// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_OMNIBOX_BROWSER_SHORTCUTS_BACKEND_H_
#define COMPONENTS_OMNIBOX_BROWSER_SHORTCUTS_BACKEND_H_

#include <map>
#include <memory>
#include <set>
#include <string>

#include "base/containers/span.h"
#include "base/files/file_path.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/scoped_observation.h"
#include "base/synchronization/lock.h"
#include "base/task/sequenced_task_runner.h"
#include "components/history/core/browser/history_service.h"
#include "components/history/core/browser/history_service_observer.h"
#include "components/keyed_service/core/refcounted_keyed_service.h"
#include "components/omnibox/browser/autocomplete_match.h"
#include "components/omnibox/browser/shortcuts_database.h"
#include "components/search_engines/search_terms_data.h"
#include "components/search_engines/template_url_service_observer.h"
#include "url/gurl.h"

class ShortcutsBackend;
class TemplateURLService;
struct TestShortcutData;

void PopulateShortcutsBackendWithTestData(
    scoped_refptr<ShortcutsBackend> backend,
    base::span<TestShortcutData> db);

class ShortcutsDatabase;

// This class manages the shortcut provider backend - access to database on the
// db thread, etc.
class ShortcutsBackend : public RefcountedKeyedService,
                         public history::HistoryServiceObserver,
                         public TemplateURLServiceObserver {
 public:
  typedef std::multimap<std::u16string, const ShortcutsDatabase::Shortcut>
      ShortcutMap;

  // Get either `contents`, `description`, or `description_class_for_shortcuts`
  // (or their classifications) depending on the method called,
  // `swap_contents_and_description`, and whether
  // `description_class_for_shortcuts` is empty.
  // TODO(manukh): Simplify these once `swap_contents_and_description` is
  //   removed.
  static const std::u16string& GetDescription(const AutocompleteMatch& match);
  static const std::u16string& GetSwappedDescription(
      const AutocompleteMatch& match);
  static const ACMatchClassifications& GetDescriptionClass(
      const AutocompleteMatch& match);
  static const std::u16string& GetContents(const AutocompleteMatch& match);
  static const std::u16string& GetSwappedContents(
      const AutocompleteMatch& match);
  static const ACMatchClassifications& GetContentsClass(
      const AutocompleteMatch& match);

  // For unit testing, set |suppress_db| to true to prevent creation
  // of the database, in which case all operations are performed in memory only.
  ShortcutsBackend(TemplateURLService* template_url_service,
                   std::unique_ptr<SearchTermsData> search_terms_data,
                   history::HistoryService* history_service,
                   base::FilePath database_path,
                   bool suppress_db);

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

  // The interface is guaranteed to be called on the thread AddObserver()
  // was called.
  class ShortcutsBackendObserver {
   public:
    // Called after the database is loaded and Init() completed.
    virtual void OnShortcutsLoaded() = 0;
    // Called when shortcuts changed (added/updated/removed) in the database.
    virtual void OnShortcutsChanged() {}

   protected:
    virtual ~ShortcutsBackendObserver() = default;
  };

  // Asynchronously initializes the ShortcutsBackend, it is safe to call
  // multiple times - only the first call will be processed.
  bool Init();

  // All of the public functions *must* be called on UI thread only!

  bool initialized() const { return current_state_ == INITIALIZED; }
  const ShortcutMap& shortcuts_map() const { return shortcuts_map_; }

  // Deletes the Shortcuts with the url.
  bool DeleteShortcutsWithURL(const GURL& shortcut_url);

  // Deletes the Shortcuts that begin with the url.
  bool DeleteShortcutsBeginningWithURL(const GURL& shortcut_url);

  void AddObserver(ShortcutsBackendObserver* obs);
  void RemoveObserver(ShortcutsBackendObserver* obs);

  // Looks for an existing shortcut to match.destination_url that starts with
  // |text|.  Updates that shortcut if found, otherwise adds a new shortcut.
  void AddOrUpdateShortcut(const std::u16string& text,
                           const AutocompleteMatch& match);

 private:
  friend class base::RefCountedThreadSafe<ShortcutsBackend>;
  friend class FakeShortcutsBackend;
  friend void PopulateShortcutsBackendWithTestData(
      scoped_refptr<ShortcutsBackend> backend,
      base::span<TestShortcutData> db);

  enum CurrentState {
    NOT_INITIALIZED,  // Backend created but not initialized.
    INITIALIZING,     // Init() called, but not completed yet.
    INITIALIZED,      // Initialization completed, all accessors can be safely
                      // called.
  };

  typedef std::map<std::string, ShortcutMap::iterator> GuidMap;

  ~ShortcutsBackend() override;

  static ShortcutsDatabase::Shortcut::MatchCore MatchToMatchCore(
      const AutocompleteMatch& match,
      TemplateURLService* template_url_service,
      SearchTermsData* search_terms_data);

  // RefcountedKeyedService:
  void ShutdownOnUIThread() override;

  // history::HistoryServiceObserver:
  void OnHistoryDeletions(history::HistoryService* history_service,
                          const history::DeletionInfo& deletion_info) override;

  // TemplateURLServiceObserver:
  void OnTemplateURLServiceChanged() override;
  void OnTemplateURLServiceShuttingDown() override;

  // Internal initialization of the back-end. Posted by Init() to the DB thread.
  // On completion posts InitCompleted() back to UI thread.
  void InitInternal();

  // Finishes initialization on UI thread, notifies all observers.
  void InitCompleted();

  // Computes and records various metrics for the database. Should only be
  // called once and only upon successful Init and before deleting old
  // shortcuts.
  void ComputeDatabaseMetrics();

  // Adds the Shortcut to the database.
  bool AddShortcut(const ShortcutsDatabase::Shortcut& shortcut);

  // Updates timing and selection count for the Shortcut.
  bool UpdateShortcut(const ShortcutsDatabase::Shortcut& shortcut);

  // Deletes the Shortcuts with these IDs.
  bool DeleteShortcutsWithIDs(
      const ShortcutsDatabase::ShortcutIDs& shortcut_ids);

  // Deletes all shortcuts whose URLs begin with |url|.  If |exact_match| is
  // true, only shortcuts from exactly |url| are deleted.
  bool DeleteShortcutsWithURL(const GURL& url, bool exact_match);

  // Deletes all shortcuts whose `keyword` no longer exists in the
  // `template_url_service_` or whose `keyword` is inactive.
  // This is called once on initialization by `DeleteOldShortcuts()` and
  // whenever the `template_url_service_` is updated.
  void DeleteShortcutsWithDeletedOrInactiveKeywords();
  ShortcutsDatabase::ShortcutIDs GetShortcutsWithDeletedOrInactiveKeywords()
      const;

  // Deletes all of the shortcuts.
  bool DeleteAllShortcuts();

  // Deletes all shortcuts whose `last_access_time` is older than the threshold
  // defined by `HistoryBackend` and all shortcuts whose `keyword` no longer
  // exists in the `template_url_service_` or whose `keyword` is inactive. This
  // is called once on initialization after a short delay in order to remove any
  // shortcuts that have not been removed by calls to `OnHistoryDeletions()` and
  // `OnTemplateURLServiceChanged()`. `OnHistoryDeletions()` is called from
  // `HistoryService`, which can be initialized and running before
  // `ShortcutsBackend` is created since the former is created at browser
  // startup but the latter is not created until a browser window has been
  // created, leading to the initialization of the autocomplete system.
  bool DeleteOldShortcuts();
  ShortcutsDatabase::ShortcutIDs GetShortcutsWithExpiredTime() const;

  raw_ptr<TemplateURLService> template_url_service_;
  std::unique_ptr<SearchTermsData> search_terms_data_;

  CurrentState current_state_;
  base::ObserverList<ShortcutsBackendObserver>::Unchecked observer_list_;
  scoped_refptr<ShortcutsDatabase> db_;

  // The |temp_shortcuts_map_| and |temp_guid_map_| used for temporary storage
  // between InitInternal() and InitComplete() to avoid doing a potentially huge
  // copy.
  std::unique_ptr<ShortcutMap> temp_shortcuts_map_;
  std::unique_ptr<GuidMap> temp_guid_map_;

  ShortcutMap shortcuts_map_;
  // This is a helper map for quick access to a shortcut by guid.
  GuidMap guid_map_;

  base::ScopedObservation<history::HistoryService,
                          history::HistoryServiceObserver>
      history_service_observation_{this};
  base::ScopedObservation<TemplateURLService, TemplateURLServiceObserver>
      template_url_service_observation_{this};

  scoped_refptr<base::SequencedTaskRunner> main_runner_;
  scoped_refptr<base::SequencedTaskRunner> db_runner_;

  // For some unit-test only.
  bool no_db_access_;

  base::WeakPtrFactory<ShortcutsBackend> weak_factory_{this};
};

#endif  // COMPONENTS_OMNIBOX_BROWSER_SHORTCUTS_BACKEND_H_