[update] added validation for AppSettings with ConfigError, ensuring non-zero port enforcement in config.rs

backend-rust/src/config.rs

@@ -1,5 +1,5 @@
 use serde::Deserialize;
-use std::env;
+use std::{env, fmt};
 use std::path::PathBuf;
 use toml::Value;
 use tracing::{error, info};
@@ -28,7 +28,29 @@ struct ConfigFile {
     server: Server,
 }
 
+#[derive(Debug)]
+pub enum ConfigError {
+    InvalidPort,
+}
+
+impl fmt::Display for ConfigError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ConfigError::InvalidPort => write!(f, "Invalid port: port cannot be 0"),
+        }
+    }
+}
+
+impl std::error::Error for ConfigError {}
+
 impl AppSettings {
+    pub fn validate(&self) -> Result<(), ConfigError> {
+        if self.config.server.port == 0 {
+            return Err(ConfigError::InvalidPort);
+        }
+        Ok(())
+    }
+
     pub fn get_app_settings() -> Self {
         let config_file = Self::load_config_file().unwrap_or_else(|| {
             info!("Using default config values");