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"""KernelConfig-mappable drop-in forwards for Hugging Face Transformers ViT encoders.

``NeuronDINOv3ViTModel``  -> ``DINOv3ViTModel``   (all DINOv3 ViT sizes: S/S+/B/L/H+; 7B needs TP)
``NeuronVJEPA2Encoder``   -> ``VJEPA2Encoder``    (V-JEPA2 video encoder, up to 2048 tokens / clip)

Both run the whole transformer stack on the NKI kernels (``encoder.EncoderRunner``) and keep the
model's own patch embedding, RoPE position computation and final LayerNorm. Weights are folded
once, on the first device forward, from the stock module's parameters (checkpoint loading is
untouched) and cached on the module. Anything the kernels do not support (off-device input,
training mode, > 2048 tokens, unsupported head size) falls back to the stock forward.

Usage (graft, works on any Transformers version)::

    import types
    model.forward = types.MethodType(kernels.NeuronDINOv3ViTModel.forward, model)
    model = torch.compile(model, backend="neuron")

``torch.compile(backend="neuron")`` is part of the intended configuration; the classes set
``can_torch_compile = True`` so the ``kernels`` library keeps them under ``Mode.TORCH_COMPILE``.
"""
from __future__ import annotations

import torch

from .encoder import LNC, BlockWeights, EncoderRunner, pack_block, rope_tables

_PACK = "_vit_enc_neuron_packed"
_TABS = "_vit_enc_neuron_tabs"
_MAX_TOKENS = 2048


def _rup(n: int, m: int) -> int:
    return ((n + m - 1) // m) * m


def _supported(H: int, heads: int) -> bool:
    D = H // heads
    return H % 128 == 0 and D in (64, 128) and H == heads * D


def _stack(hs: torch.Tensor, N: int):
    B, n, H = hs.shape
    x = hs.float()
    if N > n:
        x = torch.cat([x, x.new_zeros(B, N - n, H)], 1)
    return x.reshape(B * N, H).contiguous()


# ------------------------------------------------------------------------------------------------
# DINOv3
# ------------------------------------------------------------------------------------------------
def _dinov3_layers(model):
    enc = getattr(model, "model", None)              # newer Transformers: model.model.layer
    return enc.layer if enc is not None and hasattr(enc, "layer") else model.layer


def _dinov3_block(lyr) -> BlockWeights:
    a = lyr.attention
    bw = BlockWeights(
        ln1_w=lyr.norm1.weight, ln1_b=lyr.norm1.bias, ln1_eps=lyr.norm1.eps,
        wq=a.q_proj.weight, bq=a.q_proj.bias, wk=a.k_proj.weight, bk=a.k_proj.bias,
        wv=a.v_proj.weight, bv=a.v_proj.bias, wo=a.o_proj.weight, bo=a.o_proj.bias,
        ln2_w=lyr.norm2.weight, ln2_b=lyr.norm2.bias, ln2_eps=lyr.norm2.eps,
        ls1=lyr.layer_scale1.lambda1, ls2=lyr.layer_scale2.lambda1, scale=float(a.scaling))
    m = lyr.mlp
    if hasattr(m, "gate_proj"):
        bw.gate_w, bw.gate_b = m.gate_proj.weight, m.gate_proj.bias
        bw.up_w, bw.up_b = m.up_proj.weight, m.up_proj.bias
        bw.down_w, bw.down_b = m.down_proj.weight, m.down_proj.bias
    else:
        bw.fc1_w, bw.fc1_b = m.up_proj.weight, m.up_proj.bias
        bw.fc2_w, bw.fc2_b = m.down_proj.weight, m.down_proj.bias
    return bw


def _dinov3_ok(model) -> bool:
    c = model.config
    if not _supported(c.hidden_size, c.num_attention_heads):
        return False
    if getattr(c, "use_gated_mlp", False):
        return getattr(c, "hidden_act", "silu") == "silu"
    return getattr(c, "hidden_act", "gelu") == "gelu"


@torch._dynamo.disable
def _dinov3_freeze(model):
    if model.training:
        raise RuntimeError("NeuronDINOv3ViTModel: these kernels have no autograd rule; call model.eval() first.")
    dev = model.norm.weight.device
    heads = model.config.num_attention_heads
    packed = [pack_block(_dinov3_block(l), heads, "half", dev) for l in _dinov3_layers(model)]
    setattr(model, _PACK, EncoderRunner(packed))
    setattr(model, _TABS, {})


@torch._dynamo.disable
def _dinov3_tab(model, pixel_values, n_prefix, N):
    key = (tuple(pixel_values.shape[-2:]), N)
    tabs = getattr(model, _TABS)
    if key not in tabs:
        cos, sin = model.rope_embeddings(pixel_values[:1].float())        # [n_patches, D] each
        c = model.config
        tabs[key] = rope_tables(cos, sin, n_prefix, N, c.num_attention_heads,
                                c.hidden_size // c.num_attention_heads, "half", model.norm.weight.device)
    return tabs[key]


class NeuronDINOv3ViTModel(torch.nn.Module):
    """Drop-in forward for ``transformers.DINOv3ViTModel`` (bf16 NKI encoder, fp32 residual stream).

    Returns ``last_hidden_state`` (final-normed, ``[B, 1 + registers + patches, H]``) and
    ``pooler_output`` (CLS), like the stock model. Any batch size; images up to 2048 tokens
    (e.g. 720x720 at patch 16).
    """

    can_torch_compile = True
    has_backward = False

    def forward(self, pixel_values, bool_masked_pos=None, head_mask=None, **kwargs):
        from transformers.modeling_outputs import BaseModelOutputWithPooling
        pv = pixel_values.to(self.embeddings.patch_embeddings.weight.dtype)
        hs = self.embeddings(pv, bool_masked_pos=bool_masked_pos)           # [B, n, H]
        B, n, H = hs.shape
        N = _rup(n, 128 * LNC)
        if (hs.device.type != "neuron" or self.training or head_mask is not None or N > _MAX_TOKENS
                or not _dinov3_ok(self)):
            import transformers.models.dinov3_vit.modeling_dinov3_vit as mv
            if head_mask is not None:
                kwargs["head_mask"] = head_mask
            return mv.DINOv3ViTModel.forward(self, pixel_values, bool_masked_pos=bool_masked_pos, **kwargs)
        if not hasattr(self, _PACK):
            _dinov3_freeze(self)
        n_prefix = 1 + self.config.num_register_tokens
        tab = _dinov3_tab(self, pixel_values, n_prefix, N)
        x = getattr(self, _PACK)(_stack(hs, N), tab, n, B)
        x = x.reshape(B, N, H)[:, :n]
        out = self.norm(x.to(self.norm.weight.dtype))
        return BaseModelOutputWithPooling(last_hidden_state=out, pooler_output=out[:, 0, :])


# ------------------------------------------------------------------------------------------------
# V-JEPA2
# ------------------------------------------------------------------------------------------------
def _vjepa2_block(lyr) -> BlockWeights:
    a = lyr.attention
    return BlockWeights(
        ln1_w=lyr.norm1.weight, ln1_b=lyr.norm1.bias, ln1_eps=lyr.norm1.eps,
        wq=a.query.weight, bq=a.query.bias, wk=a.key.weight, bk=a.key.bias,
        wv=a.value.weight, bv=a.value.bias, wo=a.proj.weight, bo=a.proj.bias,
        ln2_w=lyr.norm2.weight, ln2_b=lyr.norm2.bias, ln2_eps=lyr.norm2.eps,
        fc1_w=lyr.mlp.fc1.weight, fc1_b=lyr.mlp.fc1.bias, fc2_w=lyr.mlp.fc2.weight, fc2_b=lyr.mlp.fc2.bias,
        scale=float(a.scaling))


@torch._dynamo.disable
def _vjepa2_tab(encoder, N, n):
    """Signed-sin 3D RoPE tables from the model's own position ids (interleaved pairing)."""
    a = encoder.layer[0].attention
    H, D = a.all_head_size, a.attention_head_size
    dev = a.query.weight.device
    pos = a.get_position_ids(torch.zeros(1, n, H, device=dev), masks=None)
    to1d = lambda t: (t if t.dim() == 1 else t.reshape(-1, n)[0]).float().cpu()
    cos = torch.ones(n, D)
    sin = torch.zeros(n, D)
    s = 0
    for sub, p in zip((a.d_dim, a.h_dim, a.w_dim), (to1d(pos[0]), to1d(pos[1]), to1d(pos[2]))):
        half = sub // 2
        omega = 1.0 / (10000.0 ** (torch.arange(half, dtype=torch.float32) / float(half)))
        f = p[:, None] * omega
        c, sn = f.cos(), f.sin()
        cos[:, s:s + half] = c; cos[:, s + half:s + sub] = c
        sin[:, s:s + half] = sn; sin[:, s + half:s + sub] = sn
        s += sub
    g = torch.ones(D); g[0::2] = -1.0
    return rope_tables(cos, sin * g, 0, N, H // D, D, "interleaved", dev)


@torch._dynamo.disable
def _vjepa2_freeze(encoder):
    if encoder.training:
        raise RuntimeError("NeuronVJEPA2Encoder: these kernels have no autograd rule; call model.eval() first.")
    a = encoder.layer[0].attention
    dev = a.query.weight.device
    heads = a.all_head_size // a.attention_head_size
    setattr(encoder, _PACK, EncoderRunner([pack_block(_vjepa2_block(l), heads, "interleaved", dev)
                                           for l in encoder.layer]))
    setattr(encoder, _TABS, {})


class NeuronVJEPA2Encoder(torch.nn.Module):
    """Drop-in forward for ``transformers.VJEPA2Encoder``.

    Any batch size; clips up to 2048 tokens (e.g. 16 frames at 256 px, tubelet 2, patch 16).
    """

    can_torch_compile = True
    has_backward = False

    def forward(self, pixel_values_videos=None, head_mask=None, output_attentions=False,
                output_hidden_states=False, **kwargs):
        from transformers.modeling_outputs import BaseModelOutput
        hs = self.embeddings(pixel_values_videos)                           # [B, n, H]
        B, n, H = hs.shape
        N = _rup(n, 128 * LNC)
        a = self.layer[0].attention
        if (hs.device.type != "neuron" or self.training or head_mask is not None or output_attentions
                or output_hidden_states or N > _MAX_TOKENS
                or not _supported(H, a.all_head_size // a.attention_head_size)):
            import transformers.models.vjepa2.modeling_vjepa2 as mv
            return mv.VJEPA2Encoder.forward(self, pixel_values_videos, head_mask=head_mask,
                                            output_attentions=output_attentions,
                                            output_hidden_states=output_hidden_states, **kwargs)
        if not hasattr(self, _PACK):
            _vjepa2_freeze(self)
        tabs = getattr(self, _TABS)
        if N not in tabs:
            tabs[N] = _vjepa2_tab(self, N, n)
        x = getattr(self, _PACK)(_stack(hs, N), tabs[N], n, B)
        out = self.layernorm(x.reshape(B, N, H)[:, :n])
        return BaseModelOutput(last_hidden_state=out)