add config for agent

agent/config.toml

@@ -0,0 +1,6 @@
+send_interval_seconds = 5
+
+[mqtt]
+agent = "agent-1"
+host = "0.0.0.0"
+port = 1883

agent/src/config.rs

@@ -0,0 +1,27 @@
+use serde::{Deserialize, Serialize};
+
+const CONFIG_PATH: &str = if cfg!(debug_assertions) {
+    "agent/config.toml"
+} else {
+    "config.toml"
+};
+
+#[derive(Serialize, Deserialize)]
+pub struct MqttConfig {
+    pub agent: String,
+    pub host: String,
+    pub port: u16,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct Config {
+    pub send_interval_seconds: u64,
+    pub mqtt: MqttConfig,
+}
+
+pub fn load_config() -> anyhow::Result<Config> {
+    let file = std::fs::read_to_string(CONFIG_PATH)?;
+    let config: Config = toml::from_str(&file)?;
+
+    Ok(config)
+}