Override TOML config from environment variables

hms2mqtt/src/mqtt_config.rs

@@ -1,9 +1,51 @@
 use serde_derive::Deserialize;
 
-#[derive(Debug, Deserialize)]
+#[derive(Clone, Debug, Default, Deserialize)]
 pub struct MqttConfig {
     pub host: String,
     pub port: Option<u16>,
     pub username: Option<String>,
     pub password: Option<String>,
 }
+
+impl MqttConfig {
+    pub fn is_valid(&self) -> bool {
+        !self.host.is_empty()
+    }
+}
+
+mod tests {
+    #[test]
+    fn valid_config() {
+        use super::MqttConfig;
+
+        let mqtt_config = MqttConfig {
+            host: "lala".into(),
+            port: None,
+            username: None,
+            password: None,
+        };
+        assert!(mqtt_config.is_valid());
+    }
+
+    #[test]
+    fn invalid_config() {
+        use super::MqttConfig;
+
+        let mqtt_config = MqttConfig {
+            host: "".into(),
+            port: None,
+            username: None,
+            password: None,
+        };
+        assert!(!mqtt_config.is_valid());
+    }
+
+    #[test]
+    fn default_invalid_config() {
+        use super::MqttConfig;
+
+        let mqtt_config = MqttConfig::default();
+        assert!(!mqtt_config.is_valid());
+    }
+}

src/main.rs

@@ -1,29 +1,23 @@
 // TODO: support CA33 command to take over metrics consumption
 // TODO: support publishing to S-Miles cloud, too
 
+mod config;
 mod logging;
 mod rumqttc_wrapper;
 
 use hms2mqtt::home_assistant::HomeAssistant;
 use hms2mqtt::inverter::Inverter;
 use hms2mqtt::metric_collector::MetricCollector;
-use hms2mqtt::mqtt_config;
 use hms2mqtt::simple_mqtt::SimpleMqtt;
-use mqtt_config::MqttConfig;
+use log::{error, info};
 use rumqttc_wrapper::RumqttcWrapper;
-use serde_derive::Deserialize;
-use std::fs;
+
+use std::env;
+
 use std::thread;
 use std::time::Duration;
 
-use log::{error, info};
-
-#[derive(Debug, Deserialize)]
-struct Config {
-    inverter_host: String,
-    home_assistant: Option<MqttConfig>,
-    simple_mqtt: Option<MqttConfig>,
-}
+use crate::config::Config;
 
 static REQUEST_DELAY: u64 = 30_500;
 
@@ -34,9 +28,13 @@ fn main() {
         error!("Arguments passed. Tool is configured by config.toml in its path");
     }
 
-    let filename = "config.toml";
-    let contents = fs::read_to_string(filename).expect("Could not read config.toml");
-    let config: Config = toml::from_str(&contents).expect("toml config unparsable");
+    let config = Config::load();
+    if !config.is_valid() {
+        error!("configuration is invalid: {config:?}");
+        return;
+    }
+
+    println!("{config:#?}");
 
     info!("inverter host: {}", config.inverter_host);