/* SPDX-License-Identifier: GPL-2.0-or-later */

#pragma once

/** \file
 * \ingroup fn
 *
 * This file provides an Params and ParamsBuilder structure.
 *
 * `ParamsBuilder` is used by a function caller to be prepare all parameters that are passed into
 * the function. `Params` is then used inside the called function to access the parameters.
 */

#include <mutex>
#include <variant>

#include "BLI_generic_pointer.hh"
#include "BLI_generic_vector_array.hh"
#include "BLI_generic_virtual_vector_array.hh"
#include "BLI_resource_scope.hh"

#include "FN_multi_function_signature.hh"

namespace blender::fn::multi_function {

class ParamsBuilder {
 private:
  std::unique_ptr<ResourceScope> scope_;
  const Signature *signature_;
  IndexMask mask_;
  int64_t min_array_size_;
  Vector<std::variant<GVArray, GMutableSpan, const GVVectorArray *, GVectorArray *>>
      actual_params_;

  friend class Params;

  ParamsBuilder(const Signature &signature, const IndexMask mask)
      : signature_(&signature), mask_(mask), min_array_size_(mask.min_array_size())
  {
    actual_params_.reserve(signature.params.size());
  }

 public:
  ParamsBuilder(const class MultiFunction &fn, int64_t size);
  /**
   * The indices referenced by the #mask has to live longer than the params builder. This is
   * because the it might have to destruct elements for all masked indices in the end.
   */
  ParamsBuilder(const class MultiFunction &fn, const IndexMask *mask);

  template<typename T> void add_readonly_single_input_value(T value, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForSingleInput(CPPType::get<T>()), expected_name);
    actual_params_.append_unchecked_as(std::in_place_type<GVArray>,
                                       varray_tag::single{},
                                       CPPType::get<T>(),
                                       min_array_size_,
                                       &value);
  }
  template<typename T> void add_readonly_single_input(const T *value, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForSingleInput(CPPType::get<T>()), expected_name);
    actual_params_.append_unchecked_as(std::in_place_type<GVArray>,
                                       varray_tag::single_ref{},
                                       CPPType::get<T>(),
                                       min_array_size_,
                                       value);
  }
  void add_readonly_single_input(const GSpan span, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForSingleInput(span.type()), expected_name);
    BLI_assert(span.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<GVArray>, varray_tag::span{}, span);
  }
  void add_readonly_single_input(GPointer value, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForSingleInput(*value.type()), expected_name);
    actual_params_.append_unchecked_as(std::in_place_type<GVArray>,
                                       varray_tag::single_ref{},
                                       *value.type(),
                                       min_array_size_,
                                       value.get());
  }
  void add_readonly_single_input(GVArray varray, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForSingleInput(varray.type()), expected_name);
    BLI_assert(varray.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<GVArray>, std::move(varray));
  }

  void add_readonly_vector_input(const GVectorArray &vector_array, StringRef expected_name = "")
  {
    this->add_readonly_vector_input(
        this->resource_scope().construct<GVVectorArray_For_GVectorArray>(vector_array),
        expected_name);
  }
  void add_readonly_vector_input(const GSpan single_vector, StringRef expected_name = "")
  {
    this->add_readonly_vector_input(
        this->resource_scope().construct<GVVectorArray_For_SingleGSpan>(single_vector,
                                                                        min_array_size_),
        expected_name);
  }
  void add_readonly_vector_input(const GVVectorArray &ref, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForVectorInput(ref.type()), expected_name);
    BLI_assert(ref.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<const GVVectorArray *>, &ref);
  }

  template<typename T> void add_uninitialized_single_output(T *value, StringRef expected_name = "")
  {
    this->add_uninitialized_single_output(GMutableSpan(CPPType::get<T>(), value, 1),
                                          expected_name);
  }
  void add_uninitialized_single_output(GMutableSpan ref, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForSingleOutput(ref.type()), expected_name);
    BLI_assert(ref.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<GMutableSpan>, ref);
  }
  void add_ignored_single_output(StringRef expected_name = "")
  {
    this->assert_current_param_name(expected_name);
    const int param_index = this->current_param_index();
    const ParamType &param_type = signature_->params[param_index].type;
    BLI_assert(param_type.category() == ParamCategory::SingleOutput);
    const CPPType &type = param_type.data_type().single_type();

    if (bool(signature_->params[param_index].flag & ParamFlag::SupportsUnusedOutput)) {
      /* An empty span indicates that this is ignored. */
      const GMutableSpan dummy_span{type};
      actual_params_.append_unchecked_as(std::in_place_type<GMutableSpan>, dummy_span);
    }
    else {
      this->add_unused_output_for_unsupporting_function(type);
    }
  }

  void add_vector_output(GVectorArray &vector_array, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForVectorOutput(vector_array.type()),
                                    expected_name);
    BLI_assert(vector_array.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<GVectorArray *>, &vector_array);
  }

  void add_single_mutable(GMutableSpan ref, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForMutableSingle(ref.type()), expected_name);
    BLI_assert(ref.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<GMutableSpan>, ref);
  }

  void add_vector_mutable(GVectorArray &vector_array, StringRef expected_name = "")
  {
    this->assert_current_param_type(ParamType::ForMutableVector(vector_array.type()),
                                    expected_name);
    BLI_assert(vector_array.size() >= min_array_size_);
    actual_params_.append_unchecked_as(std::in_place_type<GVectorArray *>, &vector_array);
  }

  GMutableSpan computed_array(int param_index)
  {
    BLI_assert(ELEM(signature_->params[param_index].type.category(),
                    ParamCategory::SingleOutput,
                    ParamCategory::SingleMutable));
    return std::get<GMutableSpan>(actual_params_[param_index]);
  }

  GVectorArray &computed_vector_array(int param_index)
  {
    BLI_assert(ELEM(signature_->params[param_index].type.category(),
                    ParamCategory::VectorOutput,
                    ParamCategory::VectorMutable));
    return *std::get<GVectorArray *>(actual_params_[param_index]);
  }

 private:
  void assert_current_param_type(ParamType param_type, StringRef expected_name = "")
  {
    UNUSED_VARS_NDEBUG(param_type, expected_name);
#ifdef DEBUG
    int param_index = this->current_param_index();

    if (expected_name != "") {
      StringRef actual_name = signature_->params[param_index].name;
      BLI_assert(actual_name == expected_name);
    }

    ParamType expected_type = signature_->params[param_index].type;
    BLI_assert(expected_type == param_type);
#endif
  }

  void assert_current_param_name(StringRef expected_name)
  {
    UNUSED_VARS_NDEBUG(expected_name);
#ifdef DEBUG
    if (expected_name.is_empty()) {
      return;
    }
    const int param_index = this->current_param_index();
    StringRef actual_name = signature_->params[param_index].name;
    BLI_assert(actual_name == expected_name);
#endif
  }

  int current_param_index() const
  {
    return actual_params_.size();
  }

  ResourceScope &resource_scope()
  {
    if (!scope_) {
      scope_ = std::make_unique<ResourceScope>();
    }
    return *scope_;
  }

  void add_unused_output_for_unsupporting_function(const CPPType &type);
};

class Params {
 private:
  ParamsBuilder *builder_;

 public:
  Params(ParamsBuilder &builder) : builder_(&builder)
  {
  }

  template<typename T> VArray<T> readonly_single_input(int param_index, StringRef name = "")
  {
    const GVArray &varray = this->readonly_single_input(param_index, name);
    return varray.typed<T>();
  }
  const GVArray &readonly_single_input(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::SingleInput);
    return std::get<GVArray>(builder_->actual_params_[param_index]);
  }

  /**
   * \return True when the caller provided a buffer for this output parameter. This allows the
   * called multi-function to skip some computation. It is still valid to call
   * #uninitialized_single_output when this returns false. In this case a new temporary buffer is
   * allocated.
   */
  bool single_output_is_required(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::SingleOutput);
    return !std::get<GMutableSpan>(builder_->actual_params_[param_index]).is_empty();
  }

  template<typename T>
  MutableSpan<T> uninitialized_single_output(int param_index, StringRef name = "")
  {
    return this->uninitialized_single_output(param_index, name).typed<T>();
  }
  GMutableSpan uninitialized_single_output(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::SingleOutput);
    BLI_assert(
        !bool(builder_->signature_->params[param_index].flag & ParamFlag::SupportsUnusedOutput));
    GMutableSpan span = std::get<GMutableSpan>(builder_->actual_params_[param_index]);
    BLI_assert(span.size() >= builder_->min_array_size_);
    return span;
  }

  /**
   * Same as #uninitialized_single_output, but returns an empty span when the output is not
   * required.
   */
  template<typename T>
  MutableSpan<T> uninitialized_single_output_if_required(int param_index, StringRef name = "")
  {
    return this->uninitialized_single_output_if_required(param_index, name).typed<T>();
  }
  GMutableSpan uninitialized_single_output_if_required(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::SingleOutput);
    BLI_assert(
        bool(builder_->signature_->params[param_index].flag & ParamFlag::SupportsUnusedOutput));
    return std::get<GMutableSpan>(builder_->actual_params_[param_index]);
  }

  template<typename T>
  const VVectorArray<T> &readonly_vector_input(int param_index, StringRef name = "")
  {
    const GVVectorArray &vector_array = this->readonly_vector_input(param_index, name);
    return builder_->resource_scope().construct<VVectorArray_For_GVVectorArray<T>>(vector_array);
  }
  const GVVectorArray &readonly_vector_input(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::VectorInput);
    return *std::get<const GVVectorArray *>(builder_->actual_params_[param_index]);
  }

  template<typename T>
  GVectorArray_TypedMutableRef<T> vector_output(int param_index, StringRef name = "")
  {
    return {this->vector_output(param_index, name)};
  }
  GVectorArray &vector_output(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::VectorOutput);
    return *std::get<GVectorArray *>(builder_->actual_params_[param_index]);
  }

  template<typename T> MutableSpan<T> single_mutable(int param_index, StringRef name = "")
  {
    return this->single_mutable(param_index, name).typed<T>();
  }
  GMutableSpan single_mutable(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::SingleMutable);
    return std::get<GMutableSpan>(builder_->actual_params_[param_index]);
  }

  template<typename T>
  GVectorArray_TypedMutableRef<T> vector_mutable(int param_index, StringRef name = "")
  {
    return {this->vector_mutable(param_index, name)};
  }
  GVectorArray &vector_mutable(int param_index, StringRef name = "")
  {
    this->assert_correct_param(param_index, name, ParamCategory::VectorMutable);
    return *std::get<GVectorArray *>(builder_->actual_params_[param_index]);
  }

 private:
  void assert_correct_param(int param_index, StringRef name, ParamType param_type)
  {
    UNUSED_VARS_NDEBUG(param_index, name, param_type);
#ifdef DEBUG
    BLI_assert(builder_->signature_->params[param_index].type == param_type);
    if (name.size() > 0) {
      BLI_assert(builder_->signature_->params[param_index].name == name);
    }
#endif
  }

  void assert_correct_param(int param_index, StringRef name, ParamCategory category)
  {
    UNUSED_VARS_NDEBUG(param_index, name, category);
#ifdef DEBUG
    BLI_assert(builder_->signature_->params[param_index].type.category() == category);
    if (name.size() > 0) {
      BLI_assert(builder_->signature_->params[param_index].name == name);
    }
#endif
  }
};

}  // namespace blender::fn::multi_function