Add new API function: feedbackPrivate.readLogSource

chrome/browser/extensions/api/feedback_private/log_source_access_manager.h

Index: chrome/browser/extensions/api/feedback_private/log_source_access_manager.h
diff --git a/chrome/browser/extensions/api/feedback_private/log_source_access_manager.h b/chrome/browser/extensions/api/feedback_private/log_source_access_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..0559d1cf32d5cea994d218dbae8bb18ecae39fbb
--- /dev/null
+++ b/chrome/browser/extensions/api/feedback_private/log_source_access_manager.h
@@ -0,0 +1,144 @@
+// Copyright 2017 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 CHROME_BROWSER_EXTENSIONS_API_FEEDBACK_PRIVATE_LOG_SOURCE_ACCESS_MANAGER_H_
+#define CHROME_BROWSER_EXTENSIONS_API_FEEDBACK_PRIVATE_LOG_SOURCE_ACCESS_MANAGER_H_
+
+#include <map>
+#include <string>
+#include <utility>
+
+#include "base/callback.h"
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time/tick_clock.h"
+#include "base/time/time.h"
+#include "chrome/browser/feedback/system_logs/system_logs_fetcher.h"
+#include "chrome/common/extensions/api/feedback_private.h"
+#include "content/public/browser/browser_context.h"
+
+namespace extensions {
+
+// Provides bookkeepping for SingleLogSource usage. It ensures that:
+// - Each extension can have only one SingleLogSource for a particular source.
+// - A source may not be accessed too frequently by an extension.
+class LogSourceAccessManager {
+ public:
+  using ReadLogSourceCallback =
+      base::Callback<void(const api::feedback_private::ReadLogSourceResult&)>;
+
+  explicit LogSourceAccessManager(content::BrowserContext* context);
+  ~LogSourceAccessManager();
+
+  // To override the default rate-limiting mechanism of this function, pass in
+  // a TimeDelta representing the desired minimum time between consecutive reads
+  // of a source from an extension. Does not take ownership of |timeout|. When
+  // done testing, call this function again with |timeout|=nullptr to reset to
+  // the default behavior.
+  static void SetRateLimitingTimeoutForTesting(const base::TimeDelta* timeout);
+
+  // Override the default base::Time clock with a custom clock for testing.
+  // Pass in |clock|=nullptr to revert to default behavior.
+  void SetTickClockForTesting(std::unique_ptr<base::TickClock> clock) {
+    tick_clock_ = std::move(clock);
+  }
+
+  // Initiates a fetch from a log source, as specified in |params|. See
+  // feedback_private.idl for more info about the actual parameters.
+  bool FetchFromSource(const api::feedback_private::ReadLogSourceParams& params,
+                       const std::string& extension_id,
+                       const ReadLogSourceCallback& callback);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(LogSourceAccessManagerTest,
+                           MaxNumberOfOpenLogSources);
+
+  // Contains a source/extension pair.
+  struct SourceAndExtension {
+    explicit SourceAndExtension(api::feedback_private::LogSource source,
+                                const std::string& extension_id);
+
+    bool operator<(const SourceAndExtension& other) const {
+      return std::make_pair(source, extension_id) <
+             std::make_pair(other.source, other.extension_id);
+    }
+
+    api::feedback_private::LogSource source;
+    std::string extension_id;
+  };
+
+  // Creates a new LogSourceResource for the source and extension indicated by
+  // |key|. Stores the new resource in the API Resource Manager and stores the
+  // resource ID in |sources_| as a new entry. Returns the nonzero ID of the
+  // newly created resource, or 0 if there was already an existing resource for
+  // |key|.
+  int CreateResource(const SourceAndExtension& key);
+
+  // Callback that is passed to the log source from FetchFromSource.
+  // Arguments:
+  // - key: The source that was read, and the extension requesting the read.
+  // - delete_source: Set this if the source indicated by |key| should be
+  //   removed from both the API Resource Manager and from |sources_|.
+  // - response_callback: Callback for sending the response as a
+  //   ReadLogSourceResult struct.
+  void OnFetchComplete(const SourceAndExtension& key,
+                       bool delete_source,
+                       const ReadLogSourceCallback& callback,
+                       system_logs::SystemLogsResponse* response);
+
+  // Removes an existing log source indicated by |key| from both the API
+  // Resource Manager and |sources_|.
+  void RemoveSource(const SourceAndExtension& key);
+
+  // Attempts to update the entry for |key| in |last_access_times_| to the
+  // current time, to record that the source is being accessed by the extension
+  // right now. If less than |min_time_between_reads_| has elapsed since the
+  // last successful read, do not update the timestamp in |last_access_times_|,
+  // and instead return false. Otherwise returns true.
+  //
+  // Creates a new entry in |last_access_times_| if it doesn't exist. Will not
+  // delete from |last_access_times_|.
+  bool UpdateSourceAccessTime(const SourceAndExtension& key);
+
+  // Returns the last time that |key.source| was accessed by |key.extension|.
+  // If it was never accessed by the extension, returns an empty base::TimeTicks
+  // object.
+  base::TimeTicks GetLastExtensionAccessTime(
+      const SourceAndExtension& key) const;
+
+  // Returns the number of entries in |sources_| with source=|source|.
+  size_t GetNumActiveResourcesForSource(
+      api::feedback_private::LogSource source) const;
+
+  // Every SourceAndExtension is linked to a unique SingleLogSource.
+  //
+  // Keys: SourceAndExtension for which a SingleLogSource has been created
+  //       and not yet destroyed. (i.e. currently in use).
+  // Values: ID of the API Resource containing the SingleLogSource.
+  std::map<SourceAndExtension, int> sources_;
+
+  // Keeps track of the last time each source was accessed by each extension.
+  // Each time FetchFromSource() is called, the timestamp gets updated.
+  //
+  // This intentionally kept separate from |sources_| because entries can be
+  // removed from and re-added to |sources_|, but that should not erase the
+  // recorded access times.
+  std::map<SourceAndExtension, base::TimeTicks> last_access_times_;
+
+  // For fetching browser resources like ApiResourceManager.
+  content::BrowserContext* context_;
+
+  // Provides a timer clock implementation for keeping track of access times.
+  // Can override the default clock for testing.
+  std::unique_ptr<base::TickClock> tick_clock_;
+
+  base::WeakPtrFactory<LogSourceAccessManager> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(LogSourceAccessManager);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_FEEDBACK_PRIVATE_LOG_SOURCE_ACCESS_MANAGER_H_