# -*- coding: utf-8 -*-
# Copyright (c) 2023-2025, Songlin Yang, Yu Zhang

from typing import Optional, Tuple

import torch

from fla.ops.simple_gla.fused_recurrent import fused_recurrent_simple_gla


def fused_recurrent_retention(
    q: torch.Tensor,
    k: torch.Tensor,
    v: torch.Tensor,
    scale: Optional[float] = None,
    initial_state: Optional[torch.Tensor] = None,
    output_final_state: bool = False,
    reverse: bool = False,
    cu_seqlens: Optional[torch.LongTensor] = None,
    head_first: bool = True
) -> Tuple[torch.Tensor, torch.Tensor]:
    if head_first:
        n_heads = q.shape[1]
    else:
        n_heads = q.shape[2]
    s = (1 - q.new_tensor(2., dtype=torch.float).pow(-5. - q.new_tensor(range(n_heads), dtype=torch.float))).log()
    if head_first:
        g = s[None, :, None].expand(q.shape[0], q.shape[1], q.shape[2]).contiguous()
    else:
        g = s[None, None, :].expand(q.shape[0], q.shape[1], q.shape[2]).contiguous()
    return fused_recurrent_simple_gla(
        q=q,
        k=k,
        v=v,
        g=g,
        scale=scale,
        initial_state=initial_state,
        output_final_state=output_final_state,
        reverse=reverse,
        cu_seqlens=cu_seqlens,
        head_first=head_first
    )