Add TitledUrlIndex for indexing arbitrary title/URL pairs

components/bookmarks/browser/titled_url_index.cc

Index: components/bookmarks/browser/titled_url_index.cc
diff --git a/components/bookmarks/browser/titled_url_index.cc b/components/bookmarks/browser/titled_url_index.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8ad44b24b8fa1af28464b0ea5dfc3cd373d23d13
--- /dev/null
+++ b/components/bookmarks/browser/titled_url_index.cc
@@ -0,0 +1,247 @@
+// Copyright 2016 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/bookmarks/browser/titled_url_index.h"
+
+#include <stdint.h>
+
+#include "base/i18n/case_conversion.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "base/strings/utf_offset_string_conversions.h"
+#include "build/build_config.h"
+#include "components/bookmarks/browser/bookmark_utils.h"
+#include "components/bookmarks/browser/titled_url_match.h"
+#include "components/query_parser/snippet.h"
+#include "third_party/icu/source/common/unicode/normalizer2.h"
+#include "third_party/icu/source/common/unicode/utypes.h"
+
+namespace bookmarks {
+
+namespace {
+
+// Returns a normalized version of the UTF16 string |text|.  If it fails to
+// normalize the string, returns |text| itself as a best-effort.
+base::string16 Normalize(const base::string16& text) {
+  UErrorCode status = U_ZERO_ERROR;
+  const icu::Normalizer2* normalizer2 =
+      icu::Normalizer2::getInstance(nullptr, "nfkc", UNORM2_COMPOSE, status);
+  if (U_FAILURE(status)) {
+    // Log and crash right away to capture the error code in the crash report.
+    LOG(FATAL) << "failed to create a normalizer: " << u_errorName(status);
+  }
+  icu::UnicodeString unicode_text(text.data(),
+                                  static_cast<int32_t>(text.length()));
+  icu::UnicodeString unicode_normalized_text;
+  normalizer2->normalize(unicode_text, unicode_normalized_text, status);
+  if (U_FAILURE(status)) {
+    // This should not happen. Log the error and fall back.
+    LOG(ERROR) << "normalization failed: " << u_errorName(status);
+    return text;
+  }
+  return base::string16(unicode_normalized_text.getBuffer(),
+                        unicode_normalized_text.length());
+}
+
+}  // namespace
+
+TitledUrlIndex::TitledUrlIndex() {}
+
+TitledUrlIndex::~TitledUrlIndex() {}
+
+void TitledUrlIndex::Add(const TitledUrlNode* node) {
+  if (!node->GetTitledUrlNodeUrl().is_valid())
+    return;
+  std::vector<base::string16> terms =
+      ExtractQueryWords(Normalize(node->GetTitledUrlNodeTitle()));
+  for (size_t i = 0; i < terms.size(); ++i)
+    RegisterNode(terms[i], node);
+  terms = ExtractQueryWords(
+      CleanUpUrlForMatching(node->GetTitledUrlNodeUrl(), nullptr));
+  for (size_t i = 0; i < terms.size(); ++i)
+    RegisterNode(terms[i], node);
+}
+
+void TitledUrlIndex::Remove(const TitledUrlNode* node) {
+  if (!node->GetTitledUrlNodeUrl().is_valid())
+    return;
+
+  std::vector<base::string16> terms =
+      ExtractQueryWords(Normalize(node->GetTitledUrlNodeTitle()));
+  for (size_t i = 0; i < terms.size(); ++i)
+    UnregisterNode(terms[i], node);
+  terms = ExtractQueryWords(
+      CleanUpUrlForMatching(node->GetTitledUrlNodeUrl(), nullptr));
+  for (size_t i = 0; i < terms.size(); ++i)
+    UnregisterNode(terms[i], node);
+}
+
+void TitledUrlIndex::GetResultsMatching(
+    const base::string16& input_query,
+    size_t max_count,
+    query_parser::MatchingAlgorithm matching_algorithm,
+    std::vector<TitledUrlMatch>* results) {
+  const base::string16 query = Normalize(input_query);
+  std::vector<base::string16> terms = ExtractQueryWords(query);
+  if (terms.empty())
+    return;
+
+  NodeSet matches;
+  for (size_t i = 0; i < terms.size(); ++i) {
+    if (!GetResultsMatchingTerm(terms[i], i == 0, matching_algorithm,
+                                &matches)) {
+      return;
+    }
+  }
+
+  Nodes sorted_nodes;
+  SortMatches(matches, &sorted_nodes);
+
+  // We use a QueryParser to fill in match positions for us. It's not the most
+  // efficient way to go about this, but by the time we get here we know what
+  // matches and so this shouldn't be performance critical.
+  query_parser::QueryParser parser;
+  query_parser::QueryNodeVector query_nodes;
+  parser.ParseQueryNodes(query, matching_algorithm, &query_nodes);
+
+  // The highest typed counts should be at the beginning of the results vector
+  // so that the best matches will always be included in the results. The loop
+  // that calculates result relevance in HistoryContentsProvider::ConvertResults
+  // will run backwards to assure higher relevance will be attributed to the
+  // best matches.
+  for (Nodes::const_iterator i = sorted_nodes.begin();
+       i != sorted_nodes.end() && results->size() < max_count; ++i)
+    AddMatchToResults(*i, &parser, query_nodes, results);
+}
+
+void TitledUrlIndex::SortMatches(const NodeSet& matches,
+                                 Nodes* sorted_nodes) const {
+  sorted_nodes->reserve(matches.size());
+  sorted_nodes->insert(sorted_nodes->end(), matches.begin(), matches.end());
+}
+
+void TitledUrlIndex::AddMatchToResults(
+    const TitledUrlNode* node,
+    query_parser::QueryParser* parser,
+    const query_parser::QueryNodeVector& query_nodes,
+    std::vector<TitledUrlMatch>* results) {
+  // Check that the result matches the query.  The previous search
+  // was a simple per-word search, while the more complex matching
+  // of QueryParser may filter it out.  For example, the query
+  // ["thi"] will match the title [Thinking], but since
+  // ["thi"] is quoted we don't want to do a prefix match.
+  query_parser::QueryWordVector title_words, url_words;
+  const base::string16 lower_title =
+      base::i18n::ToLower(Normalize(node->GetTitledUrlNodeTitle()));
+  parser->ExtractQueryWords(lower_title, &title_words);
+  base::OffsetAdjuster::Adjustments adjustments;
+  parser->ExtractQueryWords(
+      CleanUpUrlForMatching(node->GetTitledUrlNodeUrl(), &adjustments),
+      &url_words);
+  query_parser::Snippet::MatchPositions title_matches, url_matches;
+  for (const auto& node : query_nodes) {
+    const bool has_title_matches =
+        node->HasMatchIn(title_words, &title_matches);
+    const bool has_url_matches = node->HasMatchIn(url_words, &url_matches);
+    if (!has_title_matches && !has_url_matches)
+      return;
+    query_parser::QueryParser::SortAndCoalesceMatchPositions(&title_matches);
+    query_parser::QueryParser::SortAndCoalesceMatchPositions(&url_matches);
+  }
+  TitledUrlMatch match;
+  if (lower_title.length() == node->GetTitledUrlNodeTitle().length()) {
+    // Only use title matches if the lowercase string is the same length
+    // as the original string, otherwise the matches are meaningless.
+    // TODO(mpearson): revise match positions appropriately.
+    match.title_match_positions.swap(title_matches);
+  }
+  // Now that we're done processing this entry, correct the offsets of the
+  // matches in |url_matches| so they point to offsets in the original URL
+  // spec, not the cleaned-up URL string that we used for matching.
+  std::vector<size_t> offsets =
+      TitledUrlMatch::OffsetsFromMatchPositions(url_matches);
+  base::OffsetAdjuster::UnadjustOffsets(adjustments, &offsets);
+  url_matches =
+      TitledUrlMatch::ReplaceOffsetsInMatchPositions(url_matches, offsets);
+  match.url_match_positions.swap(url_matches);
+  match.node = node;
+  results->push_back(match);
+}
+
+bool TitledUrlIndex::GetResultsMatchingTerm(
+    const base::string16& term,
+    bool first_term,
+    query_parser::MatchingAlgorithm matching_algorithm,
+    NodeSet* matches) {
+  Index::const_iterator i = index_.lower_bound(term);
+  if (i == index_.end())
+    return false;
+
+  if (!query_parser::QueryParser::IsWordLongEnoughForPrefixSearch(
+          term, matching_algorithm)) {
+    // Term is too short for prefix match, compare using exact match.
+    if (i->first != term)
+      return false;  // No title/URL pairs with this term.
+
+    if (first_term) {
+      (*matches) = i->second;
+      return true;
+    }
+    *matches = base::STLSetIntersection<NodeSet>(i->second, *matches);
+  } else {
+    // Loop through index adding all entries that start with term to
+    // |prefix_matches|.
+    NodeSet tmp_prefix_matches;
+    // If this is the first term, then store the result directly in |matches|
+    // to avoid calling stl intersection (which requires a copy).
+    NodeSet* prefix_matches = first_term ? matches : &tmp_prefix_matches;
+    while (i != index_.end() && i->first.size() >= term.size() &&
+           term.compare(0, term.size(), i->first, 0, term.size()) == 0) {
+#if !defined(OS_ANDROID)
+      prefix_matches->insert(i->second.begin(), i->second.end());
+#else
+      // Work around a bug in the implementation of std::set::insert in the STL
+      // used on android (http://crbug.com/367050).
+      for (NodeSet::const_iterator n = i->second.begin(); n != i->second.end();
+           ++n)
+        prefix_matches->insert(prefix_matches->end(), *n);
+#endif
+      ++i;
+    }
+    if (!first_term)
+      *matches = base::STLSetIntersection<NodeSet>(*prefix_matches, *matches);
+  }
+  return !matches->empty();
+}
+
+std::vector<base::string16> TitledUrlIndex::ExtractQueryWords(
+    const base::string16& query) {
+  std::vector<base::string16> terms;
+  if (query.empty())
+    return std::vector<base::string16>();
+  query_parser::QueryParser parser;
+  parser.ParseQueryWords(base::i18n::ToLower(query),
+                         query_parser::MatchingAlgorithm::DEFAULT, &terms);
+  return terms;
+}
+
+void TitledUrlIndex::RegisterNode(const base::string16& term,
+                                  const TitledUrlNode* node) {
+  index_[term].insert(node);
+}
+
+void TitledUrlIndex::UnregisterNode(const base::string16& term,
+                                    const TitledUrlNode* node) {
+  Index::iterator i = index_.find(term);
+  if (i == index_.end()) {
+    // We can get here if the node has the same term more than once. For
+    // example, a node with the title 'foo foo' would end up here.
+    return;
+  }
+  i->second.erase(node);
+  if (i->second.empty())
+    index_.erase(i);
+}
+
+}  // namespace bookmarks