chrome/browser/autocomplete/search

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This source file includes following definitions.
LogOmniboxSuggestRequest
HasMultipleWords
GetDefaultProviderURL
GetKeywordProviderURL
providers_
GetSuggestMetadata
ResetSession
RemoveStaleResults
UpdateMatchContentsClass
CalculateRelevanceForKeywordVerbatim
Start
SortResults
GetTemplateURL
GetInput
GetResultsToFill
ShouldAppendExtraParams
StopSuggest
ClearAllResults
GetDefaultResultRelevance
RecordDeletionResult
LogFetchComplete
IsKeywordFetcher
UpdateMatches
Run
DoHistoryQuery
StartOrStopSuggestQuery
IsQuerySuitableForSuggest
RemoveAllStaleResults
ApplyCalculatedRelevance
ApplyCalculatedSuggestRelevance
ApplyCalculatedNavigationRelevance
CreateSuggestFetcher
ConvertResultsToAutocompleteMatches
FindTopMatch
IsTopMatchNavigationInKeywordMode
HasKeywordDefaultMatchInKeywordMode
IsTopMatchScoreTooLow
IsTopMatchSearchWithURLInput
HasValidDefaultMatch
AddNavigationResultsToMatches
AddHistoryResultsToMap
ScoreHistoryResults
AddSuggestResultsToMap
GetVerbatimRelevance
CalculateRelevanceForVerbatim
CalculateRelevanceForVerbatimIgnoringKeywordModeState
GetKeywordVerbatimRelevance
CalculateRelevanceForHistory
NavigationToMatch
DemoteKeywordNavigationMatchesPastTopQuery
UpdateDone
// Copyright 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.

#include "chrome/browser/autocomplete/search_provider.h"

#include <algorithm>
#include <cmath>

#include "base/callback.h"
#include "base/i18n/break_iterator.h"
#include "base/i18n/case_conversion.h"
#include "base/json/json_string_value_serializer.h"
#include "base/message_loop/message_loop.h"
#include "base/metrics/histogram.h"
#include "base/prefs/pref_service.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "chrome/browser/autocomplete/autocomplete_classifier.h"
#include "chrome/browser/autocomplete/autocomplete_classifier_factory.h"
#include "chrome/browser/autocomplete/autocomplete_provider_listener.h"
#include "chrome/browser/autocomplete/autocomplete_result.h"
#include "chrome/browser/autocomplete/keyword_provider.h"
#include "chrome/browser/autocomplete/url_prefix.h"
#include "chrome/browser/google/google_util.h"
#include "chrome/browser/history/history_service.h"
#include "chrome/browser/history/history_service_factory.h"
#include "chrome/browser/history/in_memory_database.h"
#include "chrome/browser/metrics/variations/variations_http_header_provider.h"
#include "chrome/browser/omnibox/omnibox_field_trial.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/browser/search/search.h"
#include "chrome/browser/search_engines/template_url_prepopulate_data.h"
#include "chrome/browser/search_engines/template_url_service.h"
#include "chrome/browser/search_engines/template_url_service_factory.h"
#include "chrome/browser/ui/search/instant_controller.h"
#include "chrome/common/pref_names.h"
#include "chrome/common/url_constants.h"
#include "content/public/browser/user_metrics.h"
#include "grit/generated_resources.h"
#include "net/base/escape.h"
#include "net/base/load_flags.h"
#include "net/base/net_util.h"
#include "net/http/http_request_headers.h"
#include "net/url_request/url_fetcher.h"
#include "net/url_request/url_request_status.h"
#include "ui/base/l10n/l10n_util.h"
#include "url/url_util.h"


// Helpers --------------------------------------------------------------------

namespace {

// We keep track in a histogram how many suggest requests we send, how
// many suggest requests we invalidate (e.g., due to a user typing
// another character), and how many replies we receive.
// *** ADD NEW ENUMS AFTER ALL PREVIOUSLY DEFINED ONES! ***
//     (excluding the end-of-list enum value)
// We do not want values of existing enums to change or else it screws
// up the statistics.
enum SuggestRequestsHistogramValue {
  REQUEST_SENT = 1,
  REQUEST_INVALIDATED,
  REPLY_RECEIVED,
  MAX_SUGGEST_REQUEST_HISTOGRAM_VALUE
};

// The verbatim score for an input which is not an URL.
const int kNonURLVerbatimRelevance = 1300;

// Increments the appropriate value in the histogram by one.
void LogOmniboxSuggestRequest(
    SuggestRequestsHistogramValue request_value) {
  UMA_HISTOGRAM_ENUMERATION("Omnibox.SuggestRequests", request_value,
                            MAX_SUGGEST_REQUEST_HISTOGRAM_VALUE);
}

bool HasMultipleWords(const base::string16& text) {
  base::i18n::BreakIterator i(text, base::i18n::BreakIterator::BREAK_WORD);
  bool found_word = false;
  if (i.Init()) {
    while (i.Advance()) {
      if (i.IsWord()) {
        if (found_word)
          return true;
        found_word = true;
      }
    }
  }
  return false;
}

}  // namespace

// SearchProvider::Providers --------------------------------------------------

SearchProvider::Providers::Providers(TemplateURLService* template_url_service)
    : template_url_service_(template_url_service) {}

const TemplateURL* SearchProvider::Providers::GetDefaultProviderURL() const {
  return default_provider_.empty() ? NULL :
      template_url_service_->GetTemplateURLForKeyword(default_provider_);
}

const TemplateURL* SearchProvider::Providers::GetKeywordProviderURL() const {
  return keyword_provider_.empty() ? NULL :
      template_url_service_->GetTemplateURLForKeyword(keyword_provider_);
}


// SearchProvider::CompareScoredResults ---------------------------------------

class SearchProvider::CompareScoredResults {
 public:
  bool operator()(const Result& a, const Result& b) {
    // Sort in descending relevance order.
    return a.relevance() > b.relevance();
  }
};


// SearchProvider -------------------------------------------------------------

// static
int SearchProvider::kMinimumTimeBetweenSuggestQueriesMs = 100;

SearchProvider::SearchProvider(AutocompleteProviderListener* listener,
                               Profile* profile)
    : BaseSearchProvider(listener, profile, AutocompleteProvider::TYPE_SEARCH),
      providers_(TemplateURLServiceFactory::GetForProfile(profile)) {
}

// static
std::string SearchProvider::GetSuggestMetadata(const AutocompleteMatch& match) {
  return match.GetAdditionalInfo(kSuggestMetadataKey);
}

void SearchProvider::ResetSession() {
  field_trial_triggered_in_session_ = false;
}

SearchProvider::~SearchProvider() {
}

// static
void SearchProvider::RemoveStaleResults(const base::string16& input,
                                        int verbatim_relevance,
                                        SuggestResults* suggest_results,
                                        NavigationResults* navigation_results) {
  DCHECK_GE(verbatim_relevance, 0);
  // Keep pointers to the head of (the highest scoring elements of)
  // |suggest_results| and |navigation_results|.  Iterate down the lists
  // removing non-inlineable results in order of decreasing relevance
  // scores.  Stop when the highest scoring element among those remaining
  // is inlineable or the element is less than |verbatim_relevance|.
  // This allows non-inlineable lower-scoring results to remain
  // because (i) they are guaranteed to not be inlined and (ii)
  // letting them remain reduces visual jank.  For instance, as the
  // user types the mis-spelled query "fpobar" (for foobar), the
  // suggestion "foobar" will be suggested on every keystroke.  If the
  // SearchProvider always removes all non-inlineable results, the user will
  // see visual jitter/jank as the result disappears and re-appears moments
  // later as the suggest server returns results.
  SuggestResults::iterator sug_it = suggest_results->begin();
  NavigationResults::iterator nav_it = navigation_results->begin();
  while ((sug_it != suggest_results->end()) ||
         (nav_it != navigation_results->end())) {
    const int sug_rel =
        (sug_it != suggest_results->end()) ? sug_it->relevance() : -1;
    const int nav_rel =
        (nav_it != navigation_results->end()) ? nav_it->relevance() : -1;
    if (std::max(sug_rel, nav_rel) < verbatim_relevance)
      break;
    if (sug_rel > nav_rel) {
      // The current top result is a search suggestion.
      if (sug_it->IsInlineable(input))
        break;
      sug_it = suggest_results->erase(sug_it);
    } else if (sug_rel == nav_rel) {
      // Have both results and they're tied.
      const bool sug_inlineable = sug_it->IsInlineable(input);
      const bool nav_inlineable = nav_it->IsInlineable(input);
      if (!sug_inlineable)
        sug_it = suggest_results->erase(sug_it);
      if (!nav_inlineable)
        nav_it = navigation_results->erase(nav_it);
      if (sug_inlineable || nav_inlineable)
        break;
    } else {
      // The current top result is a navigational suggestion.
      if (nav_it->IsInlineable(input))
        break;
      nav_it = navigation_results->erase(nav_it);
    }
  }
}

void SearchProvider::UpdateMatchContentsClass(const base::string16& input_text,
                                              Results* results) {
  for (SuggestResults::iterator sug_it = results->suggest_results.begin();
       sug_it != results->suggest_results.end(); ++sug_it) {
    sug_it->ClassifyMatchContents(false, input_text);
  }
  const std::string languages(
      profile_->GetPrefs()->GetString(prefs::kAcceptLanguages));
  for (NavigationResults::iterator nav_it = results->navigation_results.begin();
       nav_it != results->navigation_results.end(); ++nav_it) {
    nav_it->CalculateAndClassifyMatchContents(false, input_text, languages);
  }
}

// static
int SearchProvider::CalculateRelevanceForKeywordVerbatim(
    AutocompleteInput::Type type,
    bool prefer_keyword) {
  // This function is responsible for scoring verbatim query matches
  // for non-extension keywords.  KeywordProvider::CalculateRelevance()
  // scores verbatim query matches for extension keywords, as well as
  // for keyword matches (i.e., suggestions of a keyword itself, not a
  // suggestion of a query on a keyword search engine).  These two
  // functions are currently in sync, but there's no reason we
  // couldn't decide in the future to score verbatim matches
  // differently for extension and non-extension keywords.  If you
  // make such a change, however, you should update this comment to
  // describe it, so it's clear why the functions diverge.
  if (prefer_keyword)
    return 1500;
  return (type == AutocompleteInput::QUERY) ? 1450 : 1100;
}

void SearchProvider::Start(const AutocompleteInput& input,
                           bool minimal_changes) {
  // Do our best to load the model as early as possible.  This will reduce
  // odds of having the model not ready when really needed (a non-empty input).
  TemplateURLService* model = providers_.template_url_service();
  DCHECK(model);
  model->Load();

  matches_.clear();
  field_trial_triggered_ = false;

  // Can't return search/suggest results for bogus input or without a profile.
  if (!profile_ || (input.type() == AutocompleteInput::INVALID)) {
    Stop(true);
    return;
  }

  keyword_input_ = input;
  const TemplateURL* keyword_provider =
      KeywordProvider::GetSubstitutingTemplateURLForInput(model,
                                                          &keyword_input_);
  if (keyword_provider == NULL)
    keyword_input_.Clear();
  else if (keyword_input_.text().empty())
    keyword_provider = NULL;

  const TemplateURL* default_provider = model->GetDefaultSearchProvider();
  if (default_provider && !default_provider->SupportsReplacement())
    default_provider = NULL;

  if (keyword_provider == default_provider)
    default_provider = NULL;  // No use in querying the same provider twice.

  if (!default_provider && !keyword_provider) {
    // No valid providers.
    Stop(true);
    return;
  }

  // If we're still running an old query but have since changed the query text
  // or the providers, abort the query.
  base::string16 default_provider_keyword(default_provider ?
      default_provider->keyword() : base::string16());
  base::string16 keyword_provider_keyword(keyword_provider ?
      keyword_provider->keyword() : base::string16());
  if (!minimal_changes ||
      !providers_.equal(default_provider_keyword, keyword_provider_keyword)) {
    // Cancel any in-flight suggest requests.
    if (!done_)
      Stop(false);
  }

  providers_.set(default_provider_keyword, keyword_provider_keyword);

  if (input.text().empty()) {
    // User typed "?" alone.  Give them a placeholder result indicating what
    // this syntax does.
    if (default_provider) {
      AutocompleteMatch match;
      match.provider = this;
      match.contents.assign(l10n_util::GetStringUTF16(IDS_EMPTY_KEYWORD_VALUE));
      match.contents_class.push_back(
          ACMatchClassification(0, ACMatchClassification::NONE));
      match.keyword = providers_.default_provider();
      match.allowed_to_be_default_match = true;
      matches_.push_back(match);
    }
    Stop(true);
    return;
  }

  input_ = input;

  DoHistoryQuery(minimal_changes);
  StartOrStopSuggestQuery(minimal_changes);
  UpdateMatches();
}

void SearchProvider::SortResults(bool is_keyword,
                                 const base::ListValue* relevances,
                                 Results* results) {
  // Ignore suggested scores for non-keyword matches in keyword mode; if the
  // server is allowed to score these, it could interfere with the user's
  // ability to get good keyword results.
  const bool abandon_suggested_scores =
      !is_keyword && !providers_.keyword_provider().empty();
  // Apply calculated relevance scores to suggestions if a valid list was
  // not provided or we're abandoning suggested scores entirely.
  if ((relevances == NULL) || abandon_suggested_scores) {
    ApplyCalculatedSuggestRelevance(&results->suggest_results);
    ApplyCalculatedNavigationRelevance(&results->navigation_results);
    // If abandoning scores entirely, also abandon the verbatim score.
    if (abandon_suggested_scores)
      results->verbatim_relevance = -1;
  }

  // Keep the result lists sorted.
  const CompareScoredResults comparator = CompareScoredResults();
  std::stable_sort(results->suggest_results.begin(),
                   results->suggest_results.end(),
                   comparator);
  std::stable_sort(results->navigation_results.begin(),
                   results->navigation_results.end(),
                   comparator);
}

const TemplateURL* SearchProvider::GetTemplateURL(bool is_keyword) const {
  return is_keyword ? providers_.GetKeywordProviderURL()
                    : providers_.GetDefaultProviderURL();
}

const AutocompleteInput SearchProvider::GetInput(bool is_keyword) const {
  return is_keyword ? keyword_input_ : input_;
}

BaseSearchProvider::Results* SearchProvider::GetResultsToFill(bool is_keyword) {
  return is_keyword ? &keyword_results_ : &default_results_;
}

bool SearchProvider::ShouldAppendExtraParams(
    const SuggestResult& result) const {
  return !result.from_keyword_provider() ||
      providers_.default_provider().empty();
}

void SearchProvider::StopSuggest() {
  // Increment the appropriate field in the histogram by the number of
  // pending requests that were invalidated.
  for (int i = 0; i < suggest_results_pending_; ++i)
    LogOmniboxSuggestRequest(REQUEST_INVALIDATED);
  suggest_results_pending_ = 0;
  timer_.Stop();
  // Stop any in-progress URL fetches.
  keyword_fetcher_.reset();
  default_fetcher_.reset();
}

void SearchProvider::ClearAllResults() {
  keyword_results_.Clear();
  default_results_.Clear();
}

int SearchProvider::GetDefaultResultRelevance() const {
  return -1;
}

void SearchProvider::RecordDeletionResult(bool success) {
  if (success) {
    content::RecordAction(
        base::UserMetricsAction("Omnibox.ServerSuggestDelete.Success"));
  } else {
    content::RecordAction(
        base::UserMetricsAction("Omnibox.ServerSuggestDelete.Failure"));
  }
}

void SearchProvider::LogFetchComplete(bool success, bool is_keyword) {
  LogOmniboxSuggestRequest(REPLY_RECEIVED);
  // Record response time for suggest requests sent to Google.  We care
  // only about the common case: the Google default provider used in
  // non-keyword mode.
  const TemplateURL* default_url = providers_.GetDefaultProviderURL();
  if (!is_keyword && default_url &&
      (TemplateURLPrepopulateData::GetEngineType(*default_url) ==
       SEARCH_ENGINE_GOOGLE)) {
    const base::TimeDelta elapsed_time =
        base::TimeTicks::Now() - time_suggest_request_sent_;
    if (success) {
      UMA_HISTOGRAM_TIMES("Omnibox.SuggestRequest.Success.GoogleResponseTime",
                          elapsed_time);
    } else {
      UMA_HISTOGRAM_TIMES("Omnibox.SuggestRequest.Failure.GoogleResponseTime",
                          elapsed_time);
    }
  }
}

bool SearchProvider::IsKeywordFetcher(const net::URLFetcher* fetcher) const {
  return fetcher == keyword_fetcher_.get();
}

void SearchProvider::UpdateMatches() {
  base::TimeTicks update_matches_start_time(base::TimeTicks::Now());
  ConvertResultsToAutocompleteMatches();

  // Check constraints that may be violated by suggested relevances.
  if (!matches_.empty() &&
      (default_results_.HasServerProvidedScores() ||
       keyword_results_.HasServerProvidedScores())) {
    // These blocks attempt to repair undesirable behavior by suggested
    // relevances with minimal impact, preserving other suggested relevances.

    // True if the omnibox will reorder matches as necessary to make the first
    // one something that is allowed to be the default match.
    const bool omnibox_will_reorder_for_legal_default_match =
        OmniboxFieldTrial::ReorderForLegalDefaultMatch(
            input_.current_page_classification());
    if (IsTopMatchNavigationInKeywordMode(
        omnibox_will_reorder_for_legal_default_match)) {
      // Correct the suggested relevance scores if the top match is a
      // navigation in keyword mode, since inlining a navigation match
      // would break the user out of keyword mode.  This will only be
      // triggered in regular (non-reorder) mode; in reorder mode,
      // navigation matches are marked as not allowed to be the default
      // match and hence IsTopMatchNavigation() will always return false.
      DCHECK(!omnibox_will_reorder_for_legal_default_match);
      DemoteKeywordNavigationMatchesPastTopQuery();
      ConvertResultsToAutocompleteMatches();
      DCHECK(!IsTopMatchNavigationInKeywordMode(
          omnibox_will_reorder_for_legal_default_match));
    }
    if (!HasKeywordDefaultMatchInKeywordMode()) {
      // In keyword mode, disregard the keyword verbatim suggested relevance
      // if necessary so there at least one keyword match that's allowed to
      // be the default match.
      keyword_results_.verbatim_relevance = -1;
      ConvertResultsToAutocompleteMatches();
    }
    if (IsTopMatchScoreTooLow(omnibox_will_reorder_for_legal_default_match)) {
      // Disregard the suggested verbatim relevance if the top score is below
      // the usual verbatim value. For example, a BarProvider may rely on
      // SearchProvider's verbatim or inlineable matches for input "foo" (all
      // allowed to be default match) to always outrank its own lowly-ranked
      // "bar" matches that shouldn't be the default match.
      default_results_.verbatim_relevance = -1;
      keyword_results_.verbatim_relevance = -1;
      ConvertResultsToAutocompleteMatches();
    }
    if (IsTopMatchSearchWithURLInput(
        omnibox_will_reorder_for_legal_default_match)) {
      // Disregard the suggested search and verbatim relevances if the input
      // type is URL and the top match is a highly-ranked search suggestion.
      // For example, prevent a search for "foo.com" from outranking another
      // provider's navigation for "foo.com" or "foo.com/url_from_history".
      ApplyCalculatedSuggestRelevance(&keyword_results_.suggest_results);
      ApplyCalculatedSuggestRelevance(&default_results_.suggest_results);
      default_results_.verbatim_relevance = -1;
      keyword_results_.verbatim_relevance = -1;
      ConvertResultsToAutocompleteMatches();
    }
    if (!HasValidDefaultMatch(omnibox_will_reorder_for_legal_default_match)) {
      // If the omnibox is not going to reorder results to put a legal default
      // match at the top, then this provider needs to guarantee that its top
      // scoring result is a legal default match (i.e., it's either a verbatim
      // match or inlinable).  For example, input "foo" should not invoke a
      // search for "bar", which would happen if the "bar" search match
      // outranked all other matches.  On the other hand, if the omnibox will
      // reorder matches as necessary to put a legal default match at the top,
      // all we need to guarantee is that SearchProvider returns a legal
      // default match.  (The omnibox always needs at least one legal default
      // match, and it relies on SearchProvider to always return one.)
      ApplyCalculatedRelevance();
      ConvertResultsToAutocompleteMatches();
    }
    DCHECK(!IsTopMatchNavigationInKeywordMode(
        omnibox_will_reorder_for_legal_default_match));
    DCHECK(HasKeywordDefaultMatchInKeywordMode());
    DCHECK(!IsTopMatchScoreTooLow(
        omnibox_will_reorder_for_legal_default_match));
    DCHECK(!IsTopMatchSearchWithURLInput(
        omnibox_will_reorder_for_legal_default_match));
    DCHECK(HasValidDefaultMatch(omnibox_will_reorder_for_legal_default_match));
  }
  UMA_HISTOGRAM_CUSTOM_COUNTS(
      "Omnibox.SearchProviderMatches", matches_.size(), 1, 6, 7);

  const TemplateURL* keyword_url = providers_.GetKeywordProviderURL();
  if ((keyword_url != NULL) && HasKeywordDefaultMatchInKeywordMode()) {
    // If there is a keyword match that is allowed to be the default match,
    // then prohibit default provider matches from being the default match lest
    // such matches cause the user to break out of keyword mode.
    for (ACMatches::iterator it = matches_.begin(); it != matches_.end();
         ++it) {
      if (it->keyword != keyword_url->keyword())
        it->allowed_to_be_default_match = false;
    }
  }

  base::TimeTicks update_starred_start_time(base::TimeTicks::Now());
  UpdateStarredStateOfMatches();
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.UpdateStarredTime",
                      base::TimeTicks::Now() - update_starred_start_time);
  UpdateDone();
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.UpdateMatchesTime",
                      base::TimeTicks::Now() - update_matches_start_time);
}

void SearchProvider::Run() {
  // Start a new request with the current input.
  suggest_results_pending_ = 0;
  time_suggest_request_sent_ = base::TimeTicks::Now();

  default_fetcher_.reset(CreateSuggestFetcher(kDefaultProviderURLFetcherID,
      providers_.GetDefaultProviderURL(), input_));
  keyword_fetcher_.reset(CreateSuggestFetcher(kKeywordProviderURLFetcherID,
      providers_.GetKeywordProviderURL(), keyword_input_));

  // Both the above can fail if the providers have been modified or deleted
  // since the query began.
  if (suggest_results_pending_ == 0) {
    UpdateDone();
    // We only need to update the listener if we're actually done.
    if (done_)
      listener_->OnProviderUpdate(false);
  }
}

void SearchProvider::DoHistoryQuery(bool minimal_changes) {
  // The history query results are synchronous, so if minimal_changes is true,
  // we still have the last results and don't need to do anything.
  if (minimal_changes)
    return;

  base::TimeTicks do_history_query_start_time(base::TimeTicks::Now());

  keyword_history_results_.clear();
  default_history_results_.clear();

  if (OmniboxFieldTrial::SearchHistoryDisable(
      input_.current_page_classification()))
    return;

  base::TimeTicks start_time(base::TimeTicks::Now());
  HistoryService* const history_service =
      HistoryServiceFactory::GetForProfile(profile_, Profile::EXPLICIT_ACCESS);
  base::TimeTicks now(base::TimeTicks::Now());
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.GetHistoryServiceTime",
                      now - start_time);
  start_time = now;
  history::URLDatabase* url_db = history_service ?
      history_service->InMemoryDatabase() : NULL;
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.InMemoryDatabaseTime",
                      base::TimeTicks::Now() - start_time);
  if (!url_db)
    return;

  // Request history for both the keyword and default provider.  We grab many
  // more matches than we'll ultimately clamp to so that if there are several
  // recent multi-word matches who scores are lowered (see
  // AddHistoryResultsToMap()), they won't crowd out older, higher-scoring
  // matches.  Note that this doesn't fix the problem entirely, but merely
  // limits it to cases with a very large number of such multi-word matches; for
  // now, this seems OK compared with the complexity of a real fix, which would
  // require multiple searches and tracking of "single- vs. multi-word" in the
  // database.
  int num_matches = kMaxMatches * 5;
  const TemplateURL* default_url = providers_.GetDefaultProviderURL();
  if (default_url) {
    start_time = base::TimeTicks::Now();
    url_db->GetMostRecentKeywordSearchTerms(default_url->id(), input_.text(),
        num_matches, &default_history_results_);
    UMA_HISTOGRAM_TIMES(
        "Omnibox.SearchProvider.GetMostRecentKeywordTermsDefaultProviderTime",
        base::TimeTicks::Now() - start_time);
  }
  const TemplateURL* keyword_url = providers_.GetKeywordProviderURL();
  if (keyword_url) {
    url_db->GetMostRecentKeywordSearchTerms(keyword_url->id(),
        keyword_input_.text(), num_matches, &keyword_history_results_);
  }
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.DoHistoryQueryTime",
                      base::TimeTicks::Now() - do_history_query_start_time);
}

void SearchProvider::StartOrStopSuggestQuery(bool minimal_changes) {
  if (!IsQuerySuitableForSuggest()) {
    StopSuggest();
    ClearAllResults();
    return;
  }

  // For the minimal_changes case, if we finished the previous query and still
  // have its results, or are allowed to keep running it, just do that, rather
  // than starting a new query.
  if (minimal_changes &&
      (!default_results_.suggest_results.empty() ||
       !default_results_.navigation_results.empty() ||
       !keyword_results_.suggest_results.empty() ||
       !keyword_results_.navigation_results.empty() ||
       (!done_ &&
        input_.matches_requested() == AutocompleteInput::ALL_MATCHES)))
    return;

  // We can't keep running any previous query, so halt it.
  StopSuggest();

  // Remove existing results that cannot inline autocomplete the new input.
  RemoveAllStaleResults();

  // Update the content classifications of remaining results so they look good
  // against the current input.
  UpdateMatchContentsClass(input_.text(), &default_results_);
  if (!keyword_input_.text().empty())
    UpdateMatchContentsClass(keyword_input_.text(), &keyword_results_);

  // We can't start a new query if we're only allowed synchronous results.
  if (input_.matches_requested() != AutocompleteInput::ALL_MATCHES)
    return;

  // To avoid flooding the suggest server, don't send a query until at
  // least 100 ms since the last query.
  base::TimeTicks next_suggest_time(time_suggest_request_sent_ +
      base::TimeDelta::FromMilliseconds(kMinimumTimeBetweenSuggestQueriesMs));
  base::TimeTicks now(base::TimeTicks::Now());
  if (now >= next_suggest_time) {
    Run();
    return;
  }
  timer_.Start(FROM_HERE, next_suggest_time - now, this, &SearchProvider::Run);
}

bool SearchProvider::IsQuerySuitableForSuggest() const {
  // Don't run Suggest in incognito mode, if the engine doesn't support it, or
  // if the user has disabled it.
  const TemplateURL* default_url = providers_.GetDefaultProviderURL();
  const TemplateURL* keyword_url = providers_.GetKeywordProviderURL();
  if (profile_->IsOffTheRecord() ||
      ((!default_url || default_url->suggestions_url().empty()) &&
       (!keyword_url || keyword_url->suggestions_url().empty())) ||
      !profile_->GetPrefs()->GetBoolean(prefs::kSearchSuggestEnabled))
    return false;

  // If the input type might be a URL, we take extra care so that private data
  // isn't sent to the server.

  // FORCED_QUERY means the user is explicitly asking us to search for this, so
  // we assume it isn't a URL and/or there isn't private data.
  if (input_.type() == AutocompleteInput::FORCED_QUERY)
    return true;

  // Next we check the scheme.  If this is UNKNOWN/URL with a scheme that isn't
  // http/https/ftp, we shouldn't send it.  Sending things like file: and data:
  // is both a waste of time and a disclosure of potentially private, local
  // data.  Other "schemes" may actually be usernames, and we don't want to send
  // passwords.  If the scheme is OK, we still need to check other cases below.
  // If this is QUERY, then the presence of these schemes means the user
  // explicitly typed one, and thus this is probably a URL that's being entered
  // and happens to currently be invalid -- in which case we again want to run
  // our checks below.  Other QUERY cases are less likely to be URLs and thus we
  // assume we're OK.
  if (!LowerCaseEqualsASCII(input_.scheme(), content::kHttpScheme) &&
      !LowerCaseEqualsASCII(input_.scheme(), content::kHttpsScheme) &&
      !LowerCaseEqualsASCII(input_.scheme(), content::kFtpScheme))
    return (input_.type() == AutocompleteInput::QUERY);

  // Don't send URLs with usernames, queries or refs.  Some of these are
  // private, and the Suggest server is unlikely to have any useful results
  // for any of them.  Also don't send URLs with ports, as we may initially
  // think that a username + password is a host + port (and we don't want to
  // send usernames/passwords), and even if the port really is a port, the
  // server is once again unlikely to have and useful results.
  // Note that we only block based on refs if the input is URL-typed, as search
  // queries can legitimately have #s in them which the URL parser
  // overaggressively categorizes as a url with a ref.
  const url_parse::Parsed& parts = input_.parts();
  if (parts.username.is_nonempty() || parts.port.is_nonempty() ||
      parts.query.is_nonempty() ||
      (parts.ref.is_nonempty() && (input_.type() == AutocompleteInput::URL)))
    return false;

  // Don't send anything for https except the hostname.  Hostnames are OK
  // because they are visible when the TCP connection is established, but the
  // specific path may reveal private information.
  if (LowerCaseEqualsASCII(input_.scheme(), content::kHttpsScheme) &&
      parts.path.is_nonempty())
    return false;

  return true;
}

void SearchProvider::RemoveAllStaleResults() {
  // We only need to remove stale results (which ensures the top-scoring
  // match is inlineable) if the user is not in reorder mode.  In reorder
  // mode, the autocomplete system will reorder results to make sure the
  // top result is inlineable.
  const bool omnibox_will_reorder_for_legal_default_match =
      OmniboxFieldTrial::ReorderForLegalDefaultMatch(
          input_.current_page_classification());
  // In theory it would be better to run an algorithm like that in
  // RemoveStaleResults(...) below that uses all four results lists
  // and both verbatim scores at once.  However, that will be much
  // more complicated for little obvious gain.  For code simplicity
  // and ease in reasoning about the invariants involved, this code
  // removes stales results from the keyword provider and default
  // provider independently.
  if (!omnibox_will_reorder_for_legal_default_match) {
    RemoveStaleResults(input_.text(), GetVerbatimRelevance(NULL),
                       &default_results_.suggest_results,
                       &default_results_.navigation_results);
    if (!keyword_input_.text().empty()) {
      RemoveStaleResults(keyword_input_.text(),
                         GetKeywordVerbatimRelevance(NULL),
                         &keyword_results_.suggest_results,
                         &keyword_results_.navigation_results);
    }
  }
  if (keyword_input_.text().empty()) {
    // User is either in keyword mode with a blank input or out of
    // keyword mode entirely.
    keyword_results_.Clear();
  }
}

void SearchProvider::ApplyCalculatedRelevance() {
  ApplyCalculatedSuggestRelevance(&keyword_results_.suggest_results);
  ApplyCalculatedSuggestRelevance(&default_results_.suggest_results);
  ApplyCalculatedNavigationRelevance(&keyword_results_.navigation_results);
  ApplyCalculatedNavigationRelevance(&default_results_.navigation_results);
  default_results_.verbatim_relevance = -1;
  keyword_results_.verbatim_relevance = -1;
}

void SearchProvider::ApplyCalculatedSuggestRelevance(SuggestResults* list) {
  for (size_t i = 0; i < list->size(); ++i) {
    SuggestResult& result = (*list)[i];
    result.set_relevance(
        result.CalculateRelevance(input_, providers_.has_keyword_provider()) +
        (list->size() - i - 1));
    result.set_relevance_from_server(false);
  }
}

void SearchProvider::ApplyCalculatedNavigationRelevance(
    NavigationResults* list) {
  for (size_t i = 0; i < list->size(); ++i) {
    NavigationResult& result = (*list)[i];
    result.set_relevance(
        result.CalculateRelevance(input_, providers_.has_keyword_provider()) +
        (list->size() - i - 1));
    result.set_relevance_from_server(false);
  }
}

net::URLFetcher* SearchProvider::CreateSuggestFetcher(
    int id,
    const TemplateURL* template_url,
    const AutocompleteInput& input) {
  if (!template_url || template_url->suggestions_url().empty())
    return NULL;

  // Bail if the suggestion URL is invalid with the given replacements.
  TemplateURLRef::SearchTermsArgs search_term_args(input.text());
  search_term_args.cursor_position = input.cursor_position();
  search_term_args.page_classification = input.current_page_classification();
  GURL suggest_url(template_url->suggestions_url_ref().ReplaceSearchTerms(
      search_term_args));
  if (!suggest_url.is_valid())
    return NULL;
  // Send the current page URL if user setting and URL requirements are met and
  // the user is in the field trial.
  if (CanSendURL(current_page_url_, suggest_url, template_url,
                 input.current_page_classification(), profile_) &&
      OmniboxFieldTrial::InZeroSuggestAfterTypingFieldTrial()) {
    search_term_args.current_page_url = current_page_url_.spec();
    // Create the suggest URL again with the current page URL.
    suggest_url = GURL(template_url->suggestions_url_ref().ReplaceSearchTerms(
        search_term_args));
  }

  suggest_results_pending_++;
  LogOmniboxSuggestRequest(REQUEST_SENT);

  net::URLFetcher* fetcher =
      net::URLFetcher::Create(id, suggest_url, net::URLFetcher::GET, this);
  fetcher->SetRequestContext(profile_->GetRequestContext());
  fetcher->SetLoadFlags(net::LOAD_DO_NOT_SAVE_COOKIES);
  // Add Chrome experiment state to the request headers.
  net::HttpRequestHeaders headers;
  chrome_variations::VariationsHttpHeaderProvider::GetInstance()->AppendHeaders(
      fetcher->GetOriginalURL(), profile_->IsOffTheRecord(), false, &headers);
  fetcher->SetExtraRequestHeaders(headers.ToString());
  fetcher->Start();
  return fetcher;
}

void SearchProvider::ConvertResultsToAutocompleteMatches() {
  // Convert all the results to matches and add them to a map, so we can keep
  // the most relevant match for each result.
  base::TimeTicks start_time(base::TimeTicks::Now());
  MatchMap map;
  const base::Time no_time;
  int did_not_accept_keyword_suggestion =
      keyword_results_.suggest_results.empty() ?
      TemplateURLRef::NO_SUGGESTIONS_AVAILABLE :
      TemplateURLRef::NO_SUGGESTION_CHOSEN;

  bool relevance_from_server;
  int verbatim_relevance = GetVerbatimRelevance(&relevance_from_server);
  int did_not_accept_default_suggestion =
      default_results_.suggest_results.empty() ?
      TemplateURLRef::NO_SUGGESTIONS_AVAILABLE :
      TemplateURLRef::NO_SUGGESTION_CHOSEN;
  if (verbatim_relevance > 0) {
    const base::string16& trimmed_verbatim =
        base::CollapseWhitespace(input_.text(), false);
    SuggestResult verbatim(
        trimmed_verbatim, AutocompleteMatchType::SEARCH_WHAT_YOU_TYPED,
        trimmed_verbatim, base::string16(), base::string16(), std::string(),
        std::string(), false, verbatim_relevance, relevance_from_server, false,
        trimmed_verbatim);
    AddMatchToMap(verbatim, std::string(), did_not_accept_default_suggestion,
                  false, &map);
  }
  if (!keyword_input_.text().empty()) {
    const TemplateURL* keyword_url = providers_.GetKeywordProviderURL();
    // We only create the verbatim search query match for a keyword
    // if it's not an extension keyword.  Extension keywords are handled
    // in KeywordProvider::Start().  (Extensions are complicated...)
    // Note: in this provider, SEARCH_OTHER_ENGINE must correspond
    // to the keyword verbatim search query.  Do not create other matches
    // of type SEARCH_OTHER_ENGINE.
    if (keyword_url &&
        (keyword_url->GetType() != TemplateURL::OMNIBOX_API_EXTENSION)) {
      bool keyword_relevance_from_server;
      const int keyword_verbatim_relevance =
          GetKeywordVerbatimRelevance(&keyword_relevance_from_server);
      if (keyword_verbatim_relevance > 0) {
        const base::string16& trimmed_verbatim =
            base::CollapseWhitespace(keyword_input_.text(), false);
        SuggestResult verbatim(
            trimmed_verbatim, AutocompleteMatchType::SEARCH_OTHER_ENGINE,
            trimmed_verbatim, base::string16(), base::string16(),
            std::string(), std::string(), true, keyword_verbatim_relevance,
            keyword_relevance_from_server, false, trimmed_verbatim);
        AddMatchToMap(verbatim, std::string(),
                      did_not_accept_keyword_suggestion, false, &map);
      }
    }
  }
  AddHistoryResultsToMap(keyword_history_results_, true,
                         did_not_accept_keyword_suggestion, &map);
  AddHistoryResultsToMap(default_history_results_, false,
                         did_not_accept_default_suggestion, &map);

  AddSuggestResultsToMap(keyword_results_.suggest_results,
                         keyword_results_.metadata, &map);
  AddSuggestResultsToMap(default_results_.suggest_results,
                         default_results_.metadata, &map);

  ACMatches matches;
  for (MatchMap::const_iterator i(map.begin()); i != map.end(); ++i)
    matches.push_back(i->second);

  AddNavigationResultsToMatches(keyword_results_.navigation_results, &matches);
  AddNavigationResultsToMatches(default_results_.navigation_results, &matches);

  // Now add the most relevant matches to |matches_|.  We take up to kMaxMatches
  // suggest/navsuggest matches, regardless of origin.  If Instant Extended is
  // enabled and we have server-provided (and thus hopefully more accurate)
  // scores for some suggestions, we allow more of those, until we reach
  // AutocompleteResult::kMaxMatches total matches (that is, enough to fill the
  // whole popup).
  //
  // We will always return any verbatim matches, no matter how we obtained their
  // scores, unless we have already accepted AutocompleteResult::kMaxMatches
  // higher-scoring matches under the conditions above.
  UMA_HISTOGRAM_CUSTOM_COUNTS(
      "Omnibox.SearchProvider.NumMatchesToSort", matches.size(), 1, 50, 20);
  std::sort(matches.begin(), matches.end(), &AutocompleteMatch::MoreRelevant);
  matches_.clear();

  size_t num_suggestions = 0;
  for (ACMatches::const_iterator i(matches.begin());
       (i != matches.end()) &&
           (matches_.size() < AutocompleteResult::kMaxMatches);
       ++i) {
    // SEARCH_OTHER_ENGINE is only used in the SearchProvider for the keyword
    // verbatim result, so this condition basically means "if this match is a
    // suggestion of some sort".
    if ((i->type != AutocompleteMatchType::SEARCH_WHAT_YOU_TYPED) &&
        (i->type != AutocompleteMatchType::SEARCH_OTHER_ENGINE)) {
      // If we've already hit the limit on non-server-scored suggestions, and
      // this isn't a server-scored suggestion we can add, skip it.
      if ((num_suggestions >= kMaxMatches) &&
          (!chrome::IsInstantExtendedAPIEnabled() ||
           (i->GetAdditionalInfo(kRelevanceFromServerKey) != kTrue))) {
        continue;
      }

      ++num_suggestions;
    }

    matches_.push_back(*i);
  }
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.ConvertResultsTime",
                      base::TimeTicks::Now() - start_time);
}

ACMatches::const_iterator SearchProvider::FindTopMatch(
    bool autocomplete_result_will_reorder_for_default_match) const {
  if (!autocomplete_result_will_reorder_for_default_match)
    return matches_.begin();
  ACMatches::const_iterator it = matches_.begin();
  while ((it != matches_.end()) && !it->allowed_to_be_default_match)
    ++it;
  return it;
}

bool SearchProvider::IsTopMatchNavigationInKeywordMode(
    bool autocomplete_result_will_reorder_for_default_match) const {
  ACMatches::const_iterator first_match =
      FindTopMatch(autocomplete_result_will_reorder_for_default_match);
  return !providers_.keyword_provider().empty() &&
      (first_match != matches_.end()) &&
      (first_match->type == AutocompleteMatchType::NAVSUGGEST);
}

bool SearchProvider::HasKeywordDefaultMatchInKeywordMode() const {
  const TemplateURL* keyword_url = providers_.GetKeywordProviderURL();
  // If the user is not in keyword mode, return true to say that this
  // constraint is not violated.
  if (keyword_url == NULL)
    return true;
  for (ACMatches::const_iterator it = matches_.begin(); it != matches_.end();
       ++it) {
    if ((it->keyword == keyword_url->keyword()) &&
        it->allowed_to_be_default_match)
      return true;
  }
  return false;
}

bool SearchProvider::IsTopMatchScoreTooLow(
    bool autocomplete_result_will_reorder_for_default_match) const {
  // In reorder mode, there's no such thing as a score that's too low.
  if (autocomplete_result_will_reorder_for_default_match)
    return false;

  // Here we use CalculateRelevanceForVerbatimIgnoringKeywordModeState()
  // rather than CalculateRelevanceForVerbatim() because the latter returns
  // a very low score (250) if keyword mode is active.  This is because
  // when keyword mode is active the user probably wants the keyword matches,
  // not matches from the default provider.  Hence, we use the version of
  // the function that ignores whether keyword mode is active.  This allows
  // SearchProvider to maintain its contract with the AutocompleteController
  // that it will always provide an inlineable match with a reasonable
  // score.
  return matches_.front().relevance <
      CalculateRelevanceForVerbatimIgnoringKeywordModeState();
}

bool SearchProvider::IsTopMatchSearchWithURLInput(
    bool autocomplete_result_will_reorder_for_default_match) const {
  ACMatches::const_iterator first_match =
      FindTopMatch(autocomplete_result_will_reorder_for_default_match);
  return (input_.type() == AutocompleteInput::URL) &&
      (first_match != matches_.end()) &&
      (first_match->relevance > CalculateRelevanceForVerbatim()) &&
      (first_match->type != AutocompleteMatchType::NAVSUGGEST);
}

bool SearchProvider::HasValidDefaultMatch(
    bool autocomplete_result_will_reorder_for_default_match) const {
  // One of the SearchProvider matches may need to be the overall default.  If
  // AutocompleteResult is allowed to reorder matches, this means we simply
  // need at least one match in the list to be |allowed_to_be_default_match|.
  // If no reordering is possible, however, then our first match needs to have
  // this flag.
  for (ACMatches::const_iterator it = matches_.begin(); it != matches_.end();
       ++it) {
    if (it->allowed_to_be_default_match)
      return true;
    if (!autocomplete_result_will_reorder_for_default_match)
      return false;
  }
  return false;
}


void SearchProvider::AddNavigationResultsToMatches(
    const NavigationResults& navigation_results,
    ACMatches* matches) {
  for (NavigationResults::const_iterator it = navigation_results.begin();
        it != navigation_results.end(); ++it) {
    matches->push_back(NavigationToMatch(*it));
    // In the absence of suggested relevance scores, use only the single
    // highest-scoring result.  (The results are already sorted by relevance.)
    if (!it->relevance_from_server())
      return;
  }
}

void SearchProvider::AddHistoryResultsToMap(const HistoryResults& results,
                                            bool is_keyword,
                                            int did_not_accept_suggestion,
                                            MatchMap* map) {
  if (results.empty())
    return;

  base::TimeTicks start_time(base::TimeTicks::Now());
  bool prevent_inline_autocomplete = input_.prevent_inline_autocomplete() ||
      (input_.type() == AutocompleteInput::URL);
  const base::string16& input_text =
      is_keyword ? keyword_input_.text() : input_.text();
  bool input_multiple_words = HasMultipleWords(input_text);

  SuggestResults scored_results;
  if (!prevent_inline_autocomplete && input_multiple_words) {
    // ScoreHistoryResults() allows autocompletion of multi-word, 1-visit
    // queries if the input also has multiple words.  But if we were already
    // autocompleting a multi-word, multi-visit query, and the current input is
    // still a prefix of it, then changing the autocompletion suddenly feels
    // wrong.  To detect this case, first score as if only one word has been
    // typed, then check for a best result that is an autocompleted, multi-word
    // query.  If we find one, then just keep that score set.
    scored_results = ScoreHistoryResults(results, prevent_inline_autocomplete,
                                         false, input_text, is_keyword);
    if ((scored_results.front().relevance() <
             AutocompleteResult::kLowestDefaultScore) ||
        !HasMultipleWords(scored_results.front().suggestion()))
      scored_results.clear();  // Didn't detect the case above, score normally.
  }
  if (scored_results.empty())
    scored_results = ScoreHistoryResults(results, prevent_inline_autocomplete,
                                         input_multiple_words, input_text,
                                         is_keyword);
  for (SuggestResults::const_iterator i(scored_results.begin());
       i != scored_results.end(); ++i) {
    AddMatchToMap(*i, std::string(), did_not_accept_suggestion, true, map);
  }
  UMA_HISTOGRAM_TIMES("Omnibox.SearchProvider.AddHistoryResultsTime",
                      base::TimeTicks::Now() - start_time);
}

SearchProvider::SuggestResults SearchProvider::ScoreHistoryResults(
    const HistoryResults& results,
    bool base_prevent_inline_autocomplete,
    bool input_multiple_words,
    const base::string16& input_text,
    bool is_keyword) {
  AutocompleteClassifier* classifier =
      AutocompleteClassifierFactory::GetForProfile(profile_);
  SuggestResults scored_results;
  const bool prevent_search_history_inlining =
      OmniboxFieldTrial::SearchHistoryPreventInlining(
          input_.current_page_classification());
  const base::string16& trimmed_input =
      base::CollapseWhitespace(input_text, false);
  for (HistoryResults::const_iterator i(results.begin()); i != results.end();
       ++i) {
    const base::string16& trimmed_suggestion =
        base::CollapseWhitespace(i->term, false);

    // Don't autocomplete multi-word queries that have only been seen once
    // unless the user has typed more than one word.
    bool prevent_inline_autocomplete = base_prevent_inline_autocomplete ||
        (!input_multiple_words && (i->visits < 2) &&
         HasMultipleWords(trimmed_suggestion));

    // Don't autocomplete search terms that would normally be treated as URLs
    // when typed. For example, if the user searched for "google.com" and types
    // "goog", don't autocomplete to the search term "google.com". Otherwise,
    // the input will look like a URL but act like a search, which is confusing.
    // NOTE: We don't check this in the following cases:
    //  * When inline autocomplete is disabled, we won't be inline
    //    autocompleting this term, so we don't need to worry about confusion as
    //    much.  This also prevents calling Classify() again from inside the
    //    classifier (which will corrupt state and likely crash), since the
    //    classifier always disables inline autocomplete.
    //  * When the user has typed the whole term, the "what you typed" history
    //    match will outrank us for URL-like inputs anyway, so we need not do
    //    anything special.
    if (!prevent_inline_autocomplete && classifier &&
        (trimmed_suggestion != trimmed_input)) {
      AutocompleteMatch match;
      classifier->Classify(trimmed_suggestion, false, false,
                           input_.current_page_classification(), &match, NULL);
      prevent_inline_autocomplete =
          !AutocompleteMatch::IsSearchType(match.type);
    }

    int relevance = CalculateRelevanceForHistory(
        i->time, is_keyword, !prevent_inline_autocomplete,
        prevent_search_history_inlining);
    scored_results.push_back(SuggestResult(
        trimmed_suggestion, AutocompleteMatchType::SEARCH_HISTORY,
        trimmed_suggestion, base::string16(), base::string16(), std::string(),
        std::string(), is_keyword, relevance, false, false, trimmed_input));
  }

  // History returns results sorted for us.  However, we may have docked some
  // results' scores, so things are no longer in order.  Do a stable sort to get
  // things back in order without otherwise disturbing results with equal
  // scores, then force the scores to be unique, so that the order in which
  // they're shown is deterministic.
  std::stable_sort(scored_results.begin(), scored_results.end(),
                   CompareScoredResults());
  int last_relevance = 0;
  for (SuggestResults::iterator i(scored_results.begin());
       i != scored_results.end(); ++i) {
    if ((i != scored_results.begin()) && (i->relevance() >= last_relevance))
      i->set_relevance(last_relevance - 1);
    last_relevance = i->relevance();
  }

  return scored_results;
}

void SearchProvider::AddSuggestResultsToMap(const SuggestResults& results,
                                            const std::string& metadata,
                                            MatchMap* map) {
  for (size_t i = 0; i < results.size(); ++i)
    AddMatchToMap(results[i], metadata, i, false, map);
}

int SearchProvider::GetVerbatimRelevance(bool* relevance_from_server) const {
  // Use the suggested verbatim relevance score if it is non-negative (valid),
  // if inline autocomplete isn't prevented (always show verbatim on backspace),
  // and if it won't suppress verbatim, leaving no default provider matches.
  // Otherwise, if the default provider returned no matches and was still able
  // to suppress verbatim, the user would have no search/nav matches and may be
  // left unable to search using their default provider from the omnibox.
  // Check for results on each verbatim calculation, as results from older
  // queries (on previous input) may be trimmed for failing to inline new input.
  bool use_server_relevance =
      (default_results_.verbatim_relevance >= 0) &&
      !input_.prevent_inline_autocomplete() &&
      ((default_results_.verbatim_relevance > 0) ||
       !default_results_.suggest_results.empty() ||
       !default_results_.navigation_results.empty());
  if (relevance_from_server)
    *relevance_from_server = use_server_relevance;
  return use_server_relevance ?
      default_results_.verbatim_relevance : CalculateRelevanceForVerbatim();
}

int SearchProvider::CalculateRelevanceForVerbatim() const {
  if (!providers_.keyword_provider().empty())
    return 250;
  return CalculateRelevanceForVerbatimIgnoringKeywordModeState();
}

int SearchProvider::
    CalculateRelevanceForVerbatimIgnoringKeywordModeState() const {
  switch (input_.type()) {
    case AutocompleteInput::UNKNOWN:
    case AutocompleteInput::QUERY:
    case AutocompleteInput::FORCED_QUERY:
      return kNonURLVerbatimRelevance;

    case AutocompleteInput::URL:
      return 850;

    default:
      NOTREACHED();
      return 0;
  }
}

int SearchProvider::GetKeywordVerbatimRelevance(
    bool* relevance_from_server) const {
  // Use the suggested verbatim relevance score if it is non-negative (valid),
  // if inline autocomplete isn't prevented (always show verbatim on backspace),
  // and if it won't suppress verbatim, leaving no keyword provider matches.
  // Otherwise, if the keyword provider returned no matches and was still able
  // to suppress verbatim, the user would have no search/nav matches and may be
  // left unable to search using their keyword provider from the omnibox.
  // Check for results on each verbatim calculation, as results from older
  // queries (on previous input) may be trimmed for failing to inline new input.
  bool use_server_relevance =
      (keyword_results_.verbatim_relevance >= 0) &&
      !input_.prevent_inline_autocomplete() &&
      ((keyword_results_.verbatim_relevance > 0) ||
       !keyword_results_.suggest_results.empty() ||
       !keyword_results_.navigation_results.empty());
  if (relevance_from_server)
    *relevance_from_server = use_server_relevance;
  return use_server_relevance ?
      keyword_results_.verbatim_relevance :
      CalculateRelevanceForKeywordVerbatim(keyword_input_.type(),
                                           keyword_input_.prefer_keyword());
}

int SearchProvider::CalculateRelevanceForHistory(
    const base::Time& time,
    bool is_keyword,
    bool use_aggressive_method,
    bool prevent_search_history_inlining) const {
  // The relevance of past searches falls off over time. There are two distinct
  // equations used. If the first equation is used (searches to the primary
  // provider that we want to score aggressively), the score is in the range
  // 1300-1599 (unless |prevent_search_history_inlining|, in which case
  // it's in the range 1200-1299). If the second equation is used the
  // relevance of a search 15 minutes ago is discounted 50 points, while the
  // relevance of a search two weeks ago is discounted 450 points.
  double elapsed_time = std::max((base::Time::Now() - time).InSecondsF(), 0.0);
  bool is_primary_provider = is_keyword || !providers_.has_keyword_provider();
  if (is_primary_provider && use_aggressive_method) {
    // Searches with the past two days get a different curve.
    const double autocomplete_time = 2 * 24 * 60 * 60;
    if (elapsed_time < autocomplete_time) {
      int max_score = is_keyword ? 1599 : 1399;
      if (prevent_search_history_inlining)
        max_score = 1299;
      return max_score - static_cast<int>(99 *
          std::pow(elapsed_time / autocomplete_time, 2.5));
    }
    elapsed_time -= autocomplete_time;
  }

  const int score_discount =
      static_cast<int>(6.5 * std::pow(elapsed_time, 0.3));

  // Don't let scores go below 0.  Negative relevance scores are meaningful in
  // a different way.
  int base_score;
  if (is_primary_provider)
    base_score = (input_.type() == AutocompleteInput::URL) ? 750 : 1050;
  else
    base_score = 200;
  return std::max(0, base_score - score_discount);
}

AutocompleteMatch SearchProvider::NavigationToMatch(
    const NavigationResult& navigation) {
  base::string16 input;
  const bool trimmed_whitespace = base::TrimWhitespace(
      navigation.from_keyword_provider() ?
          keyword_input_.text() : input_.text(),
      base::TRIM_TRAILING, &input) != base::TRIM_NONE;
  AutocompleteMatch match(this, navigation.relevance(), false,
                          AutocompleteMatchType::NAVSUGGEST);
  match.destination_url = navigation.url();

  // First look for the user's input inside the formatted url as it would be
  // without trimming the scheme, so we can find matches at the beginning of the
  // scheme.
  const URLPrefix* prefix =
      URLPrefix::BestURLPrefix(navigation.formatted_url(), input);
  size_t match_start = (prefix == NULL) ?
      navigation.formatted_url().find(input) : prefix->prefix.length();
  bool trim_http = !AutocompleteInput::HasHTTPScheme(input) &&
      (!prefix || (match_start != 0));
  const net::FormatUrlTypes format_types =
      net::kFormatUrlOmitAll & ~(trim_http ? 0 : net::kFormatUrlOmitHTTP);

  const std::string languages(
      profile_->GetPrefs()->GetString(prefs::kAcceptLanguages));
  size_t inline_autocomplete_offset = (prefix == NULL) ?
      base::string16::npos : (match_start + input.length());
  match.fill_into_edit +=
      AutocompleteInput::FormattedStringWithEquivalentMeaning(navigation.url(),
          net::FormatUrl(navigation.url(), languages, format_types,
                         net::UnescapeRule::SPACES, NULL, NULL,
                         &inline_autocomplete_offset));
  // Preserve the forced query '?' prefix in |match.fill_into_edit|.
  // Otherwise, user edits to a suggestion would show non-Search results.
  if (input_.type() == AutocompleteInput::FORCED_QUERY) {
    match.fill_into_edit.insert(0, base::ASCIIToUTF16("?"));
    if (inline_autocomplete_offset != base::string16::npos)
      ++inline_autocomplete_offset;
  }
  if (inline_autocomplete_offset != base::string16::npos) {
    DCHECK(inline_autocomplete_offset <= match.fill_into_edit.length());
    match.inline_autocompletion =
        match.fill_into_edit.substr(inline_autocomplete_offset);
  }
  // An inlineable navsuggestion can only be the default match when there
  // is no keyword provider active, lest it appear first and break the user
  // out of keyword mode.  It can also only be default if either the inline
  // autocompletion is empty or we're not preventing inline autocompletion.
  // Finally, if we have an inlineable navsuggestion with an inline completion
  // that we're not preventing, make sure we didn't trim any whitespace.
  // We don't want to claim http://foo.com/bar is inlineable against the
  // input "foo.com/b ".
  match.allowed_to_be_default_match = navigation.IsInlineable(input) &&
      (providers_.GetKeywordProviderURL() == NULL) &&
      (match.inline_autocompletion.empty() ||
       (!input_.prevent_inline_autocomplete() && !trimmed_whitespace));

  match.contents = navigation.match_contents();
  match.contents_class = navigation.match_contents_class();
  match.description = navigation.description();
  AutocompleteMatch::ClassifyMatchInString(input, match.description,
      ACMatchClassification::NONE, &match.description_class);

  match.RecordAdditionalInfo(
      kRelevanceFromServerKey,
      navigation.relevance_from_server() ? kTrue : kFalse);
  match.RecordAdditionalInfo(kShouldPrefetchKey, kFalse);

  return match;
}

void SearchProvider::DemoteKeywordNavigationMatchesPastTopQuery() {
  // First, determine the maximum score of any keyword query match (verbatim or
  // query suggestion).
  bool relevance_from_server;
  int max_query_relevance = GetKeywordVerbatimRelevance(&relevance_from_server);
  if (!keyword_results_.suggest_results.empty()) {
    const SuggestResult& top_keyword = keyword_results_.suggest_results.front();
    const int suggest_relevance = top_keyword.relevance();
    if (suggest_relevance > max_query_relevance) {
      max_query_relevance = suggest_relevance;
      relevance_from_server = top_keyword.relevance_from_server();
    } else if (suggest_relevance == max_query_relevance) {
      relevance_from_server |= top_keyword.relevance_from_server();
    }
  }
  // If no query is supposed to appear, then navigational matches cannot
  // be demoted past it.  Get rid of suggested relevance scores for
  // navsuggestions and introduce the verbatim results again.  The keyword
  // verbatim match will outscore the navsuggest matches.
  if (max_query_relevance == 0) {
    ApplyCalculatedNavigationRelevance(&keyword_results_.navigation_results);
    ApplyCalculatedNavigationRelevance(&default_results_.navigation_results);
    keyword_results_.verbatim_relevance = -1;
    default_results_.verbatim_relevance = -1;
    return;
  }
  // Now we know we can enforce the minimum score constraint even after
  // the navigation matches are demoted.  Proceed to demote the navigation
  // matches to enforce the query-must-come-first constraint.
  // Cap the relevance score of all results.
  for (NavigationResults::iterator it =
           keyword_results_.navigation_results.begin();
       it != keyword_results_.navigation_results.end(); ++it) {
    if (it->relevance() < max_query_relevance)
      return;
    max_query_relevance = std::max(max_query_relevance - 1, 0);
    it->set_relevance(max_query_relevance);
    it->set_relevance_from_server(relevance_from_server);
  }
}

void SearchProvider::UpdateDone() {
  // We're done when the timer isn't running, there are no suggest queries
  // pending, and we're not waiting on Instant.
  done_ = !timer_.IsRunning() && (suggest_results_pending_ == 0);
}
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root/chrome/browser/autocomplete/search_provider.cc

DEFINITIONS
