"""Shared per-tooth ROI cropping so training / inference / evaluation are consistent."""
import numpy as np
from scipy import ndimage as ndi


def _fit(a, n):
    out = np.zeros((n, n, n), dtype=a.dtype)
    s = [min(n, a.shape[k]) for k in range(3)]
    out[:s[0], :s[1], :s[2]] = a[:s[0], :s[1], :s[2]]
    return out


def predicted_instances(d, cfg, dev, stage1_ckpt):
    """Stage-1-driven instance localization (NO GT). We predict the 4-class map and
    use the DESCRIPTOR-CORE class (3) -- eroded tooth centers that are spatially
    separated -- to connected-component into individual teeth, exactly like the
    'tooth descriptor' idea in Chen 2025 / Duan 2021. Each core's centroid drives an
    ROI. Cores are matched to GT instances ONLY for evaluation alignment.

    Returns inst_pred (full-volume instance map) and match {pred_id -> gt_id}."""
    import torch
    from monai.inferers import sliding_window_inference
    from .models import get_unet
    img = d["image"].astype(np.float32)
    s1 = cfg["stage1"]
    net = get_unet(s1["num_classes"], tuple(s1["channels"])).to(dev)
    st = torch.load(stage1_ckpt, map_location=dev)
    net.load_state_dict(st["model"]); net.eval()
    with torch.no_grad():
        x = torch.from_numpy(img[None, None]).to(dev)
        logits = sliding_window_inference(x, tuple(s1["patch_size"]), 2, net, overlap=0.25)
        pred = torch.argmax(logits, 1)[0].cpu().numpy()

    use_desc = bool(s1.get("use_descriptor", True)) and (pred == 3).any()
    seed_mask = (pred == 3) if use_desc else (pred == 1)
    tooth_pred = (pred == 1) | (pred == 3)          # full tooth region (core counts as tooth)

    # connected components on the separable seed cores
    lab, n = ndi.label(seed_mask, structure=np.ones((3, 3, 3)))
    inst_pred = np.zeros_like(lab, np.int16)
    match = {}
    gt_inst = d.get("inst")
    min_core = int(cfg["stage1"].get("min_core_voxels", 80))
    sp = np.asarray(d.get("spacing", np.ones(3)), np.float32)
    merge_mm = float(cfg["stage1"].get("core_merge_mm", 3.0))   # over-split fix

    # 1) keep valid cores + their centroids (mm)
    cores = []
    for k in range(1, n + 1):
        m = (lab == k)
        if m.sum() < min_core:
            continue
        cores.append((k, np.array(ndi.center_of_mass(m)) * sp))

    # 2) union-find: merge cores whose centroids are within merge_mm of each other.
    # Fragments of ONE tooth's eroded core sit <merge_mm apart; distinct (even touching)
    # teeth are farther, so real teeth are NOT merged. merge_mm=0 disables merging.
    parent = list(range(len(cores)))
    def _find(i):
        while parent[i] != i:
            parent[i] = parent[parent[i]]; i = parent[i]
        return i
    if merge_mm > 0:
        for i in range(len(cores)):
            for j in range(i + 1, len(cores)):
                if np.linalg.norm(cores[i][1] - cores[j][1]) < merge_mm:
                    ri, rj = _find(i), _find(j)
                    if ri != rj:
                        parent[ri] = rj
    from collections import defaultdict
    groups = defaultdict(list)
    for idx, (k, _c) in enumerate(cores):
        groups[_find(idx)].append(k)

    # 3) grow each (merged) core group back out to recover the full tooth
    next_id = 1
    erode_iter = int(cfg["preprocess"].get("descriptor_erode_iter", 3)) + 2
    for klist in groups.values():
        core = np.zeros_like(lab, bool)
        for k in klist:
            core |= (lab == k)
        grown = core.copy()
        for _ in range(erode_iter):
            grown = ndi.binary_dilation(grown, iterations=1) & tooth_pred
        cid = next_id; next_id += 1
        inst_pred[grown] = cid
        if gt_inst is not None:
            ov = gt_inst[grown]; ov = ov[ov > 0]
            if len(ov) > 0:
                vals, counts = np.unique(ov, return_counts=True)
                match[cid] = int(vals[np.argmax(counts)])
    return inst_pred, match


def crop_roi(d, iid, roi_mm, roi_vox, mask_for_center=None, center_mode="com"):
    """Crop a physical roi_mm cube around tooth `iid`, resample to roi_vox^3.

    d: processed npz dict with image/inst/cinst/spacing/origin.
    center_mode: 'com' (center of mass), 'bbox' (bounding-box center, stabler for
        tilted/multi-root teeth), or 'hybrid' (mean of the two).
    Returns dict(img, solid, canal, roi_sp, lo_world_mm, boundary_touch, ...) or None.
    """
    img = d["image"]; inst = d["inst"]; cinst = d["cinst"]
    sp = np.asarray(d["spacing"], dtype=np.float32)
    origin = np.asarray(d.get("origin", np.zeros(3)), dtype=np.float32)

    center_mask = mask_for_center if mask_for_center is not None else (inst == iid)
    if not center_mask.any():
        return None
    com_mass = np.array(ndi.center_of_mass(center_mask))
    if center_mode in ("bbox", "hybrid"):
        pts = np.argwhere(center_mask)
        com_box = 0.5 * (pts.min(0) + pts.max(0))
        com = com_box if center_mode == "bbox" else 0.5 * (com_mass + com_box)
    else:
        com = com_mass
    half_vox = (roi_mm / 2.0) / sp
    lo = np.floor(com - half_vox).astype(int)
    hi = np.ceil(com + half_vox).astype(int)
    shape = np.array(img.shape)
    lo_c = np.clip(lo, 0, shape - 1)
    hi_c = np.clip(hi, 1, shape)
    sl = tuple(slice(int(a), int(b)) for a, b in zip(lo_c, hi_c))

    img_c = img[sl]
    solid_c = (inst == iid)[sl]
    canal_c = (cinst == iid)[sl]

    # clipping diagnostic: fraction of the tooth solid lying on the 6 ROI faces.
    # >0 means crown/root is being cut off -> ROI too small or mis-centered.
    if solid_c.any():
        faces = [solid_c[0, :, :], solid_c[-1, :, :], solid_c[:, 0, :],
                 solid_c[:, -1, :], solid_c[:, :, 0], solid_c[:, :, -1]]
        boundary_touch = float(sum(int(f.sum()) for f in faces) / (solid_c.sum() + 1e-9))
    else:
        boundary_touch = 0.0

    zoom = np.array([roi_vox] * 3) / np.array(img_c.shape)
    img_r = _fit(ndi.zoom(img_c, zoom, order=1).astype(np.float32), roi_vox)
    solid_r = _fit(ndi.zoom(solid_c.astype(np.float32), zoom, order=0) > 0.5, roi_vox)
    canal_r = _fit(ndi.zoom(canal_c.astype(np.float32), zoom, order=0) > 0.5, roi_vox)

    roi_sp = np.array([roi_mm / roi_vox] * 3, dtype=np.float32)
    lo_world_mm = origin + lo_c * sp
    # the ACTUAL physical size covered (may be < roi_mm for teeth clipped at the volume
    # border). Stamp-back / NIfTI export must use this, not the nominal roi_mm.
    actual_size_mm = (hi_c - lo_c).astype(np.float32) * sp
    return dict(img=img_r, solid=solid_r, canal=canal_r, roi_sp=roi_sp,
                lo_world_mm=lo_world_mm, actual_size_mm=actual_size_mm,
                boundary_touch=boundary_touch, orig_spacing=sp)