"""Image-ONLY preprocessing for pure-CBCT inference (NO ground-truth labels)."""
import os, glob, argparse
import numpy as np
from tqdm import tqdm
from .utils import load_config, ensure_dir, load_nii, resample_to_spacing


def _normalize_image(img, clip):
    img = np.clip(img, clip[0], clip[1]).astype(np.float32)
    lo, hi = float(img.min()), float(img.max())
    if hi - lo < 1e-5:
        return np.zeros_like(img)
    return (img - lo) / (hi - lo)


def discover_images(raw_dir):
    cases = {}
    for p in glob.glob(os.path.join(raw_dir, "**", "image_from_dicom.nii.gz"),
                       recursive=True):
        case = os.path.basename(os.path.dirname(p))
        cases[case] = p
    return dict(sorted(cases.items()))


def process_image_only(cid, image_path, cfg):
    pp = cfg["preprocess"]
    img, imeta = load_nii(image_path)
    img, imeta = resample_to_spacing(img, imeta, pp["spacing"], is_label=False)
    img = _normalize_image(img, pp["clip_hu"])
    z = np.zeros(img.shape, dtype=np.uint8)
    out_dir = ensure_dir(cfg["paths"]["proc_dir"])
    np.savez_compressed(
        os.path.join(out_dir, f"{cid}.npz"),
        image=img.astype(np.float32),
        sem=z, inst=z, cinst=z, desc=z,
        spacing=np.array(imeta["spacing"], dtype=np.float32),
        origin=np.array(imeta["origin"], dtype=np.float32),
        n_instances=0,
    )
    return dict(case=cid, shape=list(img.shape))


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--config", default="configs/cbct_only.yaml")
    ap.add_argument("--raw", default=None,
                    help="folder to scan for image_from_dicom.nii.gz (default: paths.raw_dir)")
    ap.add_argument("--force", action="store_true")
    args = ap.parse_args()
    cfg = load_config(args.config)

    raw_dir = args.raw or cfg["paths"]["raw_dir"]
    cases = discover_images(raw_dir)
    if not cases:
        raise SystemExit(f"No image_from_dicom.nii.gz found under {raw_dir}")
    ensure_dir(cfg["paths"]["proc_dir"])
    items = list(cases.items())
    if not args.force:
        items = [(c, p) for c, p in items
                 if not os.path.exists(os.path.join(cfg["paths"]["proc_dir"], f"{c}.npz"))]
    print(f"[preprocess_cbct] {len(items)} case(s) to process (image-only, no GT).")
    for cid, p in tqdm(items, desc="preprocess_cbct"):
        try:
            process_image_only(cid, p, cfg)
        except Exception as e:
            print(f"[preprocess_cbct] FAILED {cid}: {e}")
    print(f"[preprocess_cbct] image-only npz -> {cfg['paths']['proc_dir']}")


if __name__ == "__main__":
    main()