Inform server of dismissed articles.

It seems that the server currently has logic to not send back excluded
IDs, but lacks the logic needed to request more. Still, that's something
that can be improved in the server later.

There should be tests for NTPSnippetsService to verify the new behavior,
but that's not possible until it uses the new server.

BUG=633613

Review-Url: https://codereview.chromium.org/2274953002
Cr-Commit-Position: refs/heads/master@{#414428}

components/ntp_snippets/ntp_snippets_fetcher.cc

@@ -70,6 +70,8 @@ const char kPersonalizationBothString[] = "both";  // the default value
 const char kHostRestrictionOnString[] = "on";  // the default value
 const char kHostRestrictionOffString[] = "off";
 
+const int kMaxExcludedIds = 100;
+
 std::string FetchResultToString(NTPSnippetsFetcher::FetchResult result) {
   switch (result) {
     case NTPSnippetsFetcher::FetchResult::SUCCESS:
@@ -216,6 +218,7 @@ void NTPSnippetsFetcher::SetCallback(
 void NTPSnippetsFetcher::FetchSnippetsFromHosts(
     const std::set<std::string>& hosts,
     const std::string& language_code,
+    const std::set<std::string>& excluded_ids,
     int count,
     bool interactive_request) {
   if (!request_throttler_.DemandQuotaForRequest(interactive_request))
@@ -223,6 +226,7 @@ void NTPSnippetsFetcher::FetchSnippetsFromHosts(
 
   hosts_ = hosts;
   fetch_start_time_ = tick_clock_->NowTicks();
+  excluded_ids_ = excluded_ids;
 
   if (UsesHostRestrictions() && hosts_.empty()) {
     FetchFinished(OptionalSnippets(), FetchResult::EMPTY_HOSTS,
@@ -317,12 +321,21 @@ std::string NTPSnippetsFetcher::RequestParams::BuildRequest() {
       if (!user_locale.empty()) {
         request->SetString("uiLanguage", user_locale);
       }
+
       auto regular_hosts = base::MakeUnique<base::ListValue>();
       for (const auto& host : host_restricts) {
         regular_hosts->AppendString(host);
       }
       request->Set("regularlyVisitedHostNames", std::move(regular_hosts));
 
+      auto excluded = base::MakeUnique<base::ListValue>();
+      for (const auto& id : excluded_ids) {
+        excluded->AppendString(id);
+        if (excluded->GetSize() >= kMaxExcludedIds)
+          break;
+      }
+      request->Set("excludedSuggestionIds", std::move(excluded));
+
       // TODO(sfiera): support authentication and personalization
       // TODO(sfiera): support count_to_fetch
       break;
@@ -392,6 +405,7 @@ void NTPSnippetsFetcher::FetchSnippetsNonAuthenticated() {
   params.fetch_api = fetch_api_;
   params.host_restricts =
       UsesHostRestrictions() ? hosts_ : std::set<std::string>();
+  params.excluded_ids = excluded_ids_;
   params.count_to_fetch = count_to_fetch_;
   FetchSnippetsImpl(url, std::string(), params.BuildRequest());
 }
@@ -407,6 +421,7 @@ void NTPSnippetsFetcher::FetchSnippetsAuthenticated(
   params.user_locale = locale_;
   params.host_restricts =
       UsesHostRestrictions() ? hosts_ : std::set<std::string>();
+  params.excluded_ids = excluded_ids_;
   params.count_to_fetch = count_to_fetch_;
   // TODO(jkrcal, treib): Add unit-tests for authenticated fetches.
   FetchSnippetsImpl(fetch_url_,

components/ntp_snippets/ntp_snippets_fetcher.h

@@ -90,7 +90,11 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   void SetCallback(const SnippetsAvailableCallback& callback);
 
   // Fetches snippets from the server. |hosts| restricts the results to a set of
-  // hosts, e.g. "www.google.com". An empty host set produces an error.
+  // hosts, e.g. "www.google.com". If host restrictions are enabled, an empty
+  // host set produces an error without issuing a fetch.
+  //
+  // |excluded_ids| will be reported to the server; the server should not return
+  // suggestions with those IDs.
   //
   // If an ongoing fetch exists, it will be cancelled and a new one started,
   // without triggering an additional callback (i.e. not noticeable by
@@ -100,6 +104,7 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   // |interactive_request| is set to true (use only for user-initiated fetches).
   void FetchSnippetsFromHosts(const std::set<std::string>& hosts,
                               const std::string& language_code,
+                              const std::set<std::string>& excluded_ids,
                               int count,
                               bool interactive_request);
 
@@ -134,6 +139,7 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
  private:
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsFetcherTest, BuildRequestAuthenticated);
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsFetcherTest, BuildRequestUnauthenticated);
+  FRIEND_TEST_ALL_PREFIXES(NTPSnippetsFetcherTest, BuildRequestExcludedIds);
 
   enum FetchAPI {
     CHROME_READER_API,
@@ -146,6 +152,7 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
     bool only_return_personalized_results;
     std::string user_locale;
     std::set<std::string> host_restricts;
+    std::set<std::string> excluded_ids;
     int count_to_fetch;
 
     RequestParams();
@@ -201,6 +208,9 @@ class NTPSnippetsFetcher : public OAuth2TokenService::Consumer,
   // Hosts to restrict the snippets to.
   std::set<std::string> hosts_;
 
+  // Snippets to exclude from the results.
+  std::set<std::string> excluded_ids_;
+
   // Count of snippets to fetch.
   int count_to_fetch_;
 

components/ntp_snippets/ntp_snippets_service.cc

@@ -265,8 +265,13 @@ void NTPSnippetsService::FetchSnippetsFromHosts(
   if (snippets_.empty())
     UpdateCategoryStatus(CategoryStatus::AVAILABLE_LOADING);
 
-  snippets_fetcher_->FetchSnippetsFromHosts(
-      hosts, application_language_code_, kMaxSnippetCount, interactive_request);
+  std::set<std::string> excluded_ids;
+  for (const auto& snippet : dismissed_snippets_) {
+    excluded_ids.insert(snippet->id());
+  }
+  snippets_fetcher_->FetchSnippetsFromHosts(hosts, application_language_code_,
+                                            excluded_ids, kMaxSnippetCount,
+                                            interactive_request);
 }
 
 void NTPSnippetsService::RescheduleFetching() {