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/config.rs

@@ -0,0 +1,85 @@
+use std::{env, fs};
+
+use hms2mqtt::mqtt_config::MqttConfig;
+use log::warn;
+use serde::Deserialize;
+
+#[derive(Clone, Debug, Default, Deserialize)]
+pub struct Config {
+    pub inverter_host: String,
+    pub home_assistant: Option<MqttConfig>,
+    pub simple_mqtt: Option<MqttConfig>,
+}
+
+impl Config {
+    pub fn is_valid(&self) -> bool {
+        !self.inverter_host.is_empty()
+            && (self.home_assistant.as_ref().is_some_and(|x| x.is_valid())
+                || self.simple_mqtt.as_ref().is_some_and(|x| x.is_valid()))
+    }
+
+    pub fn load() -> Config {
+        // parse config from TOML file if present
+        let filename = "config.toml";
+        let contents = match fs::read_to_string(filename) {
+            Ok(contents) => contents,
+            Err(e) => {
+                warn!("Could not read config.toml: {e}");
+                "".into()
+            }
+        };
+        let mut config = match toml::from_str::<Config>(&contents) {
+            Ok(config) => config,
+            Err(e) => {
+                warn!("toml config unparsable: {e}");
+                Config::default()
+            }
+        };
+
+        // overwrite config if environment variables are set
+        // $INVERTER_HOST
+        if let Ok(inverter_host) = env::var("INVERTER_HOST") {
+            config.inverter_host = inverter_host;
+        }
+        // $MQTT_BROKER_HOST
+        let mut mqtt_config_overwritten = false;
+        if let Ok(host) = env::var("MQTT_BROKER_HOST") {
+            if config.home_assistant.is_none() {
+                config.home_assistant = Some(MqttConfig::default())
+            }
+            config
+                .home_assistant
+                .get_or_insert(MqttConfig::default())
+                .host = host;
+            mqtt_config_overwritten = true;
+        }
+        // $MQTT_USERNAME (optional)
+        if let Ok(username) = env::var("MQTT_USERNAME") {
+            config
+                .home_assistant
+                .get_or_insert(MqttConfig::default())
+                .username = Some(username);
+            mqtt_config_overwritten = true;
+        }
+        // $MQTT_PASSWORD (optional)
+        if let Ok(password) = env::var("MQTT_PASSWORD") {
+            config
+                .home_assistant
+                .get_or_insert(MqttConfig::default())
+                .password = Some(password);
+            mqtt_config_overwritten = true;
+        }
+        // $MQTT_PORT (optional)
+        if let Ok(port) = env::var("MQTT_PORT") {
+            config
+                .home_assistant
+                .get_or_insert(MqttConfig::default())
+                .port = Some(port.parse().unwrap_or(1883));
+            mqtt_config_overwritten = true;
+        }
+        if mqtt_config_overwritten {
+            config.simple_mqtt = config.home_assistant.clone();
+        }
+        config
+    }
+}

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 +28,11 @@ 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;
+    }
 
     info!("inverter host: {}", config.inverter_host);