Add config and basic architecture for QUIC

substrate/src/config.rs

@@ -0,0 +1,49 @@
+use bevy::prelude::Resource;
+use figment::Figment;
+use figment::providers::{Env, Format, Serialized, Toml};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Resource, Serialize, Deserialize)]
+pub struct AppConfig {
+    pub network: QuicConfig,
+    pub simulation: SimulationConfig,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct SimulationConfig {
+    pub tick_rate_hz: u32,
+    pub max_entities: usize,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct QuicConfig {
+    pub server_port: u16,
+    pub server_interface: String,
+    pub server_cert: String,
+}
+
+impl Default for AppConfig {
+    fn default() -> Self {
+        Self {
+            network : QuicConfig {
+                server_port: 9000,
+                server_interface: "0.0.0.0".to_string(),
+                server_cert: "cert.pem".to_string(),
+            },
+            simulation: SimulationConfig {
+                tick_rate_hz: 60,
+                max_entities: 10000,
+            },
+        }
+    }
+}
+
+impl AppConfig {
+    pub fn load(config_file: &str) -> Result<Self, figment::Error> {
+        Figment::new()
+            .merge(Serialized::defaults(Self::default()))  // compiled-in defaults
+            .merge(Toml::file(config_file))                // config file
+            .merge(Env::prefixed("APP_"))            // env overrides, e.g. APP_NETWORK__PORT=9000
+            .extract()
+    }
+}