// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_
#define CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_

#include "base/containers/lru_cache.h"
#include "base/gtest_prod_util.h"
#include "base/memory/safe_ref.h"
#include "base/sequence_checker.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "content/common/content_export.h"
#include "ui/display/display_observer.h"

namespace display {
class Display;
}

namespace content {

class NavigationEntryScreenshotCacheEvictor;

// This class manages the metadata for all `NavigationEntryScreenshot`s captured
// for the backward and forward navigation entries per `FrameTree`. The
// screenshots are used to present users with previews of the previous pages
// when the users initiate back/forward-navigations. This class is owned by a
// `BrowserContext`. All primary `FrameTree`s sharing the same `BrowserContext`
// share the same manager. The manager should only be accessed by the
// `NavigationEntryScreenshotCache` and tests.
class CONTENT_EXPORT NavigationEntryScreenshotManager
    : public display::DisplayObserver {
 public:
  NavigationEntryScreenshotManager();
  NavigationEntryScreenshotManager(const NavigationEntryScreenshotManager&) =
      delete;
  NavigationEntryScreenshotManager& operator=(
      const NavigationEntryScreenshotManager&) = delete;
  ~NavigationEntryScreenshotManager() override;

  void OnDisplayAdded(const display::Display&) override;
  void OnDisplaysRemoved(const display::Displays&) override;
  void OnDisplayMetricsChanged(const display::Display&,
                               uint32_t metrics_changed) override;

  // Called when a screenshot is stashed into a `NavigationEntry`, or when a
  // screenshot is removed from the entry (for preview, or during the
  // destruction of the entry).
  void OnScreenshotCached(NavigationEntryScreenshotCacheEvictor* cache,
                          size_t size);
  void OnScreenshotRemoved(NavigationEntryScreenshotCacheEvictor* cache,
                           size_t size);
  void OnScreenshotCompressed(NavigationEntryScreenshotCacheEvictor* cache,
                              size_t old_size,
                              size_t new_size);
  void OnVisibilityChanged(NavigationEntryScreenshotCacheEvictor* cache);

  bool IsEmpty() const;

  // Returns the current time. Allows overriding for tests.
  base::TimeTicks Now() const;

  size_t GetCurrentCacheSize() const { return current_cache_size_in_bytes_; }
  size_t GetMaxCacheSize() const { return max_cache_size_in_bytes_; }

  // Allow tests to customize memory budget.
  void SetMemoryBudgetForTesting(size_t size) {
    max_cache_size_in_bytes_ = size;
    UpdateMaxCacheSizeCrashKey();
  }
  void SetUITaskRunnerForTesting(
      scoped_refptr<base::SequencedTaskRunner> task_runner) {
    cleanup_task_.SetTaskRunner(std::move(task_runner));
  }
  void set_tick_clock_for_testing(base::TickClock* clock) {
    tick_clock_ = clock;
  }

  base::SafeRef<NavigationEntryScreenshotManager> GetSafeRef() const {
    return weak_factory_.GetSafeRef();
  }

 private:
  void RecalculateCacheSize();

  // Called when the first screenshot is cached into `cache`, and when the last
  // screenshot is removed from `cache`.
  void Register(NavigationEntryScreenshotCacheEvictor* cache);
  void Unregister(NavigationEntryScreenshotCacheEvictor* cache);

  void ScheduleCleanup(base::TimeTicks last_visible_time);
  void RunCleanup();

  // Called at the end of `OnScreenshotCached`.
  void EvictIfOutOfMemoryBudget();

  // Schedules recording the cache size in time intervals based on a Poisson
  // distribution.
  void RecordScreenshotCacheSizeAfterDelay();

  // Records memory usage by the captured screenshots and calls
  // `RecordScreenshotCacheSizeAfterDelay` to continue recording the memory
  // periodically.
  void RecordScreenshotCacheSize();

  void UpdateMaxCacheSizeCrashKey();
  void UpdateCurrentCacheSizeCrashKey();

  size_t max_cache_size_in_bytes_;
  size_t current_cache_size_in_bytes_ = 0U;

  // The most recently used cache is stored at the front of the
  // `base::LRUCacheSet`. A limited interface to the tab's cache is used so that
  // this BrowserContext-wide manager does not have access to details like URLs
  // or pixels within each tab.
  base::LRUCacheSet<NavigationEntryScreenshotCacheEvictor*> managed_caches_;

  raw_ptr<const base::TickClock> tick_clock_;
  base::OneShotTimer cleanup_task_;
  const base::TimeDelta cleanup_delay_;

  SEQUENCE_CHECKER(sequence_checker_);

  base::WeakPtrFactory<NavigationEntryScreenshotManager> weak_factory_{this};
};
}  // namespace content

#endif  // CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_