// Copyright 2018 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 THIRD_PARTY_BLINK_RENDERER_CORE_DISPLAY_LOCK_DISPLAY_LOCK_CONTEXT_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_DISPLAY_LOCK_DISPLAY_LOCK_CONTEXT_H_

#include "third_party/blink/renderer/bindings/core/v8/active_script_wrappable.h"
#include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/display_lock/display_lock_budget.h"
#include "third_party/blink/renderer/core/frame/local_frame_view.h"
#include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
#include "third_party/blink/renderer/platform/wtf/compiler.h"

namespace blink {

class DisplayLockSuspendedHandle;
class Element;
class DisplayLockOptions;
class DisplayLockScopedLogger;
class CORE_EXPORT DisplayLockContext final
    : public ScriptWrappable,
      public ActiveScriptWrappable<DisplayLockContext>,
      public ContextLifecycleObserver,
      public LocalFrameView::LifecycleNotificationObserver {
  DEFINE_WRAPPERTYPEINFO();
  USING_GARBAGE_COLLECTED_MIXIN(DisplayLockContext);
  USING_PRE_FINALIZER(DisplayLockContext, Dispose);

 public:
  // Determines what type of budget to use. This can be overridden via
  // DisplayLockContext::SetBudgetType().
  // - kDoNotYield:
  //     This will effectively do all of the lifecycle phases when we're
  //     committing. That is, this is the "no budget" option.
  // - kStrictYieldBetweenLifecyclePhases:
  //     This type always yields between each lifecycle phase, even if that
  //     phase was quick (note that it still skips phases that don't need any
  //     updates).
  // - kYieldBetweenLifecyclePhases:
  //     This type will only yield between lifecycle phases (not in the middle
  //     of one). However, if there is sufficient time left (TODO(vmpstr):
  //     define this), then it will continue on to the next lifecycle phase.
  enum class BudgetType {
    kDoNotYield,
    kStrictYieldBetweenLifecyclePhases,
    kYieldBetweenLifecyclePhases,
    kDefault = kYieldBetweenLifecyclePhases
  };

  // See GetScopedPendingFrameRect() for description.
  class ScopedPendingFrameRect {
   public:
    ScopedPendingFrameRect(ScopedPendingFrameRect&&);
    ~ScopedPendingFrameRect();

   private:
    friend class DisplayLockContext;

    ScopedPendingFrameRect(DisplayLockContext*);

    UntracedMember<DisplayLockContext> context_ = nullptr;
  };

  // See GetScopedForcedUpdate() for description.
  class ScopedForcedUpdate {
   public:
    ScopedForcedUpdate(ScopedForcedUpdate&&);
    ~ScopedForcedUpdate();

   private:
    friend class DisplayLockContext;

    ScopedForcedUpdate(DisplayLockContext*);

    UntracedMember<DisplayLockContext> context_ = nullptr;
  };

  DisplayLockContext(Element*, ExecutionContext*);
  ~DisplayLockContext() override;

  // GC functions.
  void Trace(blink::Visitor*) override;
  void Dispose();

  // ContextLifecycleObserver overrides.
  void ContextDestroyed(ExecutionContext*) override;
  // ActiveScriptWrappable overrides. This keeps the context alive as long as we
  // have an element and we're not unlocked.
  bool HasPendingActivity() const final;

  // JavaScript interface implementation. See display_lock_context.idl for
  // description.
  ScriptPromise acquire(ScriptState*, DisplayLockOptions*);
  ScriptPromise update(ScriptState*);
  ScriptPromise commit(ScriptState*);

  // Lifecycle observation / state functions.
  bool ShouldStyle() const;
  void DidStyle();
  bool ShouldLayout() const;
  void DidLayout();
  bool ShouldPrePaint() const;
  void DidPrePaint();
  bool ShouldPaint() const;
  void DidPaint();

  // Returns true if the contents of the associated element should be visible
  // for find-in-page and tab order.
  bool IsSearchable() const;

  // Called when the layout tree is attached. This is used to verify
  // containment.
  void DidAttachLayoutTree();

  // Returns a ScopedPendingFrameRect object which exposes the pending layout
  // frame rect to LayoutBox. This is used to ensure that children of the locked
  // element use the pending layout frame to update the size of the element.
  // After the scoped object is destroyed, the previous frame rect is restored
  // and the pending one is stored in the context until it is needed.
  ScopedPendingFrameRect GetScopedPendingFrameRect();

  // Returns a ScopedForcedUpdate object which for the duration of its lifetime
  // will allow updates to happen on this element's subtree. For the element
  // itself, the frame rect will still be the same as at the time the lock was
  // acquired. Only one ScopedForcedUpdate can be retrieved from the same
  // context at a time.
  ScopedForcedUpdate GetScopedForcedUpdate();

  // This is called when the element with which this context is associated is
  // moved to a new document. Used to listen to the lifecycle update from the
  // right document's view.
  void DidMoveToNewDocument(Document& old_document);

  // LifecycleNotificationObserver overrides.
  void WillStartLifecycleUpdate() override;
  void DidFinishLifecycleUpdate() override;

 private:
  friend class DisplayLockContextTest;
  friend class DisplayLockSuspendedHandle;
  friend class DisplayLockBudget;

  // The current state of the lock. Note that the order of these matters.
  enum State {
    kLocked,
    kUpdating,
    kCommitting,
    kUnlocked,
    kPendingAcquire,
  };

  // Initiate a commit.
  void StartCommit();
  // Initiate an update.
  void StartUpdateIfNeeded();

  // The following functions propagate dirty bits from the locked element up to
  // the ancestors in order to be reached. They return true if the element or
  // its subtree were dirty, and false otherwise.
  bool MarkAncestorsForStyleRecalcIfNeeded();
  bool MarkAncestorsForLayoutIfNeeded();
  bool MarkAncestorsForPrePaintIfNeeded();
  bool MarkPaintLayerNeedsRepaint();

  bool IsElementDirtyForStyleRecalc() const;
  bool IsElementDirtyForLayout() const;
  bool IsElementDirtyForPrePaint() const;

  // When ScopedPendingFrameRect is destroyed, it calls this function. See
  // GetScopedPendingFrameRect() for more information.
  void NotifyPendingFrameRectScopeEnded();

  // When ScopedForcedUpdate is destroyed, it calls this function. See
  // GetScopedForcedUpdate() for more information.
  void NotifyForcedUpdateScopeEnded();

  // Creates a new update budget based on the BudgetType::kDefault enum. In
  // other words, it will create a budget of that type.
  // TODO(vmpstr): In tests, we will probably switch the value to test other
  // budgets. As well, this makes it easier to change the budget right in the
  // enum definitions.
  std::unique_ptr<DisplayLockBudget> CreateNewBudget();

  // Helper to schedule an animation to delay lifecycle updates for the next
  // frame.
  void ScheduleAnimation();

  // Timeout implementation. When the lock is acquired, we kick off a timeout
  // task that will trigger a commit (which can be canceled by other calls to
  // schedule or by a call to commit). Note that calling RescheduleTimeoutTask()
  // will cancel any previously scheduled task.
  void RescheduleTimeoutTask(double delay);
  void CancelTimeoutTask();
  void TriggerTimeout();

  // Helper functions to resolve the update/commit promises.
  enum ResolverState { kResolve, kReject, kDetach };
  void FinishUpdateResolver(ResolverState);
  void FinishCommitResolver(ResolverState);
  void FinishAcquireResolver(ResolverState);
  void FinishResolver(Member<ScriptPromiseResolver>*, ResolverState);

  // Returns true if the element supports display locking. Note that this can
  // only be called if the style is clean. It checks the layout object if it
  // exists. Otherwise, falls back to checking computed style.
  bool ElementSupportsDisplayLocking() const;

  std::unique_ptr<DisplayLockBudget> update_budget_;

  Member<ScriptPromiseResolver> commit_resolver_;
  Member<ScriptPromiseResolver> update_resolver_;
  Member<ScriptPromiseResolver> acquire_resolver_;
  WeakMember<Element> element_;

  State state_ = kUnlocked;
  LayoutRect pending_frame_rect_;
  base::Optional<LayoutRect> locked_frame_rect_;

  bool update_forced_ = false;
  bool timeout_task_is_scheduled_ = false;

  base::WeakPtrFactory<DisplayLockContext> weak_factory_;
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_DISPLAY_LOCK_DISPLAY_LOCK_CONTEXT_H_