[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..a313fc9477f453bd5fb52cd05c1dc624d92ca7dd
--- /dev/null
+++ b/components/autofill/core/common/autofill_util.cc
@@ -0,0 +1,85 @@
+// 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 <algorithm>
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/i18n/case_conversion.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_split.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 char kSplitCharacters[] = " .,-_@";
+
+template <typename Char>
+struct Compare : base::CaseInsensitiveCompareASCII<Char> {
+  explicit Compare(bool case_sensitive) : case_sensitive_(case_sensitive) {}
+  bool operator()(Char x, Char y) const {
+    return case_sensitive_ ? (x == y)
+                           : base::CaseInsensitiveCompareASCII<Char>::
+                             operator()(x, y);
+  }
+
+ private:
+  bool case_sensitive_;
+};
+
+}  // namespace
+
+bool IsFeatureSubstringMatchEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSuggestionsWithSubstringMatch);
+}
+
+bool FieldIsSuggestionSubstringStartingOnTokenBoundary(
+    const base::string16& suggestion,
+    const base::string16& field_contents,
+    bool case_sensitive) {
+  if (!IsFeatureSubstringMatchEnabled()) {
+    return base::StartsWith(suggestion, field_contents,
+                            case_sensitive
+                                ? base::CompareCase::SENSITIVE
+                                : base::CompareCase::INSENSITIVE_ASCII);
+  }
+
+  return suggestion.length() >= field_contents.length() &&
+         GetTextSelectionStart(suggestion, field_contents, case_sensitive) !=
+             base::string16::npos;
+}
+
+size_t GetTextSelectionStart(const base::string16& suggestion,
+                             const base::string16& field_contents,
+                             bool case_sensitive) {
+  const base::string16 kSplitChars = base::ASCIIToUTF16(kSplitCharacters);
+
+  // Loop until we find either the |field_contents| is a prefix of |suggestion|
+  // or character right before the match is one of the splitting characters.
+  for (base::string16::const_iterator it = suggestion.begin();
+       (it = std::search(
+            it, suggestion.end(), field_contents.begin(), field_contents.end(),
+            Compare<base::string16::value_type>(case_sensitive))) !=
+           suggestion.end();
+       ++it) {
+    if (it == suggestion.begin() ||
+        kSplitChars.find(*(it - 1)) != std::string::npos) {
+      // Returns the character position right after the |field_contents| within
+      // |suggestion| text as a caret position for text selection.
+      return it - suggestion.begin() + field_contents.size();
+    }
+  }
+
+  // Unable to find the |field_contents| in |suggestion| text.
+  return base::string16::npos;
+}
+
+}  // namespace autofill