add engine and rpc client, archive old code

engine/examples/calendar/example.rs

@@ -0,0 +1,66 @@
+use std::sync::Arc;
+use std::path::Path;
+use rhai::{Engine, Scope};
+use heromodels::models::calendar::{Calendar, Event, Attendee, AttendanceStatus};
+use engine::{create_heromodels_engine, eval_file};
+use engine::mock_db::{create_mock_db, seed_mock_db};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    println!("Calendar Rhai Example");
+    println!("=====================");
+    
+    // Create a mock database
+    let db = create_mock_db();
+    
+    // Seed the database with some initial data
+    seed_mock_db(db.clone());
+    
+    // Create the Rhai engine using our central engine creator
+    let mut engine = create_heromodels_engine(db.clone());
+    
+    // Register timestamp helper functions
+    register_timestamp_helpers(&mut engine);
+    
+    // Get the path to the script
+    let script_path = Path::new(file!())
+        .parent()
+        .unwrap()
+        .join("calendar_script.rhai");
+    
+    println!("\nRunning script: {}", script_path.display());
+    println!("---------------------");
+    
+    // Run the script
+    match eval_file(&engine, &script_path.to_string_lossy()) {
+        Ok(result) => {
+            if !result.is_unit() {
+                println!("\nScript returned: {:?}", result);
+            }
+            println!("\nScript executed successfully!");
+            Ok(())
+        },
+        Err(err) => {
+            eprintln!("\nError running script: {}", err);
+            Err(Box::new(std::io::Error::new(std::io::ErrorKind::Other, err.to_string())))
+        }
+    }
+}
+
+// Register timestamp helper functions with the engine
+fn register_timestamp_helpers(engine: &mut Engine) {
+    use chrono::{DateTime, Utc, TimeZone, NaiveDateTime};
+    
+    // Function to get current timestamp
+    engine.register_fn("timestamp_now", || {
+        Utc::now().timestamp() as i64
+    });
+    
+    // Function to format a timestamp
+    engine.register_fn("format_timestamp", |ts: i64| {
+        let dt = Utc.timestamp_opt(ts, 0).single()
+            .expect("Invalid timestamp");
+        dt.format("%Y-%m-%d %H:%M:%S UTC").to_string()
+    });
+    
+    println!("Timestamp helper functions registered successfully.");
+}