from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
import os


@dataclass(frozen=True)
class AppConfig:
    project_key: str
    app_mode: str
    root_dir: Path
    data_dir: Path
    sqlite_path: Path
    artifact_dir: Path
    cache_dir: Path
    model_registry_path: Path


def _env_path(name: str, default: str) -> Path:
    return Path(os.environ.get(name, default)).expanduser().resolve()


def load_app_config(project_key: str = 'p1', data_subdir: str | None = None) -> AppConfig:
    root_dir = Path(os.environ.get('APP_ROOT_DIR', Path.cwd())).resolve()
    data_root = _env_path('DATA_DIR', str(root_dir / 'data'))
    if data_subdir:
        data_dir = (data_root / data_subdir).resolve()
    else:
        data_dir = data_root
    sqlite_path = Path(os.environ.get('SQLITE_PATH', data_dir / 'sqlite' / f'{project_key}.sqlite3')).expanduser().resolve()
    artifact_dir = Path(os.environ.get('ARTIFACT_DIR', data_dir / 'artifacts' / project_key)).expanduser().resolve()
    cache_dir = _env_path('MODEL_CACHE_DIR', str(root_dir / 'models'))
    model_registry_path = _env_path('MODEL_REGISTRY_PATH', str(root_dir / 'configs' / 'model_registry.yaml'))
    app_mode = os.environ.get('APP_MODE', 'dev')
    return AppConfig(
        project_key=project_key,
        app_mode=app_mode,
        root_dir=root_dir,
        data_dir=data_dir,
        sqlite_path=sqlite_path,
        artifact_dir=artifact_dir,
        cache_dir=cache_dir,
        model_registry_path=model_registry_path,
    )