"""
test_3modes_equivalence.py — Verify that the OMorpher-based Scripts/OM_train_3modes.py
produces identical network outputs, losses, gradients, and weight updates as the
original DeformDDPM-based OM_train_3modes.py.

Runs one training step of each mode (diffusion, contrastive, registration) with
identical pre-computed inputs, shared initial weights, and deterministic seeding.
Compares every intermediate tensor to catch divergences.

Usage:
    python tests/test_3modes_equivalence.py
"""

import os
import sys
import copy
import random

import numpy as np
import torch
import torch.nn.functional as F

ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
sys.path.insert(0, ROOT_DIR)

from Diffusion.diffuser import DeformDDPM
from Diffusion.networks import get_net, STN
import Diffusion.losses as losses
from Diffusion.losses import Grad, LNCC, LMSE
from OMorpher import OMorpher
import utils

# ========================== Test Config ==========================

IMG_SIZE = 64       # must be >= 64 for multi-scale DDF generation
BATCHSIZE = 2
TIMESTEPS = 10
NDIMS = 3
V_SCALE = 5e-5
NOISE_SCALE = 0.1
NET_NAME = "recmulmodmutattnnet"  # supports contrastive (has img_embd)
LR = 1e-5
DEVICE = "cpu"

# Loss constants (from 3modes)
LOSS_WEIGHTS_DIFF = [2.0, 1.0, 16]
LOSS_WEIGHTS_REGIST = [1.0, 0.3, 64]
LOSS_WEIGHT_CONTRASTIVE = 1.0
MSK_EPS = 0.01

ATOL = 1e-5
RTOL = 1e-4


def make_config():
    return {
        "data_name": "test",
        "net_name": NET_NAME,
        "ndims": NDIMS,
        "img_size": IMG_SIZE,
        "batchsize": BATCHSIZE,
        "timesteps": TIMESTEPS,
        "v_scale": V_SCALE,
        "noise_scale": NOISE_SCALE,
        "num_input_chn": 1,
        "img_pad_mode": "zeros",
        "ddf_pad_mode": "border",
        "padding_mode": "border",
        "resample_mode": "bilinear",
        "lr": LR,
        "epoch": 1,
        "epoch_per_save": 1,
        "condition_type": "slice",
        "device": DEVICE,
    }


def seed_all(seed=42):
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    if torch.cuda.is_available():
        torch.cuda.manual_seed_all(seed)


# ========================== Builders ==========================

def build_original(config):
    """Build DeformDDPM + STN + losses + optimizer (original pipeline)."""
    Net = get_net(config["net_name"])
    network = Net(
        n_steps=config["timesteps"],
        ndims=config["ndims"],
        num_input_chn=config["num_input_chn"],
        res=config["img_size"],
    )
    ddpm = DeformDDPM(
        network=network,
        n_steps=config["timesteps"],
        image_chw=[1] + [config["img_size"]] * config["ndims"],
        device=config["device"],
        batch_size=config["batchsize"],
        img_pad_mode=config["img_pad_mode"],
        v_scale=config["v_scale"],
    )
    ddf_stn = STN(
        img_sz=config["img_size"], ndims=config["ndims"],
        padding_mode=config["padding_mode"], device=config["device"],
    )
    ddpm.to(config["device"])
    ddf_stn.to(config["device"])

    loss_reg = Grad(penalty=['l1', 'negdetj', 'range'], ndims=config["ndims"],
                    outrange_thresh=0.2, outrange_weight=1e3)
    loss_reg1 = Grad(penalty=['l1', 'negdetj', 'range'], ndims=config["ndims"],
                     outrange_thresh=0.6, outrange_weight=1e3)
    loss_dist = losses.MRSE(img_sz=config["img_size"])
    loss_ang = losses.NCC(img_sz=config["img_size"])
    loss_imgsim = LNCC()
    loss_imgmse = LMSE()
    optimizer = torch.optim.Adam(ddpm.parameters(), lr=config["lr"])

    return ddpm, ddf_stn, optimizer, loss_reg, loss_reg1, loss_dist, loss_ang, loss_imgsim, loss_imgmse


def build_omorpher(config):
    """Build OMorpher + losses + optimizer (Scripts pipeline)."""
    om = OMorpher(config=config, device=config["device"])

    loss_reg = Grad(penalty=['l1', 'negdetj', 'range'], ndims=om.ndims,
                    outrange_thresh=0.2, outrange_weight=1e3)
    loss_reg1 = Grad(penalty=['l1', 'negdetj', 'range'], ndims=om.ndims,
                     outrange_thresh=0.6, outrange_weight=1e3)
    loss_imgsim = LNCC()
    loss_imgmse = LMSE()
    optimizer = torch.optim.Adam(om.network.parameters(), lr=config["lr"])

    return om, optimizer, loss_reg, loss_reg1, loss_imgsim, loss_imgmse


def sync_weights(ddpm, om):
    """Copy network weights from DeformDDPM.network → OMorpher.network."""
    om.network.load_state_dict(ddpm.network.state_dict())


def params_flat(module):
    return torch.cat([p.detach().clone().flatten() for p in module.parameters()])


def grads_flat(module):
    gs = []
    for p in module.parameters():
        gs.append(p.grad.detach().clone().flatten() if p.grad is not None
                  else torch.zeros_like(p.flatten()))
    return torch.cat(gs)


def assert_close(name, a, b, atol=ATOL, rtol=RTOL):
    if isinstance(a, (int, float)):
        a, b = torch.tensor(a), torch.tensor(b)
    if torch.allclose(a, b, atol=atol, rtol=rtol):
        print(f"  PASS {name}")
        return True
    diff = (a - b).abs()
    print(f"  FAIL {name}: max_diff={diff.max().item():.6e}, mean_diff={diff.mean().item():.6e}")
    return False


# ========================== Shared Data Generators ==========================

def make_shared_data():
    """Create deterministic dummy tensors for all three modes."""
    seed_all(123)
    S = IMG_SIZE
    x0 = torch.rand(BATCHSIZE, 1, S, S, S, dtype=torch.float32)
    embd = torch.randn(BATCHSIZE, 1024, dtype=torch.float32)
    blind_mask = torch.ones(1, 1, S, S, S, dtype=torch.float32)  # deterministic
    t = torch.tensor([3, 7])  # fixed timesteps

    # Paired data (half batchsize)
    B2 = max(1, BATCHSIZE // 2)
    x1 = torch.rand(B2, 1, S, S, S, dtype=torch.float32)
    y1 = torch.rand(B2, 1, S, S, S, dtype=torch.float32)
    embd_y = torch.randn(B2, 1024, dtype=torch.float32)

    t_contra = torch.tensor([2, 5])
    return x0, embd, blind_mask, t, x1, y1, embd_y, t_contra


# ========================== Test: Mode 1 (Diffusion) ==========================

def test_mode1_diffusion():
    """Both pipelines: same noisy_img+dvf → network → loss → grad → weight update."""
    print("\n" + "=" * 60)
    print("TEST: Mode 1 — Diffusion Training Step")
    print("=" * 60)

    config = make_config()
    x0, embd, blind_mask, t, _, _, _, _ = make_shared_data()

    # Build with identical weights
    seed_all(42)
    ddpm, ddf_stn, opt_o, loss_reg_o, _, loss_dist_o, loss_ang_o, _, _ = build_original(config)
    seed_all(42)
    om, opt_m, loss_reg_m, _, _, _ = build_omorpher(config)
    sync_weights(ddpm, om)

    ok = assert_close("init_weights", params_flat(ddpm.network), params_flat(om.network))

    # Pre-compute shared tensors using OMorpher (source of truth)
    seed_all(200)
    noisy_img, dvf_gt, _ = om._get_random_ddf(x0, t)
    # Use 'none' proc_type for deterministic cond (identity)
    cond_img, _, cond_ratio = om._proc_cond_img(x0, proc_type='none')

    # --- Original pipeline ---
    ddpm.network.train()
    pre_dvf_o = ddpm.network(x=noisy_img * blind_mask, y=cond_img, t=t, rec_num=2, text=embd)

    loss_ddf_o = loss_reg_o(pre_dvf_o, img=x0)
    trm_pred_o = ddf_stn(pre_dvf_o, dvf_gt)
    loss_gen_d_o = loss_dist_o(pred=trm_pred_o, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)
    loss_gen_a_o = loss_ang_o(pred=trm_pred_o, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)

    loss_tot_o = (LOSS_WEIGHTS_DIFF[0] * loss_gen_a_o + LOSS_WEIGHTS_DIFF[1] * loss_gen_d_o
                  + LOSS_WEIGHTS_DIFF[2] * loss_ddf_o)
    loss_tot_o = torch.sqrt(torch.tensor(1. + MSK_EPS) - cond_ratio) * loss_tot_o

    opt_o.zero_grad()
    loss_tot_o.backward()
    grad_o = grads_flat(ddpm.network)
    opt_o.step()

    # --- OMorpher pipeline ---
    om.network.train()
    pre_dvf_m = om.network(x=noisy_img * blind_mask, y=cond_img, t=t, rec_num=2, text=embd)

    loss_ddf_m = loss_reg_m(pre_dvf_m, img=x0)
    trm_pred_m = om.stn_full(pre_dvf_m, dvf_gt)
    loss_gen_d_m = om._loss_dist(pred=trm_pred_m, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)
    loss_gen_a_m = om._loss_ang(pred=trm_pred_m, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)

    loss_tot_m = (LOSS_WEIGHTS_DIFF[0] * loss_gen_a_m + LOSS_WEIGHTS_DIFF[1] * loss_gen_d_m
                  + LOSS_WEIGHTS_DIFF[2] * loss_ddf_m)
    loss_tot_m = torch.sqrt(torch.tensor(1. + MSK_EPS) - cond_ratio) * loss_tot_m

    opt_m.zero_grad()
    loss_tot_m.backward()
    grad_m = grads_flat(om.network)
    opt_m.step()

    # --- Compare ---
    ok &= assert_close("pre_dvf", pre_dvf_o.detach(), pre_dvf_m.detach())
    ok &= assert_close("trm_pred", trm_pred_o.detach(), trm_pred_m.detach())
    ok &= assert_close("loss_gen_a", loss_gen_a_o.item(), loss_gen_a_m.item())
    ok &= assert_close("loss_gen_d", loss_gen_d_o.item(), loss_gen_d_m.item())
    ok &= assert_close("loss_ddf", loss_ddf_o.item(), loss_ddf_m.item())
    ok &= assert_close("loss_tot", loss_tot_o.item(), loss_tot_m.item())
    ok &= assert_close("gradients", grad_o, grad_m)
    ok &= assert_close("weights_after", params_flat(ddpm.network), params_flat(om.network))

    print(f"\nMode 1 Diffusion: {'ALL PASSED' if ok else 'SOME FAILED'}")
    return ok


# ========================== Test: Mode 2 (Contrastive) ==========================

def test_mode2_contrastive():
    """Both pipelines: same masked x0 + cond_img → network → img_embd → cosine loss → grad."""
    print("\n" + "=" * 60)
    print("TEST: Mode 2 — Contrastive Training Step")
    print("=" * 60)

    config = make_config()
    x0, embd, blind_mask, _, _, _, _, t_contra = make_shared_data()

    seed_all(42)
    ddpm, _, opt_o, *_ = build_original(config)
    seed_all(42)
    om, opt_m, *_ = build_omorpher(config)
    sync_weights(ddpm, om)

    ok = assert_close("init_weights", params_flat(ddpm.network), params_flat(om.network))

    # Shared cond_img
    cond_img, _, _ = om._proc_cond_img(x0, proc_type='none')
    x_in = (x0 * blind_mask).detach()
    y_in = cond_img.detach()
    text_in = embd.detach()

    # --- Original ---
    ddpm.network.train()
    _ = ddpm.network(x=x_in, y=y_in, t=t_contra, text=text_in)
    if not hasattr(ddpm.network, 'img_embd') or ddpm.network.img_embd is None:
        print("  SKIP: network has no img_embd attribute")
        return True
    img_embd_o = ddpm.network.img_embd
    loss_c_o = LOSS_WEIGHT_CONTRASTIVE * (1 - F.cosine_similarity(img_embd_o, embd, dim=-1).mean())

    opt_o.zero_grad()
    loss_c_o.backward()
    torch.nn.utils.clip_grad_norm_(ddpm.parameters(), max_norm=0.1)
    grad_o = grads_flat(ddpm.network)
    opt_o.step()

    # --- OMorpher ---
    om.network.train()
    _ = om.network(x=x_in, y=y_in, t=t_contra, text=text_in)
    img_embd_m = om.network.img_embd
    loss_c_m = LOSS_WEIGHT_CONTRASTIVE * (1 - F.cosine_similarity(img_embd_m, embd, dim=-1).mean())

    opt_m.zero_grad()
    loss_c_m.backward()
    torch.nn.utils.clip_grad_norm_(om.network.parameters(), max_norm=0.1)
    grad_m = grads_flat(om.network)
    opt_m.step()

    # --- Compare ---
    ok &= assert_close("img_embd", img_embd_o.detach(), img_embd_m.detach())
    ok &= assert_close("loss_contrastive", loss_c_o.item(), loss_c_m.item())
    ok &= assert_close("gradients_clipped", grad_o, grad_m)
    ok &= assert_close("weights_after", params_flat(ddpm.network), params_flat(om.network))

    print(f"\nMode 2 Contrastive: {'ALL PASSED' if ok else 'SOME FAILED'}")
    return ok


# ========================== Test: Mode 3 (Registration) ==========================

def test_mode3_registration():
    """Both pipelines: reverse diffusion loop → DDF → rec image → reg losses → grad."""
    print("\n" + "=" * 60)
    print("TEST: Mode 3 — Registration Training Step")
    print("=" * 60)

    config = make_config()
    _, _, _, _, x1, y1, embd_y, _ = make_shared_data()

    seed_all(42)
    ddpm, _, opt_o, _, loss_reg1_o, _, _, loss_imgsim_o, loss_imgmse_o = build_original(config)
    seed_all(42)
    om, opt_m, _, loss_reg1_m, loss_imgsim_m, loss_imgmse_m = build_omorpher(config)
    sync_weights(ddpm, om)

    ok = assert_close("init_weights", params_flat(ddpm.network), params_flat(om.network))
    thresh_imgsim = 0.01

    # Shared proc_cond_img
    y1_proc, _, cond_ratio = om._proc_cond_img(y1, proc_type='none')

    # Fixed timestep schedule
    T_regist = sorted([9, 7, 5, 3, 2, 1], reverse=True)
    T_regist_batched = [[t_val for _ in range(max(1, BATCHSIZE // 2))] for t_val in T_regist]

    # --- Original: call DeformDDPM.diff_recover via forward ---
    ddpm.train()
    [ddf_o, _], [img_rec_o, _, _], _ = ddpm(
        img_org=x1, cond_imgs=y1_proc, T=[None, T_regist_batched], proc_type=[], text=embd_y,
    )
    loss_sim_o = loss_imgsim_o(img_rec_o, y1, label=(y1 > thresh_imgsim))
    loss_mse_o = loss_imgmse_o(img_rec_o, y1)
    loss_ddf_o = loss_reg1_o(ddf_o, img=y1)
    loss_regist_o = (LOSS_WEIGHTS_REGIST[0] * loss_sim_o +
                     LOSS_WEIGHTS_REGIST[1] * loss_mse_o +
                     LOSS_WEIGHTS_REGIST[2] * loss_ddf_o)
    loss_regist_o = torch.sqrt(cond_ratio + MSK_EPS) * loss_regist_o

    opt_o.zero_grad()
    loss_regist_o.backward()
    torch.nn.utils.clip_grad_norm_(ddpm.parameters(), max_norm=0.4)
    grad_o = grads_flat(ddpm.network)
    opt_o.step()

    # --- OMorpher: reverse_diffuse_train logic ---
    om.network.train()
    B = x1.shape[0]
    S = om.img_size
    ddf_comp = torch.zeros([B, om.ndims] + [S] * om.ndims, dtype=torch.float32, device=om.device)
    img_rec_m = x1.clone().detach()

    k = 2
    trainable_iters = T_regist_batched[-1:-k - 1:-1]

    for i in T_regist_batched:
        t = torch.tensor(np.array([i])).to(om.device)
        if i in trainable_iters:
            pre_dvf = om.network(x=img_rec_m, y=y1_proc, t=t, rec_num=2, text=embd_y)
        else:
            with torch.no_grad():
                pre_dvf = om.network(x=img_rec_m, y=y1_proc, t=t, rec_num=2, text=embd_y)
        ddf_comp = om.stn_full(ddf_comp, pre_dvf) + pre_dvf
        img_rec_m = om.img_stn(x1.clone().detach(), ddf_comp)

    loss_sim_m = loss_imgsim_m(img_rec_m, y1, label=(y1 > thresh_imgsim))
    loss_mse_m = loss_imgmse_m(img_rec_m, y1)
    loss_ddf_m = loss_reg1_m(ddf_comp, img=y1)
    loss_regist_m = (LOSS_WEIGHTS_REGIST[0] * loss_sim_m +
                     LOSS_WEIGHTS_REGIST[1] * loss_mse_m +
                     LOSS_WEIGHTS_REGIST[2] * loss_ddf_m)
    loss_regist_m = torch.sqrt(cond_ratio + MSK_EPS) * loss_regist_m

    opt_m.zero_grad()
    loss_regist_m.backward()
    torch.nn.utils.clip_grad_norm_(om.network.parameters(), max_norm=0.4)
    grad_m = grads_flat(om.network)
    opt_m.step()

    # --- Compare ---
    ok &= assert_close("ddf_comp", ddf_o.detach(), ddf_comp.detach())
    ok &= assert_close("img_rec", img_rec_o.detach(), img_rec_m.detach())
    ok &= assert_close("loss_sim", loss_sim_o.item(), loss_sim_m.item())
    ok &= assert_close("loss_mse", loss_mse_o.item(), loss_mse_m.item())
    ok &= assert_close("loss_ddf_reg", loss_ddf_o.item(), loss_ddf_m.item())
    ok &= assert_close("loss_regist", loss_regist_o.item(), loss_regist_m.item())
    ok &= assert_close("gradients_clipped", grad_o, grad_m)
    ok &= assert_close("weights_after", params_flat(ddpm.network), params_flat(om.network))

    print(f"\nMode 3 Registration: {'ALL PASSED' if ok else 'SOME FAILED'}")
    return ok


# ========================== Test: Full Sequence ==========================

def test_full_sequence():
    """Run all 3 modes sequentially on both pipelines, compare final weights."""
    print("\n" + "=" * 60)
    print("TEST: Full Step Sequence (Diffusion → Contrastive → Registration)")
    print("=" * 60)

    config = make_config()
    x0, embd, blind_mask, t, x1, y1, embd_y, t_contra = make_shared_data()

    seed_all(42)
    ddpm, ddf_stn, opt_o, loss_reg_o, loss_reg1_o, loss_dist_o, loss_ang_o, loss_imgsim_o, loss_imgmse_o = build_original(config)
    seed_all(42)
    om, opt_m, loss_reg_m, loss_reg1_m, loss_imgsim_m, loss_imgmse_m = build_omorpher(config)
    sync_weights(ddpm, om)

    ok = assert_close("init_weights", params_flat(ddpm.network), params_flat(om.network))

    # Shared pre-computed tensors
    seed_all(200)
    noisy_img, dvf_gt, _ = om._get_random_ddf(x0, t)
    cond_img_diff, _, cond_ratio_diff = om._proc_cond_img(x0, proc_type='none')
    y1_proc, _, cond_ratio_reg = om._proc_cond_img(y1, proc_type='none')

    T_regist = sorted([9, 7, 5, 3, 2, 1], reverse=True)
    T_regist_batched = [[tv for _ in range(max(1, BATCHSIZE // 2))] for tv in T_regist]

    # ========== Step 1: Diffusion (both) ==========
    ddpm.network.train()
    om.network.train()

    # Original
    pdvf_o = ddpm.network(x=noisy_img * blind_mask, y=cond_img_diff, t=t, rec_num=2, text=embd)
    ld_o = loss_reg_o(pdvf_o, img=x0)
    tp_o = ddf_stn(pdvf_o, dvf_gt)
    lgd_o = loss_dist_o(pred=tp_o, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)
    lga_o = loss_ang_o(pred=tp_o, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)
    lt_o = (LOSS_WEIGHTS_DIFF[0] * lga_o + LOSS_WEIGHTS_DIFF[1] * lgd_o + LOSS_WEIGHTS_DIFF[2] * ld_o)
    lt_o = torch.sqrt(torch.tensor(1. + MSK_EPS) - cond_ratio_diff) * lt_o
    opt_o.zero_grad(); lt_o.backward(); opt_o.step()

    # OMorpher
    pdvf_m = om.network(x=noisy_img * blind_mask, y=cond_img_diff, t=t, rec_num=2, text=embd)
    ld_m = loss_reg_m(pdvf_m, img=x0)
    tp_m = om.stn_full(pdvf_m, dvf_gt)
    lgd_m = om._loss_dist(pred=tp_m, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)
    lga_m = om._loss_ang(pred=tp_m, inv_lab=dvf_gt, ddf_stn=None, mask=blind_mask)
    lt_m = (LOSS_WEIGHTS_DIFF[0] * lga_m + LOSS_WEIGHTS_DIFF[1] * lgd_m + LOSS_WEIGHTS_DIFF[2] * ld_m)
    lt_m = torch.sqrt(torch.tensor(1. + MSK_EPS) - cond_ratio_diff) * lt_m
    opt_m.zero_grad(); lt_m.backward(); opt_m.step()

    ok &= assert_close("weights_after_diffusion", params_flat(ddpm.network), params_flat(om.network))

    # ========== Step 2: Contrastive (both) ==========
    x_in = (x0 * blind_mask).detach()
    y_in = cond_img_diff.detach()
    text_in = embd.detach()

    _ = ddpm.network(x=x_in, y=y_in, t=t_contra, text=text_in)
    has_embd = hasattr(ddpm.network, 'img_embd') and ddpm.network.img_embd is not None
    if has_embd:
        ie_o = ddpm.network.img_embd
        lc_o = LOSS_WEIGHT_CONTRASTIVE * (1 - F.cosine_similarity(ie_o, embd, dim=-1).mean())
        opt_o.zero_grad(); lc_o.backward()
        torch.nn.utils.clip_grad_norm_(ddpm.parameters(), max_norm=0.1); opt_o.step()

        _ = om.network(x=x_in, y=y_in, t=t_contra, text=text_in)
        ie_m = om.network.img_embd
        lc_m = LOSS_WEIGHT_CONTRASTIVE * (1 - F.cosine_similarity(ie_m, embd, dim=-1).mean())
        opt_m.zero_grad(); lc_m.backward()
        torch.nn.utils.clip_grad_norm_(om.network.parameters(), max_norm=0.1); opt_m.step()

        ok &= assert_close("loss_contrastive_seq", lc_o.item(), lc_m.item())
        ok &= assert_close("weights_after_contrastive", params_flat(ddpm.network), params_flat(om.network))

    # ========== Step 3: Registration (both) ==========
    # Original
    [ddf_o, _], [rec_o, _, _], _ = ddpm(
        img_org=x1, cond_imgs=y1_proc, T=[None, T_regist_batched], proc_type=[], text=embd_y,
    )
    ls_o = loss_imgsim_o(rec_o, y1, label=(y1 > 0.01))
    lms_o = loss_imgmse_o(rec_o, y1)
    ldr_o = loss_reg1_o(ddf_o, img=y1)
    lr_o = (LOSS_WEIGHTS_REGIST[0] * ls_o + LOSS_WEIGHTS_REGIST[1] * lms_o + LOSS_WEIGHTS_REGIST[2] * ldr_o)
    lr_o = torch.sqrt(cond_ratio_reg + MSK_EPS) * lr_o
    opt_o.zero_grad(); lr_o.backward()
    torch.nn.utils.clip_grad_norm_(ddpm.parameters(), max_norm=0.4); opt_o.step()

    # OMorpher
    B = x1.shape[0]
    S = om.img_size
    ddf_m = torch.zeros([B, om.ndims] + [S] * om.ndims, dtype=torch.float32, device=om.device)
    rec_m = x1.clone().detach()
    k = 2
    trainable_iters = T_regist_batched[-1:-k - 1:-1]
    for i in T_regist_batched:
        tt = torch.tensor(np.array([i])).to(om.device)
        if i in trainable_iters:
            pdvf = om.network(x=rec_m, y=y1_proc, t=tt, rec_num=2, text=embd_y)
        else:
            with torch.no_grad():
                pdvf = om.network(x=rec_m, y=y1_proc, t=tt, rec_num=2, text=embd_y)
        ddf_m = om.stn_full(ddf_m, pdvf) + pdvf
        rec_m = om.img_stn(x1.clone().detach(), ddf_m)

    ls_m = loss_imgsim_m(rec_m, y1, label=(y1 > 0.01))
    lms_m = loss_imgmse_m(rec_m, y1)
    ldr_m = loss_reg1_m(ddf_m, img=y1)
    lr_m = (LOSS_WEIGHTS_REGIST[0] * ls_m + LOSS_WEIGHTS_REGIST[1] * lms_m + LOSS_WEIGHTS_REGIST[2] * ldr_m)
    lr_m = torch.sqrt(cond_ratio_reg + MSK_EPS) * lr_m
    opt_m.zero_grad(); lr_m.backward()
    torch.nn.utils.clip_grad_norm_(om.network.parameters(), max_norm=0.4); opt_m.step()

    ok &= assert_close("loss_regist_seq", lr_o.item(), lr_m.item())
    ok &= assert_close("weights_after_registration", params_flat(ddpm.network), params_flat(om.network))

    print(f"\nFull Sequence: {'ALL PASSED' if ok else 'SOME FAILED'}")
    return ok


# ========================== Test: Checkpoint Compatibility ==========================

def test_checkpoint_compat():
    """Checkpoints saved by one version load correctly into the other."""
    print("\n" + "=" * 60)
    print("TEST: Checkpoint Cross-Compatibility")
    print("=" * 60)
    import tempfile

    config = make_config()
    seed_all(42)
    ddpm, *_ = build_original(config)
    seed_all(42)
    om, *_ = build_omorpher(config)
    sync_weights(ddpm, om)

    ok = True
    with tempfile.TemporaryDirectory() as tmpdir:
        # Save DeformDDPM checkpoint (original format: includes network.* + stn keys)
        path_o = os.path.join(tmpdir, "orig.pth")
        torch.save({'model_state_dict': ddpm.state_dict(), 'epoch': 0}, path_o)

        # Save OMorpher checkpoint (network.* prefix only)
        path_m = os.path.join(tmpdir, "om.pth")
        sd_m = {f"network.{k}": v for k, v in om.network.state_dict().items()}
        torch.save({'model_state_dict': sd_m, 'epoch': 0}, path_m)

        # Load original → OMorpher
        om2, *_ = build_omorpher(config)
        ckpt = torch.load(path_o, map_location='cpu')
        cleaned = {}
        for k, v in ckpt['model_state_dict'].items():
            k = k.replace("module.", "")
            if k.startswith("network."):
                k = k[len("network."):]
            cleaned[k] = v
        net_keys = set(om2.network.state_dict().keys())
        om2.network.load_state_dict({k: v for k, v in cleaned.items() if k in net_keys}, strict=False)
        ok &= assert_close("orig→OMorpher", params_flat(om2.network), params_flat(ddpm.network))

        # Load OMorpher → DeformDDPM
        seed_all(42)
        ddpm2, *_ = build_original(config)
        ddpm2.load_state_dict(torch.load(path_m, map_location='cpu')['model_state_dict'], strict=False)
        ok &= assert_close("OMorpher→orig", params_flat(ddpm2.network), params_flat(om.network))

    print(f"\nCheckpoint Compat: {'ALL PASSED' if ok else 'SOME FAILED'}")
    return ok


# ========================== Main ==========================

if __name__ == "__main__":
    print("=" * 60)
    print("3-Modes Equivalence Test Suite")
    print(f"IMG_SIZE={IMG_SIZE}, BATCHSIZE={BATCHSIZE}, TIMESTEPS={TIMESTEPS}, NET={NET_NAME}")
    print("=" * 60)

    results = {}
    results["Mode 1: Diffusion"] = test_mode1_diffusion()
    results["Mode 2: Contrastive"] = test_mode2_contrastive()
    results["Mode 3: Registration"] = test_mode3_registration()
    results["Full Sequence"] = test_full_sequence()
    results["Checkpoint Compat"] = test_checkpoint_compat()

    print("\n" + "=" * 60)
    print("SUMMARY")
    print("=" * 60)
    all_ok = True
    for name, passed in results.items():
        status = "PASS" if passed else "FAIL"
        print(f"  [{status}] {name}")
        all_ok &= passed

    print(f"\nOverall: {'ALL TESTS PASSED' if all_ok else 'SOME TESTS FAILED'}")
    sys.exit(0 if all_ok else 1)