[Sync] Add interface and backend impl for typed URL syncable service

chrome/browser/history/typed_url_syncable_service.cc

Index: chrome/browser/history/typed_url_syncable_service.cc
diff --git a/chrome/browser/history/typed_url_syncable_service.cc b/chrome/browser/history/typed_url_syncable_service.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c410937f513e1a7cced0a4338c43d23c5f0145ea
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+++ b/chrome/browser/history/typed_url_syncable_service.cc
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+// Copyright (c) 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 "chrome/browser/history/typed_url_syncable_service.h"
+
+#include "base/auto_reset.h"
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "base/utf_string_conversions.h"
+#include "chrome/browser/history/history_backend.h"
+#include "net/base/net_util.h"
+#include "sync/protocol/sync.pb.h"
+#include "sync/protocol/typed_url_specifics.pb.h"
+
+namespace {
+
+// The server backend can't handle arbitrarily large node sizes, so to keep
+// the size under control we limit the visit array.
+static const int kMaxTypedUrlVisits = 100;
+
+// There's no limit on how many visits the history DB could have for a given
+// typed URL, so we limit how many we fetch from the DB to avoid crashes due to
+// running out of memory (http://crbug.com/89793). This value is different
+// from kMaxTypedUrlVisits, as some of the visits fetched from the DB may be
+// RELOAD visits, which will be stripped.
+static const int kMaxVisitsToFetch = 1000;
+
+// This is the threshold at which we start throttling sync updates for typed
+// URLs - any URLs with a typed_count >= this threshold will be throttled.
+static const int kTypedUrlVisitThrottleThreshold = 10;
+
+// This is the multiple we use when throttling sync updates. If the multiple is
+// N, we sync up every Nth update (i.e. when typed_count % N == 0).
+static const int kTypedUrlVisitThrottleMultiple = 10;
+
+}  // namespace
+
+namespace history {
+
+const char kTypedUrlTag[] = "google_chrome_typed_urls";
+
+static bool CheckVisitOrdering(const VisitVector& visits) {
+  int64 previous_visit_time = 0;
+  for (VisitVector::const_iterator visit = visits.begin();
+       visit != visits.end(); ++visit) {
+    if (visit != visits.begin()) {
+      // We allow duplicate visits here - they shouldn't really be allowed, but
+      // they still seem to show up sometimes and we haven't figured out the
+      // source, so we just log an error instead of failing an assertion.
+      // (http://crbug.com/91473).
+      if (previous_visit_time == visit->visit_time.ToInternalValue())
+        DVLOG(1) << "Duplicate visit time encountered";
+      else if (previous_visit_time > visit->visit_time.ToInternalValue())
+        return false;
+    }
+
+    previous_visit_time = visit->visit_time.ToInternalValue();
+  }
+  return true;
+}
+
+TypedUrlSyncableService::TypedUrlSyncableService(
+    HistoryBackend* history_backend)
+    : history_backend_(history_backend),
+      processing_syncer_changes_(false),
+      expected_loop_(MessageLoop::current()) {
+  DCHECK(history_backend_);
+  DCHECK(expected_loop_ == MessageLoop::current());
+}
+
+TypedUrlSyncableService::~TypedUrlSyncableService() {
+  DCHECK(expected_loop_ == MessageLoop::current());
+}
+
+syncer::SyncMergeResult TypedUrlSyncableService::MergeDataAndStartSyncing(
+    syncer::ModelType type,
+    const syncer::SyncDataList& initial_sync_data,
+    scoped_ptr<syncer::SyncChangeProcessor> sync_processor,
+    scoped_ptr<syncer::SyncErrorFactory> error_handler) {
+  DCHECK(expected_loop_ == MessageLoop::current());
+  DCHECK(!sync_processor_.get());
+  DCHECK(sync_processor.get());
+  DCHECK(error_handler.get());
+  DCHECK_EQ(type, syncer::TYPED_URLS);
+
+  syncer::SyncMergeResult merge_result(type);
+  sync_processor_ = sync_processor.Pass();
+  sync_error_handler_ = error_handler.Pass();
+
+  // TODO(mgist): Add implementation
+
+  return merge_result;
+}
+
+void TypedUrlSyncableService::StopSyncing(syncer::ModelType type) {
+  DCHECK(expected_loop_ == MessageLoop::current());
+  DCHECK_EQ(type, syncer::TYPED_URLS);
+
+  sync_processor_.reset();
+  sync_error_handler_.reset();
+}
+
+syncer::SyncDataList TypedUrlSyncableService::GetAllSyncData(
+    syncer::ModelType type) const {
+  DCHECK(expected_loop_ == MessageLoop::current());
+  syncer::SyncDataList list;
+
+  // TODO(mgist): Add implementation
+
+  return list;
+}
+
+syncer::SyncError TypedUrlSyncableService::ProcessSyncChanges(
+    const tracked_objects::Location& from_here,
+    const syncer::SyncChangeList& change_list) {
+  DCHECK(expected_loop_ == MessageLoop::current());
+
+  // TODO(mgist): Add implementation
+
+  return syncer::SyncError(FROM_HERE,
+                           "Typed url syncable service is not implemented.",
+                           syncer::TYPED_URLS);
+}
+
+void TypedUrlSyncableService::OnUrlsModified(URLRows* changed_urls) {
+  DCHECK(expected_loop_ == MessageLoop::current());
+  DCHECK(changed_urls);
+
+  if (processing_syncer_changes_)
+    return;  // These are changes originating from us, ignore.
+  if (!sync_processor_.get())
+    return;  // Sync processor not yet initialized, don't sync.
+
+  // Create SyncChangeList.
+  syncer::SyncChangeList changes;
+
+  for (URLRows::iterator url = changed_urls->begin();
+       url != changed_urls->end(); ++url) {
+    // Only care if the modified URL is typed.
+    if (url->typed_count() > 0) {
+      // If there were any errors updating the sync node, just ignore them and
+      // continue on to process the next URL.
+      CreateOrUpdateSyncNode(*url, &changes);
+    }
+  }
+
+  // Send SyncChangeList to server if there are any changes.
+  if (changes.size() > 0)
+    sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
+}
+
+void TypedUrlSyncableService::OnUrlVisited(content::PageTransition transition,
+                                           URLRow* row) {
+  DCHECK(expected_loop_ == MessageLoop::current());
+  DCHECK(row);
+
+  if (processing_syncer_changes_)
+    return;  // These are changes originating from us, ignore.
+  if (!sync_processor_.get())
+    return;  // Sync processor not yet initialized, don't sync.
+  if (!ShouldSyncVisit(transition, row))
+    return;
+
+  // Create SyncChangeList.
+  syncer::SyncChangeList changes;
+
+  CreateOrUpdateSyncNode(*row, &changes);
+
+  // Send SyncChangeList to server if there are any changes.
+  if (changes.size() > 0)
+    sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
+}
+
+void TypedUrlSyncableService::OnUrlsDeleted(bool all_history,
+                                            bool archived,
+                                            URLRows* rows) {
+  DCHECK(expected_loop_ == MessageLoop::current());
+
+  if (processing_syncer_changes_)
+    return;  // These are changes originating from us, ignore.
+  if (!sync_processor_.get())
+    return;  // Sync processor not yet initialized, don't sync.
+
+  // Ignore archivals (we don't want to sync them as deletions, to avoid
+  // extra traffic up to the server, and also to make sure that a client with
+  // a bad clock setting won't go on an archival rampage and delete all
+  // history from every client). The server will gracefully age out the sync DB
+  // entries when they've been idle for long enough.
+  if (archived)
+    return;
+
+  // Create SyncChangeList.
+  syncer::SyncChangeList changes;
+
+  if (all_history) {
+    // Delete all synced typed urls.
+    for (std::set<GURL>::const_iterator url = synced_typed_urls_.begin();
+         url != synced_typed_urls_.end(); ++url) {
+      VisitVector visits;
+      URLRow row(*url);
+      AddTypedUrlToChangeList(syncer::SyncChange::ACTION_DELETE,
+                              row, visits, url->spec(), &changes);
+    }
+    // Clear cache of server state.
+    synced_typed_urls_.clear();
+  } else {
+    DCHECK(rows);
+    // Delete rows.
+    for (URLRows::const_iterator row = rows->begin();
+         row != rows->end(); ++row) {
+      // Add specifics to change list for all synced urls that were deleted.
+      if (synced_typed_urls_.find(row->url()) != synced_typed_urls_.end()) {
+        VisitVector visits;
+        AddTypedUrlToChangeList(syncer::SyncChange::ACTION_DELETE,
+                                *row, visits, row->url().spec(), &changes);
+        // Delete typed url from cache.
+        synced_typed_urls_.erase(row->url());
+      }
+    }
+  }
+
+  // Send SyncChangeList to server if there are any changes.
+  if (changes.size() > 0)
+    sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
+}
+
+bool TypedUrlSyncableService::ShouldIgnoreUrl(const GURL& url) {
+  // Ignore empty URLs. Not sure how this can happen (maybe import from other
+  // busted browsers, or misuse of the history API, or just plain bugs) but we
+  // can't deal with them.
+  if (url.spec().empty())
+    return true;
+
+  // Ignore local file URLs.
+  if (url.SchemeIsFile())
+    return true;
+
+  // Ignore localhost URLs.
+  if (net::IsLocalhost(url.host()))
+    return true;
+
+  return false;
+}
+
+bool TypedUrlSyncableService::ShouldSyncVisit(
+    content::PageTransition page_transition,
+    URLRow* row) {
+  if (!row)
+    return false;
+  int typed_count = row->typed_count();
+  content::PageTransition transition = static_cast<content::PageTransition>(
+      page_transition & content::PAGE_TRANSITION_CORE_MASK);
+
+  // Just use an ad-hoc criteria to determine whether to ignore this
+  // notification. For most users, the distribution of visits is roughly a bell
+  // curve with a long tail - there are lots of URLs with < 5 visits so we want
+  // to make sure we sync up every visit to ensure the proper ordering of
+  // suggestions. But there are relatively few URLs with > 10 visits, and those
+  // tend to be more broadly distributed such that there's no need to sync up
+  // every visit to preserve their relative ordering.
+  return (transition == content::PAGE_TRANSITION_TYPED &&
+          typed_count > 0 &&
+          (typed_count < kTypedUrlVisitThrottleThreshold ||
+           (typed_count % kTypedUrlVisitThrottleMultiple) == 0));
+}
+
+bool TypedUrlSyncableService::CreateOrUpdateSyncNode(
+    URLRow url,
+    syncer::SyncChangeList* changes) {
+  DCHECK_GT(url.typed_count(), 0);
+
+  if (ShouldIgnoreUrl(url.url()))
+    return true;
+
+  // Get the visits for this node.
+  VisitVector visit_vector;
+  if (!FixupURLAndGetVisits(&url, &visit_vector)) {
+    DLOG(ERROR) << "Could not load visits for url: " << url.url();
+    return false;
+  }
+  DCHECK(!visit_vector.empty());
+
+  std::string title = url.url().spec();
+  syncer::SyncChange::SyncChangeType change_type;
+
+  // If server already has URL, then send a sync update, else add it.
+  change_type =
+      (synced_typed_urls_.find(url.url()) != synced_typed_urls_.end()) ?
+      syncer::SyncChange::ACTION_UPDATE :
+      syncer::SyncChange::ACTION_ADD;
+
+  // Ensure cache of server state is up to date.
+  synced_typed_urls_.insert(url.url());
+
+  AddTypedUrlToChangeList(change_type, url, visit_vector, title, changes);
+
+  return true;
+}
+
+void TypedUrlSyncableService::AddTypedUrlToChangeList(
+    syncer::SyncChange::SyncChangeType change_type,
+    const URLRow& row,
+    const VisitVector& visits,
+    std::string title,
+    syncer::SyncChangeList* change_list) {
+  sync_pb::EntitySpecifics entity_specifics;
+  sync_pb::TypedUrlSpecifics* typed_url = entity_specifics.mutable_typed_url();
+
+  if (change_type == syncer::SyncChange::ACTION_DELETE) {
+    typed_url->set_url(row.url().spec());
+  } else {
+    WriteToTypedUrlSpecifics(row, visits, typed_url);
+  }
+
+  change_list->push_back(
+      syncer::SyncChange(FROM_HERE, change_type,
+                         syncer::SyncData::CreateLocalData(
+                             kTypedUrlTag, title, entity_specifics)));
+}
+
+void TypedUrlSyncableService::WriteToTypedUrlSpecifics(
+    const URLRow& url,
+    const VisitVector& visits,
+    sync_pb::TypedUrlSpecifics* typed_url) {
+
+  DCHECK(!url.last_visit().is_null());
+  DCHECK(!visits.empty());
+  DCHECK_EQ(url.last_visit().ToInternalValue(),
+            visits.back().visit_time.ToInternalValue());
+
+  typed_url->set_url(url.url().spec());
+  typed_url->set_title(UTF16ToUTF8(url.title()));
+  typed_url->set_hidden(url.hidden());
+
+  DCHECK(CheckVisitOrdering(visits));
+
+  bool only_typed = false;
+  int skip_count = 0;
+
+  if (visits.size() > static_cast<size_t>(kMaxTypedUrlVisits)) {
+    int typed_count = 0;
+    int total = 0;
+    // Walk the passed-in visit vector and count the # of typed visits.
+    for (VisitVector::const_iterator visit = visits.begin();
+         visit != visits.end(); ++visit) {
+      content::PageTransition transition = content::PageTransitionFromInt(
+          visit->transition & content::PAGE_TRANSITION_CORE_MASK);
+      // We ignore reload visits.
+      if (transition == content::PAGE_TRANSITION_RELOAD)
+        continue;
+      ++total;
+      if (transition == content::PAGE_TRANSITION_TYPED)
+        ++typed_count;
+    }
+    // We should have at least one typed visit. This can sometimes happen if
+    // the history DB has an inaccurate count for some reason (there's been
+    // bugs in the history code in the past which has left users in the wild
+    // with incorrect counts - http://crbug.com/84258).
+    DCHECK(typed_count > 0);
+
+    if (typed_count > kMaxTypedUrlVisits) {
+      only_typed = true;
+      skip_count = typed_count - kMaxTypedUrlVisits;
+    } else if (total > kMaxTypedUrlVisits) {
+      skip_count = total - kMaxTypedUrlVisits;
+    }
+  }
+
+  for (VisitVector::const_iterator visit = visits.begin();
+       visit != visits.end(); ++visit) {
+    content::PageTransition transition = content::PageTransitionFromInt(
+        visit->transition & content::PAGE_TRANSITION_CORE_MASK);
+    // Skip reload visits.
+    if (transition == content::PAGE_TRANSITION_RELOAD)
+      continue;
+
+    // If we only have room for typed visits, then only add typed visits.
+    if (only_typed && transition != content::PAGE_TRANSITION_TYPED)
+      continue;
+
+    if (skip_count > 0) {
+      // We have too many entries to fit, so we need to skip the oldest ones.
+      // Only skip typed URLs if there are too many typed URLs to fit.
+      if (only_typed || transition != content::PAGE_TRANSITION_TYPED) {
+        --skip_count;
+        continue;
+      }
+    }
+    typed_url->add_visits(visit->visit_time.ToInternalValue());
+    typed_url->add_visit_transitions(visit->transition);
+  }
+  DCHECK_EQ(skip_count, 0);
+
+  if (typed_url->visits_size() == 0) {
+    // If we get here, it's because we don't actually have any TYPED visits
+    // even though the visit's typed_count > 0 (corrupted typed_count). So
+    // let's go ahead and add a RELOAD visit at the most recent visit since
+    // it's not legal to have an empty visit array (yet another workaround
+    // for http://crbug.com/84258).
+    typed_url->add_visits(url.last_visit().ToInternalValue());
+    typed_url->add_visit_transitions(content::PAGE_TRANSITION_RELOAD);
+  }
+  CHECK_GT(typed_url->visits_size(), 0);
+  CHECK_LE(typed_url->visits_size(), kMaxTypedUrlVisits);
+  CHECK_EQ(typed_url->visits_size(), typed_url->visit_transitions_size());
+}
+
+bool TypedUrlSyncableService::FixupURLAndGetVisits(
+    URLRow* url,
+    VisitVector* visits) {
+  ++num_db_accesses_;
+  CHECK(history_backend_);
+  if (!history_backend_->GetMostRecentVisitsForURL(
+          url->id(), kMaxVisitsToFetch, visits)) {
+    ++num_db_errors_;
+    return false;
+  }
+
+  // Sometimes (due to a bug elsewhere in the history or sync code, or due to
+  // a crash between adding a URL to the history database and updating the
+  // visit DB) the visit vector for a URL can be empty. If this happens, just
+  // create a new visit whose timestamp is the same as the last_visit time.
+  // This is a workaround for http://crbug.com/84258.
+  if (visits->empty()) {
+    DVLOG(1) << "Found empty visits for URL: " << url->url();
+    VisitRow visit(
+        url->id(), url->last_visit(), 0, content::PAGE_TRANSITION_TYPED, 0);
+    visits->push_back(visit);
+  }
+
+  // GetMostRecentVisitsForURL() returns the data in the opposite order that
+  // we need it, so reverse it.
+  std::reverse(visits->begin(), visits->end());
+
+  // Sometimes, the last_visit field in the URL doesn't match the timestamp of
+  // the last visit in our visit array (they come from different tables, so
+  // crashes/bugs can cause them to mismatch), so just set it here.
+  url->set_last_visit(visits->back().visit_time);
+  DCHECK(CheckVisitOrdering(*visits));
+  return true;
+}
+
+}  // namespace history