// Copyright 2015 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_TONIC_DART_ARGS_H_
#define LIB_TONIC_DART_ARGS_H_

#include <type_traits>
#include <utility>

#include "dart/runtime/include/dart_api.h"
#include "lib/tonic/converter/dart_converter.h"
#include "lib/tonic/dart_wrappable.h"

namespace tonic {

class DartArgIterator {
 public:
  DartArgIterator(Dart_NativeArguments args, int start_index = 1)
      : args_(args), index_(start_index), had_exception_(false) {}

  template <typename T>
  T GetNext() {
    if (had_exception_)
      return T();
    Dart_Handle exception = nullptr;
    T arg = DartConverter<T>::FromArguments(args_, index_++, exception);
    if (exception) {
      had_exception_ = true;
      Dart_ThrowException(exception);
    }
    return arg;
  }

  bool had_exception() const { return had_exception_; }

  Dart_NativeArguments args() const { return args_; }

 private:
  Dart_NativeArguments args_;
  int index_;
  bool had_exception_;

  FTL_DISALLOW_COPY_AND_ASSIGN(DartArgIterator);
};

// Classes for generating and storing an argument pack of integer indices
// (based on well-known "indices trick", see: http://goo.gl/bKKojn):
template <size_t... indices>
struct IndicesHolder {};

template <size_t requested_index, size_t... indices>
struct IndicesGenerator {
  using type = typename IndicesGenerator<requested_index - 1,
                                         requested_index - 1,
                                         indices...>::type;
};

template <size_t... indices>
struct IndicesGenerator<0, indices...> {
  using type = IndicesHolder<indices...>;
};

template <typename T>
class IndicesForSignature {};

template <typename ResultType, typename... ArgTypes>
struct IndicesForSignature<ResultType (*)(ArgTypes...)> {
  static const size_t count = sizeof...(ArgTypes);
  using type = typename IndicesGenerator<count>::type;
};

template <typename C, typename ResultType, typename... ArgTypes>
struct IndicesForSignature<ResultType (C::*)(ArgTypes...)> {
  static const size_t count = sizeof...(ArgTypes);
  using type = typename IndicesGenerator<count>::type;
};

template <size_t index, typename ArgType>
struct DartArgHolder {
  using ValueType = typename std::remove_const<
      typename std::remove_reference<ArgType>::type>::type;

  ValueType value;

  explicit DartArgHolder(DartArgIterator* it)
      : value(it->GetNext<ValueType>()) {}
};

template <typename T>
void DartReturn(T result, Dart_NativeArguments args) {
  DartConverter<T>::SetReturnValue(args, std::move(result));
}

template <typename IndicesType, typename T>
class DartDispatcher {};

template <size_t... indices, typename... ArgTypes>
struct DartDispatcher<IndicesHolder<indices...>, void (*)(ArgTypes...)>
    : public DartArgHolder<indices, ArgTypes>... {
  using FunctionPtr = void (*)(ArgTypes...);

  DartArgIterator* it_;

  explicit DartDispatcher(DartArgIterator* it)
      : DartArgHolder<indices, ArgTypes>(it)..., it_(it) {}

  void Dispatch(FunctionPtr func) {
    (*func)(DartArgHolder<indices, ArgTypes>::value...);
  }
};

template <size_t... indices, typename ResultType, typename... ArgTypes>
struct DartDispatcher<IndicesHolder<indices...>, ResultType (*)(ArgTypes...)>
    : public DartArgHolder<indices, ArgTypes>... {
  using FunctionPtr = ResultType (*)(ArgTypes...);

  DartArgIterator* it_;

  explicit DartDispatcher(DartArgIterator* it)
      : DartArgHolder<indices, ArgTypes>(it)..., it_(it) {}

  void Dispatch(FunctionPtr func) {
    DartReturn((*func)(DartArgHolder<indices, ArgTypes>::value...),
               it_->args());
  }

  ResultType DispatchCtor(FunctionPtr func) {
    return (*func)(DartArgHolder<indices, ArgTypes>::value...);
  }
};

template <size_t... indices, typename C, typename... ArgTypes>
struct DartDispatcher<IndicesHolder<indices...>, void (C::*)(ArgTypes...)>
    : public DartArgHolder<indices, ArgTypes>... {
  using FunctionPtr = void (C::*)(ArgTypes...);

  DartArgIterator* it_;

  explicit DartDispatcher(DartArgIterator* it)
      : DartArgHolder<indices, ArgTypes>(it)..., it_(it) {}

  void Dispatch(FunctionPtr func) {
    (GetReceiver<C>(it_->args())->*func)(
        DartArgHolder<indices, ArgTypes>::value...);
  }
};

template <size_t... indices,
          typename C,
          typename ResultType,
          typename... ArgTypes>
struct DartDispatcher<IndicesHolder<indices...>, ResultType (C::*)(ArgTypes...)>
    : public DartArgHolder<indices, ArgTypes>... {
  using FunctionPtr = ResultType (C::*)(ArgTypes...);

  DartArgIterator* it_;

  explicit DartDispatcher(DartArgIterator* it)
      : DartArgHolder<indices, ArgTypes>(it)..., it_(it) {}

  void Dispatch(FunctionPtr func) {
    DartReturn((GetReceiver<C>(it_->args())->*func)(
                   DartArgHolder<indices, ArgTypes>::value...),
               it_->args());
  }
};

template <typename Sig>
void DartCall(Sig func, Dart_NativeArguments args) {
  DartArgIterator it(args);
  using Indices = typename IndicesForSignature<Sig>::type;
  DartDispatcher<Indices, Sig> decoder(&it);
  if (it.had_exception())
    return;
  decoder.Dispatch(func);
}

template <typename Sig>
void DartCallStatic(Sig func, Dart_NativeArguments args) {
  DartArgIterator it(args, 0);
  using Indices = typename IndicesForSignature<Sig>::type;
  DartDispatcher<Indices, Sig> decoder(&it);
  if (it.had_exception())
    return;
  decoder.Dispatch(func);
}

template <typename Sig>
void DartCallConstructor(Sig func, Dart_NativeArguments args) {
  DartArgIterator it(args);
  using Indices = typename IndicesForSignature<Sig>::type;
  DartDispatcher<Indices, Sig> decoder(&it);
  if (it.had_exception())
    return;
  decoder.DispatchCtor(func)->AssociateWithDartWrapper(args);
}

}  // namespace tonic

#endif  // LIB_TONIC_DART_ARGS_H_