are insertable by default unless specified otherwise"""
        match getattr(cls, attr, None):
            case Field(metadata={"insert": False}) | Field(init=False):
                return False
            case _:
                return True

    @classmethod
    def clear(cls):
        cls._insert_queue.clear()

    def stage(self):
        self._insert_queue.append(
            tuple([getattr(self, col) for col in self._insert_fields])
        )

    @classmethod
    def commit(cls):
        conn = cls._conn
        with conn.cursor() as c:
            c.executemany(cls._sql_insert, cls._insert_queue)
        conn.commit()
        cls._insert_queue.clear()