"""Centralized defaults for model checkpoint/cache locations.

Goal: keep all auto-downloaded model artifacts inside this repo's `checkpoints/`
directory by default (instead of user-wide cache dirs or repo root).
"""

from __future__ import annotations

import os
from pathlib import Path


PROJECT_ROOT = Path(__file__).resolve().parent
CHECKPOINTS_DIR = PROJECT_ROOT / "checkpoints"

# Hugging Face will create subfolders like `hub/`, `datasets/`, etc under HF_HOME.
HF_HOME_DIR = CHECKPOINTS_DIR / "hf"

# Torchvision uses torch.hub.load_state_dict_from_url which respects TORCH_HOME.
TORCH_HOME_DIR = CHECKPOINTS_DIR / "torch"


def ensure_default_checkpoint_dirs() -> None:
    """Ensure checkpoint dirs exist and set cache-related env vars.

    This is intentionally a best-effort helper. If the user has explicitly set
    env vars already, we do not override them.
    """

    CHECKPOINTS_DIR.mkdir(parents=True, exist_ok=True)
    HF_HOME_DIR.mkdir(parents=True, exist_ok=True)
    TORCH_HOME_DIR.mkdir(parents=True, exist_ok=True)

    # Hugging Face
    os.environ.setdefault("HF_HOME", str(HF_HOME_DIR))
    # Compatibility env vars across transformers/huggingface-hub versions.
    os.environ.setdefault("TRANSFORMERS_CACHE", str(HF_HOME_DIR / "hub"))
    os.environ.setdefault("HUGGINGFACE_HUB_CACHE", str(HF_HOME_DIR / "hub"))

    # Torch / torchvision
    os.environ.setdefault("TORCH_HOME", str(TORCH_HOME_DIR))


def hf_cache_dir() -> Path:
    ensure_default_checkpoint_dirs()
    return HF_HOME_DIR


def torch_home_dir() -> Path:
    ensure_default_checkpoint_dirs()
    return TORCH_HOME_DIR


def checkpoints_dir() -> Path:
    ensure_default_checkpoint_dirs()
    return CHECKPOINTS_DIR


def default_checkpoint_path(filename: str) -> str:
    """Return an absolute path under `checkpoints/` for a given filename."""

    return str(checkpoints_dir() / filename)