ios/chrome/browser/favicon/favicon_loader.h

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef IOS_CHROME_BROWSER_FAVICON_FAVICON_LOADER_H_
#define IOS_CHROME_BROWSER_FAVICON_FAVICON_LOADER_H_

#import <Foundation/Foundation.h>

#include "base/task/cancelable_task_tracker.h"
#include "components/keyed_service/core/keyed_service.h"

class GURL;
@class FaviconAttributes;

namespace favicon {
class LargeIconService;
}

// A class that manages asynchronously loading favicons or fallback attributes
// from LargeIconService and caching them, given a URL.
class FaviconLoader : public KeyedService {
 public:
  // Type for completion block for FaviconForURL().
  typedef void (^FaviconAttributesCompletionBlock)(FaviconAttributes*);

  explicit FaviconLoader(favicon::LargeIconService* large_icon_service);

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

  ~FaviconLoader() override;

  // Tries to find a FaviconAttributes in `favicon_cache_` with `page_url`:
  // If found, invokes `favicon_block_handler` and exits.
  // If not found, invokes `favicon_block_handler` with a default placeholder
  // then invokes it again asynchronously with the favicon fetched by trying
  // following methods:
  //   1. Use `large_icon_service_` to fetch from local DB managed by
  //      HistoryService;
  //   2. Use `large_icon_service_` to fetch from Google Favicon server if
  //      `fallback_to_google_server=true` (`size_in_points` is ignored when
  //      fetching from the Google server);
  //   3. Create a favicon base on the fallback style from `large_icon_service`.
  void FaviconForPageUrl(
      const GURL& page_url,
      float size_in_points,
      float min_size_in_points,
      bool fallback_to_google_server,
      FaviconAttributesCompletionBlock favicon_block_handler);

  // Tries to find a FaviconAttributes in `favicon_cache_` with `page_url`:
  // If found, invokes `favicon_block_handler` and exits.
  // If not found, invokes `favicon_block_handler` with a default placeholder
  // then invokes it again asynchronously with the favicon fetched by trying
  // following methods:
  //   1. Use `large_icon_service_` to fetch from local DB managed by
  //      HistoryService;
  //   2. Create a favicon base on the fallback style from `large_icon_service`.
  void FaviconForPageUrlOrHost(
      const GURL& page_url,
      float size_in_points,
      FaviconAttributesCompletionBlock favicon_block_handler);

  // Tries to find a FaviconAttributes in `favicon_cache_` with `icon_url`:
  // If found, invokes `favicon_block_handler` and exits.
  // If not found, invokes `favicon_block_handler` with a default placeholder
  // then invokes it again asynchronously with the favicon fetched by trying
  // following methods:
  //   1. Use `large_icon_service_` to fetch from local DB managed by
  //      HistoryService;
  //   2. Create a favicon base on the fallback style from `large_icon_service`.
  void FaviconForIconUrl(
      const GURL& icon_url,
      float size_in_points,
      float min_size_in_points,
      FaviconAttributesCompletionBlock favicon_block_handler);

  // Cancel all incomplete requests.
  void CancellAllRequests();

  // Return a weak pointer to the current object.
  base::WeakPtr<FaviconLoader> AsWeakPtr();

 private:
  // The LargeIconService used to retrieve favicon.
  favicon::LargeIconService* large_icon_service_;

  // Tracks tasks sent to FaviconService.
  base::CancelableTaskTracker cancelable_task_tracker_;
  // Holds cached favicons. This NSCache is populated as favicons or fallback
  // attributes are retrieved from `large_icon_service_`. Contents will be
  // removed during low-memory conditions based on its inherent LRU removal
  // algorithm. Keyed by NSString of URL (page URL or icon URL) spec.
  NSCache<NSString*, FaviconAttributes*>* favicon_cache_;

  base::WeakPtrFactory<FaviconLoader> weak_ptr_factory_{this};
};

#endif  // IOS_CHROME_BROWSER_FAVICON_FAVICON_LOADER_H_