// Copyright 2014 The Chromium Authors. All rights reserved.
// 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/atomicops.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "base/threading/thread_checker.h"
#include "ipc/ipc_message.h"
#include "ipc/mojo/ipc.mojom.h"
#include "mojo/public/cpp/bindings/associated_binding.h"
#include "mojo/public/cpp/system/core.h"

namespace IPC {
namespace internal {

class AsyncHandleWaiter;

// 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 MessagePipeReader : public mojom::Channel {
 public:
  class Delegate {
   public:
    virtual void OnMessageReceived(const Message& message) = 0;
    virtual void OnPipeClosed(MessagePipeReader* reader) = 0;
    virtual void OnPipeError(MessagePipeReader* reader) = 0;
  };

  // Delay the object deletion using the current message loop.
  // This is intended to used by MessagePipeReader owners.
  class DelayedDeleter {
   public:
    typedef std::default_delete<MessagePipeReader> DefaultType;

    static void DeleteNow(MessagePipeReader* ptr) { delete ptr; }

    DelayedDeleter() {}
    explicit DelayedDeleter(const DefaultType&) {}
    DelayedDeleter& operator=(const DefaultType&) { return *this; }

    void operator()(MessagePipeReader* ptr) const;
  };

  // Both parameters must be non-null.
  // Build a reader that reads messages from |receive_handle| and lets
  // |delegate| know.
  // Note that MessagePipeReader doesn't delete |delegate|.
  MessagePipeReader(mojom::ChannelAssociatedPtr sender,
                    mojo::AssociatedInterfaceRequest<mojom::Channel> receiver,
                    base::ProcessId peer_pid,
                    Delegate* delegate);
  ~MessagePipeReader() override;

  // Close and destroy the MessagePipe.
  void Close();
  // Close the mesage pipe with notifying the client with the error.
  void CloseWithError(MojoResult error);

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

  bool Send(scoped_ptr<Message> message);

  base::ProcessId GetPeerPid() const { return peer_pid_; }

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

 private:
  void Receive(mojom::MessagePtr message) override;

  // |delegate_| is null once the message pipe is closed.
  Delegate* delegate_;
  base::ProcessId peer_pid_;
  mojom::ChannelAssociatedPtr sender_;
  mojo::AssociatedBinding<mojom::Channel> binding_;
  base::ThreadChecker thread_checker_;

  DISALLOW_COPY_AND_ASSIGN(MessagePipeReader);
};

}  // namespace internal
}  // namespace IPC

#endif  // IPC_IPC_MESSAGE_PIPE_READER_H_