text: /*
   * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #pragma once
  
  #include <AK/FlyString.h>
  #include <AK/HashMap.h>
  #include <AK/OwnPtr.h>
  #include <LibJS/Forward.h>
  #include <LibJS/Runtime/Cell.h>
  #include <LibJS/Runtime/Value.h>
  
  namespace JS {
  
  struct Attribute {
      enum {
          Configurable = 1 << 0,
          Enumerable = 1 << 1,
          Writable = 1 << 2,
      };
  };
  
  struct PropertyMetadata {
      size_t offset { 0 };
      u8 attributes { 0 };
  };
  
  struct TransitionKey {
      FlyString property_name;
      u8 attributes { 0 };
  
      bool operator==(const TransitionKey& other) const
      {
          return property_name == other.property_name
              && attributes == other.attributes;
      }
  };
  
  class Shape final : public Cell {
  public:
      virtual ~Shape() override;
  
      enum class TransitionType {
          Invalid,
          Put,
          Configure,
          Prototype,
      };
  
      Shape();
      Shape(Shape* previous_shape, const FlyString& property_name, u8 attributes, TransitionType);
      Shape(Shape* previous_shape, Object* new_prototype);
  
      Shape* create_put_transition(const FlyString& name, u8 attributes);
      Shape* create_configure_transition(const FlyString& name, u8 attributes);
      Shape* create_prototype_transition(Object* new_prototype);
  
      bool is_unique() const { return m_unique; }
      Shape* create_unique_clone() const;
  
      Object* prototype() { return m_prototype; }
      const Object* prototype() const { return m_prototype; }
  
      Optional<PropertyMetadata> lookup(const FlyString&) const;
      const HashMap<FlyString, PropertyMetadata>& property_table() const;
      size_t property_count() const;
  
      struct Property {
          FlyString key;
          PropertyMetadata value;
      };
  
      Vector<Property> property_table_ordered() const;
  
      void set_prototype_without_transition(Object* new_prototype) { m_prototype = new_prototype; }
  
      void remove_property_from_unique_shape(const FlyString&, size_t offset);
      void add_property_to_unique_shape(const FlyString&, u8 attributes);
      void reconfigure_property_in_unique_shape(const FlyString& property_name, u8 attributes);
  
  private:
      virtual const char* class_name() const override { return "Shape"; }
      virtual void visit_children(Visitor&) override;
  
      void ensure_property_table() const;
  
      mutable OwnPtr<HashMap<FlyString, PropertyMetadata>> m_property_table;
  
      HashMap<TransitionKey, Shape*> m_forward_transitions;
      Shape* m_previous { nullptr };
      FlyString m_property_name;
      u8 m_attributes { 0 };
      bool m_unique { false };
      Object* m_prototype { nullptr };
      TransitionType m_transition_type { TransitionType::Invalid };
  };
  
  }
  
  template<>
  struct AK::Traits<JS::TransitionKey> : public GenericTraits<JS::TransitionKey> {
      static unsigned hash(const JS::TransitionKey& key)
      {
          return pair_int_hash(int_hash(key.attributes), key.property_name.hash());
      }
  };
  