content/browser/prerender/prerender_host.h

// Copyright 2020 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 CONTENT_BROWSER_PRERENDER_PRERENDER_HOST_H_
#define CONTENT_BROWSER_PRERENDER_PRERENDER_HOST_H_

#include <memory>

#include "base/observer_list_types.h"
#include "base/types/pass_key.h"
#include "content/browser/renderer_host/back_forward_cache_impl.h"
#include "content/common/content_export.h"
#include "content/common/navigation_params.mojom.h"
#include "content/public/browser/global_routing_id.h"
#include "content/public/browser/render_frame_host.h"
#include "content/public/browser/web_contents_observer.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "third_party/blink/public/common/tokens/tokens.h"
#include "third_party/blink/public/mojom/prerender/prerender.mojom.h"
#include "url/gurl.h"

namespace content {

class FrameTree;
class PrerenderHostRegistry;
class RenderFrameHostImpl;
class WebContentsImpl;

// Prerender2:
// PrerenderHost creates a new FrameTree in WebContents associated with the page
// that triggered prerendering and starts prerendering. Then NavigationRequest
// is expected to find this host from PrerenderHostRegistry and activate the
// prerendered page upon navigation. This is created per request from a renderer
// process via PrerenderProcessor or will directly be created for
// browser-initiated prerendering (this code path is not implemented yet). This
// is owned by PrerenderHostRegistry.
class CONTENT_EXPORT PrerenderHost : public WebContentsObserver {
 public:
  class Observer : public base::CheckedObserver {
   public:
    // Called on the page activation.
    virtual void OnActivated() {}

    // Called from the PrerenderHost's destructor. The observer should drop any
    // reference to the host.
    virtual void OnHostDestroyed() {}
  };

  // These values are persisted to logs. Entries should not be renumbered and
  // numeric values should never be reused.
  enum class FinalStatus {
    kActivated = 0,
    kDestroyed = 1,
    kLowEndDevice = 2,
    kCrossOriginRedirect = 3,
    kCrossOriginNavigation = 4,
    kInvalidSchemeRedirect = 5,
    kInvalidSchemeNavigation = 6,
    kInProgressNavigation = 7,
    kNavigationRequestFailure = 8,
    kNavigationRequestBlockedByCsp = 9,
    kMainFrameNavigation = 10,
    kMojoBinderPolicy = 11,
    kPlugin = 12,
    kRendererProcessCrashed = 13,
    kRendererProcessKilled = 14,
    kDownload = 15,
    kTriggerDestroyed = 16,
    kNavigationNotCommitted = 17,
    kMaxValue = kNavigationNotCommitted,
  };

  PrerenderHost(blink::mojom::PrerenderAttributesPtr attributes,
                RenderFrameHostImpl& initiator_render_frame_host);
  ~PrerenderHost() override;

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

  // Returns false if prerendering hasn't been started.
  bool StartPrerendering();

  // WebContentsObserver implementation:
  void DidFinishNavigation(NavigationHandle* navigation_handle) override;

  // Activates the prerendered page and returns BackForwardCacheImpl::Entry
  // containing the page. This must be called after this host gets ready for
  // activation.
  //
  // TODO(https://crbug.com/1181263): Refactor BackForwardCacheImpl::Entry into
  // a generic "page" object to make clear that the same logic is also used for
  // prerendering.
  std::unique_ptr<BackForwardCacheImpl::Entry> Activate(
      NavigationRequest& navigation_request);

  // Returns true if the navigation params that were used in the initial
  // prerender navigation (i.e., in StartPrerendering()) match the navigation
  // params in `navigation_request`. This function can be used to determine
  // whether `navigation_request` may be eligible to activate this
  // PrerenderHost.
  bool AreInitialPrerenderNavigationParamsCompatibleWithNavigation(
      NavigationRequest& navigation_request);

  // Returns the main RenderFrameHost of the prerendered page.
  // This must be called after StartPrerendering() and before Activate().
  RenderFrameHostImpl* GetPrerenderedMainFrameHost();

  // Tells the reason of the destruction of this host. PrerenderHostRegistry
  // uses this before abandoning the host.
  void RecordFinalStatus(base::PassKey<PrerenderHostRegistry>,
                         FinalStatus status);

  // Waits until the page load finishes.
  void WaitForLoadStopForTesting();

  const GURL& GetInitialUrl() const;

  void AddObserver(Observer* observer);
  void RemoveObserver(Observer* observer);

  // The initial navigation id is set by the PrerenderNavigationThrottle
  // when the PrerenderHost is first navigated, which happens immediately
  // after creation.
  absl::optional<int64_t> GetInitialNavigationId() const;
  void SetInitialNavigationId(int64_t navigation_id);

  url::Origin initiator_origin() const { return initiator_origin_; }

  int frame_tree_node_id() const { return frame_tree_node_id_; }

  bool is_ready_for_activation() const { return is_ready_for_activation_; }

 private:
  class PageHolder;

  void RecordFinalStatus(FinalStatus status);

  void CreatePageHolder(WebContentsImpl& web_contents);

  // Asks the registry to cancel prerendering.
  void Cancel(FinalStatus status);

  // TODO(https://crbug.com/1217045): Flatten the params and do not rely on
  // PrerenderAttributesPtr.
  const blink::mojom::PrerenderAttributesPtr attributes_;
  const url::Origin initiator_origin_;
  const int initiator_process_id_;
  const blink::LocalFrameToken initiator_frame_token_;

  // Indicates if `page_holder_` is ready for activation.
  bool is_ready_for_activation_ = false;

  // The ID of the root node of the frame tree for the prerendered page `this`
  // is hosting. Since PrerenderHost has 1:1 correspondence with FrameTree,
  // this is also used for the ID of this PrerenderHost.
  int frame_tree_node_id_ = RenderFrameHost::kNoFrameTreeNodeId;

  absl::optional<FinalStatus> final_status_;

  std::unique_ptr<PageHolder> page_holder_;

  base::ObserverList<Observer> observers_;

  // Navigation parameters for the navigation which loaded the main document of
  // the prerendered page, copied immediately after BeginNavigation. They will
  // be compared with the navigation parameters of the potential activation when
  // attempting to reserve the prerender host for a navigation.
  mojom::BeginNavigationParamsPtr begin_params_;
  mojom::CommonNavigationParamsPtr common_params_;

  // Holds the navigation ID for the main frame initial navigation.
  absl::optional<int64_t> initial_navigation_id_;
};

}  // namespace content

#endif  // CONTENT_BROWSER_PRERENDER_PRERENDER_HOST_H_