acquisition: drive a DataSource from the registry; --source and --source-opt

src/config.hpp

@@ -6,6 +6,8 @@
 #include <cstdint>
 #include <string>
 
+#include "source/source_config.hpp"
+
 namespace udpscope {
 
 /// Everything the command line can say. Defaults are the ones the spec names
@@ -21,6 +23,23 @@ struct Config {
   /// `server` valid". The default stays a usable value for every other path.
   bool server_specified = false;
 
+  /// `--source NAME`: which registered kind opens. `udps` is the default, and `--server/--port/
+  /// --multicast/--interface` keep meaning UDPS.
+  std::string source_kind = "udps";
+  /// Whether `--source` was given (the other half of "did the user choose a source").
+  bool source_specified = false;
+  /// Repeatable `--source-opt k=v`: the kind's own settings. For `udps` they overlay the fields above.
+  SourceConfig source_opts;
+
+  /// A source was named on the command line (`--server` or `--source`), so the chooser is skipped.
+  bool has_source() const noexcept { return server_specified || source_specified; }
+  /// The settings the kind's `make()` receives: for UDPS the four connection fields plus the receive
+  /// buffer, then `source_opts` on top.
+  SourceConfig source_config() const;
+  /// The (host, port) that name this source's session file; see `session_host()` in the registry.
+  std::string session_host() const;
+  std::uint16_t session_port() const;
+
   /// Size of *each* of the two sample buffers, in megabytes. The application
   /// always allocates two identical buffers (spec item 1).
   double buffer_mb = 200.0;