just some refactoring thoughts

src2/collection.h

@@ -0,0 +1,59 @@
+#pragma once
+
+#include <string>
+#include <filesystem>
+#include <map>
+#include <set>
+#include <exception>
+
+class Collection {
+public:
+    class UnknownSource;
+    class DuplicateSource;
+    class DuplicatePath;
+
+    Collection();
+
+    unsigned int sourcesTotal() const;
+    unsigned int sourcesPending() const;
+    unsigned int sourcesError() const;
+    unsigned int sourcesSuccess() const;
+
+    bool hasSource(const std::string& source) const;
+    void addSource(const std::string& source);
+    void sourceError(const std::string& source);
+    void sourceSuccess(const std::string& source, const std::filesystem::path& path);
+
+private:
+    std::set<std::string> errorSources;
+    std::set<std::string> pendingSources;
+    std::map<std::string, std::filesystem::path> successSources;    //would be nice to have a bimap here
+};
+
+class Collection::UnknownSource : public std::exception {
+public:
+    UnknownSource(const std::string& source);
+
+    const char* what() const noexcept( true ) override;
+private:
+    std::string source;
+};
+
+class Collection::DuplicateSource : public std::exception {
+public:
+    DuplicateSource(const std::string& source);
+
+    const char* what() const noexcept( true ) override;
+private:
+    std::string source;
+};
+
+class Collection::DuplicatePath : public std::exception {
+public:
+    DuplicatePath(const std::string& source, const std::filesystem::path& path);
+
+    const char* what() const noexcept( true ) override;
+private:
+    std::string source;
+    std::filesystem::path path;
+};