plugin_mqtt: Make config type self-describing

This patch rewrites the configuration type to be self-describing and
adapts the `PluginBuilder` implementation to implement the
`PluginBuilder::kind_configuration()` interface.

Signed-off-by: Matthias Beyer <matthias.beyer@ifm.com>

2 files changed, 26 insertions, 2 deletions

diff --git a/plugins/plugin_mqtt/src/builder.rs b/plugins/plugin_mqtt/src/builder.rs
index 05c5c4c3..4deed268 100644
--- a/plugins/plugin_mqtt/src/builder.rs
+++ b/plugins/plugin_mqtt/src/builder.rs
@@ -28,6 +28,10 @@ where
         "mqtt"
     }
 
+    fn kind_configuration() -> Option<tedge_api::ConfigDescription> {
+        Some(<MqttConfig as tedge_api::AsConfig>::as_config())
+    }
+
     fn kind_message_types() -> HandleTypes
     where
         Self: Sized,
diff --git a/plugins/plugin_mqtt/src/config.rs b/plugins/plugin_mqtt/src/config.rs
index 8c17ccc7..30e0665a 100644
--- a/plugins/plugin_mqtt/src/config.rs
+++ b/plugins/plugin_mqtt/src/config.rs
@@ -1,4 +1,4 @@
-#[derive(serde::Deserialize, Debug)]
+#[derive(serde::Deserialize, Debug, tedge_api::Config)]
 pub struct MqttConfig {
     /// MQTT host to connect to
     pub host: String,
@@ -13,9 +13,12 @@ pub struct MqttConfig {
 }
 
 
-#[derive(Debug, serde::Deserialize)]
+#[derive(Debug, serde::Deserialize, tedge_api::Config)]
 pub struct Subscription {
+    /// The topic to connect to
     pub(crate) topic: String,
+
+    /// The Quality of Service to use for the subscribed topic
     pub(crate) qos: QoS,
 }
 
@@ -31,6 +34,23 @@ pub enum QoS {
     ExactlyOnce,
 }
 
+impl tedge_api::AsConfig for QoS {
+    fn as_config() -> tedge_api::ConfigDescription {
+        tedge_api::ConfigDescription::new(
+            "Qos".to_string(),
+            tedge_api::ConfigKind::Enum(
+                tedge_api::config::ConfigEnumKind::Untagged,
+                vec![
+                    ("String", Some("QOS 0"), tedge_api::config::EnumVariantRepresentation::String("at_most_once")),
+                    ("String", Some("QOS 1"), tedge_api::config::EnumVariantRepresentation::String("at_least_once")),
+                    ("String", Some("QOS 2"), tedge_api::config::EnumVariantRepresentation::String("exactly_once")),
+                ]
+            ),
+            None,
+        )
+    }
+}
+
 impl Into<i32> for QoS {
     fn into(self) -> i32 {
         match self {