Revert of Revert of Componentize HistoryURLProvider/ScoredHistoryMatch.

components/omnibox/history_url_provider.h

Index: components/omnibox/history_url_provider.h
diff --git a/components/omnibox/history_url_provider.h b/components/omnibox/history_url_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..e22c6ce14bfd122543bcb2804cbdabb01aa16a71
--- /dev/null
+++ b/components/omnibox/history_url_provider.h
@@ -0,0 +1,344 @@
+// Copyright (c) 2012 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_OMNIBOX_HISTORY_URL_PROVIDER_H_
+#define COMPONENTS_OMNIBOX_HISTORY_URL_PROVIDER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/synchronization/cancellation_flag.h"
+#include "base/threading/thread_checker.h"
+#include "components/history/core/browser/history_match.h"
+#include "components/omnibox/autocomplete_input.h"
+#include "components/omnibox/history_provider.h"
+#include "components/omnibox/omnibox_field_trial.h"
+#include "components/search_engines/template_url.h"
+
+class AutocompleteProviderListener;
+class SearchTermsData;
+
+namespace base {
+class MessageLoop;
+}
+
+namespace history {
+class HistoryBackend;
+class URLDatabase;
+}
+
+// How history autocomplete works
+// ==============================
+//
+// Read down this diagram for temporal ordering.
+//
+//   Main thread                History thread
+//   -----------                --------------
+//   AutocompleteController::Start
+//     -> HistoryURLProvider::Start
+//       -> SuggestExactInput
+//       [params_ allocated]
+//       -> DoAutocomplete (for inline autocomplete)
+//         -> URLDatabase::AutocompleteForPrefix (on in-memory DB)
+//       -> HistoryService::ScheduleAutocomplete
+//       (return to controller) ----
+//                                 /
+//                            HistoryBackend::ScheduleAutocomplete
+//                              -> HistoryURLProvider::ExecuteWithDB
+//                                -> DoAutocomplete
+//                                  -> URLDatabase::AutocompleteForPrefix
+//                              /
+//   HistoryService::QueryComplete
+//     [params_ destroyed]
+//     -> AutocompleteProviderListener::OnProviderUpdate
+//
+// The autocomplete controller calls us, and must be called back, on the main
+// thread.  When called, we run two autocomplete passes.  The first pass runs
+// synchronously on the main thread and queries the in-memory URL database.
+// This pass promotes matches for inline autocomplete if applicable.  We do
+// this synchronously so that users get consistent behavior when they type
+// quickly and hit enter, no matter how loaded the main history database is.
+// Doing this synchronously also prevents inline autocomplete from being
+// "flickery" in the AutocompleteEdit.  Because the in-memory DB does not have
+// redirect data, results other than the top match might change between the
+// two passes, so we can't just decide to use this pass' matches as the final
+// results.
+//
+// The second autocomplete pass uses the full history database, which must be
+// queried on the history thread.  Start() asks the history service schedule to
+// callback on the history thread with a pointer to the main database.  When we
+// are done doing queries, we schedule a task on the main thread that notifies
+// the AutocompleteController that we're done.
+//
+// The communication between these threads is done using a
+// HistoryURLProviderParams object.  This is allocated in the main thread, and
+// normally deleted in QueryComplete().  So that both autocomplete passes can
+// use the same code, we also use this to hold results during the first
+// autocomplete pass.
+//
+// While the second pass is running, the AutocompleteController may cancel the
+// request.  This can happen frequently when the user is typing quickly.  In
+// this case, the main thread sets params_->cancel, which the background thread
+// checks periodically.  If it finds the flag set, it stops what it's doing
+// immediately and calls back to the main thread.  (We don't delete the params
+// on the history thread, because we should only do that when we can safely
+// NULL out params_, and that must be done on the main thread.)
+
+// Used to communicate autocomplete parameters between threads via the history
+// service.
+struct HistoryURLProviderParams {
+  // See comments on |promote_type| below.
+  enum PromoteType {
+    WHAT_YOU_TYPED_MATCH,
+    FRONT_HISTORY_MATCH,
+    NEITHER,
+  };
+
+  HistoryURLProviderParams(const AutocompleteInput& input,
+                           bool trim_http,
+                           const AutocompleteMatch& what_you_typed_match,
+                           const std::string& languages,
+                           TemplateURL* default_search_provider,
+                           const SearchTermsData& search_terms_data);
+  ~HistoryURLProviderParams();
+
+  base::MessageLoop* message_loop;
+
+  // A copy of the autocomplete input. We need the copy since this object will
+  // live beyond the original query while it runs on the history thread.
+  AutocompleteInput input;
+
+  // Should inline autocompletion be disabled? This is initalized from
+  // |input.prevent_inline_autocomplete()|, but set to false is the input
+  // contains trailing white space.
+  bool prevent_inline_autocomplete;
+
+  // Set when "http://" should be trimmed from the beginning of the URLs.
+  bool trim_http;
+
+  // A match corresponding to what the user typed.
+  AutocompleteMatch what_you_typed_match;
+
+  // Set by the main thread to cancel this request.  If this flag is set when
+  // the query runs, the query will be abandoned.  This allows us to avoid
+  // running queries that are no longer needed.  Since we don't care if we run
+  // the extra queries, the lack of signaling is not a problem.
+  base::CancellationFlag cancel_flag;
+
+  // Set by ExecuteWithDB() on the history thread when the query could not be
+  // performed because the history system failed to properly init the database.
+  // If this is set when the main thread is called back, it avoids changing
+  // |matches_| at all, so it won't delete the default match Start() creates.
+  bool failed;
+
+  // List of matches written by DoAutocomplete().  Upon its return the provider
+  // converts this list to ACMatches and places them in |matches_|.
+  history::HistoryMatches matches;
+
+  // True if the suggestion for exactly what the user typed appears as a known
+  // URL in the user's history.  In this case, this will also be the first match
+  // in |matches|.
+  //
+  // NOTE: There are some complications related to keeping things consistent
+  // between passes and how we deal with intranet URLs, which are too complex to
+  // explain here; see the implementations of DoAutocomplete() and
+  // FixupExactSuggestion() for specific comments.
+  bool exact_suggestion_is_in_history;
+
+  // Tells the provider whether to promote the what you typed match, the first
+  // element of |matches|, or neither as the first AutocompleteMatch.  If
+  // |exact_suggestion_is_in_history| is true (and thus "the what you typed
+  // match" and "the first element of |matches|" represent the same thing), this
+  // will be set to WHAT_YOU_TYPED_MATCH.
+  //
+  // NOTE: The second pass of DoAutocomplete() checks what the first pass set
+  // this to.  See comments in DoAutocomplete().
+  PromoteType promote_type;
+
+  // True if |what_you_typed_match| is eligible for display.  If this is true,
+  // PromoteMatchesIfNecessary() may choose to place |what_you_typed_match| on
+  // |matches_| even when |promote_type| is not WHAT_YOU_TYPED_MATCH.
+  bool have_what_you_typed_match;
+
+  // Languages we should pass to gfx::GetCleanStringFromUrl.
+  std::string languages;
+
+  // The default search provider and search terms data necessary to cull results
+  // that correspond to searches (on the default engine).  These can only be
+  // obtained on the UI thread, so we have to copy them into here to pass them
+  // to the history thread.  We use a scoped_ptr<TemplateURL> for the DSP since
+  // TemplateURLs can't be copied by value. We use a scoped_ptr<SearchTermsData>
+  // so that we can store a snapshot of the SearchTermsData accessible from the
+  // history thread.
+  scoped_ptr<TemplateURL> default_search_provider;
+  scoped_ptr<SearchTermsData> search_terms_data;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HistoryURLProviderParams);
+};
+
+// This class is an autocomplete provider and is also a pseudo-internal
+// component of the history system.  See comments above.
+class HistoryURLProvider : public HistoryProvider {
+ public:
+  // Various values used in scoring, made public so other providers
+  // can insert results in appropriate ranges relative to these.
+  static const int kScoreForBestInlineableResult;
+  static const int kScoreForUnvisitedIntranetResult;
+  static const int kScoreForWhatYouTypedResult;
+  static const int kBaseScoreForNonInlineableResult;
+
+  HistoryURLProvider(AutocompleteProviderClient* client,
+                     AutocompleteProviderListener* listener);
+
+  // HistoryProvider:
+  void Start(const AutocompleteInput& input,
+             bool minimal_changes,
+             bool called_due_to_focus) override;
+  void Stop(bool clear_cached_results, bool due_to_user_inactivity) override;
+
+  // Returns a match representing a navigation to |destination_url| given user
+  // input of |text|.  |trim_http| controls whether the match's |fill_into_edit|
+  // and |contents| should have any HTTP scheme stripped off, and should not be
+  // set to true if |text| contains an http prefix.
+  // NOTES: This does not set the relevance of the returned match, as different
+  //        callers want different behavior. Callers must set this manually.
+  //        This function should only be called on the UI thread.
+  AutocompleteMatch SuggestExactInput(const base::string16& text,
+                                      const GURL& destination_url,
+                                      bool trim_http);
+
+  // Runs the history query on the history thread, called by the history
+  // system. The history database MAY BE NULL in which case it is not
+  // available and we should return no data. Also schedules returning the
+  // results to the main thread
+  void ExecuteWithDB(HistoryURLProviderParams* params,
+                     history::HistoryBackend* backend,
+                     history::URLDatabase* db);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(HistoryURLProviderTest, HUPScoringExperiment);
+
+  enum MatchType {
+    NORMAL,
+    WHAT_YOU_TYPED,
+    INLINE_AUTOCOMPLETE,
+    UNVISITED_INTRANET,  // An intranet site that has never been visited.
+  };
+  class VisitClassifier;
+
+  ~HistoryURLProvider() override;
+
+  // Determines the relevance for a match, given its type.  If |match_type| is
+  // NORMAL, |match_number| is a number indicating the relevance of the match
+  // (higher == more relevant).  For other values of |match_type|,
+  // |match_number| is ignored.  Only called some of the time; for some matches,
+  // relevancy scores are assigned consecutively decreasing (1416, 1415, ...).
+  static int CalculateRelevance(MatchType match_type, int match_number);
+
+  // Returns a set of classifications that highlight all the occurrences of
+  // |input_text| at word breaks in |description|.
+  static ACMatchClassifications ClassifyDescription(
+      const base::string16& input_text,
+      const base::string16& description);
+
+  // Actually runs the autocomplete job on the given database, which is
+  // guaranteed not to be NULL.  Used by both autocomplete passes, and therefore
+  // called on multiple different threads (though not simultaneously).
+  void DoAutocomplete(history::HistoryBackend* backend,
+                      history::URLDatabase* db,
+                      HistoryURLProviderParams* params);
+
+  // May promote the what you typed match, the first history match in
+  // params->matches, or both to the front of |matches_|, depending on the
+  // values of params->promote_type, params->have_what_you_typed_match, and
+  // params->prevent_inline_autocomplete.
+  void PromoteMatchesIfNecessary(const HistoryURLProviderParams& params);
+
+  // Dispatches the results to the autocomplete controller. Called on the
+  // main thread by ExecuteWithDB when the results are available.
+  // Frees params_gets_deleted on exit.
+  void QueryComplete(HistoryURLProviderParams* params_gets_deleted);
+
+  // Looks up the info for params->what_you_typed_match in the DB.  If found,
+  // fills in the title, promotes the match's priority to that of an inline
+  // autocomplete match (maybe it should be slightly better?), and places it on
+  // the front of params->matches (so we pick the right matches to throw away
+  // when culling redirects to/from it).  Returns whether a match was promoted.
+  bool FixupExactSuggestion(history::URLDatabase* db,
+                            const VisitClassifier& classifier,
+                            HistoryURLProviderParams* params) const;
+
+  // Helper function for FixupExactSuggestion, this returns true if the input
+  // corresponds to some intranet URL where the user has previously visited the
+  // host in question.  In this case the input should be treated as a URL.
+  bool CanFindIntranetURL(history::URLDatabase* db,
+                          const AutocompleteInput& input) const;
+
+  // Sees if a shorter version of the best match should be created, and if so
+  // places it at the front of params->matches.  This can suggest history URLs
+  // that are prefixes of the best match (if they've been visited enough,
+  // compared to the best match), or create host-only suggestions even when they
+  // haven't been visited before: if the user visited http://example.com/asdf
+  // once, we'll suggest http://example.com/ even if they've never been to it.
+  // Returns true if a match was successfully created/promoted that we're
+  // willing to inline autocomplete.
+  bool PromoteOrCreateShorterSuggestion(
+      history::URLDatabase* db,
+      HistoryURLProviderParams* params);
+
+  // Removes results that have been rarely typed or visited, and not any time
+  // recently.  The exact parameters for this heuristic can be found in the
+  // function body. Also culls results corresponding to queries from the default
+  // search engine. These are low-quality, difficult-to-understand matches for
+  // users, and the SearchProvider should surface past queries in a better way
+  // anyway.
+  void CullPoorMatches(HistoryURLProviderParams* params) const;
+
+  // Removes results that redirect to each other, leaving at most |max_results|
+  // results.
+  void CullRedirects(history::HistoryBackend* backend,
+                     history::HistoryMatches* matches,
+                     size_t max_results) const;
+
+  // Helper function for CullRedirects, this removes all but the first
+  // occurance of [any of the set of strings in |remove|] from the |matches|
+  // list.
+  //
+  // The return value is the index of the item that is after the item in the
+  // input identified by |source_index|. If |source_index| or an item before
+  // is removed, the next item will be shifted, and this allows the caller to
+  // pick up on the next one when this happens.
+  size_t RemoveSubsequentMatchesOf(history::HistoryMatches* matches,
+                                   size_t source_index,
+                                   const std::vector<GURL>& remove) const;
+
+  // Converts a specified |match_number| from params.matches into an
+  // autocomplete match for display.  If experimental scoring is enabled, the
+  // final relevance score might be different from the given |relevance|.
+  // NOTE: This function should only be called on the UI thread.
+  AutocompleteMatch HistoryMatchToACMatch(
+      const HistoryURLProviderParams& params,
+      size_t match_number,
+      MatchType match_type,
+      int relevance);
+
+  AutocompleteProviderListener* listener_;
+
+  // Params for the current query.  The provider should not free this directly;
+  // instead, it is passed as a parameter through the history backend, and the
+  // parameter itself is freed once it's no longer needed.  The only reason we
+  // keep this member is so we can set the cancel bit on it.
+  HistoryURLProviderParams* params_;
+
+  // Params controlling experimental behavior of this provider.
+  HUPScoringParams scoring_params_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(HistoryURLProvider);
+};
+
+#endif  // COMPONENTS_OMNIBOX_HISTORY_URL_PROVIDER_H_