Upstream Chrome on iOS source code [7/11].

ios/chrome/browser/ui/reader_mode/reader_mode_checker.mm

+// Copyright 2015 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.
+
+#import "ios/chrome/browser/ui/reader_mode/reader_mode_checker.h"
+
+#include "base/logging.h"
+#include "base/strings/sys_string_conversions.h"
+#include "components/dom_distiller/core/distillable_page_detector.h"
+#include "components/dom_distiller/core/experiments.h"
+#include "components/dom_distiller/core/page_features.h"
+#include "components/dom_distiller/core/url_utils.h"
+#include "components/grit/components_resources.h"
+#include "ios/web/public/web_state/js/crw_js_injection_evaluator.h"
+#include "ios/web/public/web_state/web_state.h"
+#include "ui/base/resource/resource_bundle.h"
+
+ReaderModeCheckerObserver::ReaderModeCheckerObserver(
+    ReaderModeChecker* readerModeChecker)
+    : readerModeChecker_(readerModeChecker) {
+  DCHECK(readerModeChecker);
+  readerModeChecker_->AddObserver(this);
+}
+
+ReaderModeCheckerObserver::~ReaderModeCheckerObserver() {
+  readerModeChecker_->RemoveObserver(this);
+}
+
+enum class ReaderModeChecker::Status {
+  kSwitchNo,        // There is no way a switch could happen.
+  kSwitchMaybe,     // Not sure, it may be possible.
+  kSwitchPossible,  // It is possible to switch to reader mode.
+};
+
+ReaderModeChecker::ReaderModeChecker(web::WebState* web_state)
+    : web::WebStateObserver(web_state),
+      is_distillable_(Status::kSwitchNo),
+      weak_factory_(this) {
+  DCHECK(web_state);
+}
+
+ReaderModeChecker::~ReaderModeChecker() {
+  for (auto& observer : observers_)
+    observer.ReaderModeCheckerDestroyed();
+}
+
+bool ReaderModeChecker::CanSwitchToReaderMode() {
+  return is_distillable_ != ReaderModeChecker::Status::kSwitchNo;
+}
+
+void ReaderModeChecker::PageLoaded(
+    web::PageLoadCompletionStatus load_completion_status) {
+  if (load_completion_status != web::PageLoadCompletionStatus::SUCCESS)
+    return;
+
+  if (is_distillable_ == Status::kSwitchPossible)
+    return;
+
+  CheckIsDistillable();
+}
+
+void ReaderModeChecker::NavigationItemCommitted(
+    const web::LoadCommittedDetails& load_details) {
+  // When NavigationItemCommitted the page may not be completely loaded. But in
+  // order to get reader mode data faster this class tries to inject the
+  // javascript early. If it fails, it will be retried at PageLoaded().
+  is_distillable_ = Status::kSwitchNo;
+  CheckIsDistillable();
+}
+
+void ReaderModeChecker::CheckIsDistillableOG(CRWJSInjectionReceiver* receiver) {
+  // Retrieve the javascript used to figure out if the page is at all
+  // distillable.
+  NSString* is_distillable_js =
+      base::SysUTF8ToNSString(dom_distiller::url_utils::GetIsDistillableJs());
+  DCHECK(is_distillable_js);
+
+  // In case |this| gets deallocated before the block executes, the block only
+  // references a weak pointer.
+  base::WeakPtr<ReaderModeChecker> weak_this(weak_factory_.GetWeakPtr());
+  [receiver executeJavaScript:is_distillable_js
+            completionHandler:^(id result, NSError* error) {
+              if (!weak_this || error || !result)
+                return;  // Inconclusive.
+              if ([result isEqual:@YES]) {
+                weak_this->is_distillable_ = Status::kSwitchPossible;
+                for (auto& observer : weak_this->observers_)
+                  observer.PageIsDistillable();
+              } else {
+                weak_this->is_distillable_ = Status::kSwitchMaybe;
+              }
+            }];
+}
+
+void ReaderModeChecker::CheckIsDistillableDetector(
+    CRWJSInjectionReceiver* receiver) {
+  // Retrieve the javascript used to figure out if the page is at all
+  // distillable.
+  NSString* extract_features_js = base::SysUTF8ToNSString(
+      ResourceBundle::GetSharedInstance()
+          .GetRawDataResource(IDR_EXTRACT_PAGE_FEATURES_JS)
+          .as_string());
+  DCHECK(extract_features_js);
+
+  // In case |this| gets deallocated before the block executes, the block only
+  // references a weak pointer.
+  base::WeakPtr<ReaderModeChecker> weak_this(weak_factory_.GetWeakPtr());
+  [receiver
+      executeJavaScript:extract_features_js
+      completionHandler:^(id result, NSError* error) {
+        if (!weak_this || error || ![result isKindOfClass:[NSString class]]) {
+          return;  // Inconclusive.
+        }
+        const dom_distiller::DistillablePageDetector* detector =
+            dom_distiller::DistillablePageDetector::GetDefault();
+        const base::StringValue value(base::SysNSStringToUTF8(result));
+        std::vector<double> features(
+            dom_distiller::CalculateDerivedFeaturesFromJSON(&value));
+        if (detector->Classify(features)) {
+          weak_this->is_distillable_ = Status::kSwitchPossible;
+          for (auto& observer : weak_this->observers_)
+            observer.PageIsDistillable();
+        } else {
+          weak_this->is_distillable_ = Status::kSwitchMaybe;
+        }
+      }];
+}
+
+void ReaderModeChecker::CheckIsDistillable() {
+  CRWJSInjectionReceiver* receiver = web_state()->GetJSInjectionReceiver();
+
+  if (!receiver || !web_state()->ContentIsHTML() ||
+      web_state()->IsShowingWebInterstitial()) {
+    is_distillable_ = Status::kSwitchNo;
+    return;
+  }
+
+  switch (dom_distiller::GetDistillerHeuristicsType()) {
+    case dom_distiller::DistillerHeuristicsType::NONE:
+      is_distillable_ = Status::kSwitchMaybe;
+      break;
+    case dom_distiller::DistillerHeuristicsType::OG_ARTICLE:
+      CheckIsDistillableOG(receiver);
+      break;
+    case dom_distiller::DistillerHeuristicsType::ADABOOST_MODEL:
+      CheckIsDistillableDetector(receiver);
+      break;
+    case dom_distiller::DistillerHeuristicsType::ALWAYS_TRUE:
+      is_distillable_ = Status::kSwitchPossible;
+      break;
+  }
+}
+
+void ReaderModeChecker::WebStateDestroyed() {
+  is_distillable_ = Status::kSwitchNo;
+}
+
+void ReaderModeChecker::AddObserver(ReaderModeCheckerObserver* observer) {
+  DCHECK(!observers_.HasObserver(observer));
+  observers_.AddObserver(observer);
+}
+
+void ReaderModeChecker::RemoveObserver(ReaderModeCheckerObserver* observer) {
+  DCHECK(observers_.HasObserver(observer));
+  observers_.RemoveObserver(observer);
+}