/* Copyright (c) 2018 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. */

#pragma once
#include <cmath>
#include <string>
#include "paddle/fluid/operators/math/jit_kernel_impl.h"
#include "paddle/fluid/platform/enforce.h"

namespace paddle {
namespace operators {
namespace math {
namespace jitkernel {
namespace refer {
/* Refer code only focus on correctness */

template <typename T>
void VMul(const T* x, const T* y, T* z, int n) {
  for (int i = 0; i < n; ++i) {
    z[i] = x[i] * y[i];
  }
}

template <typename T>
void VAdd(const T* x, const T* y, T* z, int n) {
  for (int i = 0; i < n; ++i) {
    z[i] = x[i] + y[i];
  }
}

template <typename T>
void VAddRelu(const T* x, const T* y, T* z, int n) {
  for (int i = 0; i < n; ++i) {
    z[i] = x[i] + y[i];
    z[i] = z[i] > 0 ? z[i] : 0;
  }
}

template <typename T>
void VScal(const T* a, const T* x, T* y, int n) {
  for (int i = 0; i < n; ++i) {
    y[i] = a[0] * x[i];
  }
}

template <typename T>
void VAddBias(const T* a, const T* x, T* y, int n) {
  for (int i = 0; i < n; ++i) {
    y[i] = a[0] + x[i];
  }
}

template <typename T>
void VRelu(const T* x, T* y, int n) {
  for (int i = 0; i < n; ++i) {
    y[i] = x[i] > 0 ? x[i] : 0;
  }
}

template <typename T>
inline void VIdentity(const T* x, T* y, int n) {}

template <typename T>
void VExp(const T* x, T* y, int n) {
  for (int i = 0; i < n; ++i) {
    y[i] = std::exp(x[i]);
  }
}

template <typename T>
void VSigmoid(const T* x, T* y, int n) {
  // y = 1 / (1 + e^-x)
  const T min = SIGMOID_THRESHOLD_MIN;
  const T max = SIGMOID_THRESHOLD_MAX;
  for (int i = 0; i < n; ++i) {
    T tmp = (x[i] < min) ? min : ((x[i] > max) ? max : x[i]);
    y[i] = static_cast<T>(1) / (static_cast<T>(1) + std::exp(-tmp));
  }
}

template <typename T>
void VTanh(const T* x, T* y, int n) {
  // y = 2 * sigmoid(2x) - 1
  for (int i = 0; i < n; ++i) {
    y[i] = static_cast<T>(2) * x[i];
  }
  VSigmoid(y, y, n);
  for (int i = 0; i < n; ++i) {
    y[i] = static_cast<T>(2) * y[i] - static_cast<T>(1);
  }
}

template <typename T>
void (*getActFunc(const std::string& type))(const T*, T*, int) {  // NOLINT
  if (type == "sigmoid") {
    return VSigmoid<T>;
  } else if (type == "relu") {
    return VRelu<T>;
  } else if (type == "tanh") {
    return VTanh<T>;
  } else if (type == "identity" || type == "") {
    return VIdentity<T>;
  }
  PADDLE_THROW("Not support type: %s", type);
  return nullptr;
}

template <typename T>
void LSTMCtHt(lstm_t* step, const lstm_attr_t* attr) {
  T* gates = reinterpret_cast<T*>(step->gates);
  const T* ct_1 = reinterpret_cast<const T*>(step->ct_1);
  T* ct = reinterpret_cast<T*>(step->ct);
  T* ht = reinterpret_cast<T*>(step->ht);
  const T* wp = reinterpret_cast<const T*>(step->wp);
  T* checked = reinterpret_cast<T*>(step->checked);
  auto act_gate = getActFunc<T>(attr->act_gate);
  auto act_cand = getActFunc<T>(attr->act_cand);
  auto act_cell = getActFunc<T>(attr->act_cell);
  int d = attr->d;
  int d2 = d * 2;
  int d3 = d * 3;
  // gates: W_ch, W_ih, W_fh, W_oh
  if (attr->use_peephole) {
    VMul(wp, ct_1, checked, d);
    VMul(wp + d, ct_1, checked + d, d);
    VAdd(checked, gates + d, gates + d, d2);
    act_gate(gates + d, gates + d, d2);
  } else {
    act_gate(gates + d, gates + d, d3);
  }

  // C_t = C_t-1 * fgated + cand_gated * igated
  act_cand(gates, gates, d);
  VMul(gates, gates + d, gates + d, d);
  VMul(ct_1, gates + d2, gates + d2, d);
  VAdd(gates + d, gates + d2, ct, d);

  if (attr->use_peephole) {
    // get ogated
    VMul(wp + d2, ct, gates + d, d);
    VAdd(gates + d, gates + d3, gates + d3, d);
    act_gate(gates + d3, gates + d3, d);
  }
  // H_t = act_cell(C_t) * ogated
  act_cell(ct, gates + d2, d);
  VMul(gates + d2, gates + d3, ht, d);
}

// compute c1 and h1 without c0 or h0
template <typename T>
void LSTMC1H1(lstm_t* step, const lstm_attr_t* attr) {
  T* gates = reinterpret_cast<T*>(step->gates);
  T* ct = reinterpret_cast<T*>(step->ct);
  T* ht = reinterpret_cast<T*>(step->ht);
  auto act_gate = getActFunc<T>(attr->act_gate);
  auto act_cand = getActFunc<T>(attr->act_cand);
  auto act_cell = getActFunc<T>(attr->act_cell);
  int d = attr->d;
  int d2 = d * 2;
  int d3 = d * 3;
  /* C_t = igated * cgated*/
  act_gate(gates + d, gates + d, d);
  act_cand(gates, gates, d);
  VMul(gates, gates + d, ct, d);
  if (attr->use_peephole) {
    // get outgated, put W_oc * C_t on igated
    const T* wp = reinterpret_cast<const T*>(step->wp);
    VMul(wp + d2, ct, gates + d, d);
    VAdd(gates + d, gates + d3, gates + d3, d);
  }
  /* H_t = act_cell(C_t) * ogated */
  act_gate(gates + d3, gates + d3, d);
  act_cell(ct, gates + d2, d);
  VMul(gates + d2, gates + d3, ht, d);
}

}  // namespace refer
}  // namespace jitkernel
}  // namespace math
}  // namespace operators
}  // namespace paddle