Directory monitoring ignores unchanged bad ZIMs

When a change to a monitored directory is detected, any bad ZIM files
in it (that could not be added to the library during the previous
update) are ignored unless their modification timestamp has changed.

src/contentmanager.cpp

@@ -927,7 +927,8 @@ const char* monitoredDirZimFileHandlingMsgs[] = {
     "",
     "it is being downloaded by us, ignoring...",
     "the file was added to the library",
-    "the file could not be added to the library"
+    "the file could not be added to the library",
+    "it is an unchanged known bad zim file"
 };
 
 #endif
@@ -942,14 +943,32 @@ bool ContentManager::handleZimFileInMonitoredDirLogged(QString dir, QString file
     return status == MonitoredZimFileInfo::ADDED_TO_THE_LIBRARY;
 }
 
+void ContentManager::MonitoredZimFileInfo::updateStatus(const MonitoredZimFileInfo& prevInfo)
+{
+    Q_ASSERT(prevInfo.status != ADDED_TO_THE_LIBRARY);
+
+    if ( this->lastModified == prevInfo.lastModified ) {
+        this->status = UNCHANGED_KNOWN_BAD_ZIM_FILE;
+    } else {
+        this->status = PROCESS_NOW;
+    }
+}
+
 ContentManager::MonitoredZimFileInfo ContentManager::getMonitoredZimFileInfo(QString dir, QString fileName) const
 {
-    Q_UNUSED(dir);
-    Q_UNUSED(fileName);
-    // TODO: implement properly
-    MonitoredZimFileInfo zfi;
-    zfi.status = MonitoredZimFileInfo::PROCESS_NOW;
-    return zfi;
+    const auto bookPath = QDir::toNativeSeparators(dir + "/" + fileName);
+
+    MonitoredZimFileInfo zimFileInfo;
+
+    zimFileInfo.lastModified = QFileInfo(bookPath).lastModified();
+
+    const auto& zimsInDir = m_knownZimsInDir[dir];
+    const auto fileInfoEntry = zimsInDir.constFind(fileName);
+    if ( fileInfoEntry != zimsInDir.constEnd() ) {
+        zimFileInfo.updateStatus(fileInfoEntry.value());
+    }
+
+    return zimFileInfo;
 }
 
 int ContentManager::handleZimFileInMonitoredDir(QString dir, QString fileName)

src/contentmanager.h

@@ -123,10 +123,17 @@ public slots:
             ADDED_TO_THE_LIBRARY,
 
             // the attempt to add the file to the library failed
-            COULD_NOT_BE_ADDED_TO_THE_LIBRARY
+            COULD_NOT_BE_ADDED_TO_THE_LIBRARY,
+
+            // the file couldn't be added to the library earlier and hasn't
+            // changed since then
+            UNCHANGED_KNOWN_BAD_ZIM_FILE
         };
 
+        void updateStatus(const MonitoredZimFileInfo& prevInfo);
+
         ZimFileStatus status = PROCESS_NOW;
+        QDateTime lastModified;
     };
 
     typedef QMap<QString, MonitoredZimFileInfo> ZimFileName2InfoMap;