cli: Handle interrupt so setting tags is not force-canceled

This should prevent damaged files in case CTRL + C is used to
terminate the application during rewrite.

cli/helper.cpp

@@ -12,6 +12,7 @@
 
 #include <iostream>
 #include <cstring>
+#include <csignal>
 
 using namespace std;
 using namespace std::placeholders;
@@ -20,9 +21,48 @@ using namespace ConversionUtilities;
 using namespace ChronoUtilities;
 using namespace Media;
 using namespace Settings;
+using namespace EscapeCodes;
 
 namespace Cli {
 
+std::function<void()> InterruptHandler::s_handler;
+bool InterruptHandler::s_handlerRegistered = false;
+
+InterruptHandler::InterruptHandler(std::function<void ()> handler)
+{
+    // set handler function or throw if an instance has already been created
+    if(s_handler) {
+        throw runtime_error("Only one instance of InterruptHandler can exist at a time.");
+    }
+    s_handler = handler;
+
+    // register handler if not registered yet
+    if(!s_handlerRegistered) {
+        s_handlerRegistered = true;
+        signal(SIGINT, &InterruptHandler::handler);
+    }
+}
+
+InterruptHandler::~InterruptHandler()
+{
+    s_handler = function<void()>();
+}
+
+void InterruptHandler::handler(int signum)
+{
+    // just exit if no custom handler has been defined
+    if(!s_handler) {
+        exit(signum);
+    }
+
+    // print warning
+    finalizeLog();
+    cout << Phrases::Warning << "Interrupt received, trying to abort ongoing process ..." << Phrases::End << flush;
+
+    // call custom handler
+    s_handler();
+}
+
 string incremented(const string &str, unsigned int toIncrement)
 {
     string res;

cli/helper.h

@@ -158,6 +158,19 @@ inline FieldValue::FieldValue(DenotationType type, unsigned int fileIndex, const
     value(value)
 {}
 
+class InterruptHandler
+{
+public:
+    InterruptHandler(std::function<void()> handler);
+    ~InterruptHandler();
+
+private:
+    static void handler(int signum);
+
+    static std::function<void()> s_handler;
+    static bool s_handlerRegistered;
+};
+
 }
 
 // define hash functions for custom data types

cli/mainfeatures.cpp

@@ -400,6 +400,9 @@ void setTagInfo(const SetTagInfoArgs &args)
     fileInfo.setIndexPosition(parsePositionDenotation(args.indexPosArg, args.indexPosValueArg, ElementPosition::BeforeData));
     fileInfo.setForceIndexPosition(args.forceIndexPosArg.isPresent());
     fileInfo.setForceRewrite(args.forceRewriteArg.isPresent());
+    InterruptHandler handler([&fileInfo] {
+        fileInfo.tryToAbort();
+    });
     // iterate through all specified files
     unsigned int fileIndex = 0;
     static const string context("setting tags");
@@ -626,6 +629,10 @@ void setTagInfo(const SetTagInfoArgs &args)
                 fileInfo.gatherRelatedNotifications(notifications);
                 finalizeLog();
                 cout << " - Changes have been applied." << endl;
+            } catch(const Media::OperationAbortedException &) {
+                finalizeLog();
+                cerr << Phrases::Warning << "The operation has been aborted." << endl;
+                return;
             } catch(const Media::Failure &) {
                 finalizeLog();
                 cerr << " - " << Phrases::Error << "Failed to apply changes." << endl;