import asyncio
import json
import os

import psycopg
import psycopg.abc
import psycopg_pool
import tornado


class DatabaseHandler(tornado.web.RequestHandler):
    async def query(self, query: psycopg.abc.Query, *args, **kwargs) -> list:
        connection_string = os.environ.get("DBTESTS_DATABASE")
        if not connection_string:
            raise ValueError("Connection string is not set")
        async with await psycopg.AsyncConnection.connect(
            connection_string
        ) as connection:
            async with connection.cursor() as cursor:
                await cursor.execute(query, *args, **kwargs)
                return await cursor.fetchall()


class CounterHandler(DatabaseHandler):
    async def get(self, name: str):
        result = await self.query(
            """
            SELECT value
              FROM counters
             WHERE name = %(name)s
            """,
            {"name": name},
        )

        self.set_header("Content-Type", "application/json")
        self.write(json.dumps(result[0][0] if result else 0))

    async def post(self, name: str):
        result = await self.query(
            """
            INSERT INTO counters (name, value)
                 VALUES (%(name)s, 1)
            ON CONFLICT (name) DO UPDATE
                    SET value = counters.value + 1
              RETURNING value
            """,
            {"name": name},
        )

        self.set_header("Content-Type", "application/json")
        self.write(json.dumps(result[0][0]))


class MyApplication(tornado.web.Application):
    def __init__(self) -> None:
        self._db_pool: psycopg_pool.AsyncConnectionPool | None = None

        handlers = [(r"/counters/(?P<name>.*)", CounterHandler)]
        super().__init__(handlers)

    async def initialize_db_pool(self) -> psycopg_pool.AsyncConnectionPool:
        if not self._db_pool:
            connection_string = os.environ.get("DBTESTS_DATABASE")
            if not connection_string:
                raise ValueError("Connection string is not set")
            self._db_pool = psycopg_pool.AsyncConnectionPool(connection_string)
        return self._db_pool

    async def cleanup(self) -> None:
        if self._db_pool:
            await self._db_pool.close()


async def main() -> None:
    app = MyApplication()
    app.listen(8000)
    await asyncio.Event().wait()
    await app.cleanup()


if __name__ == "__main__":
    asyncio.run(main())