"""Minimal GradeEye classifier loader for Hugging Face Hub.

Requires the GradeEye source package on PYTHONPATH plus torch, timm, and
safetensors. The architecture is the same DRGradingModel used during training.
EMA files are the primary weights and reproduce the paper evaluation protocol.
"""
from __future__ import annotations

from pathlib import Path
import sys
import torch

# For local source checkout usage. Users may instead install the GradeEye package.
try:
    from src.models.dr_model import DRGradingModel
except ImportError as exc:
    raise ImportError(
        "Install/clone GradeEye and make its repository root available on PYTHONPATH."
    ) from exc
from safetensors.torch import load_file


def load_model(weights_path: str | Path, config: dict, device: str = "cpu") -> DRGradingModel:
    """Instantiate DRGradingModel and strictly load a .safetensors state dict."""
    model = DRGradingModel(
        pretrained=False,
        use_cbam=config["use_cbam"],
        cbam_num_stages=config["cbam_num_stages"],
        num_thresholds=config["num_thresholds"],
        head_hidden_dim=config["head_hidden_dim"],
        dropout=config["dropout"],
        output_mode="corn",
        arch=config["architecture"],
        in_chans=config["in_channels"],
        img_size=config["image_size"],
    )
    state_dict = load_file(str(weights_path), device="cpu")
    result = model.load_state_dict(state_dict, strict=True)
    if result.missing_keys or result.unexpected_keys:
        raise RuntimeError(
            f"State-dict mismatch: missing={result.missing_keys}, "
            f"unexpected={result.unexpected_keys}"
        )
    return model.to(device).eval()