// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef IPC_IPC_MESSAGE_PIPE_READER_H_
#define IPC_IPC_MESSAGE_PIPE_READER_H_

#include <stdint.h>

#include <memory>
#include <vector>

#include "base/compiler_specific.h"
#include "base/component_export.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/process/process_handle.h"
#include "base/task/sequenced_task_runner.h"
#include "base/threading/thread_checker.h"
#include "ipc/ipc.mojom.h"
#include "mojo/public/cpp/bindings/associated_receiver.h"
#include "mojo/public/cpp/bindings/associated_remote.h"
#include "mojo/public/cpp/bindings/generic_pending_associated_receiver.h"
#include "mojo/public/cpp/bindings/pending_associated_receiver.h"
#include "mojo/public/cpp/bindings/scoped_interface_endpoint_handle.h"
#include "mojo/public/cpp/bindings/shared_remote.h"
#include "mojo/public/cpp/system/message_pipe.h"

namespace IPC {
namespace internal {

// A helper class to handle bytestream directly over mojo::MessagePipe
// in template-method pattern. MessagePipeReader manages the lifetime
// of given MessagePipe and participates the event loop, and
// read the stream and call the client when it is ready.
//
// Each client has to:
//
//  * Provide a subclass implemenation of a specific use of a MessagePipe
//    and implement callbacks.
//  * Create the subclass instance with a MessagePipeHandle.
//    The constructor automatically start listening on the pipe.
//
// All functions must be called on the IO thread, except for Send(), which can
// be called on any thread. All |Delegate| functions will be called on the IO
// thread.
//
class COMPONENT_EXPORT(IPC) MessagePipeReader : public mojom::Channel {
 public:
  class Delegate {
   public:
    virtual void OnPeerPidReceived(int32_t peer_pid) = 0;
    virtual void OnPipeError() = 0;
    virtual void OnAssociatedInterfaceRequest(
        mojo::GenericPendingAssociatedReceiver receiver) = 0;
  };

  // Builds a reader that reads messages from |receive_handle| and lets
  // |delegate| know.
  //
  // |pipe| is the message pipe handle corresponding to the channel's primary
  // interface. This is the message pipe underlying both |sender| and
  // |receiver|.
  //
  // Both |sender| and |receiver| must be non-null.
  //
  // Note that MessagePipeReader doesn't delete |delegate|.
  MessagePipeReader(mojo::MessagePipeHandle pipe,
                    mojo::PendingAssociatedRemote<mojom::Channel> sender,
                    mojo::PendingAssociatedReceiver<mojom::Channel> receiver,
                    scoped_refptr<base::SequencedTaskRunner> task_runner,
                    Delegate* delegate);

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

  ~MessagePipeReader() override;

  void FinishInitializationOnIOThread(base::ProcessId self_pid);

  // Close and destroy the MessagePipe.
  void Close();

  // Return true if the MessagePipe is alive.
  bool IsValid() { return sender_.is_bound(); }

  // Requests an associated interface from the other end of the pipe.
  void GetRemoteInterface(mojo::GenericPendingAssociatedReceiver receiver);

  mojo::AssociatedRemote<mojom::Channel>& sender() { return sender_; }
  mojom::Channel& thread_safe_sender() { return thread_safe_sender_->proxy(); }

 protected:
  void OnPipeClosed();
  void OnPipeError(MojoResult error);

 private:
  // mojom::Channel:
  void SetPeerPid(int32_t peer_pid) override;
  void GetAssociatedInterface(
      mojo::GenericPendingAssociatedReceiver receiver) override;

  void ForwardMessage(mojo::Message message);

  // |delegate_| is null once the message pipe is closed.
  raw_ptr<Delegate> delegate_;
  mojo::AssociatedRemote<mojom::Channel> sender_;
  std::unique_ptr<mojo::ThreadSafeForwarder<mojom::Channel>>
      thread_safe_sender_;
  mojo::AssociatedReceiver<mojom::Channel> receiver_;
  base::ThreadChecker thread_checker_;
  base::WeakPtrFactory<MessagePipeReader> weak_ptr_factory_{this};
};

}  // namespace internal
}  // namespace IPC

#endif  // IPC_IPC_MESSAGE_PIPE_READER_H_