text: // Copyright 2019 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 CHROMECAST_RENDERER_NATIVE_BINDINGS_HELPER_H_
  #define CHROMECAST_RENDERER_NATIVE_BINDINGS_HELPER_H_
  
  #include <string>
  
  #include "base/bind.h"
  #include "base/macros.h"
  #include "content/public/renderer/render_frame_observer.h"
  #include "gin/function_template.h"
  #include "v8/include/v8.h"
  namespace content {
  class RenderFrame;
  }
  
  namespace chromecast {
  
  // Returns the reference to "cast.__platform__", creating it if necessary.
  v8::Local<v8::Object> GetOrCreateCastPlatformObject(
      v8::Isolate* isolate,
      v8::Local<v8::Object> global);
  
  // Returns parent[key], creating it as a v8::Object if necessary. This will
  // aggressively overwrite things that are not objects.
  v8::Local<v8::Object> EnsureObjectExists(v8::Isolate* isolate,
                                           v8::Local<v8::Object> parent,
                                           const std::string& key);
  
  // Binds |method| and |args| into a JS function named |method_name| which will
  // be attached to |parent_object|. Return the bound function to caller.
  template <typename Functor, typename... Args>
  v8::Local<v8::Function> InstallBinding(v8::Isolate* isolate,
                                         v8::Local<v8::Object> parent_object,
                                         std::string method_name,
                                         Functor method,
                                         Args&&... args) {
    v8::Local<v8::FunctionTemplate> temp(gin::CreateFunctionTemplate(
        isolate, base::BindRepeating(method, std::forward<Args>(args)...)));
    v8::Local<v8::Function> func =
        temp->GetFunction(isolate->GetCurrentContext()).ToLocalChecked();
    v8::Maybe<bool> result = parent_object->Set(
        isolate->GetCurrentContext(),
        gin::StringToSymbol(isolate, std::move(method_name)), func);
    if (result.IsNothing() || !result.FromJust())
      LOG(ERROR) << "Failed to install binging for method " << method_name;
  
    return func;
  }
  
  // Template for managing the lifetime of a cast_shell binding. Derive from
  // from CastBinding and the class will be destroyed when the frame is
  // destroyed.
  class CastBinding : public content::RenderFrameObserver {
   public:
    CastBinding(const CastBinding&) = delete;
    CastBinding& operator=(const CastBinding&) = delete;
  
    void TryInstall();
  
   protected:
    explicit CastBinding(content::RenderFrame* render_frame);
    ~CastBinding() override;
  
    // content::RenderFrameObserver implementation:
    void DidClearWindowObject() final;
    void OnDestruct() final;
  
    // Adds function bindings to the cast.__platform__ object.
    // The function can be called multiple times, sub classes should make sure
    // the binding is updated in every call.
    virtual void Install(v8::Local<v8::Object> cast_platform,
                         v8::Isolate* isolate) = 0;
  };
  
  }  // namespace chromecast
  
  #endif  // CHROMECAST_RENDERER_NATIVE_BINDINGS_HELPER_H_
  