Add caching for apps list search results.

chrome/browser/ui/app_list/search/common/webservice_cache.cc

 // Copyright 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/ui/app_list/search/common/webservice_cache.h"
 
+#include "base/strings/string_number_conversions.h"
 #include "base/values.h"
+#include "content/public/browser/browser_context.h"
 
 namespace app_list {
 namespace {
 
-const int kWebserviceCacheMaxSize = 100;
-const int kWebserviceCacheTimeLimitInMinutes = 1;
+const unsigned int kWebserviceCacheMaxSize = 1000;
+const unsigned int kWebserviceCacheTimeLimitInMinutes = 1;
+
+const char kKeyResultTime[] = "time";
+const char kKeyResult[] = "result";
+
+const char kWebstoreQueryPrefix[] = "webstore:";
+const char kPeopleQueryPrefix[] = "people:";
 
 }  // namespace
 
-void WebserviceCache::CacheDeletor::operator()(
-    WebserviceCache::Payload& payload) {
-  delete payload.second;
+void WebserviceCache::CacheDeletor::operator()(Payload& payload) {
+  delete payload.result;
 }
 
-WebserviceCache::WebserviceCache()
-    : cache_(kWebserviceCacheMaxSize) {
+WebserviceCache::WebserviceCache(content::BrowserContext* context)
+    : cache_(Cache::NO_AUTO_EVICT),
+      cache_loaded_(false) {
+  const char kStoreDataFileName[] = "Webservice Search Cache";
+  const base::FilePath data_file =
+      context->GetPath().AppendASCII(kStoreDataFileName);
+  data_store_ = new DictionaryDataStore(data_file);
+  data_store_->Load(base::Bind(&WebserviceCache::OnCacheLoaded, AsWeakPtr()));
 }
 
 WebserviceCache::~WebserviceCache() {
 }
 
-const base::DictionaryValue* WebserviceCache::Get(const std::string& query) {
-  Cache::iterator iter = cache_.Get(query);
+const CacheResult WebserviceCache::Get(QueryType type,
+                                       const std::string& query) {
+  std::string typed_query = PrependType(type, query);
+  Cache::iterator iter = cache_.Get(typed_query);
   if (iter != cache_.end()) {
-    if (base::Time::Now() - iter->second.first <=
+    if (base::Time::Now() - iter->second.time <=
         base::TimeDelta::FromMinutes(kWebserviceCacheTimeLimitInMinutes)) {
-      return iter->second.second;
+      return std::make_pair(FRESH, iter->second.result);
     } else {
-      cache_.Erase(iter);
+      return std::make_pair(STALE, iter->second.result);
     }
   }
-  return NULL;
+  return std::make_pair(STALE, static_cast<base::DictionaryValue*>(NULL));
 }
 
-void WebserviceCache::Put(const std::string& query,
+void WebserviceCache::Put(QueryType type,
+                          const std::string& query,
                           scoped_ptr<base::DictionaryValue> result) {
-  if (result)
-    cache_.Put(query, std::make_pair(base::Time::Now(), result.release()));
+  if (result) {
+    std::string typed_query = PrependType(type, query);
+    Payload payload(base::Time::Now(), result.release());
+
+    cache_.Put(typed_query, payload);
+    // If the cache isn't loaded yet, we're fine with losing queries since
+    // a 1000 entry cache should load really quickly so the chance of a user
+    // already having typed a 3 character search before the cache has loaded is
+    // very unlikely.
+    if (cache_loaded_) {
+      data_store_->cached_dict()->Set(typed_query, DictFromPayload(payload));
+      data_store_->ScheduleWrite();
+      if (cache_.size() > kWebserviceCacheMaxSize)
+        TrimCache();
+    }
+  }
+}
+
+void WebserviceCache::OnCacheLoaded(scoped_ptr<base::DictionaryValue>) {
+  if (!data_store_->cached_dict())
+    return;
+
+  std::vector<std::string> cleanup_keys;
+  for (DictionaryValue::Iterator it(*data_store_->cached_dict());
+      !it.IsAtEnd();
+      it.Advance()) {
+    const base::DictionaryValue* payload_dict;
+    Payload payload;
+    if (!it.value().GetAsDictionary(&payload_dict) ||
+        !payload_dict ||
+        !PayloadFromDict(payload_dict, &payload)) {
+      // In case we don't have a valid payload associated with a given query,
+      // clean up that query from our data store.
+      cleanup_keys.push_back(it.key());
+      continue;
+    }
+    cache_.Put(it.key(), payload);
+  }
+
+  if (!cleanup_keys.empty()) {
+    for (size_t i = 0; i < cleanup_keys.size(); ++i)
+      data_store_->cached_dict()->Remove(cleanup_keys[i], NULL);
+    data_store_->ScheduleWrite();
+  }
+  cache_loaded_ = true;
+}
+
+bool WebserviceCache::PayloadFromDict(const base::DictionaryValue* dict,
+                                      Payload* payload) {
+  std::string time_string;
+  if (!dict->GetString(kKeyResultTime, &time_string))
+    return false;
+  const base::DictionaryValue* result;
+  if (!dict->GetDictionary(kKeyResult, &result))
+    return false;
+
+  int64 time_val;
+  base::StringToInt64(time_string, &time_val);
+
+  // The result dictionary will be owned by the cache, hence create a copy
+  // instead of returning the original reference. The new dictionary will be
+  // owned by our MRU cache.
+  *payload = Payload(base::Time::FromInternalValue(time_val),
+                     result->DeepCopy());
+  return true;
+}
+
+base::DictionaryValue* WebserviceCache::DictFromPayload(
+    const Payload& payload) {
+  base::DictionaryValue* dict = new base::DictionaryValue();
+  dict->SetString(kKeyResultTime, base::Int64ToString(
+      payload.time.ToInternalValue()));
+  // The payload will still keep ownership of it's result dict, hence put a
+  // a copy of the result dictionary here. This dictionary will be owned by
+  // data_store_->cached_dict().
+  dict->Set(kKeyResult, payload.result->DeepCopy());
+
+  return dict;
+}
+
+void WebserviceCache::TrimCache() {
+  for (Cache::size_type i = cache_.size(); i > kWebserviceCacheMaxSize; i--) {
+    Cache::reverse_iterator rbegin = cache_.rbegin();
+    data_store_->cached_dict()->Remove(rbegin->first, NULL);
+    cache_.Erase(rbegin);
+  }
+  data_store_->ScheduleWrite();
+}
+
+std::string WebserviceCache::PrependType(
+    QueryType type, const std::string& query) {
+  switch (type) {
+    case WEBSTORE:
+      return kWebstoreQueryPrefix + query;
+    case PEOPLE:
+      return kPeopleQueryPrefix + query;
+    default:
+      return query;
+  }
 }
 
 }  // namespace app_list