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

components/autofill/core/browser/autocomplete_history_manager.cc

Index: components/autofill/core/browser/autocomplete_history_manager.cc
diff --git a/components/autofill/core/browser/autocomplete_history_manager.cc b/components/autofill/core/browser/autocomplete_history_manager.cc
index 79d75b8c18d257b686c4121a9dbc5f7dedc8772a..537cf7932de822e1e83944cc8ca16d4334db1ab9 100644
--- a/components/autofill/core/browser/autocomplete_history_manager.cc
+++ b/components/autofill/core/browser/autocomplete_history_manager.cc
@@ -9,12 +9,14 @@
 #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 {
@@ -81,7 +83,30 @@ void AutocompleteHistoryManager::OnWebDataServiceRequestDone(
   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(
@@ -101,8 +126,10 @@ void AutocompleteHistoryManager::OnGetAutocompleteSuggestions(
   }
 
   if (database_.get()) {
+    user_input_ = prefix;
     pending_query_handle_ = database_->GetFormValuesForElementName(
-        name, prefix, kMaxAutocompleteMenuItems, this);
+        name, IsFeatureSubStringMatchEnabled() ? base::string16() : prefix,
+        kMaxAutocompleteMenuItems, this);
   }
 }