Avoid implicit conversions in Zeek utility classes

doc/_examples/ping.cc

@@ -25,12 +25,15 @@ int main() {
   // Do five ping / pong.
   for (int n = 0; n < 5; n++) {
     // Send event "ping(n)".
-    zeek::Event ping("ping", {n});
-    ep.publish("/topic/test", ping);
+    ep.publish("/topic/test", zeek::Event{"ping", {n}});
 
     // Wait for "pong" reply event.
     auto msg = sub.get();
-    zeek::Event pong(move_data(msg));
-    std::cout << "received " << pong.name() << pong.args() << std::endl;
+    auto pong = zeek::Event{std::move(msg)};
+    if (pong.valid())
+      std::cout << "received " << pong.name() << pong.args() << std::endl;
+    else
+      std::cout << "received invalid pong message: " << to_string(pong)
+                << std::endl;
   }
 }

doc/_examples/pong.cc

@@ -26,11 +26,14 @@ int main() {
   for (int n = 0; n < 5; n++) {
     // Wait for a "ping" event.
     auto msg = sub.get();
-    zeek::Event ping(move_data(msg));
-    std::cout << "received " << ping.name() << ping.args() << std::endl;
+    auto ping = zeek::Event{std::move(msg)};
+    if (ping.valid())
+      std::cout << "received " << ping.name() << ping.args() << std::endl;
+    else
+      std::cout << "received invalid ping message: " << to_string(ping)
+                << std::endl;
 
     // Send event "pong" response.
-    zeek::Event pong("pong", {n});
-    ep.publish("/topic/test", pong);
+    ep.publish("/topic/test", zeek::Event{"pong", {n}});
   }
 }

include/broker/data.hh

@@ -138,6 +138,8 @@ public:
     return *this;
   }
 
+  // -- properties -------------------------------------------------------------
+
   /// Returns a string representation of the stored type.
   const char* get_type_name() const;
 
@@ -156,6 +158,171 @@ public:
     return data_;
   }
 
+  /// Checks whether this view contains the `nil` value.
+  bool is_none() const noexcept {
+    return get_type() == type::none;
+  }
+
+  /// Checks whether this view contains a boolean.
+  bool is_boolean() const noexcept {
+    return get_type() == type::boolean;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_count() const noexcept {
+    return get_type() == type::count;
+  }
+
+  /// Checks whether this view contains a integer.
+  bool is_integer() const noexcept {
+    return get_type() == type::integer;
+  }
+
+  /// Checks whether this view contains a real.
+  bool is_real() const noexcept {
+    return get_type() == type::real;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_string() const noexcept {
+    return get_type() == type::string;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_address() const noexcept {
+    return get_type() == type::address;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_subnet() const noexcept {
+    return get_type() == type::subnet;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_port() const noexcept {
+    return get_type() == type::port;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_timestamp() const noexcept {
+    return get_type() == type::timestamp;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_timespan() const noexcept {
+    return get_type() == type::timespan;
+  }
+
+  /// Checks whether this view contains a count.
+  bool is_enum_value() const noexcept {
+    return get_type() == type::enum_value;
+  }
+
+  /// Checks whether this view contains a set.
+  bool is_set() const noexcept {
+    return get_type() == type::set;
+  }
+
+  /// Checks whether this view contains a table.
+  bool is_table() const noexcept {
+    return get_type() == type::table;
+  }
+
+  /// Checks whether this view contains a list.
+  bool is_list() const noexcept {
+    return get_type() == type::vector;
+  }
+
+  // -- conversions ------------------------------------------------------------
+
+  /// Retrieves the @c boolean value or returns @p fallback if this object does
+  /// not contain a @c boolean.
+  bool to_boolean(bool fallback = false) const noexcept {
+    if (auto* val = std::get_if<boolean>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c count value or returns @p fallback if this object does
+  /// not contain a @c count.
+  count to_count(count fallback = 0) const noexcept {
+    if (auto* val = std::get_if<count>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c integer value or returns @p fallback if this object does
+  /// not contain a @c integer.
+  integer to_integer(integer fallback = 0) const noexcept {
+    if (auto* val = std::get_if<integer>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c real value or returns @p fallback if this object does
+  /// not contain a @c real.
+  real to_real(real fallback = 0) const noexcept {
+    if (auto* val = std::get_if<real>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the string value or returns an empty string if this object does
+  /// not contain a string.
+  std::string_view to_string() const noexcept {
+    if (auto* val = std::get_if<std::string>(&data_))
+      return *val;
+    return std::string_view{};
+  }
+
+  /// Retrieves the @c address value or returns @p fallback if this object does
+  /// not contain a @c address.
+  address to_address(const address& fallback = {}) const noexcept {
+    if (auto* val = std::get_if<address>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c subnet value or returns @p fallback if this object does
+  /// not contain a @c subnet.
+  subnet to_subnet(const subnet& fallback = {}) const noexcept {
+    if (auto* val = std::get_if<subnet>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c port value or returns @p fallback if this object does
+  /// not contain a @c port.
+  port to_port(port fallback = {}) const noexcept {
+    if (auto* val = std::get_if<port>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c timestamp value or returns @p fallback if this object
+  /// does not contain a @c timestamp.
+  timestamp to_timestamp(timestamp fallback = {}) const noexcept {
+    if (auto* val = std::get_if<timestamp>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the @c timespan value or returns @p fallback if this object does
+  /// not contain a @c timespan.
+  timespan to_timespan(timespan fallback = {}) const noexcept {
+    if (auto* val = std::get_if<timespan>(&data_))
+      return *val;
+    return fallback;
+  }
+
+  /// Retrieves the enum_value value or returns @p fallback if this object does
+  /// not contain a enum_value.
+  const enum_value& to_enum_value() const noexcept;
+
+  /// Converts the stored data as a list (`vector`). If the stored data is
+  /// not a list, the result is an empty list.
+  [[nodiscard]] const vector& to_list() const;
+
 private:
   data_variant data_;
 };

include/broker/endpoint.hh

@@ -39,6 +39,12 @@ struct endpoint_context;
 
 } // namespace broker::internal
 
+namespace broker::zeek {
+
+class Message;
+
+} // namespace broker::zeek
+
 namespace broker {
 
 /// The main publish/subscribe abstraction. Endpoints can *peer* with each
@@ -258,6 +264,17 @@ public:
   /// @param d The message data.
   void publish(const endpoint_info& dst, topic t, data d);
 
+  /// Publishes a message.
+  /// @param t The topic of the message.
+  /// @param d The message data.
+  void publish(std::string_view t, zeek::Message&& d);
+
+  /// Publishes a message to a specific peer endpoint only.
+  /// @param dst The destination endpoint.
+  /// @param t The topic of the message.
+  /// @param d The message data.
+  void publish(const endpoint_info& dst, std::string_view t, zeek::Message&& d);
+
   /// Publishes a message as vector.
   /// @param t The topic of the messages.
   /// @param xs The contents of the messages.

include/broker/message.hh

@@ -212,6 +212,12 @@ inline const topic& get_topic(const data_message& x) {
   return get<0>(x);
 }
 
+/// Retrieves the topic from a ::command_message as a string.
+/// @relates data_message
+inline std::string get_topic_str(const data_message& x) {
+  return get_topic(x).string();
+}
+
 /// Retrieves the topic from a ::command_message.
 /// @relates data_message
 inline const topic& get_topic(const command_message& x) {