[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/core/browser/autocomplete_history_manager.cc

 // Copyright 2013 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 "components/autofill/core/browser/autocomplete_history_manager.h"
 
 #include <vector>
 
 #include "base/prefs/pref_service.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/strings/string16.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/autofill/core/browser/autofill_client.h"
 #include "components/autofill/core/browser/autofill_driver.h"
 #include "components/autofill/core/browser/autofill_external_delegate.h"
 #include "components/autofill/core/browser/validation.h"
 #include "components/autofill/core/common/autofill_pref_names.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/autofill/core/common/form_data.h"
 
 namespace autofill {
 namespace {
 
 // Limit on the number of suggestions to appear in the pop-up menu under an
 // text input element in a form.
 const int kMaxAutocompleteMenuItems = 6;
 
 bool IsTextField(const FormFieldData& field) {
@@ skipping 46 matching lines @@
   // See http://crbug.com/68783.
   if (!result) {
     SendSuggestions(NULL);
     return;
   }
 
   DCHECK_EQ(AUTOFILL_VALUE_RESULT, result->GetType());
   const WDResult<std::vector<base::string16> >* autofill_result =
       static_cast<const WDResult<std::vector<base::string16> >*>(result);
   std::vector<base::string16> suggestions = autofill_result->GetValue();
-  SendSuggestions(&suggestions);
+
+  if (!IsFeatureSubStringMatchEnabled() || user_input_.empty()) {
+    SendSuggestions(&suggestions);
+  } else {
+    std::vector<base::string16> prefix_suggestions;
+    std::vector<base::string16> substring_suggestions;
+    for (auto suggestion : suggestions) {

[Evan Stade, 2015/03/24 00:48:26]

please don't use auto for simple types like base::string16

[Pritam Nikam, 2015/03/24 11:39:36]

Done.

+      // Populate all suggestions with prefix matched followed by sub-string
+      // matched.
+      if (StartsWith(suggestion, user_input_, false)) {

[Evan Stade, 2015/03/24 00:48:26]

I feel like you should be using sql for this, as is done currently

sqlite's LIKE is your friend

[Pritam Nikam, 2015/03/24 11:39:36]

In my opinion, doing it in SQL will be bit difficult as we are not performing
just any substring matching, instead we have to match tokens within suggestions
to be match to first token from user input.

Moreover, I've tried using LIKE, but for me it didn't work (may be I'd goofed up
in query statement) even to fetch prefixes.

+        prefix_suggestions.push_back(suggestion);
+      } else if (HasTokoneStartsWith(suggestion, user_input_)) {
+        substring_suggestions.push_back(suggestion);
+      }
+    }
+
+    // Now append sub-string matched suggestions to the prefix matched
+    // suggestion list.
+    for (auto substring_match : substring_suggestions) {
+      prefix_suggestions.push_back(substring_match);
+    }
+
+    SendSuggestions(&prefix_suggestions);
+  }
 }
 
 void AutocompleteHistoryManager::OnGetAutocompleteSuggestions(
     int query_id,
     const base::string16& name,
     const base::string16& prefix,
     const std::string& form_control_type,
     const std::vector<Suggestion>& suggestions) {
   CancelPendingQuery();
 
   query_id_ = query_id;
   autofill_suggestions_ = suggestions;
   if (!autofill_client_->IsAutocompleteEnabled() ||
       form_control_type == "textarea") {
     SendSuggestions(NULL);
     return;
   }
 
   if (database_.get()) {
+    user_input_ = prefix;
     pending_query_handle_ = database_->GetFormValuesForElementName(
-        name, prefix, kMaxAutocompleteMenuItems, this);
+        name, IsFeatureSubStringMatchEnabled() ? base::string16() : prefix,
+        kMaxAutocompleteMenuItems, this);
   }
 }
 
 void AutocompleteHistoryManager::OnFormSubmitted(const FormData& form) {
   if (!autofill_client_->IsAutocompleteEnabled())
     return;
 
   if (driver_->IsOffTheRecord())
     return;
 
@@ skipping 64 matching lines @@
     }
   }
 
   external_delegate_->OnSuggestionsReturned(query_id_, autofill_suggestions_);
 
   query_id_ = 0;
   autofill_suggestions_.clear();
 }
 
 }  // namespace autofill