"""Readiness checks shared by HTTP and background process roles."""

from __future__ import annotations

import os

from backup_tool.cli import build_alembic_config
from backup_tool.config import Settings
from backup_tool.db.engine import assert_schema_current, create_engine


class ReadinessError(RuntimeError):
    """A dependency needed by the selected role is unavailable."""


def _require_access(path: object, mode: int) -> None:
    try:
        candidate = path if isinstance(path, str) else str(path)
        if not os.path.isdir(candidate) or not os.access(candidate, mode):
            raise ReadinessError("required storage is unavailable")
    except OSError as error:
        raise ReadinessError("required storage is unavailable") from error


async def check_role_readiness(settings: Settings, role: str) -> None:
    engine = create_engine(settings)
    try:
        await assert_schema_current(engine, build_alembic_config(settings))
    except Exception as error:
        raise ReadinessError("metadata is unavailable") from error
    finally:
        await engine.dispose()
    if role == "scheduler":
        return
    _require_access(settings.data_dir, os.R_OK | os.W_OK | os.X_OK)
    for root in settings.repository_roots + settings.restore_roots:
        _require_access(root, os.R_OK | os.W_OK | os.X_OK)
    for root in settings.local_source_roots:
        _require_access(root, os.R_OK | os.X_OK)