# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
# SPDX-FileCopyrightText: Songlin Yang, Yu Zhang
#
# This file contains code copied from the flash-linear-attention project.
# The original source code was licensed under the MIT license and included
# the following copyright notice:
# Copyright (c) 2023-2025, Songlin Yang, Yu Zhang
# ruff: noqa: E501
import warnings
from typing import Optional

import cocopod  # noqa
import torch
import torch.nn.functional as F
from einops import rearrange

from .index import prepare_chunk_indices, prepare_chunk_offsets
from .l2norm import l2norm_fwd
from .utils import SUPPRESS_LEVEL, input_guard


def torch_solve_tril(
    A: torch.Tensor,
    cu_seqlens: Optional[torch.LongTensor] = None,
    output_dtype: torch.dtype = torch.float,
):
    chunk_size = 64
    A = -A.transpose(1, 2)
    sequence_length = A.shape[-2]
    pad_size = (chunk_size - sequence_length % chunk_size) % chunk_size
    A = F.pad(A, (0, 0, 0, pad_size))
    A = A.reshape(A.shape[0], A.shape[1], -1, chunk_size, A.shape[-1])
    # mask = torch.triu(torch.ones(chunk_size, chunk_size, dtype=torch.bool, device=A.device), diagonal=0)

    # A = A.masked_fill(mask, 0)
    for i in range(1, chunk_size):
        row = A[..., i, :i].clone()
        sub = A[..., :i, :i].clone()
        A[..., i, :i] = row + (row.unsqueeze(-1) * sub).sum(-2)
    A = A + torch.eye(chunk_size, dtype=A.dtype, device=A.device)
    return A.reshape(A.shape[0], A.shape[1], -1, A.shape[-1])[
        :, :, :sequence_length, :
    ].transpose(1, 2)


def recompute_w_u_fwd_torch(
    k: torch.Tensor,  # [B, T, H, K]
    v: torch.Tensor,  # [B, T, H, V]
    beta: torch.Tensor,  # [B, T, H]
    g: torch.Tensor,  # [B, T, H]
    A: torch.Tensor,  # [B, H, T, T]
):
    """
    最简单版本：假设等长序列，key和value头数相同
    """
    chunk_size = 64
    num_v_heads, num_k_heads = v.shape[2], k.shape[2]
    k = k.repeat_interleave(num_v_heads // num_k_heads, dim=2)
    k, v, beta, g, A = [
        x.transpose(1, 2).contiguous().to(torch.float32) for x in (k, v, beta, g, A)
    ]

    batch_size, num_heads, sequence_length, k_head_dim = k.shape
    pad_size = (chunk_size - sequence_length % chunk_size) % chunk_size
    k = F.pad(k, (0, 0, 0, pad_size))
    v = F.pad(v, (0, 0, 0, pad_size))
    beta = F.pad(beta, (0, pad_size))
    g = F.pad(g, (0, pad_size))
    A = F.pad(A, (0, 0, 0, pad_size))
    A = A.reshape(A.shape[0], A.shape[1], -1, chunk_size, A.shape[-1])

    v_beta = v * beta.unsqueeze(-1)
    k_beta = k * beta.unsqueeze(-1)

    k, v, k_beta, v_beta = [
        x.reshape(x.shape[0], x.shape[1], -1, chunk_size, x.shape[-1])
        for x in (k, v, k_beta, v_beta)
    ]
    g = g.reshape(g.shape[0], g.shape[1], -1, chunk_size)

    u = A @ v_beta
    w = A @ (k_beta * g.exp().unsqueeze(-1))
    w = (
        w.reshape(w.shape[0], w.shape[1], -1, w.shape[-1])[:, :, :sequence_length, :]
        .transpose(1, 2)
        .contiguous()
    )
    u = (
        u.reshape(u.shape[0], u.shape[1], -1, u.shape[-1])[:, :, :sequence_length, :]
        .transpose(1, 2)
        .contiguous()
    )

    return w, u


def split_by_value(tensor, chunk_size=64):
    indices = tensor.tolist()
    result = set(indices)  # 使用集合避免重复

    for i in range(len(indices) - 1):
        start = indices[i]
        end = indices[i + 1]

        # 计算第一个对齐边界
        # 我们要找的是 start + n*chunk_size，其中n是使结果大于start的最小整数
        first_boundary = start + chunk_size

        # 在(start, end)范围内插入所有对齐边界
        boundary = first_boundary
        while boundary < end:
            result.add(boundary)
            boundary += chunk_size

    return torch.tensor(sorted(result), dtype=tensor.dtype, device=tensor.device)


def chunk_gated_delta_rule_fwd(
    q: torch.Tensor,
    k: torch.Tensor,
    v: torch.Tensor,
    g: torch.Tensor,
    beta: torch.Tensor,
    scale: float,
    initial_state: torch.Tensor,
    output_final_state: bool,
    cu_seqlens: Optional[torch.LongTensor] = None,
):
    chunk_size = 64
    chunk_indices = (
        prepare_chunk_indices(cu_seqlens, 64) if cu_seqlens is not None else None
    )
    chunk_offsets = (
        prepare_chunk_offsets(cu_seqlens, chunk_size)
        if cu_seqlens is not None
        else None
    )

    # !
    # g = chunk_local_cumsum(g, chunk_size=64, cu_seqlens=cu_seqlens)
    g = torch.ops.xspeedgate_ops.chunk_local_cumsum(
        g,
        chunk_size=64,
        reverse=False,
        cu_seqlens=cu_seqlens,
        chunk_indices=chunk_indices,
        head_first=False,
    )

    # !
    # A = chunk_scaled_dot_kkt_fwd(k=k,
    #                              beta=beta,
    #                              g_cumsum=g,
    #                              cu_seqlens=cu_seqlens,
    #                              output_dtype=q.dtype)
    A = torch.ops.xspeedgate_ops.chunk_scaled_dot_kkt_fwd(
        k, beta, g, cu_seqlens, chunk_indices, chunk_size
    )

    # torch版
    # if get_tensor_model_parallel_rank() == 0:
    #     torch.save(A, "A_in")
    #     torch.save(cu_seqlens, "cu_seqlens")
    # A2 = A.clone()
    torch.ops.xspeedgate_ops.solve_tril_ns(A, cu_seqlens, chunk_indices, chunk_size)

    # !
    # torch.ops.xspeedgate_ops.solve_tril_fwd(A, cu_seqlens)
    # if get_tensor_model_parallel_rank() == 0:
    #     err = torch.max(torch.abs(A - A2))
    #     print("err", err)
    #     if err > 1e-3:
    #         raise
    # A = solve_tril(A=A, cu_seqlens=cu_seqlens, output_dtype=k.dtype)
    # for i in range(len(cu_seqlens)-1):
    #     A_i = A[:, cu_seqlens[i]:cu_seqlens[i+1], :, :]
    #     A[:, cu_seqlens[i]:cu_seqlens[i+1], :, :] = torch_solve_tril(A=A_i, cu_seqlens=torch.tensor([0, cu_seqlens[i+1]-cu_seqlens[i]], device=q.device), output_dtype=k.dtype)

    """
    B, T, Hg, K, V = *k.shape, v.shape[-1]
    H = v.shape[-2]
    u = torch.empty_like(v)
    w = k.new_empty(B, T, H, K)
    for i in range(len(cu_seqlens)-1):
        k_i = k[:, cu_seqlens[i]:cu_seqlens[i+1], :, :]
        v_i = v[:, cu_seqlens[i]:cu_seqlens[i+1], :, :]
        beta_i = beta[:, cu_seqlens[i]:cu_seqlens[i+1], :]
        A_i = A[:, cu_seqlens[i]:cu_seqlens[i+1], :, :]
        g_i = g[:, cu_seqlens[i]:cu_seqlens[i+1], :]

        w_i, u_i = recompute_w_u_fwd_torch(
            k=k_i,
            v=v_i,
            beta=beta_i,
            A=A_i,
            g=g_i,
        )
        w[:, cu_seqlens[i]:cu_seqlens[i+1], :, :] = w_i
        u[:, cu_seqlens[i]:cu_seqlens[i+1], :, :] = u_i
    """
    w, u = torch.ops.xspeedgate_ops.recompute_w_u_fwd(
        k=k,
        v=v,
        beta=beta,
        A=A,
        g_cumsum=g,
        cu_seqlens=cu_seqlens,
        chunk_indices=chunk_indices,
        chunk_size=64,
    )
    """
    w, u = recompute_w_u_fwd(
        k=k,
        v=v,
        beta=beta,
        A=A,
        g_cumsum=g,
        cu_seqlens=cu_seqlens,
    )
    """

    # i
    # import os
    # if not os.path.exists("/qwen-next/in"):
    #     os.makedirs("/qwen-next/in")
    #     torch.save(k, "/qwen-next/in/k.pt")
    #     torch.save(u, "/qwen-next/in/u.pt")
    #     torch.save(w, "/qwen-next/in/w.pt")
    #     torch.save(g, "/qwen-next/in/g.pt")
    #     torch.save(initial_state, "/qwen-next/in/initial_state.pt")
    #     torch.save(cu_seqlens, "/qwen-next/in/cu_seqlens.pt")
    #     torch.save(chunk_indices, "/qwen-next/in/chunk_indices.pt")
    #     torch.save(chunk_offsets.to(torch.int32), "/qwen-next/in/chunk_offsets.pt")
    #     torch.save(chunk_size, "/qwen-next/in/chunk_size.pt")
    #     torch.save(output_final_state, "/qwen-next/in/output_final_state.pt")

    h, v_new, final_state = torch.ops.xspeedgate_ops.chunk_gated_delta_rule_fwd_h(
        k,
        u,
        w,
        g,
        initial_state,
        cu_seqlens,
        chunk_indices,
        chunk_offsets.to(torch.int32),
        chunk_size,
        output_final_state,
        True,
    )

    # h, v_new, final_state = chunk_gated_delta_rule_fwd_h(
    #     k=k,
    #     w=w,
    #     u=u,
    #     g=g,
    #     initial_state=initial_state,
    #     output_final_state=output_final_state,
    #     cu_seqlens=cu_seqlens,
    # )
    # if not os.path.exists("/qwen-next/out"):
    #     os.makedirs("/qwen-next/out")
    #     torch.save(h, "/qwen-next/out/h.pt")
    #     torch.save(v_new, "/qwen-next/out/v_new.pt")
    #     torch.save(final_state, "/qwen-next/out/final_state.pt")

    o = torch.ops.xspeedgate_ops.chunk_fwd_o(
        q=q,
        k=k,
        v=v_new,
        h=h,
        g=g,
        scale=scale,
        cu_seqlens=cu_seqlens,
        chunk_indices=chunk_indices,
        chunk_size=64,
    )
    """
    o = chunk_fwd_o(
        q=q,
        k=k,
        v=v_new,
        h=h,
        g=g,
        scale=scale,
        cu_seqlens=cu_seqlens,
    )
    """
    if SUPPRESS_LEVEL < 3:
        return g, o, A, final_state, None, None, None
    elif SUPPRESS_LEVEL >= 3:
        return g, o, A, final_state, w, h, v_new


class ChunkGatedDeltaRuleFunction(torch.autograd.Function):

    @staticmethod
    @input_guard
    @torch.amp.custom_fwd(device_type="cuda")
    def forward(
        ctx,
        q: torch.Tensor,
        k: torch.Tensor,
        v: torch.Tensor,
        g: torch.Tensor,
        beta: torch.Tensor,
        scale: float,
        initial_state: torch.Tensor,
        output_final_state: bool,
        cu_seqlens: Optional[torch.LongTensor] = None,
        use_qk_l2norm_in_kernel: bool = False,
    ):
        if use_qk_l2norm_in_kernel:
            q = l2norm_fwd(q)
            k = l2norm_fwd(k)

        g, o, A, final_state, w, h, v_new = chunk_gated_delta_rule_fwd(
            q=q,
            k=k,
            v=v,
            g=g,
            beta=beta,
            scale=scale,
            initial_state=initial_state,
            output_final_state=output_final_state,
            cu_seqlens=cu_seqlens,
        )
        ctx.scale = scale
        ctx.use_qk_l2norm_in_kernel = use_qk_l2norm_in_kernel
        return o.to(q.dtype), final_state


@torch.compiler.disable
def chunk_gated_delta_rule(
    q: torch.Tensor,
    k: torch.Tensor,
    v: torch.Tensor,
    g: torch.Tensor,
    beta: torch.Tensor,
    scale: float = None,
    initial_state: torch.Tensor = None,
    output_final_state: bool = False,
    cu_seqlens: Optional[torch.LongTensor] = None,
    head_first: bool = False,
    use_qk_l2norm_in_kernel: bool = False,
):
    r"""
    Args:
        q (torch.Tensor):
            queries of shape `[B, T, H, K]` if `head_first=False` else `[B, H, T, K]`.
        k (torch.Tensor):
            keys of shape `[B, T, H, K]` if `head_first=False` else `[B, H, T, K]`.
        v (torch.Tensor):
            values of shape `[B, T, H, V]` if `head_first=False` else `[B, H, T, V]`.
        g (torch.Tensor):
            (forget) gating tensor (in log space!) of shape `[B, T, H]` if `head_first=False` else `[B, H, T]`.
        beta (torch.Tensor):
            betas of shape `[B, T, H]` if `head_first=False` else `[B, H, T]`.
        scale (Optional[int]):
            Scale factor for the RetNet attention scores.
            If not provided, it will default to `1 / sqrt(K)`. Default: `None`.
        initial_state (Optional[torch.Tensor]):
            Initial state of shape `[N, H, K, V]` for `N` input sequences.
            For equal-length input sequences, `N` equals the batch size `B`.
            Default: `None`.
        output_final_state (Optional[bool]):
            Whether to output the final state of shape `[N, H, K, V]`. Default: `False`.
        cu_seqlens (torch.LongTensor):
            Cumulative sequence lengths of shape `[N+1]` used for variable-length training,
            consistent with the FlashAttention API.
        head_first (Optional[bool]):
            Whether the inputs are in the head-first format, which is not supported for variable-length inputs.
            Default: `False`.

    Returns:
        o (torch.Tensor):
            Outputs of shape `[B, T, H, V]` if `head_first=False` else `[B, H, T, V]`.
        final_state (torch.Tensor):
            Final state of shape `[N, H, K, V]` if `output_final_state=True` else `None`.

    Examples::
        >>> import torch
        >>> import torch.nn.functional as F
        >>> from einops import rearrange
        >>> from fla.ops.gated_delta_rule import chunk_gated_delta_rule
        # inputs with equal lengths
        >>> B, T, H, K, V = 4, 2048, 4, 512, 512
        >>> q = torch.randn(B, T, H, K, dtype=torch.bfloat16, device='cuda')
        >>> k = F.normalize(torch.randn(B, T, H, K, dtype=torch.bfloat16, device='cuda'), p=2, dim=-1)
        >>> v = torch.randn(B, T, H, V, dtype=torch.bfloat16, device='cuda')
        >>> beta = torch.rand(B, T, H, dtype=torch.bfloat16, device='cuda').sigmoid()
        >>> g = F.logsigmoid(torch.rand(B, T, H, dtype=torch.bfloat16, device='cuda'))
        >>> h0 = torch.randn(B, H, K, V, dtype=torch.bfloat16, device='cuda')
        >>> o, ht = chunk_gated_delta_rule(
            q, k, v, g, beta,
            initial_state=h0,
            output_final_state=True
        )
        # for variable-length inputs, the batch size `B` is expected to be 1 and `cu_seqlens` is required
        >>> q, k, v, beta, g = map(lambda x: rearrange(x, 'b t ... -> 1 (b t) ...'), (q, k, v, beta, g))
        # for a batch with 4 sequences, `cu_seqlens` with 5 start/end positions are expected
        >>> cu_seqlens = q.new_tensor([0, 2048, 4096, 6144, 8192], dtype=torch.long)
        >>> o_var, ht_var = chunk_gated_delta_rule(
            q, k, v, g, beta,
            initial_state=h0,
            output_final_state=True,
            cu_seqlens=cu_seqlens
        )
    """
    assert q.dtype == k.dtype == v.dtype
    assert (
        q.dtype != torch.float32
    ), "ChunkGatedDeltaRuleFunction does not support float32. Please use bfloat16."
    assert (
        len(beta.shape) == 3
    ), "beta must be of shape [B, T, H] if head_first=False, or [B, H, T] otherwise."

    if head_first:
        raise DeprecationWarning(
            "head_first is deprecated and will be removed in a future version. "
            "Please use head_first=False for now instead.",
            stacklevel=2,
        )
        q, k, v, beta, g = map(
            lambda x: rearrange(x, "b h t ... -> b t h ..."), (q, k, v, beta, g)
        )
    if not head_first and q.shape[1] < q.shape[2]:
        warnings.warn(
            f"Input tensor shape suggests potential format mismatch: seq_len ({q.shape[1]}) < num_heads ({q.shape[2]}). "
            "This may indicate the inputs were passed in head-first format [B, H, T, ...] "
            "when head_first=False was specified. "
            "Please verify your input tensor format matches the expected shape [B, T, H, ...].",
            stacklevel=2,
        )
    if cu_seqlens is not None:
        if q.shape[0] != 1:
            raise ValueError(
                f"The batch size is expected to be 1 rather than {q.shape[0]} when using `cu_seqlens`."
                f"Please flatten variable-length inputs before processing."
            )
        if initial_state is not None and initial_state.shape[0] != len(cu_seqlens) - 1:
            raise ValueError(
                f"The number of initial states is expected to be equal to the number of input sequences, "
                f"i.e., {len(cu_seqlens) - 1} rather than {initial_state.shape[0]}."
            )
    if scale is None:
        scale = k.shape[-1] ** -0.5

    if False:
        q = q.contiguous()
        k = k.contiguous()
        v = v.contiguous()
        g = g.contiguous()
        beta = beta.contiguous()
        initial_state = initial_state.contiguous()

        o = torch.empty_like(v)
        final_state = torch.empty_like(initial_state)
        import kunlun_ops

        kunlun_ops.gated_delta_rule(
            q,
            k,
            v,
            initial_state,
            g,
            beta,
            final_state,
            o,
            scale,
            cu_seqlens.cpu(),
            cu_seqlens,
            cu_seqlens.cpu(),
            cu_seqlens,
            use_qk_l2norm_in_kernel=True,
        )
    else:
        o, final_state = ChunkGatedDeltaRuleFunction.apply(
            q,
            k,
            v,
            g,
            beta,
            scale,
            initial_state,
            output_final_state,
            cu_seqlens,
            use_qk_l2norm_in_kernel,
        )
    if head_first:
        o = rearrange(o, "b t h ... -> b h t ...")
    return o, final_state