"""Daemon configuration resolution (REQ-005, REQ-010)."""
from __future__ import annotations

import os
from dataclasses import dataclass


def _load_dotenv() -> None:
    """Best-effort load of a .env file into os.environ (REQ-010).

    Real OS environment variables take precedence over .env (override=False),
    matching 12-factor expectations. If python-dotenv is not installed or no
    .env exists, this is a no-op (no regression).
    """
    try:
        from dotenv import find_dotenv, load_dotenv
    except ImportError:  # pragma: no cover - optional at runtime
        return
    load_dotenv(find_dotenv(usecwd=True), override=False)


@dataclass(frozen=True)
class DaemonConfig:
    dsn: str
    total_slots: int
    host: str
    port: int

    @staticmethod
    def from_env() -> "DaemonConfig":
        _load_dotenv()
        dsn = os.environ.get("TREX_POSTGRESQL_DSN")
        if not dsn:
            raise RuntimeError(
                "TREX_POSTGRESQL_DSN is required to start the slot-core daemon."
            )
        return DaemonConfig(
            dsn=dsn,
            total_slots=int(os.environ.get("TREX_TOTAL_SLOTS", "10")),
            host=os.environ.get("TREX_API_HOST", "127.0.0.1"),
            port=int(os.environ.get("TREX_API_PORT", "8080")),
        )