Refactor formatting list of values

diagnostics.cpp

@@ -61,4 +61,28 @@ DiagLevel Diagnostics::level() const
     return level;
 }
 
+/*!
+ * \brief Concatenates the specified string \a values to a list.
+ */
+string DiagMessage::formatList(const std::vector<string> &values)
+{
+    auto size = values.size() * 4;
+    for (const auto &str : values) {
+        size += str.size();
+    }
+    std::string res;
+    res.reserve(size);
+    for (auto value = values.cbegin(), end = values.cend(), last = values.cend() - 1; value != end; ++value) {
+        if (value == last) {
+            res += " and ";
+        } else if (!res.empty()) {
+            res += ", ";
+        }
+        res += '\"';
+        res += *value;
+        res += '\"';
+    }
+    return res;
+}
+
 } // namespace TagParser

diagnostics.h

@@ -52,6 +52,8 @@ public:
     const ChronoUtilities::DateTime &creationTime() const;
     bool operator==(const DiagMessage &other) const;
 
+    static std::string formatList(const std::vector<std::string> &values);
+
 private:
     DiagLevel m_level;
     std::string m_message;

id3/id3v2frame.cpp

@@ -340,20 +340,7 @@ void Id3v2Frame::parse(BinaryReader &reader, uint32 version, uint32 maximalSize,
                 if (additionalValues.size() == 1) {
                     return argsToString("value \"", additionalValues.front().toString(TagTextEncoding::Utf8), "\" is ignored.");
                 }
-                string valuesString = "values";
-                for (auto value = additionalValues.cbegin(), end = additionalValues.cend() - 1; value != end; ++value) {
-                    valuesString += ' ';
-                    valuesString += '\"';
-                    valuesString += value->toString(TagTextEncoding::Utf8);
-                    valuesString += '\"';
-                    if (value != end) {
-                        valuesString += ',';
-                    }
-                }
-                valuesString += " and \"";
-                valuesString += additionalValues.back().toString(TagTextEncoding::Utf8);
-                valuesString += "\" are ignored.";
-                return valuesString;
+                return argsToString("values ", DiagMessage::formatList(TagValue::toStrings(additionalValues)), " are ignored.");
             }();
 
             // emplace diag message

tagvalue.h

@@ -6,6 +6,7 @@
 #include <c++utilities/chrono/datetime.h>
 #include <c++utilities/chrono/timespan.h>
 #include <c++utilities/conversion/binaryconversion.h>
+#include <c++utilities/misc/traits.h>
 
 #include <cstring>
 #include <iosfwd>
@@ -132,6 +133,11 @@ public:
 
     static void stripBom(const char *&text, std::size_t &length, TagTextEncoding encoding);
     static void ensureHostByteOrder(std::u16string &u16str, TagTextEncoding currentEncoding);
+    template <typename ContainerType,
+        Traits::EnableIf<Traits::IsIteratable<ContainerType>,
+            std::is_same<typename std::add_const<typename std::remove_pointer<typename ContainerType::value_type>::type>::type, const TagValue>>
+            * = nullptr>
+    static std::vector<std::string> toStrings(const ContainerType &values, TagTextEncoding encoding = TagTextEncoding::Utf8);
 
 private:
     std::unique_ptr<char[]> m_ptr;
@@ -547,6 +553,24 @@ inline TagTextEncoding TagValue::descriptionEncoding() const
     return m_descEncoding;
 }
 
+/*!
+ * \brief Converts the specified \a values to string using the specified \a encoding.
+ * \throws Throws ConversionException on failure.
+ * \sa toString()
+ */
+template <typename ContainerType,
+    Traits::EnableIf<Traits::IsIteratable<ContainerType>,
+        std::is_same<typename std::add_const<typename std::remove_pointer<typename ContainerType::value_type>::type>::type, const TagValue>> *>
+std::vector<std::string> TagValue::toStrings(const ContainerType &values, TagTextEncoding encoding)
+{
+    std::vector<std::string> res;
+    res.reserve(values.size());
+    for (const auto &value : values) {
+        res.emplace_back(Traits::dereferenceMaybe(value).toString(encoding));
+    }
+    return res;
+}
+
 } // namespace TagParser
 
 #endif // TAG_PARSER_TAGVALUE_H

tests/overallmp3.cpp

@@ -129,7 +129,7 @@ void OverallTests::checkMp3Testfile2()
         CPPUNIT_ASSERT_EQUAL(DiagLevel::Warning, m_diag[1].level());
         CPPUNIT_ASSERT_EQUAL("parsing TCON frame"s, m_diag[1].context());
         CPPUNIT_ASSERT_EQUAL(
-            "Multiple strings found. This is not supported so far. Hence the additional values \"Test\", \"Example\", and \"Hard Dance\" are ignored."s,
+            "Multiple strings found. This is not supported so far. Hence the additional values \"Test\", \"Example\" and \"Hard Dance\" are ignored."s,
             m_diag[1].message());
         break;
     case TagStatus::TestMetaDataPresent: