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

components/autofill/core/common/autofill_util.cc

Index: components/autofill/core/common/autofill_util.cc
diff --git a/components/autofill/core/common/autofill_util.cc b/components/autofill/core/common/autofill_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..424229c6a3c9223a7cfee6f8c814942bbca511ac
--- /dev/null
+++ b/components/autofill/core/common/autofill_util.cc
@@ -0,0 +1,76 @@
+// Copyright 2015 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/common/autofill_util.h"
+
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/i18n/case_conversion.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "components/autofill/core/common/autofill_switches.h"
+
+namespace autofill {
+
+namespace {
+
+const base::string16 kSplitCharacters = base::ASCIIToUTF16(" .,-_@");
+
+}  // namespace
+
+bool IsFeatureSubstringMatchEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSuggestionsWithSubstringMatch);
+}
+
+bool ContainsTokenThatStartsWith(const base::string16& suggestion,
+                                 const base::string16& field_contents,
+                                 bool case_sensitive) {
+  if (!IsFeatureSubstringMatchEnabled())
+    return false;
+
+  std::vector<base::string16> suggestion_tokens;
+  Tokenize(suggestion, kSplitCharacters, &suggestion_tokens);
+
+  // Check whether the |field_contents| prefixes any of the |suggestion|'s
+  // token.
+  for (const base::string16& token : suggestion_tokens) {
+    if (StartsWith(token, field_contents, case_sensitive))
+      return true;
+  }
+
+  return false;
+}
+
+size_t GetTextSelectionStart(const base::string16& suggestion,
+                             const base::string16& field_contents) {
+  size_t offset = 0;
+  // Loop until we find either the |field_contents| begins with the |suggestion|
+  // or character right before |offset| is one of the splitting characters.
+  for (base::string16::const_iterator it = suggestion.begin();
+       (it = std::search(
+            offset + suggestion.begin(), suggestion.end(),
+            field_contents.begin(), field_contents.end(),
+            base::CaseInsensitiveCompare<base::string16::value_type>())) !=
+           suggestion.end();) {
+    offset = it - suggestion.begin();
+    if (offset == 0 ||
+        ContainsOnlyChars(suggestion.substr(offset - 1, 1), kSplitCharacters)) {
+      // Set caret position to the end of the |field_contents|.
+      offset += field_contents.size();
+      return offset;
+    }
+
+    // Search didn't meet the criteria, advance the suggestion range.
+    ++offset;
+  }
+
+  // Unable to find the |field_contents| in |suggestion| text.
+  NOTREACHED();
+  return base::string16::npos;
+}
+
+}  // namespace autofill