"""
SVAE-Patch — Patch-based SVD Autoencoder
==========================================
Image → patches → per-patch encode → sphere normalize → SVD →
cross-patch spectral attention → per-patch decode → stitch → boundary smooth.

Proven configurations:
  TinyImageNet 64×64:   16 patches of 16×16, (256,16), 0.000478 MSE, 17M params
  ImageNet-1K 128×128:  64 patches of 16×16, (256,16), 0.000206 MSE, 17M params
  ImageNet-1K 256×256: 256 patches of 16×16, (256,16), 17M params
"""

import os
import torch
import torch.nn as nn
import torch.nn.functional as F
import torchvision
import torchvision.transforms as T
import math
import time
from tqdm import tqdm

# ── SVD Backend ──────────────────────────────────────────────────

try:
    from geolip_core.linalg.eigh import FLEigh, _FL_MAX_N
    HAS_FL = True
except ImportError:
    HAS_FL = False


def gram_eigh_svd_fp64(A):
    """Thin SVD via Gram + eigh in fp64."""
    orig_dtype = A.dtype
    with torch.amp.autocast('cuda', enabled=False):
        A_d = A.double()
        G = torch.bmm(A_d.transpose(1, 2), A_d)
        eigenvalues, V = torch.linalg.eigh(G)
        eigenvalues = eigenvalues.flip(-1)
        V = V.flip(-1)
        S = torch.sqrt(eigenvalues.clamp(min=1e-24))
        U = torch.bmm(A_d, V) / S.unsqueeze(1).clamp(min=1e-16)
        Vh = V.transpose(-2, -1).contiguous()
    return U.to(orig_dtype), S.to(orig_dtype), Vh.to(orig_dtype)


def svd_fp64(A):
    """Auto-dispatch SVD with fp64 internals."""
    B, M, N = A.shape
    if HAS_FL and N <= _FL_MAX_N and A.is_cuda:
        orig_dtype = A.dtype
        with torch.amp.autocast('cuda', enabled=False):
            A_d = A.double()
            G = torch.bmm(A_d.transpose(1, 2), A_d)
            eigenvalues, V = FLEigh()(G.float())
            eigenvalues = eigenvalues.double().flip(-1)
            V = V.double().flip(-1)
            S = torch.sqrt(eigenvalues.clamp(min=1e-24))
            U = torch.bmm(A_d, V) / S.unsqueeze(1).clamp(min=1e-16)
            Vh = V.transpose(-2, -1).contiguous()
        return U.to(orig_dtype), S.to(orig_dtype), Vh.to(orig_dtype)
    else:
        return gram_eigh_svd_fp64(A)


# ── CV Monitoring ────────────────────────────────────────────────

def cayley_menger_vol2(points):
    """Squared simplex volume via Cayley-Menger determinant, fp64."""
    B, N, D = points.shape
    pts = points.double()
    gram = torch.bmm(pts, pts.transpose(1, 2))
    norms = torch.diagonal(gram, dim1=1, dim2=2)
    d2 = F.relu(norms.unsqueeze(2) + norms.unsqueeze(1) - 2 * gram)
    cm = torch.zeros(B, N + 1, N + 1, device=points.device, dtype=torch.float64)
    cm[:, 0, 1:] = 1.0
    cm[:, 1:, 0] = 1.0
    cm[:, 1:, 1:] = d2
    k = N - 1
    sign = (-1.0) ** (k + 1)
    fact = math.factorial(k)
    return sign * torch.linalg.det(cm) / ((2 ** k) * (fact ** 2))


def cv_of(emb, n_samples=200):
    """CV of pentachoron volumes for a (V, D) embedding."""
    if emb.dim() != 2 or emb.shape[0] < 5:
        return 0.0
    N, D = emb.shape
    pool = min(N, 512)
    indices = torch.stack([torch.randperm(pool, device=emb.device)[:5] for _ in range(n_samples)])
    vol2 = cayley_menger_vol2(emb[:pool][indices])
    valid = vol2 > 1e-20
    if valid.sum() < 10:
        return 0.0
    vols = vol2[valid].sqrt()
    return (vols.std() / (vols.mean() + 1e-8)).item()


# ── Data ─────────────────────────────────────────────────────────

class HFImageDataset(torch.utils.data.Dataset):
    def __init__(self, hf_split, transform):
        self.data = hf_split
        self.transform = transform
    def __len__(self):
        return len(self.data)
    def __getitem__(self, idx):
        item = self.data[idx]
        img = item['image']
        if img.mode != 'RGB':
            img = img.convert('RGB')
        return self.transform(img), item['label']


def get_tiny_imagenet(batch_size=256):
    from datasets import load_dataset
    ds = load_dataset('zh-plus/tiny-imagenet')
    transform = T.Compose([
        T.ToTensor(),
        T.Normalize((0.4802, 0.4481, 0.3975), (0.2770, 0.2691, 0.2821)),
    ])
    train_ds = HFImageDataset(ds['train'], transform)
    val_ds = HFImageDataset(ds['valid'], transform)
    return (torch.utils.data.DataLoader(train_ds, batch_size=batch_size, shuffle=True, num_workers=2),
            torch.utils.data.DataLoader(val_ds, batch_size=batch_size, shuffle=False, num_workers=2))


def get_cifar10(batch_size=256):
    transform = T.Compose([
        T.ToTensor(),
        T.Normalize((0.4914, 0.4822, 0.4465), (0.2470, 0.2435, 0.2616)),
    ])
    train_ds = torchvision.datasets.CIFAR10(root='./data', train=True, download=True, transform=transform)
    test_ds = torchvision.datasets.CIFAR10(root='./data', train=False, download=True, transform=transform)
    return (torch.utils.data.DataLoader(train_ds, batch_size=batch_size, shuffle=True, num_workers=2),
            torch.utils.data.DataLoader(test_ds, batch_size=batch_size, shuffle=False, num_workers=2))


def get_imagenet_128(batch_size=128):
    from datasets import load_dataset
    ds = load_dataset('benjamin-paine/imagenet-1k-128x128')
    transform = T.Compose([
        T.ToTensor(),
        T.Normalize((0.485, 0.456, 0.406), (0.229, 0.224, 0.225)),
    ])
    train_ds = HFImageDataset(ds['train'], transform)
    val_ds = HFImageDataset(ds['validation'], transform)
    return (torch.utils.data.DataLoader(train_ds, batch_size=batch_size, shuffle=True, num_workers=4, pin_memory=True),
            torch.utils.data.DataLoader(val_ds, batch_size=batch_size, shuffle=False, num_workers=4, pin_memory=True))


def get_imagenet_256(batch_size=64):
    from datasets import load_dataset
    ds = load_dataset('benjamin-paine/imagenet-1k-256x256')
    transform = T.Compose([
        T.ToTensor(),
        T.Normalize((0.485, 0.456, 0.406), (0.229, 0.224, 0.225)),
    ])
    train_ds = HFImageDataset(ds['train'], transform)
    val_ds = HFImageDataset(ds['validation'], transform)
    return (torch.utils.data.DataLoader(train_ds, batch_size=batch_size, shuffle=True, num_workers=4, pin_memory=True),
            torch.utils.data.DataLoader(val_ds, batch_size=batch_size, shuffle=False, num_workers=4, pin_memory=True))


# ── Patch Utilities ──────────────────────────────────────────────

def extract_patches(images, patch_size=16):
    B, C, H, W = images.shape
    ph, pw = patch_size, patch_size
    gh, gw = H // ph, W // pw
    patches = images.reshape(B, C, gh, ph, gw, pw)
    patches = patches.permute(0, 2, 4, 1, 3, 5)
    patches = patches.reshape(B, gh * gw, C * ph * pw)
    return patches, gh, gw


def stitch_patches(patches, gh, gw, patch_size=16):
    B = patches.shape[0]
    C = 3
    ph, pw = patch_size, patch_size
    patches = patches.reshape(B, gh, gw, C, ph, pw)
    patches = patches.permute(0, 3, 1, 4, 2, 5)
    return patches.reshape(B, C, gh * ph, gw * pw)


class BoundarySmooth(nn.Module):
    """Post-stitch boundary refinement. ~600 params, zero-initialized."""
    def __init__(self, channels=3, mid=16):
        super().__init__()
        self.net = nn.Sequential(
            nn.Conv2d(channels, mid, 3, padding=1),
            nn.GELU(),
            nn.Conv2d(mid, channels, 3, padding=1),
        )
        nn.init.zeros_(self.net[-1].weight)
        nn.init.zeros_(self.net[-1].bias)

    def forward(self, x):
        return x + self.net(x)


# ── Spectral Cross-Attention ────────────────────────────────────

class SpectralCrossAttention(nn.Module):
    """Multiplicative spectral coordination with learnable per-mode alpha.
    S_out = S * (1 + α_d * tanh(attention_output_d))
    """
    def __init__(self, D, n_heads=4, max_alpha=0.2, alpha_init=-2.0):
        super().__init__()
        self.n_heads = n_heads
        self.head_dim = D // n_heads
        self.max_alpha = max_alpha
        assert D % n_heads == 0

        self.qkv = nn.Linear(D, 3 * D)
        self.out_proj = nn.Linear(D, D)
        self.norm = nn.LayerNorm(D)
        self.scale = self.head_dim ** -0.5
        self.alpha_logits = nn.Parameter(torch.full((D,), alpha_init))

    @property
    def alpha(self):
        return self.max_alpha * torch.sigmoid(self.alpha_logits)

    def forward(self, S):
        B, N, D = S.shape
        S_normed = self.norm(S)
        qkv = self.qkv(S_normed).reshape(B, N, 3, self.n_heads, self.head_dim)
        qkv = qkv.permute(2, 0, 3, 1, 4)
        q, k, v = qkv[0], qkv[1], qkv[2]
        attn = (q @ k.transpose(-2, -1)) * self.scale
        attn = attn.softmax(dim=-1)
        out = (attn @ v).transpose(1, 2).reshape(B, N, D)
        gate = torch.tanh(self.out_proj(out))
        alpha = self.alpha
        return S * (1.0 + alpha.unsqueeze(0).unsqueeze(0) * gate)


# ── Patch SVAE ───────────────────────────────────────────────────

class PatchSVAE(nn.Module):
    def __init__(self, matrix_v=256, D=16, patch_size=16, hidden=768,
                 depth=4, n_cross_layers=2):
        super().__init__()
        self.matrix_v = matrix_v
        self.D = D
        self.patch_size = patch_size
        self.patch_dim = 3 * patch_size * patch_size
        self.mat_dim = matrix_v * D

        self.enc_in = nn.Linear(self.patch_dim, hidden)
        self.enc_blocks = nn.ModuleList([
            nn.Sequential(nn.LayerNorm(hidden), nn.Linear(hidden, hidden),
                          nn.GELU(), nn.Linear(hidden, hidden))
            for _ in range(depth)
        ])
        self.enc_out = nn.Linear(hidden, self.mat_dim)

        self.dec_in = nn.Linear(self.mat_dim, hidden)
        self.dec_blocks = nn.ModuleList([
            nn.Sequential(nn.LayerNorm(hidden), nn.Linear(hidden, hidden),
                          nn.GELU(), nn.Linear(hidden, hidden))
            for _ in range(depth)
        ])
        self.dec_out = nn.Linear(hidden, self.patch_dim)

        nn.init.orthogonal_(self.enc_out.weight)

        self.cross_attn = nn.ModuleList([
            SpectralCrossAttention(D, n_heads=min(4, D))
            for _ in range(n_cross_layers)
        ])
        self.boundary_smooth = BoundarySmooth(channels=3, mid=16)

    def encode_patches(self, patches):
        B, N, _ = patches.shape
        flat = patches.reshape(B * N, -1)
        h = F.gelu(self.enc_in(flat))
        for block in self.enc_blocks:
            h = h + block(h)
        M = self.enc_out(h).reshape(B * N, self.matrix_v, self.D)
        M = F.normalize(M, dim=-1)
        U, S, Vt = svd_fp64(M)
        U = U.reshape(B, N, self.matrix_v, self.D)
        S = S.reshape(B, N, self.D)
        Vt = Vt.reshape(B, N, self.D, self.D)
        M = M.reshape(B, N, self.matrix_v, self.D)
        S_coord = S
        for layer in self.cross_attn:
            S_coord = layer(S_coord)
        return {'U': U, 'S_orig': S, 'S': S_coord, 'Vt': Vt, 'M': M}

    def decode_patches(self, U, S, Vt):
        B, N, V, D = U.shape
        U_flat = U.reshape(B * N, V, D)
        S_flat = S.reshape(B * N, D)
        Vt_flat = Vt.reshape(B * N, D, D)
        M_hat = torch.bmm(U_flat * S_flat.unsqueeze(1), Vt_flat)
        h = F.gelu(self.dec_in(M_hat.reshape(B * N, -1)))
        for block in self.dec_blocks:
            h = h + block(h)
        patches = self.dec_out(h)
        return patches.reshape(B, N, -1)

    def forward(self, images):
        patches, gh, gw = extract_patches(images, self.patch_size)
        svd = self.encode_patches(patches)
        decoded_patches = self.decode_patches(svd['U'], svd['S'], svd['Vt'])
        recon = stitch_patches(decoded_patches, gh, gw, self.patch_size)
        recon = self.boundary_smooth(recon)
        return {'recon': recon, 'svd': svd, 'gh': gh, 'gw': gw}

    @staticmethod
    def effective_rank(S):
        p = S / (S.sum(-1, keepdim=True) + 1e-8)
        p = p.clamp(min=1e-8)
        return (-(p * p.log()).sum(-1)).exp()


# ── Training ─────────────────────────────────────────────────────

def train(epochs=200, lr=1e-4, V=256, D=16, patch_size=16,
          hidden=768, depth=4, batch_size=None,
          target_cv=0.125, cv_weight=0.3, boost=0.5, sigma=0.15,
          n_cross_layers=2, dataset='tiny_imagenet', device='cuda',
          save_dir='/content/checkpoints', save_every=1,
          hf_repo='AbstractPhil/geolip-SVAE', hf_version='v11_prod',
          tb_dir='/content/runs'):

    os.makedirs(save_dir, exist_ok=True)
    device = torch.device(device if torch.cuda.is_available() else 'cpu')

    # ── TensorBoard ──
    from torch.utils.tensorboard import SummaryWriter
    run_name = f"patchsvae_V{V}_D{D}_p{patch_size}_h{hidden}_d{depth}"
    tb_path = os.path.join(tb_dir, run_name)
    writer = SummaryWriter(tb_path)
    print(f"  TensorBoard: {tb_path}")

    # ── HuggingFace ──
    hf_enabled = False
    try:
        from huggingface_hub import HfApi
        api = HfApi()
        api.whoami()
        hf_enabled = True
        hf_prefix = f"{hf_version}/checkpoints"
        print(f"  HuggingFace: {hf_repo}/{hf_prefix}")
    except Exception as e:
        print(f"  HuggingFace: disabled ({e})")

    def upload_to_hf(local_path, remote_name):
        if not hf_enabled:
            return
        try:
            remote_path = f"{hf_prefix}/{remote_name}"
            api.upload_file(path_or_fileobj=local_path, path_in_repo=remote_path,
                            repo_id=hf_repo, repo_type="model")
            print(f"  ☁️  Uploaded: {hf_repo}/{remote_path}")
        except Exception as e:
            print(f"  ⚠️  HF upload failed: {e}")

    # ── Dataset ──
    if dataset == 'imagenet_256':
        bs = batch_size or 64
        train_loader, test_loader = get_imagenet_256(batch_size=bs)
        img_h, n_classes = 256, 1000
        mean_t = torch.tensor([0.485, 0.456, 0.406]).reshape(1, 3, 1, 1).to(device)
        std_t = torch.tensor([0.229, 0.224, 0.225]).reshape(1, 3, 1, 1).to(device)
    elif dataset == 'imagenet_128':
        bs = batch_size or 128
        train_loader, test_loader = get_imagenet_128(batch_size=bs)
        img_h, n_classes = 128, 1000
        mean_t = torch.tensor([0.485, 0.456, 0.406]).reshape(1, 3, 1, 1).to(device)
        std_t = torch.tensor([0.229, 0.224, 0.225]).reshape(1, 3, 1, 1).to(device)
    elif dataset == 'tiny_imagenet':
        bs = batch_size or 256
        train_loader, test_loader = get_tiny_imagenet(batch_size=bs)
        img_h, n_classes = 64, 200
        mean_t = torch.tensor([0.4802, 0.4481, 0.3975]).reshape(1, 3, 1, 1).to(device)
        std_t = torch.tensor([0.2770, 0.2691, 0.2821]).reshape(1, 3, 1, 1).to(device)
    else:
        bs = batch_size or 256
        train_loader, test_loader = get_cifar10(batch_size=bs)
        img_h, n_classes = 32, 10
        mean_t = torch.tensor([0.4914, 0.4822, 0.4465]).reshape(1, 3, 1, 1).to(device)
        std_t = torch.tensor([0.2470, 0.2435, 0.2616]).reshape(1, 3, 1, 1).to(device)

    # ── Model ──
    n_patches = (img_h // patch_size) ** 2
    model = PatchSVAE(matrix_v=V, D=D, patch_size=patch_size,
                      hidden=hidden, depth=depth,
                      n_cross_layers=n_cross_layers).to(device)
    opt = torch.optim.Adam(model.parameters(), lr=lr)
    sched = torch.optim.lr_scheduler.CosineAnnealingLR(opt, T_max=epochs)

    total_params = sum(p.numel() for p in model.parameters())
    cross_params = sum(p.numel() for p in model.cross_attn.parameters())

    svd_info = f"fp64 Gram+eigh (FL={'available, N<=12' if HAS_FL else 'not available'})"
    print(f"Using geolip-core SVD ({svd_info})")
    print(f"PatchSVAE - {n_patches} patches of {patch_size}×{patch_size}")
    print(f"  Dataset: {dataset} ({img_h}×{img_h}, {n_classes} classes, batch={bs})")
    print(f"  Per-patch: ({V}, {D}) = {V*D} elements, rows on S^{D-1}")
    print(f"  Encoder/Decoder: hidden={hidden}, depth={depth} (residual blocks)")
    print(f"  Cross-attention: {n_cross_layers} layers on S vectors ({cross_params:,} params)")
    print(f"  Soft hand: boost={1+boost:.1f}x near CV={target_cv}, penalty={cv_weight} far")
    print(f"  Total params: {total_params:,}")
    print(f"  Checkpoints: {save_dir} (best + every {save_every} epochs)")
    print("=" * 100)
    print(f" {'ep':>3} | {'loss':>7} {'recon':>7} {'t/ep':>5} | "
          f"{'t_rec':>7} | "
          f"{'S0':>6} {'SD':>6} {'ratio':>5} {'erank':>5} | "
          f"{'row_cv':>7} {'prox':>5} {'rw':>5} | "
          f"{'S_delta':>7}")
    print("-" * 100)

    best_recon = float('inf')

    def save_checkpoint(path, epoch, test_mse, extra=None, upload=True):
        ckpt = {
            'epoch': epoch, 'test_mse': test_mse,
            'model_state_dict': model.state_dict(),
            'optimizer_state_dict': opt.state_dict(),
            'scheduler_state_dict': sched.state_dict(),
            'config': {
                'V': V, 'D': D, 'patch_size': patch_size,
                'hidden': hidden, 'depth': depth,
                'n_cross_layers': n_cross_layers,
                'target_cv': target_cv, 'cv_weight': cv_weight,
                'boost': boost, 'sigma': sigma,
                'dataset': dataset, 'lr': lr,
            },
        }
        if extra:
            ckpt.update(extra)
        torch.save(ckpt, path)
        size_mb = os.path.getsize(path) / (1024 * 1024)
        print(f"  💾 Saved: {path} ({size_mb:.1f}MB, ep{epoch}, MSE={test_mse:.6f})")
        if upload:
            upload_to_hf(path, os.path.basename(path))

    # ── Training Loop ──
    for epoch in range(1, epochs + 1):
        model.train()
        total_loss, total_recon, n = 0, 0, 0
        last_cv, last_prox, recon_w = target_cv, 1.0, 1.0 + boost
        t0 = time.time()

        pbar = tqdm(train_loader, desc=f"Ep {epoch}/{epochs}", leave=False,
                    bar_format='{l_bar}{bar:20}{r_bar}')
        for batch_idx, (images, labels) in enumerate(pbar):
            images = images.to(device)
            opt.zero_grad()
            out = model(images)
            recon_loss = F.mse_loss(out['recon'], images)

            with torch.no_grad():
                if batch_idx % 10 == 0:
                    current_cv = cv_of(out['svd']['M'][0, 0])
                    if current_cv > 0:
                        last_cv = current_cv
                    delta = last_cv - target_cv
                    last_prox = math.exp(-delta**2 / (2 * sigma**2))
                    pbar.set_postfix_str(
                        f"loss={recon_loss.item():.4f} cv={last_cv:.3f} prox={last_prox:.2f}",
                        refresh=False)

            recon_w = 1.0 + boost * last_prox
            cv_pen = cv_weight * (1.0 - last_prox)
            cv_l = (last_cv - target_cv) ** 2
            loss = recon_w * recon_loss + cv_pen * cv_l
            loss.backward()

            torch.nn.utils.clip_grad_norm_(model.cross_attn.parameters(), max_norm=0.5)
            opt.step()

            total_loss += loss.item() * len(images)
            total_recon += recon_loss.item() * len(images)
            n += len(images)

        pbar.close()
        sched.step()
        epoch_time = time.time() - t0

        # ── TensorBoard: train ──
        writer.add_scalar('train/loss', total_loss / n, epoch)
        writer.add_scalar('train/recon', total_recon / n, epoch)
        writer.add_scalar('train/lr', sched.get_last_lr()[0], epoch)
        writer.add_scalar('train/epoch_time', epoch_time, epoch)

        # ── Evaluation ──
        if epoch % 2 == 0 or epoch <= 3:
            model.eval()
            test_recon, test_n = 0, 0
            test_S_orig, test_S_coord = None, None
            test_erank, row_cvs, nb = 0, [], 0

            with torch.no_grad():
                for images, labels in test_loader:
                    images = images.to(device)
                    out = model(images)
                    test_recon += F.mse_loss(out['recon'], images).item() * len(images)
                    test_n += len(images)
                    S_mean = out['svd']['S'].mean(dim=(0, 1))
                    S_orig_mean = out['svd']['S_orig'].mean(dim=(0, 1))
                    test_erank += model.effective_rank(out['svd']['S'].reshape(-1, D)).mean().item()
                    if nb < 3:
                        for b in range(min(2, len(images))):
                            for p in range(min(2, out['svd']['M'].shape[1])):
                                row_cvs.append(cv_of(out['svd']['M'][b, p]))
                    if test_S_orig is None:
                        test_S_orig = S_orig_mean.cpu()
                        test_S_coord = S_mean.cpu()
                    else:
                        test_S_orig += S_orig_mean.cpu()
                        test_S_coord += S_mean.cpu()
                    nb += 1

            test_erank /= nb
            test_S_orig /= nb
            test_S_coord /= nb
            ratio = (test_S_coord[0] / (test_S_coord[-1] + 1e-8)).item()
            mean_cv = sum(row_cvs) / len(row_cvs) if row_cvs else 0
            s_delta = (test_S_coord - test_S_orig).abs().mean().item()

            with torch.no_grad():
                all_alphas = torch.cat([layer.alpha for layer in model.cross_attn])
                alpha_mean = all_alphas.mean().item()
                alpha_max = all_alphas.max().item()

            print(f" {epoch:3d} | {total_loss/n:7.4f} {total_recon/n:7.4f} {epoch_time:5.1f} | "
                  f"{test_recon/test_n:7.4f} | "
                  f"{test_S_coord[0]:6.3f} {test_S_coord[-1]:6.3f} {ratio:5.2f} "
                  f"{test_erank:5.2f} | "
                  f"{mean_cv:7.4f} {last_prox:5.3f} {recon_w:5.2f} | "
                  f"{s_delta:7.5f} a:{alpha_mean:.4f}/{alpha_max:.4f}")

            # ── TensorBoard: eval ──
            test_mse = test_recon / test_n
            writer.add_scalar('test/recon_mse', test_mse, epoch)
            writer.add_scalar('geo/row_cv', mean_cv, epoch)
            writer.add_scalar('geo/ratio', ratio, epoch)
            writer.add_scalar('geo/erank', test_erank, epoch)
            writer.add_scalar('geo/S0', test_S_coord[0].item(), epoch)
            writer.add_scalar('geo/SD', test_S_coord[-1].item(), epoch)
            writer.add_scalar('cross_attn/s_delta', s_delta, epoch)
            writer.add_scalar('cross_attn/alpha_mean', alpha_mean, epoch)

            if epoch % 20 == 0 or epoch <= 3:
                writer.add_histogram('spectrum/S_coordinated', test_S_coord, epoch)
                for li, layer in enumerate(model.cross_attn):
                    writer.add_histogram(f'alpha/layer_{li}', layer.alpha.detach().cpu(), epoch)

            if epoch % 50 == 0 or epoch == 1:
                with torch.no_grad():
                    sample_imgs, _ = next(iter(test_loader))
                    sample_imgs = sample_imgs[:8].to(device)
                    sample_out = model(sample_imgs)
                    orig_vis = (sample_imgs * std_t + mean_t).clamp(0, 1)
                    recon_vis = (sample_out['recon'] * std_t + mean_t).clamp(0, 1)
                    comparison = torch.cat([orig_vis, recon_vis], dim=0)
                    grid = torchvision.utils.make_grid(comparison, nrow=8, padding=2)
                    writer.add_image('recon/comparison', grid, epoch)

            # ── Checkpoints ──
            geo_stats = {
                'row_cv': mean_cv, 'ratio': ratio, 'erank': test_erank,
                'S0': test_S_coord[0].item(), 'SD': test_S_coord[-1].item(),
                's_delta': s_delta, 'alpha_mean': alpha_mean, 'alpha_max': alpha_max,
            }

            if test_mse < best_recon:
                best_recon = test_mse
                save_checkpoint(os.path.join(save_dir, 'best.pt'),
                                epoch, test_mse, extra={'geo': geo_stats}, upload=False)

            if epoch % save_every == 0:
                save_checkpoint(os.path.join(save_dir, f'epoch_{epoch:04d}.pt'),
                                epoch, test_mse, extra={'geo': geo_stats})
                best_path = os.path.join(save_dir, 'best.pt')
                if os.path.exists(best_path):
                    upload_to_hf(best_path, 'best.pt')
                writer.flush()
                if hf_enabled:
                    try:
                        api.upload_folder(folder_path=tb_path,
                                          path_in_repo=f"{hf_version}/tensorboard/{run_name}",
                                          repo_id=hf_repo, repo_type="model")
                        print(f"  ☁️  TB logs synced")
                    except Exception as e:
                        print(f"  ⚠️  TB sync failed: {e}")

    # ── Final Analysis ──
    print("\n" + "=" * 90)
    print("FINAL ANALYSIS")
    print("=" * 90)

    model.eval()
    all_recon_err = []
    with torch.no_grad():
        for images, labels in test_loader:
            images = images.to(device)
            out = model(images)
            all_recon_err.append(
                F.mse_loss(out['recon'], images, reduction='none')
                .mean(dim=(1, 2, 3)).cpu())
    all_recon_err = torch.cat(all_recon_err)

    print(f"\n  PatchSVAE: {n_patches} patches × ({V}, {D})")
    print(f"  Target CV: {target_cv}")
    print(f"  Recon MSE: {all_recon_err.mean():.6f} +/- {all_recon_err.std():.6f}")

    print(f"\n  Learned alpha per mode:")
    for li, layer in enumerate(model.cross_attn):
        alpha = layer.alpha.detach().cpu()
        print(f"    Layer {li}: mean={alpha.mean():.4f}  max={alpha.max():.4f}  min={alpha.min():.4f}")
        bar_scale = 40 / (alpha.max().item() + 1e-8)
        for d in range(len(alpha)):
            bar = "#" * int(alpha[d].item() * bar_scale)
            print(f"      α[{d:2d}]: {alpha[d]:.4f}  {bar}")

    print(f"\n  Singular value profile:")
    total_energy = (test_S_coord ** 2).sum()
    cumulative = 0
    for i in range(len(test_S_coord)):
        e = (test_S_coord[i] ** 2).item()
        cumulative += e
        pct = cumulative / total_energy * 100
        bar = "#" * int(test_S_coord[i].item() * 30 / (test_S_coord[0].item() + 1e-8))
        print(f"    S[{i:2d}]: {test_S_coord[i]:8.4f}  cum={pct:5.1f}%  {bar}")

    # ── Recon grid ──
    import matplotlib
    matplotlib.use('Agg')
    import matplotlib.pyplot as plt

    with torch.no_grad():
        images, labels = next(iter(test_loader))
        images = images[:20].to(device)
        recon = model(images)['recon']

    def denorm(t):
        return (t * std_t + mean_t).clamp(0, 1).cpu()

    n_show = min(10, len(images))
    fig, axes = plt.subplots(n_show, 3, figsize=(6, n_show * 2))
    for i in range(n_show):
        axes[i, 0].imshow(denorm(images[i:i+1])[0].permute(1, 2, 0).numpy())
        axes[i, 1].imshow(denorm(recon[i:i+1])[0].permute(1, 2, 0).numpy())
        diff = (denorm(images[i:i+1]) - denorm(recon[i:i+1])).abs() * 5
        axes[i, 2].imshow(diff.clamp(0, 1)[0].permute(1, 2, 0).numpy())
    axes[0, 0].set_title('Original', fontsize=8)
    axes[0, 1].set_title('Recon', fontsize=8)
    axes[0, 2].set_title('|Err|×5', fontsize=8)
    for ax in axes.flat:
        ax.axis('off')
    plt.tight_layout()
    plt.savefig('/content/svae_patch_recon.png', dpi=200, bbox_inches='tight')
    print(f"\n  Saved to /content/svae_patch_recon.png")
    try:
        plt.show()
    except:
        pass
    plt.close()

    # ── Final save ──
    save_checkpoint(os.path.join(save_dir, 'final.pt'),
                    epochs, all_recon_err.mean().item(), extra={'geo': geo_stats})

    writer.close()
    if hf_enabled:
        try:
            api.upload_folder(folder_path=tb_path,
                              path_in_repo=f"{hf_version}/tensorboard/{run_name}",
                              repo_id=hf_repo, repo_type="model")
        except:
            pass
    recon_grid_path = '/content/svae_patch_recon.png'
    if os.path.exists(recon_grid_path):
        upload_to_hf(recon_grid_path, 'recon_grid.png')

    print(f"\n  Best MSE: {best_recon:.6f}")
    print(f"  Checkpoints: {save_dir}/")
    print(f"  TensorBoard: {tb_path}")
    print(f"  HuggingFace: {hf_repo}/{hf_version}/")


if __name__ == "__main__":
    torch.set_float32_matmul_precision('high')

    # ImageNet-1K 256×256: 256 patches of 16×16, each (256, 16)
    # Latent: (16, 16, 16) = 4096 values — diffusion-ready
    train(epochs=20, lr=1e-4, V=256, D=16, patch_size=16,
          hidden=768, depth=4, batch_size=64,
          target_cv=0.2915, n_cross_layers=2,
          dataset='imagenet_256',
          hf_version='v13_imagenet256',
          save_every=1)