feat: add timeturner for time offsets and migrate config to YAML

Co-authored-by: aider (gemini/gemini-2.5-pro-preview-05-06) <aider@aider.chat>

src/main.rs

@@ -7,7 +7,7 @@ mod serial_input;
 mod ui;
 
 use crate::api::start_api_server;
-use crate::config::watch_config;
+use crate::config::{watch_config, Config};
 use crate::sync_logic::LtcState;
 use crate::serial_input::start_serial_thread;
 use crate::ui::start_ui;
@@ -21,17 +21,26 @@ use std::{
 use tokio::task::{self, LocalSet};
 
 /// Default config content, embedded in the binary.
-const DEFAULT_CONFIG: &str = r#"{
-  "hardware_offset_ms": 20
-}"#;
+const DEFAULT_CONFIG: &str = r#"
+# Hardware offset in milliseconds for correcting capture latency.
+hardwareOffsetMs: 20
 
-/// If no `config.json` exists alongside the binary, write out the default.
+# Time-turning offsets. All values are added to the incoming LTC time.
+# These can be positive or negative.
+timeturnerOffset:
+  hours: 0
+  minutes: 0
+  seconds: 0
+  frames: 0
+"#;
+
+/// If no `config.yml` exists alongside the binary, write out the default.
 fn ensure_config() {
-    let p = Path::new("config.json");
+    let p = Path::new("config.yml");
     if !p.exists() {
-        fs::write(p, DEFAULT_CONFIG)
-            .expect("Failed to write default config.json");
-        eprintln!("⚙️  Emitted default config.json");
+        fs::write(p, DEFAULT_CONFIG.trim())
+            .expect("Failed to write default config.yml");
+        eprintln!("⚙️  Emitted default config.yml");
     }
 }
 
@@ -40,9 +49,9 @@ async fn main() {
     // 🔄 Ensure there's always a config.json present
     ensure_config();
 
-    // 1️⃣ Start watching config.json for changes
-    let hw_offset = watch_config("config.json");
-    println!("🔧 Watching config.json (hardware_offset_ms)...");
+    // 1️⃣ Start watching config.yml for changes
+    let config = watch_config("config.yml");
+    println!("🔧 Watching config.yml...");
 
     // 2️⃣ Channel for raw LTC frames
     let (tx, rx) = mpsc::channel();
@@ -68,14 +77,14 @@ async fn main() {
         });
     }
 
-    // 5️⃣ Spawn the UI renderer thread, passing the live offset Arc
+    // 5️⃣ Spawn the UI renderer thread, passing the live config Arc
     {
         let ui_state     = ltc_state.clone();
-        let offset_clone = hw_offset.clone();
+        let config_clone = config.clone();
         let port         = "/dev/ttyACM0".to_string();
         thread::spawn(move || {
             println!("🖥️ UI thread launched");
-            start_ui(ui_state, port, offset_clone);
+            start_ui(ui_state, port, config_clone);
         });
     }
 
@@ -86,9 +95,9 @@ async fn main() {
             // 7️⃣ Spawn the API server thread
             {
                 let api_state = ltc_state.clone();
-                let offset_clone = hw_offset.clone();
+                let config_clone = config.clone();
                 task::spawn_local(async move {
-                    if let Err(e) = start_api_server(api_state, offset_clone).await {
+                    if let Err(e) = start_api_server(api_state, config_clone).await {
                         eprintln!("API server error: {}", e);
                     }
                 });
@@ -118,7 +127,7 @@ mod tests {
 
     impl Drop for ConfigGuard {
         fn drop(&mut self) {
-            let _ = fs::remove_file("config.json");
+            let _ = fs::remove_file("config.yml");
         }
     }
 
@@ -127,28 +136,28 @@ mod tests {
         let _guard = ConfigGuard; // Cleanup when _guard goes out of scope.
 
         // --- Test 1: File creation ---
-        // Pre-condition: config.json does not exist.
-        let _ = fs::remove_file("config.json");
+        // Pre-condition: config.yml does not exist.
+        let _ = fs::remove_file("config.yml");
 
         ensure_config();
 
-        // Post-condition: config.json exists and has default content.
-        let p = Path::new("config.json");
-        assert!(p.exists(), "config.json should have been created");
-        let contents = fs::read_to_string(p).expect("Failed to read created config.json");
-        assert_eq!(contents, DEFAULT_CONFIG, "config.json content should match default");
+        // Post-condition: config.yml exists and has default content.
+        let p = Path::new("config.yml");
+        assert!(p.exists(), "config.yml should have been created");
+        let contents = fs::read_to_string(p).expect("Failed to read created config.yml");
+        assert_eq!(contents, DEFAULT_CONFIG.trim(), "config.yml content should match default");
 
         // --- Test 2: File is not overwritten ---
-        // Pre-condition: config.json exists with different content.
-        let custom_content = "{\"hardware_offset_ms\": 999}";
-        fs::write("config.json", custom_content)
-            .expect("Failed to write custom config.json for test");
+        // Pre-condition: config.yml exists with different content.
+        let custom_content = "hardwareOffsetMs: 999";
+        fs::write("config.yml", custom_content)
+            .expect("Failed to write custom config.yml for test");
 
         ensure_config();
 
-        // Post-condition: config.json still has the custom content.
-        let contents_after = fs::read_to_string("config.json")
-            .expect("Failed to read config.json after second ensure_config call");
-        assert_eq!(contents_after, custom_content, "config.json should not be overwritten");
+        // Post-condition: config.yml still has the custom content.
+        let contents_after = fs::read_to_string("config.yml")
+            .expect("Failed to read config.yml after second ensure_config call");
+        assert_eq!(contents_after, custom_content, "config.yml should not be overwritten");
     }
 }