backend/core/model_loader.py

import os
import glob
import importlib.util
from typing import Optional

PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..'))
_MODEL = None

def _import_model_definition(path: str):
    try:
        spec = importlib.util.spec_from_file_location('model_definition', path)
        mod = importlib.util.module_from_spec(spec)
        spec.loader.exec_module(mod)
        return mod
    except Exception:
        return None

def _find_weights() -> Optional[str]:
    candidates = glob.glob(os.path.join(PROJECT_ROOT, 'models', '**', '*.h5'), recursive=True)
    candidates += glob.glob(os.path.join(PROJECT_ROOT, 'models', '**', '*.hdf5'), recursive=True)
    return candidates[0] if candidates else None

def _try_load_sciann_model():
    try:
        import sciann as sn
    except Exception:
        return None

    model_def_path = os.path.join(PROJECT_ROOT, 'model_definition.py')
    if os.path.exists(model_def_path):
        mod = _import_model_definition(model_def_path)
        if mod and hasattr(mod, 'create_model'):
            try:
                return mod.create_model()
            except Exception:
                pass

    loader_path = os.path.join(PROJECT_ROOT, 'models', 'load_model.py')
    if os.path.exists(loader_path):
        mod = _import_model_definition(loader_path)
        if mod and hasattr(mod, 'load_model'):
            try:
                return mod.load_model(PROJECT_ROOT)
            except Exception:
                pass
    return None

def get_model():
    global _MODEL
    if _MODEL is not None:
        return _MODEL

    model = _try_load_sciann_model()
    if model is None:
        _MODEL = None
        return None

    weights = _find_weights()
    if weights:
        try:
            if hasattr(model, 'load_weights'):
                model.load_weights(weights)
        except Exception:
            pass

    _MODEL = model
    return _MODEL