Issue 5617 - Provide with async executor bound to Platform in the future

include/AdblockPlus/Platform.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 12 matching lines @@
 #include "IFileSystem.h"
 #include "IWebRequest.h"
 #include "AppInfo.h"
 #include "Scheduler.h"
 #include "FilterEngine.h"
 #include <mutex>
 #include <future>
 
 namespace AdblockPlus
 {
-  /**
-   * A factory to construct DefaultTimer.
-   */
-  TimerPtr CreateDefaultTimer();
-
-  /**
-   * A factory to construct DefaultFileSystem.
-   */
-  FileSystemPtr CreateDefaultFileSystem(const Scheduler& scheduler, const std::string& basePath = std::string());
-
-  /**
-   * A factory to construct DefaultWebRequest.
-   */
-  WebRequestPtr CreateDefaultWebRequest(const Scheduler& scheduler, WebRequestSyncPtr syncImpl = nullptr);
-
-  /**
-   * A factory to construct LogSystem.
-   */
-  LogSystemPtr CreateDefaultLogSystem();
-
   class IV8IsolateProvider;
   class JsEngine;
 
   /**
    * AdblockPlus platform is the main component providing access to other
    * modules.
    *
    * It manages the functionality modules, e.g. JsEngine and FilterEngine as
    * well as allows to correctly work with asynchronous functionality.
    */
@@ skipping 21 matching lines @@
      */
     typedef std::function<void(const FilterEngine&)> OnFilterEngineCreatedCallback;
 
     /**
      * Platform constructor.
      *
      * When a parameter value is nullptr the corresponding default
      * implementation is chosen.
      */
     explicit Platform(CreationParameters&& creationParameters = CreationParameters());
-    ~Platform();
+    virtual ~Platform();
 
     /**
      * Ensures that JsEngine is constructed. If JsEngine is already present
      * then the parameters are ignored.
      *
      * @param appInfo Information about the app, 
      * @param isolate A provider of v8::Isolate, if the value is nullptr then
      *        a default implementation is used.
      */
     void SetUpJsEngine(const AppInfo& appInfo = AppInfo(), std::unique_ptr<IV8IsolateProvider> isolate = nullptr);
@@ skipping 45 matching lines @@
   private:
     LogSystemPtr logSystem;
     TimerPtr timer;
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     // used for creation and deletion of modules.
     std::mutex modulesMutex;
     std::shared_ptr<JsEngine> jsEngine;
     std::shared_future<FilterEnginePtr> filterEngine;
   };
+
+  /**
+   * A helper class allowing to construct a default Platform and to obtain
+   * the Scheduler used by Platform before the latter is constructed.
+   */
+  class DefaultPlatformBuilder : public Platform::CreationParameters
+  {
+  public:
+    /**
+     * Constructs a default executor for asynchronous tasks. When Platform
+     * is being destroyed it starts to ignore new tasks and waits for finishing
+     * of already running tasks.
+     * @return Scheduler allowing to execute tasks asynchronously.
+     */
+    Scheduler GetDefaultAsyncExecutor();
+
+    /**
+     * Constructs default implementation of `ITimer`.
+     */
+    void CreateDefaultTimer();
+
+    /**
+     * Constructs default implementation of `IFileSystem`.
+     * @param basePath A working directory for file system operations.
+     */
+    void CreateDefaultFileSystem(const std::string& basePath = std::string());
+
+    /**
+     * Constructs default implementation of `IWebRequest`.
+     */
+    void CreateDefaultWebRequest(WebRequestSyncPtr webRequest = nullptr);
+
+    /**
+     * Constructs default implementation of `LogSystem`.
+     */
+    void CreateDefaultLogSystem();
+
+    /**
+     * Constructs Platform with default implementations of platform interfaces
+     * when a corresponding field is nullptr and with a default Scheduler.
+     */
+    std::unique_ptr<Platform> CreatePlatform();
+  private:
+    std::shared_ptr<Scheduler> asyncExecutor;
+    Scheduler defaultScheduler;
+  };
 }
 
 #endif // ADBLOCK_PLUS_PLATFORM_H