Parse JSON in Blink for CopylessPaste.

third_party/WebKit/Source/modules/document_metadata/CopylessPasteExtractor.cpp

 // Copyright 2017 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 "modules/document_metadata/CopylessPasteExtractor.h"
 
+#include <algorithm>
+#include <memory>
+#include <utility>
 #include "core/HTMLNames.h"
 #include "core/dom/Document.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLElement.h"
 #include "platform/Histogram.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
+#include "platform/json/JSONParser.h"
+#include "public/platform/modules/document_metadata/copyless_paste.mojom-blink.h"
+#include "wtf/Vector.h"
+#include "wtf/text/AtomicString.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace blink {
 
 namespace {
 
-String extractMetadata(Element& root) {
-  StringBuilder result;
-  result.append("[");
-  bool multiple = false;
+using mojom::blink::Entity;
+using mojom::blink::EntityPtr;
+using mojom::blink::Property;
+using mojom::blink::PropertyPtr;
+using mojom::blink::Values;
+using mojom::blink::ValuesPtr;
+using mojom::blink::WebPage;
+using mojom::blink::WebPagePtr;
+
+// App Indexing enforces a max nesting depth of 5. Our top level message
+// corresponds to the WebPage, so this only leaves 4 more levels. We will parse
+// entites up to this depth, and ignore any further nesting. If an object at the
+// max nesting depth has a property corresponding to an entity, that property
+// will be dropped. Note that we will still parse json-ld blocks deeper than
+// this, but it won't be passed to App Indexing.
+constexpr int kMaxDepth = 4;
+// Some strings are very long, and we don't currently use those, so limit string
+// length to something reasonable to avoid undue pressure on Icing. Note that
+// App Indexing supports strings up to length 20k.
+constexpr int kMaxStringLength = 200;
+// Enforced by App Indexing, so stop processing early if possible.
+constexpr size_t kMaxNumFields = 20;
+// Enforced by App Indexing, so stop processing early if possible.
+constexpr size_t kMaxRepeatedSize = 100;
+
+constexpr char kJSONLDKeyType[] = "@type";
+constexpr char kJSONLDKeyGraph[] = "@graph";
+bool isWhitelistedType(AtomicString type) {
+  DEFINE_STATIC_LOCAL(HashSet<AtomicString>, elements,
+                      ({// Common types that include addresses.
+                        "AutoDealer", "Hotel", "LocalBusiness", "Organization",
+                        "Person", "Place", "PostalAddress", "Product",
+                        "Residence", "Restaurant", "SingleFamilyResidence",
+                        // Common types including phone numbers
+                        "Store", "ContactPoint", "LodgingBusiness"}));
+  return type && elements.contains(type);
+}
+
+void extractEntity(const JSONObject&, Entity&, int recursionLevel);
+
+bool parseRepeatedValue(const JSONArray& arr,
+                        Values& values,
+                        int recursionLevel) {
+  if (arr.size() < 1) {
+    return false;
+  }
+
+  const JSONValue::ValueType type = arr.at(0)->getType();
+  if (type == JSONArray::ValueType::TypeArray) {
+    // App Indexing doesn't support nested arrays.
+    return false;
+  }
+  for (size_t j = 0; j < std::min(arr.size(), kMaxRepeatedSize); ++j) {
+    const JSONValue* innerVal = arr.at(j);
+    if (innerVal->getType() != type) {
+      // App Indexing doesn't support mixed types. If there are mixed
+      // types in the parsed object, we will drop the property.
+      return false;
+    }
+    switch (innerVal->getType()) {
+      case JSONValue::ValueType::TypeBoolean: {
+        if (!values.is_bool_values()) {
+          values.set_bool_values(Vector<bool>());
+        }
+        bool v;
+        innerVal->asBoolean(&v);
+        values.get_bool_values().push_back(v);
+      } break;
+      case JSONValue::ValueType::TypeInteger: {
+        if (!values.is_long_values()) {
+          values.set_long_values(Vector<int64_t>());
+        }
+        int v;
+        innerVal->asInteger(&v);
+        values.get_long_values().push_back(v);
+      } break;
+      case JSONValue::ValueType::TypeDouble: {
+        // App Indexing doesn't support double type, so just encode its decimal
+        // value as a string instead.
+        if (!values.is_string_values()) {
+          values.set_string_values(Vector<String>());
+        }
+        double v;
+        innerVal->asDouble(&v);
+        String s = String::number(v);
+        s.truncate(kMaxStringLength);
+        values.get_string_values().push_back(s);
+      } break;
+      case JSONValue::ValueType::TypeString: {
+        if (!values.is_string_values()) {
+          values.set_string_values(Vector<String>());
+        }
+        String v;
+        innerVal->asString(&v);
+        v.truncate(kMaxStringLength);
+        values.get_string_values().push_back(v);
+      } break;
+      case JSONValue::ValueType::TypeObject:
+        if (recursionLevel + 1 >= kMaxDepth) {
+          return false;
+        }
+        if (!values.is_entity_values()) {
+          values.set_entity_values(Vector<EntityPtr>());
+        }
+        values.get_entity_values().push_back(Entity::New());
+        extractEntity(*(JSONObject::cast(innerVal)),
+                      *(values.get_entity_values().at(j)), recursionLevel + 1);
+        break;
+      default:
+        break;
+    }
+  }
+  return true;
+}
+
+void extractEntity(const JSONObject& val, Entity& entity, int recursionLevel) {
+  if (recursionLevel >= kMaxDepth) {
+    return;
+  }
+
+  String type;
+  val.getString(kJSONLDKeyType, &type);
+  if (!type) {
+    type = "Thing";
+  }
+  entity.type = type;
+  for (size_t i = 0; i < std::min(val.size(), kMaxNumFields); ++i) {
+    PropertyPtr property = Property::New();
+    const JSONObject::Entry& entry = val.at(i);
+    property->name = entry.first;
+    if (property->name == kJSONLDKeyType) {
+      continue;
+    }
+    property->values = Values::New();
+
+    bool addProperty = true;
+
+    switch (entry.second->getType()) {
+      case JSONValue::ValueType::TypeBoolean: {
+        bool v;
+        val.getBoolean(entry.first, &v);
+        property->values->set_bool_values(Vector<bool>(1, v));
+      } break;
+      case JSONValue::ValueType::TypeInteger: {
+        int v;
+        val.getInteger(entry.first, &v);
+        property->values->set_long_values(Vector<int64_t>(1, v));
+      } break;
+      case JSONValue::ValueType::TypeDouble: {
+        double v;
+        val.getDouble(entry.first, &v);
+        String s = String::number(v);
+        s.truncate(kMaxStringLength);
+        property->values->set_string_values(Vector<String>(1, s));
+      } break;
+      case JSONValue::ValueType::TypeString: {
+        String v;
+        val.getString(entry.first, &v);
+        v.truncate(kMaxStringLength);
+        property->values->set_string_values(Vector<String>(1, v));
+      } break;
+      case JSONValue::ValueType::TypeObject: {
+        if (recursionLevel + 1 >= kMaxDepth) {
+          addProperty = false;
+          break;
+        }
+        property->values->set_entity_values(Vector<EntityPtr>());
+        property->values->get_entity_values().push_back(Entity::New());
+
+        extractEntity(*(val.getObject(entry.first)),
+                      *(property->values->get_entity_values().at(0)),
+                      recursionLevel + 1);
+      } break;
+      case JSONValue::ValueType::TypeArray:
+        addProperty = parseRepeatedValue(*(val.getArray(entry.first)),
+                                         *(property->values), recursionLevel);
+        break;
+      default:
+        break;
+    }
+    if (addProperty)
+      entity.properties.push_back(std::move(property));
+  }
+}
+
+void extractTopLevelEntity(const JSONObject& val, Vector<EntityPtr>& entities) {
+  // Now we have a JSONObject which corresponds to a single (possibly nested)
+  // entity.
+  EntityPtr entity = Entity::New();
+  String type;
+  val.getString(kJSONLDKeyType, &type);
+  if (!isWhitelistedType(AtomicString(type))) {
+    return;
+  }
+  extractEntity(val, *(entity.get()), 0);
+  entities.push_back(std::move(entity));
+}
+
+void extractEntitiesFromArray(const JSONArray& arr,
+                              Vector<EntityPtr>& entities) {
+  for (size_t i = 0; i < arr.size(); ++i) {
+    const JSONValue* val = arr.at(i);
+    if (val->getType() == JSONValue::ValueType::TypeObject) {
+      extractTopLevelEntity(*(JSONObject::cast(val)), entities);
+    }
+  }
+}
+
+void extractEntityFromTopLevelObject(const JSONObject& val,
+                                     Vector<EntityPtr>& entities) {
+  const JSONArray* graph = val.getArray(kJSONLDKeyGraph);
+  if (graph) {
+    extractEntitiesFromArray(*graph, entities);
+  }
+  extractTopLevelEntity(val, entities);
+}
+
+bool extractMetadata(const Element& root, Vector<EntityPtr>& entities) {
   for (Element& element : ElementTraversal::descendantsOf(root)) {
     if (element.hasTagName(HTMLNames::scriptTag) &&
         element.getAttribute(HTMLNames::typeAttr) == "application/ld+json") {
-      if (multiple) {
-        result.append(",");
+      std::unique_ptr<JSONValue> json = parseJSON(element.textContent());
+      if (!json.get()) {
+        LOG(ERROR) << "Failed to parse json.";
+        return false;
       }
-      result.append(element.textContent());
-      multiple = true;
-    }
-  }
-  result.append("]");
-  return result.toString();
+      switch (json->getType()) {
+        case JSONValue::ValueType::TypeArray:
+          extractEntitiesFromArray(*(JSONArray::cast(json.get())), entities);
+          break;
+        case JSONValue::ValueType::TypeObject:
+          extractEntityFromTopLevelObject(*(JSONObject::cast(json.get())),
+                                          entities);
+          break;
+        default:
+          return false;
+      }
+    }
+  }
+  return !entities.isEmpty();
 }
 
 }  // namespace
 
-String CopylessPasteExtractor::extract(Document& document) {
+WebPagePtr CopylessPasteExtractor::extract(const Document& document) {
   TRACE_EVENT0("blink", "CopylessPasteExtractor::extract");
 
   if (!document.frame() || !document.frame()->isMainFrame())
-    return emptyString;
-
-  DCHECK(document.hasFinishedParsing());
+    return nullptr;
 
   Element* html = document.documentElement();
   if (!html)
-    return emptyString;
+    return nullptr;
 
   double startTime = monotonicallyIncreasingTime();
 
+  WebPagePtr page = WebPage::New();
+
   // Traverse the DOM tree and extract the metadata.
-  String result = extractMetadata(*html);
+  if (!extractMetadata(*html, page->entities))
+    return nullptr;
+  page->url = document.url();
+  page->title = document.title();
 
   double elapsedTime = monotonicallyIncreasingTime() - startTime;
 
   DEFINE_STATIC_LOCAL(CustomCountHistogram, extractionHistogram,
                       ("CopylessPaste.ExtractionUs", 1, 1000000, 50));
   extractionHistogram.count(static_cast<int>(1e6 * elapsedTime));
-  return result;
+  return page;
 }
 
 }  // namespace blink