// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef LIB_FIDL_CPP_CODING_TRAITS_H_
#define LIB_FIDL_CPP_CODING_TRAITS_H_

#include <lib/stdcompat/optional.h>

#include <array>
#include <memory>

#include "lib/fidl/cpp/decoder.h"
#include "lib/fidl/cpp/encoder.h"
#include "lib/fidl/cpp/traits.h"
#include "lib/fidl/cpp/types.h"
#include "lib/fidl/cpp/vector.h"

namespace fidl {

// Used for handle rights and type checking during write and decode.
struct HandleInformation {
  zx_obj_type_t object_type;
  zx_rights_t rights;
};

template <typename T, class Enable = void>
struct CodingTraits;

template <typename T, class EncoderImpl = Encoder>
size_t EncodingInlineSize(EncoderImpl* encoder) {
  return CodingTraits<T>::kInlineSize;
}

template <typename T, class DecoderImpl = Decoder>
size_t DecodingInlineSize(DecoderImpl* decoder) {
  return CodingTraits<T>::kInlineSize;
}

template <typename T>
struct CodingTraits<T, typename std::enable_if<IsPrimitive<T>::value>::type> {
  static constexpr size_t kInlineSize = sizeof(T);
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, T* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    ZX_DEBUG_ASSERT(maybe_handle_info == cpp17::nullopt);
    *encoder->template GetPtr<T>(offset) = *value;
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, T* value, size_t offset) {
    *value = *decoder->template GetPtr<T>(offset);
  }
};

template <>
struct CodingTraits<bool> {
  static constexpr size_t kInlineSize = sizeof(bool);
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, bool* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    *encoder->template GetPtr<bool>(offset) = *value;
  }
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, std::vector<bool>::iterator value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    *encoder->template GetPtr<bool>(offset) = *value;
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, bool* value, size_t offset) {
    *value = *decoder->template GetPtr<bool>(offset);
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, std::vector<bool>::iterator value, size_t offset) {
    *value = *decoder->template GetPtr<bool>(offset);
  }
};

#ifdef __Fuchsia__
template <typename T>
struct CodingTraits<T, typename std::enable_if<std::is_base_of<zx::object_base, T>::value>::type> {
  static constexpr size_t kInlineSize = sizeof(zx_handle_t);
  static void Encode(Encoder* encoder, zx::object_base* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    ZX_ASSERT(maybe_handle_info);
    encoder->EncodeHandle(value, maybe_handle_info->object_type, maybe_handle_info->rights, offset);
  }
  static void Decode(Decoder* decoder, zx::object_base* value, size_t offset) {
    decoder->DecodeHandle(value, offset);
  }
};
#endif

template <typename T>
struct CodingTraits<std::unique_ptr<T>, typename std::enable_if<!IsFidlXUnion<T>::value>::type> {
  static constexpr size_t kInlineSize = sizeof(uintptr_t);
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, std::unique_ptr<T>* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    if (value->get()) {
      *encoder->template GetPtr<uintptr_t>(offset) = FIDL_ALLOC_PRESENT;

      size_t alloc_size = EncodingInlineSize<T>(encoder);
      CodingTraits<T>::Encode(encoder, value->get(), encoder->Alloc(alloc_size), maybe_handle_info);
    } else {
      *encoder->template GetPtr<uintptr_t>(offset) = FIDL_ALLOC_ABSENT;
    }
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, std::unique_ptr<T>* value, size_t offset) {
    uintptr_t ptr = *decoder->template GetPtr<uintptr_t>(offset);
    if (!ptr)
      return value->reset();
    *value = std::make_unique<T>();
    CodingTraits<T>::Decode(decoder, value->get(), decoder->GetOffset(ptr));
  }
};

template <class EncoderImpl>
void EncodeNullVector(EncoderImpl* encoder, size_t offset) {
  fidl_vector_t* vector = encoder->template GetPtr<fidl_vector_t>(offset);
  vector->count = 0u;
  vector->data = reinterpret_cast<void*>(FIDL_ALLOC_ABSENT);
}

template <class EncoderImpl>
void EncodeVectorPointer(EncoderImpl* encoder, size_t count, size_t offset) {
  fidl_vector_t* vector = encoder->template GetPtr<fidl_vector_t>(offset);
  vector->count = count;
  vector->data = reinterpret_cast<void*>(FIDL_ALLOC_PRESENT);
}

template <typename T>
struct CodingTraits<VectorPtr<T>> {
  static constexpr size_t kInlineSize = sizeof(fidl_vector_t);
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, VectorPtr<T>* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    if (!value->has_value())
      return EncodeNullVector(encoder, offset);
    std::vector<T>& vector = **value;
    CodingTraits<::std::vector<T>>::Encode(encoder, &vector, offset, maybe_handle_info);
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, VectorPtr<T>* value, size_t offset) {
    fidl_vector_t* encoded = decoder->template GetPtr<fidl_vector_t>(offset);
    if (!encoded->data) {
      *value = VectorPtr<T>();
      return;
    }
    std::vector<T> vector;
    CodingTraits<std::vector<T>>::Decode(decoder, &vector, offset);
    (*value) = std::move(vector);
  }
};

namespace internal {

template <bool Value>
class UseStdCopy {};

template <typename T, typename EncoderImpl>
void EncodeVectorBody(UseStdCopy<true>, EncoderImpl* encoder,
                      typename std::vector<T>::iterator in_begin,
                      typename std::vector<T>::iterator in_end, size_t out_offset,
                      cpp17::optional<HandleInformation> maybe_handle_info) {
  static_assert(CodingTraits<T>::kInlineSize == sizeof(T), "stride doesn't match object size");
  std::copy(in_begin, in_end, encoder->template GetPtr<T>(out_offset));
}

template <typename T, typename EncoderImpl>
void EncodeVectorBody(UseStdCopy<false>, EncoderImpl* encoder,
                      typename std::vector<T>::iterator in_begin,
                      typename std::vector<T>::iterator in_end, size_t out_offset,
                      cpp17::optional<HandleInformation> maybe_handle_info) {
  size_t stride = EncodingInlineSize<T>(encoder);
  for (typename std::vector<T>::iterator in_it = in_begin; in_it != in_end;
       in_it++, out_offset += stride) {
    CodingTraits<T>::Encode(encoder, &*in_it, out_offset, maybe_handle_info);
  }
}

template <typename T, typename DecoderImpl>
void DecodeVectorBody(UseStdCopy<true>, DecoderImpl* decoder, size_t in_begin_offset,
                      size_t in_end_offset, std::vector<T>* out, size_t count) {
  static_assert(CodingTraits<T>::kInlineSize == sizeof(T), "stride doesn't match object size");
  *out = std::vector<T>(decoder->template GetPtr<T>(in_begin_offset),
                        decoder->template GetPtr<T>(in_end_offset));
}

template <typename T, typename DecoderImpl>
void DecodeVectorBody(UseStdCopy<false>, DecoderImpl* decoder, size_t in_begin_offset,
                      size_t in_end_offset, std::vector<T>* out, size_t count) {
  out->resize(count);
  size_t stride = DecodingInlineSize<T>(decoder);
  size_t in_offset = in_begin_offset;
  typename std::vector<T>::iterator out_it = out->begin();
  for (; in_offset < in_end_offset; in_offset += stride, out_it++) {
    CodingTraits<T>::Decode(decoder, &*out_it, in_offset);
  }
}

}  // namespace internal

template <typename T>
struct CodingTraits<::std::vector<T>> {
  static constexpr size_t kInlineSize = sizeof(fidl_vector_t);
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, ::std::vector<T>* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    size_t count = value->size();
    EncodeVectorPointer(encoder, count, offset);
    size_t stride = EncodingInlineSize<T>(encoder);
    size_t base = encoder->Alloc(count * stride);
    internal::EncodeVectorBody<T>(internal::UseStdCopy<IsMemcpyCompatible<T>::value>(), encoder,
                                  value->begin(), value->end(), base, maybe_handle_info);
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, ::std::vector<T>* value, size_t offset) {
    fidl_vector_t* encoded = decoder->template GetPtr<fidl_vector_t>(offset);
    size_t stride = DecodingInlineSize<T>(decoder);
    size_t base = decoder->GetOffset(encoded->data);
    size_t count = encoded->count;
    internal::DecodeVectorBody<T>(internal::UseStdCopy<IsMemcpyCompatible<T>::value>(), decoder,
                                  base, base + stride * count, value, count);
  }
};

template <typename T, size_t N>
struct CodingTraits<::std::array<T, N>> {
  static constexpr size_t kInlineSize = CodingTraits<T>::kInlineSize * N;
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, std::array<T, N>* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    size_t stride;
    stride = EncodingInlineSize<T>(encoder);
    if (IsMemcpyCompatible<T>::value) {
      memcpy(encoder->template GetPtr<void>(offset), &value[0], N * stride);
      return;
    }
    for (size_t i = 0; i < N; ++i) {
      CodingTraits<T>::Encode(encoder, &value->at(i), offset + i * stride, maybe_handle_info);
    }
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, std::array<T, N>* value, size_t offset) {
    size_t stride = DecodingInlineSize<T>(decoder);
    if (IsMemcpyCompatible<T>::value) {
      memcpy(&value[0], decoder->template GetPtr<void>(offset), N * stride);
      return;
    }
    for (size_t i = 0; i < N; ++i) {
      CodingTraits<T>::Decode(decoder, &value->at(i), offset + i * stride);
    }
  }
};

template <class DecoderImpl>
void DecodeUnknownBytesContents(DecoderImpl* decoder, std::vector<uint8_t>* value, size_t offset) {
  memcpy(value->data(), decoder->template GetPtr<void>(offset), value->size());
}

template <class EncoderImpl>
void EncodeUnknownBytesContents(EncoderImpl* encoder, std::vector<uint8_t>* value, size_t offset) {
  std::copy(value->begin(), value->end(), encoder->template GetPtr<uint8_t>(offset));
}

template <class EncoderImpl>
void EncodeUnknownBytes(EncoderImpl* encoder, std::vector<uint8_t>* value, size_t envelope_offset) {
  fidl_envelope_t* envelope = encoder->template GetPtr<fidl_envelope_t>(envelope_offset);

  if (value->size() <= FIDL_ENVELOPE_INLINING_SIZE_THRESHOLD) {
    std::copy(value->begin(), value->end(), envelope->inline_value);
    envelope->num_handles = 0;
    envelope->flags = FIDL_ENVELOPE_FLAGS_INLINING_MASK;
    EncodeUnknownBytesContents(encoder, value, envelope_offset);
    return;
  }

  envelope->num_bytes = static_cast<uint32_t>(value->size());
  envelope->num_handles = 0;
  envelope->flags = 0;
  EncodeUnknownBytesContents(encoder, value, encoder->Alloc(value->size()));
}

#ifdef __Fuchsia__
template <class DecoderImpl>
void DecodeUnknownDataContents(DecoderImpl* decoder, UnknownData* value, size_t offset) {
  DecodeUnknownBytesContents(decoder, &value->bytes, offset);
  for (auto& h : value->handles) {
    h = decoder->ClaimUnknownHandle();
  }
}

template <class EncoderImpl>
void EncodeUnknownDataContents(EncoderImpl* encoder, UnknownData* value, size_t offset) {
  EncodeUnknownBytesContents(encoder, &value->bytes, offset);
  for (auto& handle : value->handles) {
    encoder->EncodeUnknownHandle(&handle);
  }
}

template <class EncoderImpl>
void EncodeUnknownData(EncoderImpl* encoder, UnknownData* value, size_t envelope_offset) {
  fidl_envelope_t* envelope = encoder->template GetPtr<fidl_envelope_t>(envelope_offset);

  if (value->bytes.size() <= FIDL_ENVELOPE_INLINING_SIZE_THRESHOLD) {
    memcpy(envelope->inline_value, value->bytes.data(), value->bytes.size());
    envelope->num_handles = static_cast<uint16_t>(value->handles.size());
    envelope->flags = FIDL_ENVELOPE_FLAGS_INLINING_MASK;
    EncodeUnknownDataContents(encoder, value, envelope_offset);
    return;
  }

  envelope->num_bytes = static_cast<uint32_t>(value->bytes.size());
  envelope->num_handles = static_cast<uint16_t>(value->handles.size());
  envelope->flags = 0;
  EncodeUnknownDataContents(encoder, value, encoder->Alloc(value->bytes.size()));
}
#endif

template <typename T, size_t InlineSizeV2>
struct EncodableCodingTraits {
  static constexpr size_t kInlineSize = InlineSizeV2;
  template <class EncoderImpl>
  static void Encode(EncoderImpl* encoder, T* value, size_t offset,
                     cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
    value->Encode(encoder, offset, maybe_handle_info);
  }
  template <class DecoderImpl>
  static void Decode(DecoderImpl* decoder, T* value, size_t offset) {
    T::Decode(decoder, value, offset);
  }
};

template <typename T, class EncoderImpl>
void Encode(EncoderImpl* encoder, T* value, size_t offset,
            cpp17::optional<HandleInformation> maybe_handle_info = cpp17::nullopt) {
  CodingTraits<T>::Encode(encoder, value, offset, maybe_handle_info);
}

template <typename T, class DecoderImpl>
void Decode(DecoderImpl* decoder, T* value, size_t offset) {
  CodingTraits<T>::Decode(decoder, value, offset);
}

template <typename T, class DecoderImpl>
T DecodeAs(DecoderImpl* decoder, size_t offset) {
  T value;
  Decode(decoder, &value, offset);
  return value;
}

}  // namespace fidl

#endif  // LIB_FIDL_CPP_CODING_TRAITS_H_