text: /*
   * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
   * Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
   * Copyright (c) 2021-2022, David Tuin <davidot@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/Heap/MarkedVector.h>
  #include <LibJS/Runtime/CommonPropertyNames.h>
  #include <LibJS/Runtime/Completion.h>
  #include <LibJS/Runtime/Error.h>
  #include <LibJS/Runtime/ErrorTypes.h>
  #include <LibJS/Runtime/ExecutionContext.h>
  #include <LibJS/Runtime/Iterator.h>
  #include <LibJS/Runtime/Promise.h>
  #include <LibJS/Runtime/Value.h>
  
  namespace JS {
  
  class Identifier;
  struct BindingPattern;
  
  class VM : public RefCounted<VM> {
  public:
      struct CustomData {
          virtual ~CustomData() = default;
      };
  
      static NonnullRefPtr<VM> create(OwnPtr<CustomData> = {});
      ~VM() = default;
  
      enum class HostResizeArrayBufferResult {
          Unhandled,
          Handled,
      };
  
      Heap& heap() { return m_heap; }
      Heap const& heap() const { return m_heap; }
  
      Interpreter& interpreter();
      Interpreter* interpreter_if_exists();
  
      void push_interpreter(Interpreter&);
      void pop_interpreter(Interpreter&);
  
      void dump_backtrace() const;
  
      class InterpreterExecutionScope {
      public:
          InterpreterExecutionScope(Interpreter&);
          ~InterpreterExecutionScope();
  
          Interpreter& interpreter() { return m_interpreter; }
  
      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(String const& description);
  
      HashMap<String, PrimitiveString*>& string_cache() { return m_string_cache; }
      PrimitiveString& empty_string() { return *m_empty_string; }
      PrimitiveString& single_ascii_character_string(u8 character)
      {
          VERIFY(character < 0x80);
          return *m_single_ascii_character_strings[character];
      }
  
      bool did_reach_stack_space_limit() const
      {
          // Address sanitizer (ASAN) used to check for more space but
          // currently we can't detect the stack size with it enabled.
          return m_stack_info.size_free() < 32 * KiB;
      }
  
      void push_execution_context(ExecutionContext& context)
      {
          m_execution_context_stack.append(&context);
      }
  
      ThrowCompletionOr<void> push_execution_context(ExecutionContext& context, GlobalObject& global_object)
      {
          // Ensure we got some stack space left, so the next function call doesn't kill us.
          if (did_reach_stack_space_limit())
              return throw_completion<InternalError>(global_object, ErrorType::CallStackSizeExceeded);
          m_execution_context_stack.append(&context);
          return {};
      }
  
      void pop_execution_context()
      {
          m_execution_context_stack.take_last();
          if (m_execution_context_stack.is_empty() && on_call_stack_emptied)
              on_call_stack_emptied();
      }
  
      ExecutionContext& running_execution_context() { return *m_execution_context_stack.last(); }
      ExecutionContext const& running_execution_context() const { return *m_execution_context_stack.last(); }
      Vector<ExecutionContext*> const& execution_context_stack() const { return m_execution_context_stack; }
      Vector<ExecutionContext*>& execution_context_stack() { return m_execution_context_stack; }
  
      Environment const* lexical_environment() const { return running_execution_context().lexical_environment; }
      Environment* lexical_environment() { return running_execution_context().lexical_environment; }
  
      Environment const* variable_environment() const { return running_execution_context().variable_environment; }
      Environment* variable_environment() { return running_execution_context().variable_environment; }
  
      // https://tc39.es/ecma262/#current-realm
      // The value of the Realm component of the running execution context is also called the current Realm Record.
      Realm const* current_realm() const { return running_execution_context().realm; }
      Realm* current_realm() { return running_execution_context().realm; }
  
      // https://tc39.es/ecma262/#active-function-object
      // The value of the Function component of the running execution context is also called the active function object.
      FunctionObject const* active_function_object() const { return running_execution_context().function; }
      FunctionObject* active_function_object() { return running_execution_context().function; }
  
      bool in_strict_mode() const;
  
      size_t argument_count() const
      {
          if (m_execution_context_stack.is_empty())
              return 0;
          return running_execution_context().arguments.size();
      }
  
      Value argument(size_t index) const
      {
          if (m_execution_context_stack.is_empty())
              return {};
          auto& arguments = running_execution_context().arguments;
          return index < arguments.size() ? arguments[index] : js_undefined();
      }
  
      Value this_value(Object& global_object) const
      {
          if (m_execution_context_stack.is_empty())
              return &global_object;
          return running_execution_context().this_value;
      }
  
      ThrowCompletionOr<Value> resolve_this_binding(GlobalObject&);
  
      StackInfo const& stack_info() const { return m_stack_info; };
  
      u32 execution_generation() const { return m_execution_generation; }
      void finish_execution_generation() { ++m_execution_generation; }
  
      ThrowCompletionOr<Reference> resolve_binding(FlyString const&, Environment* = nullptr);
      ThrowCompletionOr<Reference> get_identifier_reference(Environment*, FlyString, bool strict, size_t hops = 0);
  
      // 5.2.3.2 Throw an Exception, https://tc39.es/ecma262/#sec-throw-an-exception
      template<typename T, typename... Args>
      Completion throw_completion(GlobalObject& global_object, Args&&... args)
      {
          return JS::throw_completion(T::create(global_object, forward<Args>(args)...));
      }
  
      template<typename T, typename... Args>
      Completion throw_completion(GlobalObject& global_object, ErrorType type, Args&&... args)
      {
          return throw_completion<T>(global_object, String::formatted(type.message(), forward<Args>(args)...));
      }
  
      Value construct(FunctionObject&, FunctionObject& new_target, Optional<MarkedVector<Value>> arguments);
  
      String join_arguments(size_t start_index = 0) const;
  
      Value get_new_target();
  
      CommonPropertyNames names;
  
      void run_queued_promise_jobs();
      void enqueue_promise_job(Function<ThrowCompletionOr<Value>()> job, Realm*);
  
      void run_queued_finalization_registry_cleanup_jobs();
      void enqueue_finalization_registry_cleanup_job(FinalizationRegistry&);
  
      void promise_rejection_tracker(Promise&, Promise::RejectionOperation) const;
  
      Function<void()> on_call_stack_emptied;
      Function<void(Promise&)> on_promise_unhandled_rejection;
      Function<void(Promise&)> on_promise_rejection_handled;
  
      ThrowCompletionOr<void> initialize_instance_elements(Object& object, ECMAScriptFunctionObject& constructor);
  
      CustomData* custom_data() { return m_custom_data; }
  
      ThrowCompletionOr<void> destructuring_assignment_evaluation(NonnullRefPtr<BindingPattern> const& target, Value value, GlobalObject& global_object);
      ThrowCompletionOr<void> binding_initialization(FlyString const& target, Value value, Environment* environment, GlobalObject& global_object);
      ThrowCompletionOr<void> binding_initialization(NonnullRefPtr<BindingPattern> const& target, Value value, Environment* environment, GlobalObject& global_object);
  
      ThrowCompletionOr<Value> named_evaluation_if_anonymous_function(GlobalObject& global_object, ASTNode const& expression, FlyString const& name);
  
      void save_execution_context_stack();
      void restore_execution_context_stack();
  
      // Do not call this method unless you are sure this is the only and first module to be loaded in this vm.
      ThrowCompletionOr<void> link_and_eval_module(Badge<Interpreter>, SourceTextModule& module);
  
      ScriptOrModule get_active_script_or_module() const;
  
      Function<ThrowCompletionOr<NonnullRefPtr<Module>>(ScriptOrModule, ModuleRequest const&)> host_resolve_imported_module;
      Function<void(ScriptOrModule, ModuleRequest, PromiseCapability)> host_import_module_dynamically;
      Function<void(ScriptOrModule, ModuleRequest const&, PromiseCapability, Promise*)> host_finish_dynamic_import;
  
      Function<HashMap<PropertyKey, Value>(SourceTextModule const&)> host_get_import_meta_properties;
      Function<void(Object*, SourceTextModule const&)> host_finalize_import_meta;
  
      Function<Vector<String>()> host_get_supported_import_assertions;
  
      void enable_default_host_import_module_dynamically_hook();
  
      Function<void(Promise&, Promise::RejectionOperation)> host_promise_rejection_tracker;
      Function<ThrowCompletionOr<Value>(GlobalObject&, JobCallback&, Value, MarkedVector<Value>)> host_call_job_callback;
      Function<void(FinalizationRegistry&)> host_enqueue_finalization_registry_cleanup_job;
      Function<void(Function<ThrowCompletionOr<Value>()>, Realm*)> host_enqueue_promise_job;
      Function<JobCallback(FunctionObject&)> host_make_job_callback;
      Function<ThrowCompletionOr<HostResizeArrayBufferResult>(GlobalObject&, size_t)> host_resize_array_buffer;
      Function<ThrowCompletionOr<void>(Realm&)> host_ensure_can_compile_strings;
  
  private:
      explicit VM(OwnPtr<CustomData>);
  
      ThrowCompletionOr<void> property_binding_initialization(BindingPattern const& binding, Value value, Environment* environment, GlobalObject& global_object);
      ThrowCompletionOr<void> iterator_binding_initialization(BindingPattern const& binding, Iterator& iterator_record, Environment* environment, GlobalObject& global_object);
  
      ThrowCompletionOr<NonnullRefPtr<Module>> resolve_imported_module(ScriptOrModule referencing_script_or_module, ModuleRequest const& module_request);
      ThrowCompletionOr<void> link_and_eval_module(Module& module);
  
      void import_module_dynamically(ScriptOrModule referencing_script_or_module, ModuleRequest module_request, PromiseCapability promise_capability);
      void finish_dynamic_import(ScriptOrModule referencing_script_or_module, ModuleRequest module_request, PromiseCapability promise_capability, Promise* inner_promise);
  
      HashMap<String, PrimitiveString*> m_string_cache;
  
      Heap m_heap;
      Vector<Interpreter*> m_interpreters;
  
      Vector<ExecutionContext*> m_execution_context_stack;
  
      Vector<Vector<ExecutionContext*>> m_saved_execution_context_stacks;
  
      StackInfo m_stack_info;
  
      HashMap<String, Symbol*> m_global_symbol_map;
  
      Vector<Function<ThrowCompletionOr<Value>()>> m_promise_jobs;
  
      Vector<FinalizationRegistry*> m_finalization_registry_cleanup_jobs;
  
      PrimitiveString* m_empty_string { nullptr };
      PrimitiveString* m_single_ascii_character_strings[128] {};
  
      struct StoredModule {
          ScriptOrModule referencing_script_or_module;
          String filepath;
          String type;
          NonnullRefPtr<Module> module;
          bool has_once_started_linking { false };
      };
  
      StoredModule* get_stored_module(ScriptOrModule const& script_or_module, String const& filepath, String const& type);
  
      Vector<StoredModule> m_loaded_modules;
  
  #define __JS_ENUMERATE(SymbolName, snake_name) \
      Symbol* m_well_known_symbol_##snake_name { nullptr };
      JS_ENUMERATE_WELL_KNOWN_SYMBOLS
  #undef __JS_ENUMERATE
  
      u32 m_execution_generation { 0 };
  
      OwnPtr<CustomData> m_custom_data;
  };
  
  ALWAYS_INLINE Heap& Cell::heap() const
  {
      return HeapBlock::from_cell(this)->heap();
  }
  
  ALWAYS_INLINE VM& Cell::vm() const
  {
      return heap().vm();
  }
  
  }
  