/// @file
/// Contains private (implementation) declarations and definitions for
/// mg_procedure.h
#pragma once

#include "mg_procedure.h"

#include <optional>

#include "query/db_accessor.hpp"
#include "query/procedure/cypher_types.hpp"
#include "query/typed_value.hpp"
#include "storage/v2/view.hpp"
#include "utils/memory.hpp"
#include "utils/pmr/map.hpp"
#include "utils/pmr/string.hpp"
#include "utils/pmr/vector.hpp"

/// Wraps memory resource used in custom procedures.
///
/// This should have been `using mgp_memory = utils::MemoryResource`, but that's
/// not valid C++ because we have a forward declare `struct mgp_memory` in
/// mg_procedure.h
/// TODO: Make this extendable in C API, so that custom procedure writer can add
/// their own memory management wrappers.
struct mgp_memory {
  utils::MemoryResource *impl;
};

/// Immutable container of various values that appear in openCypher.
struct mgp_value {
  /// Allocator type so that STL containers are aware that we need one.
  using allocator_type = utils::Allocator<mgp_value>;

  // Construct MGP_VALUE_TYPE_NULL.
  explicit mgp_value(utils::MemoryResource *) noexcept;

  mgp_value(bool, utils::MemoryResource *) noexcept;
  mgp_value(int64_t, utils::MemoryResource *) noexcept;
  mgp_value(double, utils::MemoryResource *) noexcept;
  /// @throw std::bad_alloc
  mgp_value(const char *, utils::MemoryResource *);
  /// Take ownership of the mgp_list, MemoryResource must match.
  mgp_value(mgp_list *, utils::MemoryResource *) noexcept;
  /// Take ownership of the mgp_map, MemoryResource must match.
  mgp_value(mgp_map *, utils::MemoryResource *) noexcept;
  /// Take ownership of the mgp_vertex, MemoryResource must match.
  mgp_value(mgp_vertex *, utils::MemoryResource *) noexcept;
  /// Take ownership of the mgp_edge, MemoryResource must match.
  mgp_value(mgp_edge *, utils::MemoryResource *) noexcept;
  /// Take ownership of the mgp_path, MemoryResource must match.
  mgp_value(mgp_path *, utils::MemoryResource *) noexcept;

  /// Construct by copying query::TypedValue using utils::MemoryResource.
  /// mgp_graph is needed to construct mgp_vertex and mgp_edge.
  /// @throw std::bad_alloc
  mgp_value(const query::TypedValue &, const mgp_graph *,
            utils::MemoryResource *);

  /// Construct by copying PropertyValue using utils::MemoryResource.
  /// @throw std::bad_alloc
  mgp_value(const PropertyValue &, utils::MemoryResource *);

  /// Copy construction without utils::MemoryResource is not allowed.
  mgp_value(const mgp_value &) = delete;

  /// Copy construct using given utils::MemoryResource.
  /// @throw std::bad_alloc
  mgp_value(const mgp_value &, utils::MemoryResource *);

  /// Move construct using given utils::MemoryResource.
  /// @throw std::bad_alloc if MemoryResource is different, so we cannot move.
  mgp_value(mgp_value &&, utils::MemoryResource *);

  /// Move construct, utils::MemoryResource is inherited.
  mgp_value(mgp_value &&other) noexcept : mgp_value(other, other.memory) {}

  /// Copy-assignment is not allowed to preserve immutability.
  mgp_value &operator=(const mgp_value &) = delete;

  /// Move-assignment is not allowed to preserve immutability.
  mgp_value &operator=(mgp_value &&) = delete;

  ~mgp_value() noexcept;

  utils::MemoryResource *GetMemoryResource() const noexcept { return memory; }

  mgp_value_type type;
  utils::MemoryResource *memory;

  union {
    bool bool_v;
    int64_t int_v;
    double double_v;
    utils::pmr::string string_v;
    // We use pointers so that taking ownership via C API is easier. Besides,
    // mgp_map cannot use incomplete mgp_value type, because that would be
    // undefined behaviour.
    mgp_list *list_v;
    mgp_map *map_v;
    mgp_vertex *vertex_v;
    mgp_edge *edge_v;
    mgp_path *path_v;
  };
};

struct mgp_list {
  /// Allocator type so that STL containers are aware that we need one.
  using allocator_type = utils::Allocator<mgp_list>;

  explicit mgp_list(utils::MemoryResource *memory) : elems(memory) {}

  mgp_list(utils::pmr::vector<mgp_value> &&elems, utils::MemoryResource *memory)
      : elems(std::move(elems), memory) {}

  mgp_list(const mgp_list &other, utils::MemoryResource *memory)
      : elems(other.elems, memory) {}

  mgp_list(mgp_list &&other, utils::MemoryResource *memory)
      : elems(std::move(other.elems), memory) {}

  mgp_list(mgp_list &&other) noexcept : elems(std::move(other.elems)) {}

  /// Copy construction without utils::MemoryResource is not allowed.
  mgp_list(const mgp_list &) = delete;

  mgp_list &operator=(const mgp_list &) = delete;
  mgp_list &operator=(mgp_list &&) = delete;

  ~mgp_list() = default;

  utils::MemoryResource *GetMemoryResource() const noexcept {
    return elems.get_allocator().GetMemoryResource();
  }

  // C++17 vector can work with incomplete type.
  utils::pmr::vector<mgp_value> elems;
};

struct mgp_map {
  /// Allocator type so that STL containers are aware that we need one.
  using allocator_type = utils::Allocator<mgp_map>;

  explicit mgp_map(utils::MemoryResource *memory) : items(memory) {}

  mgp_map(utils::pmr::map<utils::pmr::string, mgp_value> &&items,
          utils::MemoryResource *memory)
      : items(std::move(items), memory) {}

  mgp_map(const mgp_map &other, utils::MemoryResource *memory)
      : items(other.items, memory) {}

  mgp_map(mgp_map &&other, utils::MemoryResource *memory)
      : items(std::move(other.items), memory) {}

  mgp_map(mgp_map &&other) noexcept : items(std::move(other.items)) {}

  /// Copy construction without utils::MemoryResource is not allowed.
  mgp_map(const mgp_map &) = delete;

  mgp_map &operator=(const mgp_map &) = delete;
  mgp_map &operator=(mgp_map &&) = delete;

  ~mgp_map() = default;

  utils::MemoryResource *GetMemoryResource() const noexcept {
    return items.get_allocator().GetMemoryResource();
  }

  // Unfortunately using incomplete type with map is undefined, so mgp_map
  // needs to be defined after mgp_value.
  utils::pmr::map<utils::pmr::string, mgp_value> items;
};

struct mgp_map_item {
  const char *key;
  const mgp_value *value;
};

struct mgp_map_items_iterator {
  using allocator_type = utils::Allocator<mgp_map_items_iterator>;

  mgp_map_items_iterator(const mgp_map *map, utils::MemoryResource *memory)
      : memory(memory), map(map), current_it(map->items.begin()) {
    if (current_it != map->items.end()) {
      current.key = current_it->first.c_str();
      current.value = &current_it->second;
    }
  }

  mgp_map_items_iterator(const mgp_map_items_iterator &) = delete;
  mgp_map_items_iterator(mgp_map_items_iterator &&) = delete;
  mgp_map_items_iterator &operator=(const mgp_map_items_iterator &) = delete;
  mgp_map_items_iterator &operator=(mgp_map_items_iterator &&) = delete;

  ~mgp_map_items_iterator() = default;

  utils::MemoryResource *GetMemoryResource() const { return memory; }

  utils::MemoryResource *memory;
  const mgp_map *map;
  decltype(map->items.begin()) current_it;
  mgp_map_item current;
};

struct mgp_vertex {
  /// Allocator type so that STL containers are aware that we need one.
  /// We don't actually need this, but it simplifies the C API, because we store
  /// the allocator which was used to allocate `this`.
  using allocator_type = utils::Allocator<mgp_vertex>;

  // Hopefully VertexAccessor copy constructor remains noexcept, so that we can
  // have everything noexcept here.
  static_assert(std::is_nothrow_copy_constructible_v<query::VertexAccessor>);

  mgp_vertex(query::VertexAccessor v, const mgp_graph *graph,
             utils::MemoryResource *memory) noexcept
      : memory(memory), impl(v), graph(graph) {}

  mgp_vertex(const mgp_vertex &other, utils::MemoryResource *memory) noexcept
      : memory(memory), impl(other.impl), graph(other.graph) {}

  mgp_vertex(mgp_vertex &&other, utils::MemoryResource *memory) noexcept
      : memory(memory), impl(other.impl), graph(other.graph) {}

  mgp_vertex(mgp_vertex &&other) noexcept
      : memory(other.memory), impl(other.impl), graph(other.graph) {}

  /// Copy construction without utils::MemoryResource is not allowed.
  mgp_vertex(const mgp_vertex &) = delete;

  mgp_vertex &operator=(const mgp_vertex &) = delete;
  mgp_vertex &operator=(mgp_vertex &&) = delete;

  ~mgp_vertex() = default;

  utils::MemoryResource *GetMemoryResource() const noexcept { return memory; }

  utils::MemoryResource *memory;
  query::VertexAccessor impl;
  const mgp_graph *graph;
};

struct mgp_edge {
  /// Allocator type so that STL containers are aware that we need one.
  /// We don't actually need this, but it simplifies the C API, because we store
  /// the allocator which was used to allocate `this`.
  using allocator_type = utils::Allocator<mgp_edge>;

  // Hopefully EdgeAccessor copy constructor remains noexcept, so that we can
  // have everything noexcept here.
  static_assert(std::is_nothrow_copy_constructible_v<query::EdgeAccessor>);

  mgp_edge(const query::EdgeAccessor &impl, const mgp_graph *graph,
           utils::MemoryResource *memory) noexcept
      : memory(memory),
        impl(impl),
        from(impl.From(), graph, memory),
        to(impl.To(), graph, memory) {}

  mgp_edge(const mgp_edge &other, utils::MemoryResource *memory) noexcept
      : memory(memory),
        impl(other.impl),
        from(other.from, memory),
        to(other.to, memory) {}

  mgp_edge(mgp_edge &&other, utils::MemoryResource *memory) noexcept
      : memory(other.memory),
        impl(other.impl),
        from(std::move(other.from), memory),
        to(std::move(other.to), memory) {}

  mgp_edge(mgp_edge &&other) noexcept
      : memory(other.memory),
        impl(other.impl),
        from(std::move(other.from)),
        to(std::move(other.to)) {}

  /// Copy construction without utils::MemoryResource is not allowed.
  mgp_edge(const mgp_edge &) = delete;

  mgp_edge &operator=(const mgp_edge &) = delete;
  mgp_edge &operator=(mgp_edge &&) = delete;

  ~mgp_edge() = default;

  utils::MemoryResource *GetMemoryResource() const noexcept { return memory; }

  utils::MemoryResource *memory;
  query::EdgeAccessor impl;
  mgp_vertex from;
  mgp_vertex to;
};

struct mgp_path {
  /// Allocator type so that STL containers are aware that we need one.
  using allocator_type = utils::Allocator<mgp_path>;

  explicit mgp_path(utils::MemoryResource *memory)
      : vertices(memory), edges(memory) {}

  mgp_path(const mgp_path &other, utils::MemoryResource *memory)
      : vertices(other.vertices, memory), edges(other.edges, memory) {}

  mgp_path(mgp_path &&other, utils::MemoryResource *memory)
      : vertices(std::move(other.vertices), memory),
        edges(std::move(other.edges), memory) {}

  mgp_path(mgp_path &&other) noexcept
      : vertices(std::move(other.vertices)), edges(std::move(other.edges)) {}

  /// Copy construction without utils::MemoryResource is not allowed.
  mgp_path(const mgp_path &) = delete;

  mgp_path &operator=(const mgp_path &) = delete;
  mgp_path &operator=(mgp_path &&) = delete;

  ~mgp_path() = default;

  utils::MemoryResource *GetMemoryResource() const noexcept {
    return vertices.get_allocator().GetMemoryResource();
  }

  utils::pmr::vector<mgp_vertex> vertices;
  utils::pmr::vector<mgp_edge> edges;
};

struct mgp_result_record {
  utils::pmr::map<utils::pmr::string, query::TypedValue> values;
};

struct mgp_result {
  explicit mgp_result(utils::MemoryResource *mem) : rows(mem) {}

  utils::pmr::vector<mgp_result_record> rows;
  std::optional<utils::pmr::string> error_msg;
};

struct mgp_graph {
  query::DbAccessor *impl;
  storage::View view;
};

struct mgp_properties_iterator {
  using allocator_type = utils::Allocator<mgp_properties_iterator>;

  // Define members at the start because we use decltype a lot here, so members
  // need to be visible in method definitions.

  utils::MemoryResource *memory;
  const mgp_graph *graph;
  std::remove_reference_t<decltype(
      *std::declval<query::VertexAccessor>().Properties(graph->view))>
      pvs;
  decltype(pvs.begin()) current_it;
  std::optional<std::pair<utils::pmr::string, mgp_value>> current;
  mgp_property property{nullptr, nullptr};

  // Construct with no properties.
  explicit mgp_properties_iterator(const mgp_graph *graph,
                                   utils::MemoryResource *memory)
      : memory(memory), graph(graph), current_it(pvs.begin()) {}

  // May throw who the #$@! knows what because PropertyValueStore doesn't
  // document what it throws, and it may surely throw some piece of !@#$
  // exception because it's built on top of STL and other libraries.
  mgp_properties_iterator(const mgp_graph *graph, decltype(pvs) pvs,
                          utils::MemoryResource *memory)
      : memory(memory),
        graph(graph),
        pvs(std::move(pvs)),
        current_it(this->pvs.begin()) {
    if (current_it != this->pvs.end()) {
      current.emplace(
          utils::pmr::string(graph->impl->PropertyToName(current_it->first),
                             memory),
          mgp_value(current_it->second, memory));
      property.name = current->first.c_str();
      property.value = &current->second;
    }
  }

  mgp_properties_iterator(const mgp_properties_iterator &) = delete;
  mgp_properties_iterator(mgp_properties_iterator &&) = delete;

  mgp_properties_iterator &operator=(const mgp_properties_iterator &) = delete;
  mgp_properties_iterator &operator=(mgp_properties_iterator &&) = delete;

  ~mgp_properties_iterator() = default;

  utils::MemoryResource *GetMemoryResource() const { return memory; }
};

struct mgp_edges_iterator {
  using allocator_type = utils::Allocator<mgp_edges_iterator>;

  // Hopefully mgp_vertex copy constructor remains noexcept, so that we can
  // have everything noexcept here.
  static_assert(std::is_nothrow_constructible_v<mgp_vertex, const mgp_vertex &,
                                                utils::MemoryResource *>);

  mgp_edges_iterator(const mgp_vertex &v,
                     utils::MemoryResource *memory) noexcept
      : memory(memory), source_vertex(v, memory) {}

  mgp_edges_iterator(mgp_edges_iterator &&other) noexcept
      : memory(other.memory),
        source_vertex(std::move(other.source_vertex)),
        in(std::move(other.in)),
        in_it(std::move(other.in_it)),
        out(std::move(other.out)),
        out_it(std::move(other.out_it)),
        current_e(std::move(other.current_e)) {}

  mgp_edges_iterator(const mgp_edges_iterator &) = delete;
  mgp_edges_iterator &operator=(const mgp_edges_iterator &) = delete;
  mgp_edges_iterator &operator=(mgp_edges_iterator &&) = delete;

  ~mgp_edges_iterator() = default;

  utils::MemoryResource *GetMemoryResource() const { return memory; }

  utils::MemoryResource *memory;
  mgp_vertex source_vertex;
  std::optional<std::remove_reference_t<decltype(
      *source_vertex.impl.InEdges(source_vertex.graph->view))>>
      in;
  std::optional<decltype(in->begin())> in_it;
  std::optional<std::remove_reference_t<decltype(
      *source_vertex.impl.OutEdges(source_vertex.graph->view))>>
      out;
  std::optional<decltype(out->begin())> out_it;
  std::optional<mgp_edge> current_e;
};

struct mgp_vertices_iterator {
  using allocator_type = utils::Allocator<mgp_vertices_iterator>;

  /// @throw anything VerticesIterable may throw
  mgp_vertices_iterator(const mgp_graph *graph, utils::MemoryResource *memory)
      : memory(memory),
        graph(graph),
        vertices(graph->impl->Vertices(graph->view)),
        current_it(vertices.begin()) {
    if (current_it != vertices.end()) {
      current_v.emplace(*current_it, graph, memory);
    }
  }

  utils::MemoryResource *GetMemoryResource() const { return memory; }

  utils::MemoryResource *memory;
  const mgp_graph *graph;
  decltype(graph->impl->Vertices(graph->view)) vertices;
  decltype(vertices.begin()) current_it;
  std::optional<mgp_vertex> current_v;

};

struct mgp_type {
  query::procedure::CypherTypePtr impl;
  // Optional for globally allocated mgp_type.
  utils::MemoryResource *memory{nullptr};
};