#ifndef SRC_NODE_MESSAGING_H_

#define SRC_NODE_MESSAGING_H_

#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#include "env.h"

#include "node_mutex.h"

#include "v8.h"

#include <deque>

#include <string>

#include <unordered_map>

#include <set>

namespace node {

namespace worker {

class MessagePortData;

class MessagePort;

typedef MaybeStackBuffer<v8::Local<v8::Value>, 8> TransferList;

// Used to represent the in-flight structure of an object that is being

// transferred or cloned using postMessage().

class TransferData : public MemoryRetainer {

 public:

  // Deserialize this object on the receiving end after a .postMessage() call.

  // - `context` may not be the same as `env->context()`. This method should

  //    not produce JS objects coming from Contexts other than `context`.

  // - `self` is a unique_ptr for the object that this is being called on.

  // - The return value is treated like a `Maybe`, i.e. if `nullptr` is

  //   returned, any further deserialization of the message is stopped and

  //   control is returned to the event loop or JS as soon as possible.

  virtual BaseObjectPtr<BaseObject> Deserialize(

      Environment* env,

      v8::Local<v8::Context> context,

      std::unique_ptr<TransferData> self) = 0;

  // FinalizeTransferWrite() is the counterpart to

  // BaseObject::FinalizeTransferRead(). It is called right after the transfer

  // data was created, and defaults to doing nothing. After this function,

  // this object should not hold any more Isolate-specific data.

  virtual v8::Maybe<bool> FinalizeTransferWrite(

      v8::Local<v8::Context> context, v8::ValueSerializer* serializer);

};

// Represents a single communication message.

class Message : public MemoryRetainer {

 public:

  // Create a Message with a specific underlying payload, in the format of the

  // V8 ValueSerializer API. If `payload` is empty, this message indicates

  // that the receiving message port should close itself.

  explicit Message(MallocedBuffer<char>&& payload = MallocedBuffer<char>());

  Message(Message&& other) = default;

  Message& operator=(Message&& other) = default;

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

  Message(const Message&) = delete;

  // Whether this is a message indicating that the port is to be closed.

  // This is the last message to be received by a MessagePort.

  bool IsCloseMessage() const;

  // Deserialize the contained JS value. May only be called once, and only

  // after Serialize() has been called (e.g. by another thread).

  v8::MaybeLocal<v8::Value> Deserialize(

      Environment* env,

      v8::Local<v8::Context> context,

      v8::Local<v8::Value>* port_list = nullptr);

  // Serialize a JS value, and optionally transfer objects, into this message.

  // The Message object retains ownership of all transferred objects until

  // deserialization.

  // The source_port parameter, if provided, will make Serialize() throw a

  // "DataCloneError" DOMException if source_port is found in transfer_list.

  v8::Maybe<bool> Serialize(Environment* env,

                            v8::Local<v8::Context> context,

                            v8::Local<v8::Value> input,

                            const TransferList& transfer_list,

                            v8::Local<v8::Object> source_port =

                                v8::Local<v8::Object>());

  // Internal method of Message that is called when a new SharedArrayBuffer

  // object is encountered in the incoming value's structure.

  void AddSharedArrayBuffer(std::shared_ptr<v8::BackingStore> backing_store);

  // Internal method of Message that is called once serialization finishes

  // and that transfers ownership of `data` to this message.

  void AddTransferable(std::unique_ptr<TransferData>&& data);

  // Internal method of Message that is called when a new WebAssembly.Module

  // object is encountered in the incoming value's structure.

  uint32_t AddWASMModule(v8::CompiledWasmModule&& mod);

  // The host objects that will be transferred, as recorded by Serialize()

  // (e.g. MessagePorts).

  // Used for warning user about posting the target MessagePort to itself,

  // which will as a side effect destroy the communication channel.

  }

  }

  void MemoryInfo(MemoryTracker* tracker) const override;

 private:

  MallocedBuffer<char> main_message_buf_;

  // TODO(addaleax): Make this a std::variant to save storage size in the common

  // case (which is that all of these vectors are empty) once that is available

  // with C++17.

  std::vector<std::shared_ptr<v8::BackingStore>> array_buffers_;

  std::vector<std::shared_ptr<v8::BackingStore>> shared_array_buffers_;

  std::vector<std::unique_ptr<TransferData>> transferables_;

  std::vector<v8::CompiledWasmModule> wasm_modules_;

  friend class MessagePort;

};

class SiblingGroup final : public std::enable_shared_from_this<SiblingGroup> {

 public:

  // Named SiblingGroup, Used for one-to-many BroadcastChannels.

  static std::shared_ptr<SiblingGroup> Get(const std::string& name);

  // Anonymous SiblingGroup, Used for one-to-one MessagePort pairs.

  explicit SiblingGroup(const std::string& name);

  ~SiblingGroup();

  // Dispatches the Message to the collection of associated

  // ports. If there is more than one destination port and

  // the Message contains transferables, Dispatch will fail.

  // Returns Just(true) if successful and the message was

  // dispatched to at least one destination. Returns Just(false)

  // if there were no destinations. Returns Nothing<bool>()

  // if there was an error. If error is not nullptr, it will

  // be set to an error message or warning message as appropriate.

  v8::Maybe<bool> Dispatch(

      MessagePortData* source,

      std::shared_ptr<Message> message,

      std::string* error = nullptr);

  void Entangle(MessagePortData* data);

  void Entangle(std::initializer_list<MessagePortData*> data);

  void Disentangle(MessagePortData* data);

  const std::string& name() const { return name_; }

 private:

  const std::string name_;

  RwLock group_mutex_;  // Protects ports_.

  std::set<MessagePortData*> ports_;

  static void CheckSiblingGroup(const std::string& name);

  using Map =

      std::unordered_map<std::string, std::weak_ptr<SiblingGroup>>;

  static Mutex groups_mutex_;

  static Map groups_;

};

// This contains all data for a `MessagePort` instance that is not tied to

// a specific Environment/Isolate/event loop, for easier transfer between those.

class MessagePortData : public TransferData {

 public:

  explicit MessagePortData(MessagePort* owner);

  ~MessagePortData() override;

  MessagePortData(MessagePortData&& other) = delete;

  MessagePortData& operator=(MessagePortData&& other) = delete;

  MessagePortData(const MessagePortData& other) = delete;

  MessagePortData& operator=(const MessagePortData& other) = delete;

  // Add a message to the incoming queue and notify the receiver.

  // This may be called from any thread.

  void AddToIncomingQueue(std::shared_ptr<Message> message);

  v8::Maybe<bool> Dispatch(

      std::shared_ptr<Message> message,

      std::string* error = nullptr);

  // Turns `a` and `b` into siblings, i.e. connects the sending side of one

  // to the receiving side of the other. This is not thread-safe.

  static void Entangle(MessagePortData* a, MessagePortData* b);

  // Removes any possible sibling. This is thread-safe (it acquires both

  // `sibling_mutex_` and `mutex_`), and has to be because it is called once

  // the corresponding JS handle handle wants to close

  // which can happen on either side of a worker.

  void Disentangle();

  void MemoryInfo(MemoryTracker* tracker) const override;

  BaseObjectPtr<BaseObject> Deserialize(

      Environment* env,

      v8::Local<v8::Context> context,

      std::unique_ptr<TransferData> self) override;

 private:

  // This mutex protects all fields below it, with the exception of

  // sibling_.

  mutable Mutex mutex_;

  // TODO(addaleax): Make this a std::variant<std::shared_ptr, std::unique_ptr>

  // once that is available with C++17, because std::shared_ptr comes with

  // overhead that is only necessary for BroadcastChannel.

  std::deque<std::shared_ptr<Message>> incoming_messages_;

  MessagePort* owner_ = nullptr;

  std::shared_ptr<SiblingGroup> group_;

  friend class MessagePort;

  friend class SiblingGroup;

};

// A message port that receives messages from other threads, including

// the uv_async_t handle that is used to notify the current event loop of

// new incoming messages.

class MessagePort : public HandleWrap {

 private:

  // Create a new MessagePort. The `context` argument specifies the Context

  // instance that is used for creating the values emitted from this port.

  // This is called by MessagePort::New(), which is the public API used for

  // creating MessagePort instances.

  MessagePort(Environment* env,

              v8::Local<v8::Context> context,

              v8::Local<v8::Object> wrap);

 public:

  ~MessagePort() override;

  // Create a new message port instance, optionally over an existing

  // `MessagePortData` object.

  static MessagePort* New(Environment* env,

                          v8::Local<v8::Context> context,

                          std::unique_ptr<MessagePortData> data = {},

                          std::shared_ptr<SiblingGroup> sibling_group = {});

  // Send a message, i.e. deliver it into the sibling's incoming queue.

  // If this port is closed, or if there is no sibling, this message is

  // serialized with transfers, then silently discarded.

  v8::Maybe<bool> PostMessage(Environment* env,

                              v8::Local<v8::Context> context,

                              v8::Local<v8::Value> message,

                              const TransferList& transfer);

  // Start processing messages on this port as a receiving end.

  void Start();

  // Stop processing messages on this port as a receiving end.

  void Stop();

  /* constructor */

  static void New(const v8::FunctionCallbackInfo<v8::Value>& args);

  /* prototype methods */

  static void PostMessage(const v8::FunctionCallbackInfo<v8::Value>& args);

  static void Start(const v8::FunctionCallbackInfo<v8::Value>& args);

  static void Stop(const v8::FunctionCallbackInfo<v8::Value>& args);

  static void CheckType(const v8::FunctionCallbackInfo<v8::Value>& args);

  static void Drain(const v8::FunctionCallbackInfo<v8::Value>& args);

  static void ReceiveMessage(const v8::FunctionCallbackInfo<v8::Value>& args);

  /* static */

  static void MoveToContext(const v8::FunctionCallbackInfo<v8::Value>& args);

  // Turns `a` and `b` into siblings, i.e. connects the sending side of one

  // to the receiving side of the other. This is not thread-safe.

  static void Entangle(MessagePort* a, MessagePort* b);

  static void Entangle(MessagePort* a, MessagePortData* b);

  // Detach this port's data for transferring. After this, the MessagePortData

  // is no longer associated with this handle, although it can still receive

  // messages.

  std::unique_ptr<MessagePortData> Detach();

  void Close(

      v8::Local<v8::Value> close_callback = v8::Local<v8::Value>()) override;

  // Returns true if either data_ has been freed, or if the handle is being

  // closed. Equivalent to the [[Detached]] internal slot in the HTML Standard.

  //

  // If checking if a JavaScript MessagePort object is detached, this method

  // alone is often not enough, since the backing C++ MessagePort object may

  // have been deleted already. For all intents and purposes, an object with a

  // NULL pointer to the C++ MessagePort object is also detached.

  inline bool IsDetached() const;

  TransferMode GetTransferMode() const override;

  std::unique_ptr<TransferData> TransferForMessaging() override;

  void MemoryInfo(MemoryTracker* tracker) const override;

 private:

  enum class MessageProcessingMode {

    kNormalOperation,

    kForceReadMessages

  };

  void OnClose() override;

  void OnMessage(MessageProcessingMode mode);

  void TriggerAsync();

  v8::MaybeLocal<v8::Value> ReceiveMessage(

      v8::Local<v8::Context> context,

      MessageProcessingMode mode,

      v8::Local<v8::Value>* port_list = nullptr);

  std::unique_ptr<MessagePortData> data_ = nullptr;

  bool receiving_messages_ = false;

  uv_async_t async_;

  v8::Global<v8::Function> emit_message_fn_;

  friend class MessagePortData;

};

// Provide a base class from which JS classes that should be transferable or

// cloneable by postMesssage() can inherit.

// See e.g. FileHandle in internal/fs/promises.js for an example.

class JSTransferable : public BaseObject {

 public:

  JSTransferable(Environment* env, v8::Local<v8::Object> obj);

  static void New(const v8::FunctionCallbackInfo<v8::Value>& args);

  TransferMode GetTransferMode() const override;

  std::unique_ptr<TransferData> TransferForMessaging() override;

  std::unique_ptr<TransferData> CloneForMessaging() const override;

  v8::Maybe<std::vector<BaseObjectPtr<BaseObject>>>

      NestedTransferables() const override;

  v8::Maybe<bool> FinalizeTransferRead(

      v8::Local<v8::Context> context,

      v8::ValueDeserializer* deserializer) override;

 private:

  std::unique_ptr<TransferData> TransferOrClone(TransferMode mode) const;

  class Data : public TransferData {

   public:

    Data(std::string&& deserialize_info, v8::Global<v8::Value>&& data);

    BaseObjectPtr<BaseObject> Deserialize(

        Environment* env,

        v8::Local<v8::Context> context,

        std::unique_ptr<TransferData> self) override;

    v8::Maybe<bool> FinalizeTransferWrite(

        v8::Local<v8::Context> context,

        v8::ValueSerializer* serializer) override;

   private:

    std::string deserialize_info_;

    v8::Global<v8::Value> data_;

  };

};

v8::Local<v8::FunctionTemplate> GetMessagePortConstructorTemplate(

    Environment* env);

}  // namespace worker

}  // namespace node

#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#endif  // SRC_NODE_MESSAGING_H_