[iOS Reading List] Only allow offline URL when the offline file exists.

ios/chrome/browser/reading_list/offline_url_utils.cc

 // 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 "ios/chrome/browser/reading_list/offline_url_utils.h"
 
 #include "base/logging.h"
 #include "base/md5.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/reading_list/core/offline_url_utils.h"
+#include "components/reading_list/core/reading_list_entry.h"
+#include "components/reading_list/core/reading_list_model.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #include "net/base/url_util.h"
 
 namespace {
 const char kEntryURLQueryParam[] = "entryURL";
 const char kVirtualURLQueryParam[] = "virtualURL";
 }
 
 namespace reading_list {
 
 GURL OfflineURLForPath(const base::FilePath& distilled_path,
                        const GURL& entry_url,
                        const GURL& virtual_url) {
-  if (distilled_path.empty()) {
-    return GURL();
-  }
+  DCHECK(!distilled_path.empty());
+  DCHECK(entry_url.is_valid());
+  DCHECK(virtual_url.is_valid());
   GURL page_url(kChromeUIOfflineURL);
   GURL::Replacements replacements;
   replacements.SetPathStr(distilled_path.value());
   page_url = page_url.ReplaceComponents(replacements);
-  if (entry_url.is_valid()) {
-    page_url = net::AppendQueryParameter(page_url, kEntryURLQueryParam,
-                                         entry_url.spec());
-  }
-  if (virtual_url.is_valid()) {
-    page_url = net::AppendQueryParameter(page_url, kVirtualURLQueryParam,
-                                         virtual_url.spec());
-  }
+  page_url = net::AppendQueryParameter(page_url, kEntryURLQueryParam,
+                                       entry_url.spec());
+
+  page_url = net::AppendQueryParameter(page_url, kVirtualURLQueryParam,
+                                       virtual_url.spec());
+
   return page_url;
 }
 
 GURL EntryURLForOfflineURL(const GURL& offline_url) {
   std::string entry_url_string;
   if (net::GetValueForKeyInQuery(offline_url, kEntryURLQueryParam,
                                  &entry_url_string)) {
     GURL entry_url = GURL(entry_url_string);
     if (entry_url.is_valid()) {
       return entry_url;
     }
   }
-  return offline_url;
+  return GURL::EmptyGURL();
 }
 
 GURL VirtualURLForOfflineURL(const GURL& offline_url) {
   std::string virtual_url_string;
   if (net::GetValueForKeyInQuery(offline_url, kVirtualURLQueryParam,
                                  &virtual_url_string)) {
     GURL virtual_url = GURL(virtual_url_string);
     if (virtual_url.is_valid()) {
       return virtual_url;
     }
   }
-  return EntryURLForOfflineURL(offline_url);
+  return GURL::EmptyGURL();
 }
 
 GURL FileURLForDistilledURL(const GURL& distilled_url,
                             const base::FilePath& offline_path,
                             GURL* resources_root_url) {
   if (!distilled_url.is_valid()) {
     return GURL();
   }
   DCHECK(distilled_url.SchemeIs(kChromeUIScheme));
   GURL file_url(base::StringPrintf("%s%s", url::kFileScheme,
                                    url::kStandardSchemeSeparator) +
                 offline_path.value() + distilled_url.path());
   if (resources_root_url) {
     *resources_root_url = file_url.Resolve(".");
   }
   return file_url;
 }
 
 bool IsOfflineURL(const GURL& url) {
   return url.SchemeIs(kChromeUIScheme) && url.host() == kChromeUIOfflineHost;
 }
+
+bool IsOfflineURLValid(const GURL& url, ReadingListModel* model) {
+  if (!IsOfflineURL(url)) {
+    return false;
+  }
+  GURL entry_url = EntryURLForOfflineURL(url);
+  if (!entry_url.is_valid() || !model || !model->loaded()) {

[Eugene But (OOO till 7-30), 2017/04/07 15:17:52]

Is it ok to pass null model? Please document in header's comments

[Olivier, 2017/04/07 15:44:27]

Done.

+    return false;
+  }
+  const ReadingListEntry* entry = model->GetEntryByURL(entry_url);
+  if (!entry || entry->DistilledState() != ReadingListEntry::PROCESSED) {
+    return false;
+  }
+  // It is possible (unlikely) for a user to type directly a URL that passes all
+  // the tests above but still is not the correct one.

[Eugene But (OOO till 7-30), 2017/04/07 15:17:52]

What does "not the correct one" mean? URL which does not point to HTTP server
that is online?

[Olivier, 2017/04/07 15:44:27]

The one that is returned by |OfflineURLForPath|.
Main issue is to point to another offline file or display a different
virtualURL.
 But as user has to type it, it is unlikely.

+  // Make a final test to check it.
+  return url == reading_list::OfflineURLForPath(entry->DistilledPath(),
+                                                entry->URL(),
+                                                entry->DistilledURL());
 }
+}