closes #4 Refactor DBC parsing into TypeFactory statement handlers

tests/dbc_parser_test.cpp

@@ -1,4 +1,5 @@
 #include "dbc_parser.h"
+#include "dbc_statement_handler.h"
 
 #include <chrono>
 #include <filesystem>
@@ -19,6 +20,17 @@ struct Fixture {
   }
 };
 
+class CountingHandler : public DbcStatementHandler {
+  public:
+    inline static int instances = 0;
+    inline static int calls = 0;
+    CountingHandler() { ++instances; }
+    void Handle (const std::string &, DbcParseContext &context) const override {
+      ++calls;
+      context.database.frames.emplace_back();
+    }
+};
+
 int main() {
   Fixture fixture;
   int failures = 0;
@@ -88,6 +100,33 @@ int main() {
     check (std::string (error.what()).find (fixture.path.string() + ":2: ") == 0U,
            "Signal error location");
   }
+  DbcDatabase dispatchDatabase;
+  DbcParseContext context {dispatchDatabase, nullptr};
+  DbcStatementDispatcher dispatcher;
+  dispatcher.RegisterType<CountingHandler> ("TEST_");
+  check (dispatcher.Dispatch ("TEST_ first", context) &&
+         dispatcher.Dispatch ("TEST_ second", context) &&
+         CountingHandler::instances == 1 && CountingHandler::calls == 2 &&
+         dispatchDatabase.frames.size() == 2U, "Factory dispatch and handler reuse");
+  check (!dispatcher.Dispatch ("TEST_OTHER data", context) &&
+         !dispatcher.Dispatch ("BO_TX_BU_ 1 : ECU;", context) &&
+         !dispatcher.Dispatch ("VAL_ 1 Speed 0 \"Stopped\";", context) &&
+         CountingHandler::calls == 2, "Exact and unknown keyword dispatch");
+  const DbcParser parser;
+  fixture.Write ("BO_ 1 First: 8 ECU\n");
+  check (parser.ParseFile (fixture.path.string()).frames.size() == 1U, "First parse");
+  fixture.Write ("SG_ Speed : invalid\n");
+  try {
+    parser.ParseFile (fixture.path.string());
+    check (false, "Independent parse context");
+  } catch (const std::runtime_error &error) {
+    check (std::string (error.what()).find ("Signal found before any frame") !=
+           std::string::npos, "Independent parse context");
+  }
+  fixture.Write ("BO_ 2 Second: 8 ECU\n");
+  const auto recovered = parser.ParseFile (fixture.path.string());
+  check (recovered.frames.size() == 1U && recovered.frames[0].canId == 2U,
+         "Fresh parse after error");
   if (failures != 0) return 1;
   std::cout << "All " << count << " parser cases passed.\n";
   return 0;