// Copyright (c) 2025 PaddlePaddle Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "helper.h"

__global__ void recover_decode_task(bool *stop_flags,
                                   int *seq_lens_this_time,
                                   int *seq_lens_encoder,
                                   int *seq_lens_decoder,
                                   int *step_seq_lens_decoder,
                                   int *block_tables,
                                   bool *is_block_step,
                                   const int bsz,
                                   const int block_num_per_seq,
                                   const int block_size) {
    int thread_idx = threadIdx.x;
    if (thread_idx < bsz) {
        if(is_block_step[thread_idx] == true) {
            int *block_table_now = block_tables + thread_idx * block_num_per_seq;
            if (block_table_now[step_seq_lens_decoder[thread_idx] / block_size] != -1) {
                    // can be recovered for decoding
                    is_block_step[thread_idx] = false;
                    seq_lens_this_time[thread_idx]= 1;
                    stop_flags[thread_idx] = false;
                    seq_lens_encoder[thread_idx] = 0;
                    seq_lens_decoder[thread_idx] = step_seq_lens_decoder[thread_idx];
                }
        }
    }
}

void RecoverDecodeTask(const paddle::Tensor &stop_flags,
                   const paddle::Tensor &seq_lens_this_time,
                   const paddle::Tensor &seq_lens_encoder,
                   const paddle::Tensor &seq_lens_decoder,
                   const paddle::Tensor &step_seq_lens_decoder,
                   const paddle::Tensor &block_tables,
                   const paddle::Tensor &is_block_step,
                   const int block_size) {
#ifdef PADDLE_WITH_CUSTOM_DEVICE
    auto dev_ctx = static_cast<const phi::CustomContext*>(paddle::experimental::DeviceContextPool::Instance().Get(seq_lens_this_time.place()));
    auto cu_stream = dev_ctx->stream();
#else
    auto cu_stream = seq_lens_this_time.stream();
#endif
    const int bsz = seq_lens_this_time.shape()[0];
    const int block_num_per_seq = block_tables.shape()[1];
    recover_decode_task<<<1, 1024, 0, cu_stream>>>(
        const_cast<bool *>(stop_flags.data<bool>()),
        const_cast<int *>(seq_lens_this_time.data<int>()),
        const_cast<int *>(seq_lens_encoder.data<int>()),
        const_cast<int *>(seq_lens_decoder.data<int>()),
        const_cast<int *>(step_seq_lens_decoder.data<int>()),
        const_cast<int *>(block_tables.data<int>()),
        const_cast<bool *>(is_block_step.data<bool>()),
        bsz,
        block_num_per_seq,
        block_size);
}

PD_BUILD_STATIC_OP(recover_decode_task)
    .Inputs({"stop_flags",
             "seq_lens_this_time",
             "seq_lens_encoder",
             "seq_lens_decoder",
             "step_seq_lens_decoder",
             "block_tables",
             "is_block_step"})
    .Attrs({"block_size: int"})
    .Outputs({"seq_lens_this_time_out",
              "seq_lens_encoder_out",
              "seq_lens_decoder_out",
              "stop_flags_out",
              "is_block_step_out"})
    .SetInplaceMap({{"seq_lens_this_time", "seq_lens_this_time_out"},
                    {"seq_lens_encoder", "seq_lens_encoder_out"},
                    {"seq_lens_decoder", "seq_lens_decoder_out"},
                    {"stop_flags", "stop_flags_out"},
                    {"is_block_step", "is_block_step_out"}})
    .SetKernelFn(PD_KERNEL(RecoverDecodeTask));