chromium/extensions/browser/api/messaging/message_service.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef EXTENSIONS_BROWSER_API_MESSAGING_MESSAGE_SERVICE_H_
#define EXTENSIONS_BROWSER_API_MESSAGING_MESSAGE_SERVICE_H_

#include <map>
#include <memory>
#include <set>
#include <string>
#include <vector>

#include "base/compiler_specific.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/weak_ptr.h"
#include "extensions/browser/api/messaging/message_port.h"
#include "extensions/browser/api/messaging/native_message_host.h"
#include "extensions/browser/browser_context_keyed_api_factory.h"
#include "extensions/browser/lazy_context_id.h"
#include "extensions/browser/lazy_context_task_queue.h"
#include "extensions/common/api/messaging/message.h"
#include "extensions/common/api/messaging/port_id.h"
#include "extensions/common/extension_id.h"

class GURL;

namespace content {
class BrowserContext;
}

namespace extensions {

namespace mojom {
enum class ChannelType;
}

class ChannelEndpoint;
class Extension;
class ExtensionHost;
class MessagingDelegate;
struct MessagingEndpoint;
struct PortContext;

// This class manages message and event passing between renderer processes.
// It maintains a list of processes that are listening to events and a set of
// open channels.
//
// Messaging works this way:
// - An extension-owned script context (like a background page or a content
//   script) adds an event listener to the "onConnect" event.
// - Another context calls "runtime.connect()" to open a channel to the
// extension process, or an extension context calls "tabs.connect(tabId)" to
// open a channel to the content scripts for the given tab.  The EMS notifies
// the target process/tab, which then calls the onConnect event in every
// context owned by the connecting extension in that process/tab.
// - Once the channel is established, either side can call postMessage to send
// a message to the opposite side of the channel, which may have multiple
// listeners.
//
// Terminology:
// channel: connection between two ports
// port: One sender or receiver tied to one or more RenderFrameHost instances.
class MessageService : public BrowserContextKeyedAPI,
                       public MessagePort::ChannelDelegate { … };

}  // namespace extensions

#endif  // EXTENSIONS_BROWSER_API_MESSAGING_MESSAGE_SERVICE_H_