from contextlib import contextmanager
from functools import wraps
import time

import psycopg2
from psycopg2 import errors

from app.core.config import settings


@contextmanager
def get_db():
    conn = psycopg2.connect(
        host=settings.db_host,
        port=settings.db_port,
        dbname=settings.db_database,
        user=settings.db_user,
        password=settings.db_password,
    )
    try:
        yield conn
    finally:
        conn.close()


_RETRYABLE_READ_ERRORS = (
    errors.DeadlockDetected,
    errors.SerializationFailure,
    errors.LockNotAvailable,
)


def is_retryable_read_error(exc: Exception) -> bool:
    return isinstance(exc, _RETRYABLE_READ_ERRORS)


def is_retryable_db_error(exc: Exception) -> bool:
    return isinstance(exc, _RETRYABLE_READ_ERRORS)


def db_read_retry(*, attempts: int = 3, initial_delay_seconds: float = 0.05, backoff: float = 2.0):
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            delay = max(0.0, float(initial_delay_seconds or 0.0))
            for attempt in range(1, max(1, int(attempts or 1)) + 1):
                try:
                    return func(*args, **kwargs)
                except Exception as exc:
                    if not is_retryable_read_error(exc) or attempt >= max(1, int(attempts or 1)):
                        raise
                    if delay > 0:
                        time.sleep(delay)
                    delay *= max(1.0, float(backoff or 1.0))
            return func(*args, **kwargs)

        return wrapper

    return decorator