# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
Based on:
Chen, L., Ye, Z., Wu, Y., Zhuo, D., Ceze, L., & Krishnamurthy, A. (2023). 
Punica: Multi-Tenant LoRA Serving. 
https://arxiv.org/abs/2310.18547
"""

import torch

from vllm.lora.ops.triton_ops.kernel_utils import do_shrink_kernel
from vllm.lora.ops.triton_ops.utils import _get_lora_a_ptr
from vllm.triton_utils import tl, triton
from vllm.utils import direct_register_custom_op


@triton.jit
def _lora_shrink_kernel(input_ptr, lora_ptr, out_ptr, M, N, K,
                        token_indices_sorted_by_lora_ids, num_tokens_per_lora,
                        lora_token_start_loc, lora_ids, scaling,
                        input_d0_stride, input_d1_stride, lora_d0_stride,
                        lora_d1_stride, lora_d2_stride, output_d0_stride,
                        output_d1_stride, output_d2_stride,
                        BLOCK_M: tl.constexpr, BLOCK_N: tl.constexpr,
                        BLOCK_K: tl.constexpr, EVEN_K: tl.constexpr,
                        SPLIT_K: tl.constexpr, SLICE_NUM: tl.constexpr):

    cta_n_num = tl.cdiv(N, BLOCK_N)
    cta_m_num = tl.cdiv(M, BLOCK_M)

    pid_sk_m_n = tl.program_id(axis=0)
    pid_sk = pid_sk_m_n % SPLIT_K
    pid_m = (pid_sk_m_n // SPLIT_K) % cta_m_num
    pid_n = pid_sk_m_n // (SPLIT_K * cta_m_num) % cta_n_num

    slice_id = tl.program_id(axis=1)
    lora_idx = tl.program_id(axis=2)

    lora_id = tl.load(lora_ids + lora_idx)
    if lora_id == -1:
        # Early exit for the no-lora case.
        return

    lora_m_size = tl.load(num_tokens_per_lora + lora_idx)

    cta_m_offset = pid_m * BLOCK_M
    if cta_m_offset >= lora_m_size:
        # Early exit CTA.
        return

    # num rows this CTA should process.
    cta_m_len = min(BLOCK_M, lora_m_size - cta_m_offset)

    # Identify all rows that this CTA should process.
    lora_m_indices_start = tl.load(lora_token_start_loc + lora_idx)
    cta_lora_seq_indices = (token_indices_sorted_by_lora_ids +
                            lora_m_indices_start + cta_m_offset)

    # Load all relevant row indices.
    offset_m = tl.arange(0, BLOCK_M) % cta_m_len
    ram = tl.load(cta_lora_seq_indices + offset_m)

    do_shrink_kernel(
        pid_n,
        pid_sk,
        slice_id,
        lora_id,
        input_ptr,
        lora_ptr,
        out_ptr,
        N,
        K,
        cta_m_len,
        ram,  # array identifying the rows of Input ptr to operate on
        # input strides
        input_d0_stride,
        input_d1_stride,
        # lora strides
        lora_d0_stride,
        lora_d1_stride,
        lora_d2_stride,
        # output strides
        output_d0_stride,
        output_d1_stride,
        output_d2_stride,
        scaling,
        BLOCK_M,
        BLOCK_N,
        BLOCK_K,
        EVEN_K,
        SPLIT_K,
        SLICE_NUM)


@torch.inference_mode()
def _lora_shrink(
    inputs: torch.Tensor,  #  shape [num_tokens, hidden_size]
    lora_a_weights: list[
        torch.Tensor],  # shape [num_loras, lora_rank, hidden_size]
    output_tensor: torch.Tensor,  # shape [num_slices, num_tokens, lora_rank]
    token_lora_mapping: torch.Tensor,  # shape [num_tokens]
    token_indices_sorted_by_lora_ids: torch.Tensor,  # shape [num_tokens] 
    num_tokens_per_lora: torch.Tensor,  # shape [max-loras + 1]
    lora_token_start_loc: torch.Tensor,  # shape [max-loras + 2]
    lora_ids: torch.Tensor,  # shape [max-loras + 1]
    no_lora_flag_cpu: torch.Tensor,  # shape [1]
    scaling: float,
) -> None:
    """
    Args:
        inputs (torch.Tensor): Input tensor
        lora_a_weights (list[torch.Tensor]): LoRA weights
        output_tensor (torch.Tensor): output tensor
        token_lora_mapping (torch.Tensor): A tensor mapping each input token
            to the lora-id related to that token. A value of -1 indicates that
            LoRA doesn't apply to that token.
        token_indices_sorted_by_lora_ids (torch.Tensor): Row/Token indices from
            the A matrix grouped by LoRA IDs.
        num_tokens_per_lora (torch.Tensor): num_tokens_per_lora[i] is the number
            of tokens that are to be processed by LoRA ID lora_ids[i] 
        lora_token_start_loc (torch.Tensor): A cumulative sum of
            num_tokens_per_lora. lora_token_start_loc[0] is always 0 so that
            lora_token_start_loc[i], along with num_tokens_per_lora[i]
            identifies the region in token_indices_sorted_by_lora_ids that
            LoRA lora_ids[i] should process.
        lora_ids (torch.Tensor): LoRA ids to process.
        no_lora_flag_cpu (torch.Tensor): A CPU tensor of size 1, that indicates
            if there are any requests that require LoRA.
        scaling (float): Scaling factor.
    """

    assert no_lora_flag_cpu.numel() == 1
    if no_lora_flag_cpu.item():
        # None of the inputs require LoRA.
        return

    assert inputs.dtype == lora_a_weights[0].dtype
    assert inputs.dtype in [torch.float16, torch.bfloat16]
    for weight in lora_a_weights:
        assert weight.dtype in [torch.float16, torch.bfloat16]

    assert inputs.size(1) == lora_a_weights[0].size(-1)
    assert inputs.is_contiguous()
    assert output_tensor.is_contiguous()

    # metadata sanity check
    M = inputs.size(0)
    assert token_lora_mapping.size(0) == M
    assert token_lora_mapping.size(0) == token_indices_sorted_by_lora_ids.size(
        0)
    assert lora_ids.size(0) == num_tokens_per_lora.size(0)
    assert lora_token_start_loc.size(0) == lora_ids.size(0) + 1

    (lora_ptr_tensor, lora_strides_d0, lora_strides_d1,
     lora_strides_d2) = _get_lora_a_ptr(lora_a_weights, inputs.device)
    N, K = lora_a_weights[0].shape[-2:]  # K=hidden_size,N=rank
    NUM_SLICES = len(lora_a_weights)
    MAX_LORAS = lora_ids.size(0)

    # Triton kernel configs
    BLOCK_M = 32
    BLOCK_N = 16
    BLOCK_K = 256 if M < 128 else 32
    SPLIT_K = 64 if M < 128 else 8
    NUM_WARPS = 4
    NUM_CTAS = 1
    NUM_STAGES = 2

    EVEN_K = K % (BLOCK_K * SPLIT_K) == 0  # type: ignore

    # TODO (varun): This grid formulation maximizes parallelization at the
    # cost of wasteful thread block launch when only few of the input tokens
    # require LoRA. This might not be the best in all cases.
    grid = (
        SPLIT_K * triton.cdiv(M, BLOCK_M) * triton.cdiv(N, BLOCK_N),
        NUM_SLICES,
        # Each LoRA receives its own set of thread blocks for output
        # computation. If some LoRA doesn't have any tokens to process, its
        # thread blocks exit early.
        MAX_LORAS,
    )

    _lora_shrink_kernel[grid](
        inputs,
        lora_ptr_tensor,
        output_tensor,
        M,
        N,
        K,
        token_indices_sorted_by_lora_ids,
        num_tokens_per_lora,
        lora_token_start_loc,
        lora_ids,
        scaling,
        inputs.stride(0),
        inputs.stride(1),
        lora_strides_d0,
        lora_strides_d1,
        lora_strides_d2,
        output_tensor.stride(0),
        output_tensor.stride(1),
        output_tensor.stride(2),
        BLOCK_M,
        BLOCK_N,
        BLOCK_K,
        EVEN_K,
        SPLIT_K,
        NUM_SLICES,
        num_warps=NUM_WARPS,
        num_ctas=NUM_CTAS,
        num_stages=NUM_STAGES,
    )

    return


def _lora_shrink_fake(
    inputs: torch.Tensor,
    lora_a_weights: list[torch.Tensor],
    output_tensor: torch.Tensor,
    token_lora_mapping: torch.Tensor,
    token_indices_sorted_by_lora_ids: torch.Tensor,
    num_tokens_per_lora: torch.Tensor,
    lora_token_start_loc: torch.Tensor,
    lora_ids: torch.Tensor,
    no_lora_flag_cpu: torch.Tensor,
    scaling: float,
) -> None:
    return


try:
    direct_register_custom_op(
        op_name="lora_shrink",
        op_func=_lora_shrink,
        mutates_args=["output_tensor"],
        fake_impl=_lora_shrink_fake,
    )
    lora_shrink = torch.ops.vllm.lora_shrink

except AttributeError:
    lora_shrink = _lora_shrink
