text: /*
   * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
   * Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #pragma once
  
  #include <AK/FlyString.h>
  #include <AK/Function.h>
  #include <AK/HashMap.h>
  #include <AK/RefCounted.h>
  #include <AK/StackInfo.h>
  #include <AK/Variant.h>
  #include <LibJS/Heap/Heap.h>
  #include <LibJS/Runtime/CommonPropertyNames.h>
  #include <LibJS/Runtime/Error.h>
  #include <LibJS/Runtime/ErrorTypes.h>
  #include <LibJS/Runtime/Exception.h>
  #include <LibJS/Runtime/MarkedValueList.h>
  #include <LibJS/Runtime/Promise.h>
  #include <LibJS/Runtime/Value.h>
  
  namespace JS {
  
  class Identifier;
  struct BindingPattern;
  
  enum class ScopeType {
      None,
      Function,
      Block,
      Try,
      Breakable,
      Continuable,
  };
  
  struct ScopeFrame {
      ScopeType type;
      NonnullRefPtr<ScopeNode> scope_node;
      bool pushed_environment { false };
  };
  
  struct CallFrame {
      const ASTNode* current_node { nullptr };
      FlyString function_name;
      Value callee;
      Value this_value;
      Vector<Value> arguments;
      Array* arguments_object { nullptr };
      ScopeObject* scope { nullptr };
      bool is_strict_mode { false };
  };
  
  class VM : public RefCounted<VM> {
  public:
      static NonnullRefPtr<VM> create();
      ~VM();
  
      Heap& heap() { return m_heap; }
      const Heap& heap() const { return m_heap; }
  
      Interpreter& interpreter();
      Interpreter* interpreter_if_exists();
  
      void push_interpreter(Interpreter&);
      void pop_interpreter(Interpreter&);
  
      Exception* exception() { return m_exception; }
      void set_exception(Exception& exception) { m_exception = &exception; }
      void clear_exception() { m_exception = nullptr; }
  
      void dump_backtrace() const;
  
      class InterpreterExecutionScope {
      public:
          InterpreterExecutionScope(Interpreter&);
          ~InterpreterExecutionScope();
  
      private:
          Interpreter& m_interpreter;
      };
  
      void gather_roots(HashTable<Cell*>&);
  
  #define __JS_ENUMERATE(SymbolName, snake_name) \
      Symbol* well_known_symbol_##snake_name() const { return m_well_known_symbol_##snake_name; }
      JS_ENUMERATE_WELL_KNOWN_SYMBOLS
  #undef __JS_ENUMERATE
  
      Symbol* get_global_symbol(const String& description);
  
      PrimitiveString& empty_string() { return *m_empty_string; }
      PrimitiveString& single_ascii_character_string(u8 character)
      {
          VERIFY(character < 0x80);
          return *m_single_ascii_character_strings[character];
      }
  
      void push_call_frame(CallFrame& call_frame, GlobalObject& global_object)
      {
          VERIFY(!exception());
          // Ensure we got some stack space left, so the next function call doesn't kill us.
          // Note: the 32 kiB used to be 16 kiB, but that turned out to not be enough with ASAN enabled.
          if (m_stack_info.size_free() < 32 * KiB)
              throw_exception<Error>(global_object, "Call stack size limit exceeded");
          else
              m_call_stack.append(&call_frame);
      }
  
      void pop_call_frame()
      {
          m_call_stack.take_last();
          if (m_call_stack.is_empty() && on_call_stack_emptied)
              on_call_stack_emptied();
      }
  
      CallFrame& call_frame() { return *m_call_stack.last(); }
      const CallFrame& call_frame() const { return *m_call_stack.last(); }
      const Vector<CallFrame*>& call_stack() const { return m_call_stack; }
      Vector<CallFrame*>& call_stack() { return m_call_stack; }
  
      const ScopeObject* current_scope() const { return call_frame().scope; }
      ScopeObject* current_scope() { return call_frame().scope; }
  
      bool in_strict_mode() const;
  
      template<typename Callback>
      void for_each_argument(Callback callback)
      {
          if (m_call_stack.is_empty())
              return;
          for (auto& value : call_frame().arguments)
              callback(value);
      }
  
      size_t argument_count() const
      {
          if (m_call_stack.is_empty())
              return 0;
          return call_frame().arguments.size();
      }
  
      Value argument(size_t index) const
      {
          if (m_call_stack.is_empty())
              return {};
          auto& arguments = call_frame().arguments;
          return index < arguments.size() ? arguments[index] : js_undefined();
      }
  
      Value this_value(Object& global_object) const
      {
          if (m_call_stack.is_empty())
              return &global_object;
          return call_frame().this_value;
      }
  
      Value last_value() const { return m_last_value; }
      void set_last_value(Badge<Bytecode::Interpreter>, Value value) { m_last_value = value; }
      void set_last_value(Badge<Interpreter>, Value value) { m_last_value = value; }
  
      const StackInfo& stack_info() const { return m_stack_info; };
  
      bool underscore_is_last_value() const { return m_underscore_is_last_value; }
      void set_underscore_is_last_value(bool b) { m_underscore_is_last_value = b; }
  
      void unwind(ScopeType type, FlyString label = {})
      {
          m_unwind_until = type;
          m_unwind_until_label = move(label);
      }
      void stop_unwind()
      {
          m_unwind_until = ScopeType::None;
          m_unwind_until_label = {};
      }
      bool should_unwind_until(ScopeType type, FlyString const& label) const
      {
          if (m_unwind_until_label.is_null())
              return m_unwind_until == type;
          return m_unwind_until == type && m_unwind_until_label == label;
      }
      bool should_unwind() const { return m_unwind_until != ScopeType::None; }
  
      ScopeType unwind_until() const { return m_unwind_until; }
  
      Value get_variable(const FlyString& name, GlobalObject&);
      void set_variable(const FlyString& name, Value, GlobalObject&, bool first_assignment = false, ScopeObject* specific_scope = nullptr);
      bool delete_variable(FlyString const& name);
      void assign(const Variant<NonnullRefPtr<Identifier>, NonnullRefPtr<BindingPattern>>& target, Value, GlobalObject&, bool first_assignment = false, ScopeObject* specific_scope = nullptr);
      void assign(const FlyString& target, Value, GlobalObject&, bool first_assignment = false, ScopeObject* specific_scope = nullptr);
      void assign(const NonnullRefPtr<BindingPattern>& target, Value, GlobalObject&, bool first_assignment = false, ScopeObject* specific_scope = nullptr);
  
      Reference get_reference(const FlyString& name);
  
      template<typename T, typename... Args>
      void throw_exception(GlobalObject& global_object, Args&&... args)
      {
          return throw_exception(global_object, T::create(global_object, forward<Args>(args)...));
      }
  
      void throw_exception(Exception&);
      void throw_exception(GlobalObject& global_object, Value value)
      {
          return throw_exception(*heap().allocate<Exception>(global_object, value));
      }
  
      template<typename T, typename... Args>
      void throw_exception(GlobalObject& global_object, ErrorType type, Args&&... args)
      {
          return throw_exception(global_object, T::create(global_object, String::formatted(type.message(), forward<Args>(args)...)));
      }
  
      Value construct(Function&, Function& new_target, Optional<MarkedValueList> arguments);
  
      String join_arguments(size_t start_index = 0) const;
  
      Value resolve_this_binding(GlobalObject&) const;
      const ScopeObject* find_this_scope() const;
      Value get_new_target() const;
  
      template<typename... Args>
      [[nodiscard]] ALWAYS_INLINE Value call(Function& function, Value this_value, Args... args)
      {
          if constexpr (sizeof...(Args) > 0) {
              MarkedValueList arglist { heap() };
              (..., arglist.append(move(args)));
              return call(function, this_value, move(arglist));
          }
  
          return call(function, this_value);
      }
  
      CommonPropertyNames names;
  
      Shape& scope_object_shape() { return *m_scope_object_shape; }
  
      void run_queued_promise_jobs();
      void enqueue_promise_job(NativeFunction&);
  
      void promise_rejection_tracker(const Promise&, Promise::RejectionOperation) const;
  
      AK::Function<void()> on_call_stack_emptied;
      AK::Function<void(const Promise&)> on_promise_unhandled_rejection;
      AK::Function<void(const Promise&)> on_promise_rejection_handled;
  
  private:
      VM();
  
      [[nodiscard]] Value call_internal(Function&, Value this_value, Optional<MarkedValueList> arguments);
  
      Exception* m_exception { nullptr };
  
      Heap m_heap;
      Vector<Interpreter*> m_interpreters;
  
      Vector<CallFrame*> m_call_stack;
  
      Value m_last_value;
      ScopeType m_unwind_until { ScopeType::None };
      FlyString m_unwind_until_label;
  
      StackInfo m_stack_info;
  
      HashMap<String, Symbol*> m_global_symbol_map;
  
      Vector<NativeFunction*> m_promise_jobs;
  
      PrimitiveString* m_empty_string { nullptr };
      PrimitiveString* m_single_ascii_character_strings[128] {};
  
  #define __JS_ENUMERATE(SymbolName, snake_name) \
      Symbol* m_well_known_symbol_##snake_name { nullptr };
      JS_ENUMERATE_WELL_KNOWN_SYMBOLS
  #undef __JS_ENUMERATE
  
      Shape* m_scope_object_shape { nullptr };
  
      bool m_underscore_is_last_value { false };
  };
  
  template<>
  [[nodiscard]] ALWAYS_INLINE Value VM::call(Function& function, Value this_value, MarkedValueList arguments) { return call_internal(function, this_value, move(arguments)); }
  
  template<>
  [[nodiscard]] ALWAYS_INLINE Value VM::call(Function& function, Value this_value, Optional<MarkedValueList> arguments) { return call_internal(function, this_value, move(arguments)); }
  
  template<>
  [[nodiscard]] ALWAYS_INLINE Value VM::call(Function& function, Value this_value) { return call(function, this_value, Optional<MarkedValueList> {}); }
  
  ALWAYS_INLINE Heap& Cell::heap() const
  {
      return HeapBlock::from_cell(this)->heap();
  }
  
  ALWAYS_INLINE VM& Cell::vm() const
  {
      return heap().vm();
  }
  
  }
  