[Sync] Initial implementation of foreign sessions suggestions provider.

components/ntp_snippets/sessions/foreign_sessions_suggestions_provider.cc

Index: components/ntp_snippets/sessions/foreign_sessions_suggestions_provider.cc
diff --git a/components/ntp_snippets/sessions/foreign_sessions_suggestions_provider.cc b/components/ntp_snippets/sessions/foreign_sessions_suggestions_provider.cc
new file mode 100644
index 0000000000000000000000000000000000000000..06257845dc786bfdaac123103377178722b76555
--- /dev/null
+++ b/components/ntp_snippets/sessions/foreign_sessions_suggestions_provider.cc
@@ -0,0 +1,304 @@
+// 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/ntp_snippets/sessions/foreign_sessions_suggestions_provider.h"
+
+#include <algorithm>
+#include <map>
+#include <tuple>
+#include <utility>
+
+#include "base/strings/string_piece.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/time/time.h"
+#include "components/ntp_snippets/category_factory.h"
+#include "components/ntp_snippets/category_info.h"
+#include "components/ntp_snippets/content_suggestion.h"
+#include "components/ntp_snippets/features.h"
+#include "components/ntp_snippets/pref_names.h"
+#include "components/ntp_snippets/pref_util.h"
+#include "components/prefs/pref_registry_simple.h"
+#include "components/prefs/pref_service.h"
+#include "components/sessions/core/session_types.h"
+#include "components/sync_sessions/synced_session.h"
+#include "grit/components_strings.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/gfx/image/image.h"
+#include "url/gurl.h"
+
+using base::TimeDelta;
+using sessions::SerializedNavigationEntry;
+using sessions::SessionTab;
+using sessions::SessionWindow;
+using sync_sessions::SyncedSession;
+
+namespace ntp_snippets {
+namespace {
+
+const int kMaxForeignTabsTotal = 10;
+const int kMaxForeignTabsPerDevice = 3;
+const int kMaxForeignTabAgeInMinutes = 180;
+
+const char* kMaxForeignTabsTotalParamName = "max_foreign_tabs_total";
+const char* kMaxForeignTabsPerDeviceParamName = "max_foreign_tabs_per_device";
+const char* kMaxForeignTabAgeInMinutesParamName =
+    "max_foreign_tabs_age_in_minutes";
+
+int GetMaxForeignTabsTotal() {
+  return GetParamAsInt(ntp_snippets::kForeignSessionsSuggestionsFeature,
+                       kMaxForeignTabsTotalParamName, kMaxForeignTabsTotal);
+}
+
+int GetMaxForeignTabsPerDevice() {
+  return GetParamAsInt(ntp_snippets::kForeignSessionsSuggestionsFeature,
+                       kMaxForeignTabsPerDeviceParamName,
+                       kMaxForeignTabsPerDevice);
+}
+
+TimeDelta GetMaxForeignTabAge() {
+  return TimeDelta::FromMinutes(GetParamAsInt(
+      ntp_snippets::kForeignSessionsSuggestionsFeature,
+      kMaxForeignTabAgeInMinutesParamName, kMaxForeignTabAgeInMinutes));
+}
+
+}  // namespace
+
+ForeignSessionsSuggestionsProvider::ForeignSessionsSuggestionsProvider(
+    ContentSuggestionsProvider::Observer* observer,
+    CategoryFactory* category_factory,
+    std::unique_ptr<ForeignSessionsProvider> foreign_sessions_provider,
+    PrefService* pref_service)
+    : ContentSuggestionsProvider(observer, category_factory),
+      category_status_(CategoryStatus::INITIALIZING),
+      provided_category_(
+          category_factory->FromKnownCategory(KnownCategories::FOREIGN_TABS)),
+      foreign_sessions_provider_(std::move(foreign_sessions_provider)),
+      pref_service_(pref_service) {
+  foreign_sessions_provider_->SubscribeForForeignTabChange(
+      base::Bind(&ForeignSessionsSuggestionsProvider::OnForeignTabChange,
+                 base::Unretained(this)));
+
+  // If sync is already initialzed, try suggesting now, though this is unlikely.
+  OnForeignTabChange();
+}
+
+ForeignSessionsSuggestionsProvider::~ForeignSessionsSuggestionsProvider() {}
+
+// static
+void ForeignSessionsSuggestionsProvider::RegisterProfilePrefs(
+    PrefRegistrySimple* registry) {
+  registry->RegisterListPref(prefs::kDismissedForeignSessionsSuggestions);
+}
+
+CategoryStatus ForeignSessionsSuggestionsProvider::GetCategoryStatus(
+    Category category) {
+  DCHECK_EQ(category, provided_category_);
+  return category_status_;
+}
+
+CategoryInfo ForeignSessionsSuggestionsProvider::GetCategoryInfo(
+    Category category) {
+  DCHECK_EQ(category, provided_category_);
+  return CategoryInfo(l10n_util::GetStringUTF16(
+                          IDS_NTP_FOREIGN_SESSIONS_SUGGESTIONS_SECTION_HEADER),
+                      ContentSuggestionsCardLayout::MINIMAL_CARD,
+                      /* has_more_button */ true,

[tschumann, 2016/09/17 15:52:57]

nit: if you follow the pattern /*has_more_button=*/true, then clang_tidy will
issue warnings in case you the comment wrong
(https://g3doc.corp.google.com/devtools/cymbal/clang_tidy/g3doc/checks/misc-ar...).

[Marc Treib, 2016/09/19 09:24:08]

Do we have that in Chrome? If so, that should resolve the
param-name-comment-style discussion once and for all :)

[tschumann, 2016/09/19 12:19:23]

Apparently, you can run it manually -- not sure how hard it is to get it run
automatically though:
https://chromium.googlesource.com/chromium/src/+show/master/docs/clang_tidy.md
But for me, that would already be reason enough to settle on that style.

[skym, 2016/09/19 18:54:48]

Cool, had no idea this was a thing, done. Also updated
bookmark_suggestion_provider.cc and offline_page_suggestions_provider.cc to use
this formatting as well.

+                      /* show_if_empty */ false);
+}
+
+void ForeignSessionsSuggestionsProvider::DismissSuggestion(
+    const std::string& suggestion_id) {
+  // TODO(skym): Right now this continuously grows, without clearing out old and
+  // irrelevant entries. Could either use a timestamp and expire after a
+  // threshold, or compare with current foreign tabs and remove anything that
+  // isn't actively blockign a foreign_sessions tab.
+  std::set<std::string> dismissed_ids = prefs::ReadDismissedIDsFromPrefs(
+      *pref_service_, prefs::kDismissedForeignSessionsSuggestions);
+  dismissed_ids.insert(suggestion_id);
+  prefs::StoreDismissedIDsToPrefs(pref_service_,
+                                  prefs::kDismissedForeignSessionsSuggestions,
+                                  dismissed_ids);
+}
+
+void ForeignSessionsSuggestionsProvider::FetchSuggestionImage(
+    const std::string& suggestion_id,
+    const ImageFetchedCallback& callback) {
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(callback, gfx::Image()));
+}
+
+void ForeignSessionsSuggestionsProvider::ClearHistory(
+    base::Time begin,
+    base::Time end,
+    const base::Callback<bool(const GURL& url)>& filter) {
+  std::set<std::string> dismissed_ids = prefs::ReadDismissedIDsFromPrefs(
+      *pref_service_, prefs::kDismissedForeignSessionsSuggestions);
+  for (auto iter = dismissed_ids.begin(); iter != dismissed_ids.end();) {
+    if (filter.Run(GURL(base::StringPiece(*iter)))) {
+      iter = dismissed_ids.erase(iter);
+    } else {
+      ++iter;
+    }
+  }
+  prefs::StoreDismissedIDsToPrefs(pref_service_,
+                                  prefs::kDismissedForeignSessionsSuggestions,
+                                  dismissed_ids);
+}
+
+void ForeignSessionsSuggestionsProvider::ClearCachedSuggestions(
+    Category category) {
+  DCHECK_EQ(category, provided_category_);
+  // Ignored.
+}
+
+void ForeignSessionsSuggestionsProvider::GetDismissedSuggestionsForDebugging(
+    Category category,
+    const DismissedSuggestionsCallback& callback) {
+  DCHECK_EQ(category, provided_category_);
+  callback.Run(std::vector<ContentSuggestion>());
+}
+
+void ForeignSessionsSuggestionsProvider::ClearDismissedSuggestionsForDebugging(
+    Category category) {
+  DCHECK_EQ(category, provided_category_);
+  pref_service_->ClearPref(prefs::kDismissedForeignSessionsSuggestions);
+}
+
+void ForeignSessionsSuggestionsProvider::OnForeignTabChange() {
+  if (!foreign_sessions_provider_->HasSessionsData()) {
+    if (category_status_ == CategoryStatus::AVAILABLE) {
+      // This is to handle the case where the user disabled sync [sessions] or
+      // logs out after we've already provided actual suggestions.
+      category_status_ = CategoryStatus::NOT_PROVIDED;
+      observer()->OnCategoryStatusChanged(this, provided_category_,
+                                          category_status_);
+    }
+    return;
+  }
+
+  if (category_status_ != CategoryStatus::AVAILABLE) {
+    // The further below logic will overwrite any error state. This is
+    // currently okay because no where in the current implementation does the
+    // status get set to an error state. Should this change, reconsider the
+    // overwriting logic.
+    DCHECK(category_status_ == CategoryStatus::INITIALIZING ||
+           category_status_ == CategoryStatus::NOT_PROVIDED);
+
+    // It is difficult to tell if sync simply has not initialized yet or there
+    // will never be data because the user is signed out or has disabled the
+    // sessions data type. Because this provider is hidden when there are no
+    // results, always just update to AVAILABLE once we might have results.
+    category_status_ = CategoryStatus::AVAILABLE;
+    observer()->OnCategoryStatusChanged(this, provided_category_,
+                                        category_status_);
+  }
+
+  // observer()->OnNewSuggestions must be called even when we have no
+  // suggestions to remove previous suggestions that are now filtered out.
+  observer()->OnNewSuggestions(
+      this, provided_category_,
+      BuildSuggestions(foreign_sessions_provider_->GetAllForeignSessions()));
+}
+
+std::vector<ContentSuggestion>
+ForeignSessionsSuggestionsProvider::BuildSuggestions(
+    const std::vector<const SyncedSession*>& foreign_sessions) {
+  const int max_foreign_tabs_total = GetMaxForeignTabsTotal();
+  const int max_foreign_tabs_per_device = GetMaxForeignTabsPerDevice();
+
+  std::vector<SessionData> suggestion_candidates =
+      GetSuggestionCandidates(foreign_sessions);
+  // This sorts by recency so that we keep the most recent entries and they
+  // appear as

[Marc Treib, 2016/09/19 09:24:08]

nit: remove the extra line break

[skym, 2016/09/19 18:54:48]

Done.

+  // suggestions in reverse chronological order.
+  std::sort(suggestion_candidates.begin(), suggestion_candidates.end());
+
+  std::vector<ContentSuggestion> suggestions;
+  std::set<std::string> included_urls;
+  std::map<std::string, int> suggestions_per_session;
+  for (const SessionData& candidate : suggestion_candidates) {
+    /*const SyncedSession& session = *std::get<0>(tuple);

[tschumann, 2016/09/17 15:52:57]

please remove ;-)

[skym, 2016/09/19 18:54:48]

Whooops, done!

+    const SessionTab& tab = *std::get<1>(tuple);
+    const SerializedNavigationEntry& navigation = *std::get<2>(tuple);*/
+    const std::string& session_tag = candidate.session->session_tag;
+    auto duplicates_iter =
+        included_urls.find(candidate.navigation->virtual_url().spec());
+    auto count_iter = suggestions_per_session.find(session_tag);
+    int count =
+        count_iter == suggestions_per_session.end() ? 0 : count_iter->second;
+
+    // Pick up to max (total and per device) tabs, and ensure no duplicates
+    // are selected. This filtering must be done in a second pass because
+    // this can cause newer tabs occluding less recent tabs, requiring more
+    // than |max_foreign_tabs_per_device| to be considered per device.
+    if (static_cast<int>(suggestions.size()) >= max_foreign_tabs_total ||
+        duplicates_iter != included_urls.end() ||
+        count >= max_foreign_tabs_per_device) {
+      continue;
+    }
+    included_urls.insert(candidate.navigation->virtual_url().spec());
+    suggestions_per_session[session_tag] = count + 1;
+    suggestions.push_back(BuildSuggestion(candidate));
+  }
+
+  return suggestions;
+}
+
+std::vector<ForeignSessionsSuggestionsProvider::SessionData>
+ForeignSessionsSuggestionsProvider::GetSuggestionCandidates(
+    const std::vector<const SyncedSession*>& foreign_sessions) {
+  // TODO(skym): If a tab was previously dismissed, but was since updated,
+  // should it be resurrected and removed from the dismissed list? This would
+  // likely require a change to the dismissed ids.
+  // TODO(skym): No sense in keeping around dismissals for urls that no longer
+  // exist on any current foreign devices. Should prune and save the pref back.
+  std::set<std::string> dismissed_ids = prefs::ReadDismissedIDsFromPrefs(
+      *pref_service_, prefs::kDismissedForeignSessionsSuggestions);

[tschumann, 2016/09/17 15:52:56]

I'm not feeling strongly, just want to mention the option.
if you pass in the dismissed_ids into this function and provided_category_ in
BuildSuggestion(), you can move these methods off the class into an unnamed
namespace and don't have to define SessionData in the header.
(you can still keep the functions and struct close to BuildSuggestions() -- no
need to have only one unnamed namespace).
It's not a big difference, but removes some distracting implementation details
from the header.

[Marc Treib, 2016/09/19 09:24:08]

This seems like a good idea. If you keep the member functions (which is fine
too), I'd prefer to remove the |foreign_sessions| param from
GetSuggestionCandidates and BuildSuggestions, and instead just get the foreign
sessions here where you need them.

[skym, 2016/09/19 18:54:48]

I like keeping this a member function. Going forward, I'm thinking this method
will need even more member state (pref service to save pruned dismissed ids).

Hopefully just forward declaring the struct will keep the header clean enough.
Removed |foreign_sessions| parameter from this function.

[skym, 2016/09/19 18:54:48]

Acknowledged.

+  const TimeDelta max_foreign_tab_age = GetMaxForeignTabAge();
+  std::vector<SessionData> suggestion_candidates;
+
+  for (const SyncedSession* session : foreign_sessions) {
+    for (const std::pair<const SessionID::id_type, SessionWindow*>& key_value :
+         session->windows) {
+      for (const SessionTab* tab : key_value.second->tabs) {
+        if (tab->navigations.empty())
+          continue;
+
+        const SerializedNavigationEntry& navigation = tab->navigations.back();
+        const std::string unique_id =
+            MakeUniqueID(provided_category_, navigation.virtual_url().spec());
+        // TODO(skym): Filter out internal pages. Tabs that contain only
+        // non-syncable content should never reach the local client, but
+        // sometimes the most recent navigation may be internal while one
+        // of the previous ones was more valid.
+        if (dismissed_ids.find(unique_id) == dismissed_ids.end() &&
+            (base::Time::Now() - tab->timestamp) < max_foreign_tab_age) {
+          suggestion_candidates.push_back(
+              SessionData{session, tab, &navigation});
+        }
+      }
+    }
+  }
+  return suggestion_candidates;
+}
+
+ContentSuggestion ForeignSessionsSuggestionsProvider::BuildSuggestion(
+    const SessionData& data) {
+  ContentSuggestion suggestion(
+      MakeUniqueID(provided_category_, data.navigation->virtual_url().spec()),
+      data.navigation->virtual_url());
+  suggestion.set_title(data.navigation->title());
+  suggestion.set_publish_date(data.tab->timestamp);
+  // TODO(skym): It's unclear if this single approach is sufficient for

[Marc Treib, 2016/09/19 09:24:09]

s/single/simple/

[skym, 2016/09/19 18:54:47]

Done.

+  // right-to-left languages.
+  // This field is sandwiched between the url's favicon, which is on the left,
+  // and the |publish_date|, which is to the right. The domain always appear

[Marc Treib, 2016/09/19 09:24:09]

nit: should this be "The domain always appear*s*", or "The domain *should*
always appear"?

[skym, 2016/09/19 18:54:47]

Going with should.

+  // next to the favicon.
+  suggestion.set_publisher_name(
+      base::UTF8ToUTF16(data.navigation->virtual_url().host() + " - " +
+                        data.session->session_name));
+  return suggestion;
+}
+
+}  // namespace ntp_snippets