// Copyright 2015 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 COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_
#define COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_

#include <stddef.h>

#include <string>
#include <vector>

#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/sequenced_task_runner.h"
#include "base/timer/timer.h"
#include "components/keyed_service/core/keyed_service.h"
#include "components/ntp_snippets/inner_iterator.h"
#include "components/ntp_snippets/ntp_snippet.h"
#include "components/ntp_snippets/ntp_snippets_fetcher.h"
#include "components/ntp_snippets/ntp_snippets_scheduler.h"
#include "components/suggestions/suggestions_service.h"

class PrefService;

namespace base {
class FilePath;
class ListValue;
}

namespace suggestions {
class SuggestionsProfile;
}

namespace user_prefs {
class PrefRegistrySyncable;
}

namespace ntp_snippets {

class NTPSnippetsServiceObserver;

// Stores and vend fresh content data for the NTP.
class NTPSnippetsService : public KeyedService, NTPSnippetsFetcher::Observer {
 public:
  using NTPSnippetStorage = std::vector<scoped_ptr<NTPSnippet>>;
  using const_iterator =
      InnerIterator<NTPSnippetStorage::const_iterator, const NTPSnippet>;

  // |application_language_code| should be a ISO 639-1 compliant string. Aka
  // 'en' or 'en-US'. Note that this code should only specify the language, not
  // the locale, so 'en_US' (english language with US locale) and 'en-GB_US'
  // (British english person in the US) are not language code.
  NTPSnippetsService(PrefService* pref_service,
                     suggestions::SuggestionsService* suggestions_service,
                     scoped_refptr<base::SequencedTaskRunner> file_task_runner,
                     const std::string& application_language_code,
                     NTPSnippetsScheduler* scheduler,
                     scoped_ptr<NTPSnippetsFetcher> snippets_fetcher);
  ~NTPSnippetsService() override;

  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);

  void Init(bool enabled);

  // Fetches snippets from the server and adds them to the current ones.
  void FetchSnippets();

  // Inherited from KeyedService.
  void Shutdown() override;

  // True once the data is loaded in memory and available to loop over.
  bool is_loaded() { return loaded_; }

  // Observer accessors.
  void AddObserver(NTPSnippetsServiceObserver* observer);
  void RemoveObserver(NTPSnippetsServiceObserver* observer);

  // Number of snippets available. Can only be called when is_loaded() is true.
  NTPSnippetStorage::size_type size() {
    DCHECK(loaded_);
    return snippets_.size();
  }

  // The snippets can be iterated upon only via a const_iterator. Recommended
  // way to iterate is as follows:
  //
  // NTPSnippetsService service; // Assume is set.
  //  for (auto& snippet : *service) {
  //    // Snippet here is a const object.
  //  }
  const_iterator begin() {
    DCHECK(loaded_);
    return const_iterator(snippets_.begin());
  }
  const_iterator end() {
    DCHECK(loaded_);
    return const_iterator(snippets_.end());
  }

 private:
  void OnSuggestionsChanged(const suggestions::SuggestionsProfile& suggestions);
  void OnSnippetsDownloaded(const base::FilePath& download_path);
  void OnFileReadDone(const std::string* json, bool success);

  // Expects a top-level dictionary containing a "recos" list, which will be
  // passed to |LoadFromJSONList|.
  bool LoadFromJSONString(const std::string& str);

  // Expects a list of dictionaries each containing a "contentInfo" dictionary
  // with keys matching the properties of a  snippet (url, title, site_title,
  // etc...). The url is the only mandatory value.
  bool LoadFromJSONList(const base::ListValue& list);

  // TODO(treib): Investigate a better storage, maybe LevelDB or SQLite?
  void LoadFromPrefs();
  void StoreToPrefs();

  void RemoveExpiredSnippets();

  PrefService* pref_service_;

  suggestions::SuggestionsService* suggestions_service_;

  // True if the suggestions are loaded.
  bool loaded_;

  // The SequencedTaskRunner on which file system operations will be run.
  scoped_refptr<base::SequencedTaskRunner> file_task_runner_;

  // All the suggestions.
  NTPSnippetStorage snippets_;

  // The ISO 639-1 code of the language used by the application.
  const std::string application_language_code_;

  // The observers.
  base::ObserverList<NTPSnippetsServiceObserver> observers_;

  // Scheduler for fetching snippets. Not owned.
  NTPSnippetsScheduler* scheduler_;

  // The subscription to the SuggestionsService. When the suggestions change,
  // SuggestionsService will call |OnSuggestionsChanged|, which triggers an
  // update to the set of snippets.
  using SuggestionsSubscription =
      suggestions::SuggestionsService::ResponseCallbackList::Subscription;
  scoped_ptr<SuggestionsSubscription> suggestions_service_subscription_;

  // The snippets fetcher.
  scoped_ptr<NTPSnippetsFetcher> snippets_fetcher_;

  // The subscription to the snippets fetcher.
  scoped_ptr<NTPSnippetsFetcher::SnippetsAvailableCallbackList::Subscription>
      snippets_fetcher_callback_;

  // Timer that calls us back when the next snippet expires.
  base::OneShotTimer expiry_timer_;

  base::WeakPtrFactory<NTPSnippetsService> weak_ptr_factory_;

  friend class NTPSnippetsServiceTest;
  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, Loop);
  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, Full);
  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, CreationTimestampParseFail);
  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, RemoveExpiredContent);
  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, ObserverLoaded);
  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, ObserverNotLoaded);

  DISALLOW_COPY_AND_ASSIGN(NTPSnippetsService);
};

class NTPSnippetsServiceObserver {
 public:
  // Send everytime the service loads a new set of data.
  virtual void NTPSnippetsServiceLoaded(NTPSnippetsService* service) = 0;
  // Send when the service is shutting down.
  virtual void NTPSnippetsServiceShutdown(NTPSnippetsService* service) = 0;

 protected:
  virtual ~NTPSnippetsServiceObserver() {}
};

}  // namespace ntp_snippets

#endif  // COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_