/*
 * Copyright (c) 2019-2023, NVIDIA CORPORATION.  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.
 */

#pragma once

#include <vector>

#include "src/fastertransformer/kernels/add_residual_kernels.h"
#include "src/fastertransformer/kernels/layernorm_kernels.h"
#include "src/fastertransformer/layers/BaseLayer.h"
#include "src/fastertransformer/layers/FfnLayer.h"
#include "src/fastertransformer/layers/attention_layers/DecoderCrossAttentionLayer.h"
#include "src/fastertransformer/layers/attention_layers/DecoderSelfAttentionLayer.h"
#include "src/fastertransformer/models/decoder/DecoderLayerWeight.h"
#include "src/fastertransformer/utils/Tensor.h"
#include "src/fastertransformer/utils/allocator.h"
#include "src/fastertransformer/utils/cublasMMWrapper.h"

namespace fastertransformer {

template<typename T>
class Decoder: public BaseLayer {
private:
    // buffer handling
    size_t max_batch_size_ = 0;
    // meta data
    size_t                 head_num_;
    size_t                 size_per_head_;
    size_t                 inter_size_;
    size_t                 num_layer_;
    size_t                 hidden_units_;
    static constexpr float layernorm_eps_ = 1e-6f;

    BaseAttentionLayer<T>* self_attention_layer_;
    BaseAttentionLayer<T>* cross_attention_layer_;
    FfnLayer<T>*           ffn_layer_;

    void allocateBuffer() override;
    void allocateBuffer(size_t batch_size);
    void freeBuffer() override;
    bool isValidBatchSize(size_t batch_size);

    void initialize();

protected:
    T* decoder_normed_input_     = nullptr;
    T* self_attn_output_         = nullptr;
    T* normed_self_attn_output_  = nullptr;
    T* cross_attn_output_        = nullptr;
    T* normed_cross_attn_output_ = nullptr;
    T* decoder_layer_output_     = nullptr;

public:
    Decoder(size_t           max_batch_size,
            size_t           head_num,
            size_t           size_per_head,
            size_t           inter_size,
            size_t           num_layer,
            cudaStream_t     stream,
            cublasMMWrapper* cublas_wrapper,
            IAllocator*      allocator,
            bool             is_free_buffer_after_forward);

    Decoder(Decoder<T> const& decoder);

    ~Decoder();

    void forward(std::vector<Tensor>*                      output_tensors,
                 const std::vector<Tensor>*                input_tensors,
                 const std::vector<DecoderLayerWeight<T>>* decoder_layer_weights);
};

}  // namespace fastertransformer
