refactor: Overhaul Rhai scripting with multi-file hot reloading

This commit represents a major refactoring of our Rhai scripting system,
transforming it from a factory-based approach to a more robust system-based
architecture with improved hot reloading capabilities.

Key Changes:
- Renamed package from rhai_factory to rhai_system to better reflect its purpose
- Renamed system_factory.rs to factory.rs for consistency and clarity
- Implemented support for multiple script files in hot reloading
- Added cross-script function calls, allowing functions in one script to call functions in another
- Improved file watching to monitor all script files for changes
- Enhanced error handling for script compilation failures
- Simplified the API with a cleaner create_hot_reloadable_system function
- Removed unused modules (error.rs, factory.rs, hot_reload_old.rs, module_cache.rs, relative_resolver.rs)
- Updated all tests to work with the new architecture

The new architecture:
- Uses a System struct that holds references to script paths and provides a clean API
- Compiles and merges multiple Rhai script files into a single AST
- Automatically detects changes to any script file and recompiles them
- Maintains thread safety with proper synchronization primitives
- Provides better error messages when scripts fail to compile

This refactoring aligns with our BasePathModuleResolver approach for module imports,
making the resolution process more predictable and consistent. The hot reload example
has been updated to demonstrate the new capabilities, showing how to:
1. Load and execute multiple script files
2. Watch for changes to these files
3. Automatically reload scripts when they change
4. Call functions across different script files

All tests are passing, and the example demonstrates the improved functionality.

rhai_system/tests/common/mod.rs

@@ -0,0 +1,52 @@
+//! Common utilities for integration tests.
+
+use std::fs;
+use std::path::PathBuf;
+use std::time::{SystemTime, UNIX_EPOCH};
+use rand;
+
+/// Test fixture for integration tests.
+pub struct TestFixture {
+    pub scripts_dir: PathBuf,
+}
+
+impl TestFixture {
+    /// Create a new test fixture.
+    pub fn new() -> Self {
+        let scripts_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .join("tests")
+            .join("rhai_scripts");
+        
+        Self {
+            scripts_dir,
+        }
+    }
+    
+    /// Get the path to a test script.
+    pub fn script_path(&self, name: &str) -> PathBuf {
+        self.scripts_dir.join(name)
+    }
+}
+
+/// Create a temporary test directory with a unique name.
+pub fn setup_test_dir(prefix: &str) -> PathBuf {
+    let timestamp = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_millis();
+    
+    let test_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests")
+        .join("temp")
+        .join(format!("{}_{}_{}", prefix, timestamp, rand::random::<u16>()));
+    
+    fs::create_dir_all(&test_dir).unwrap();
+    test_dir
+}
+
+/// Clean up a temporary test directory.
+pub fn cleanup_test_dir(dir: PathBuf) {
+    if dir.exists() && dir.starts_with(PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests").join("temp")) {
+        let _ = fs::remove_dir_all(dir);
+    }
+}

rhai_system/tests/hot_reload_callback_tests.rs

@@ -0,0 +1,125 @@
+use std::fs;
+use std::sync::{Arc, RwLock};
+
+use rhai::Engine;
+use rhai_system::{System, hot_reload_callback};
+
+#[test]
+fn test_hot_reload_callback() {
+    // Create temporary script files
+    let temp_dir = tempfile::tempdir().unwrap();
+    let script_path = temp_dir.path().join("test_script.rhai");
+    
+    // Write initial script content
+    let initial_script = r#"
+        fn greet(name) {
+            "Hello, " + name + "! This is the original script."
+        }
+        
+        fn add(a, b) {
+            a + b
+        }
+    "#;
+    fs::write(&script_path, initial_script).unwrap();
+    
+    // Create engine and compile initial script
+    let engine = Engine::new();
+    let ast = engine.compile_file(script_path.clone()).unwrap();
+    let shared_ast = Arc::new(RwLock::new(ast));
+    
+    // Create a system with the initial script
+    let script_paths = vec![script_path.clone()];
+    let system = System::new(engine, shared_ast, script_paths);
+    
+    // Test initial script functionality
+    let result: String = system.call_fn("greet", ("User",)).unwrap();
+    assert_eq!(result, "Hello, User! This is the original script.");
+    
+    let add_result: i32 = system.call_fn("add", (40, 2)).unwrap();
+    assert_eq!(add_result, 42);
+    
+    // Write modified script content with new functions
+    let modified_script = r#"
+        fn greet(name) {
+            "Hello, " + name + "! This is the MODIFIED script!"
+        }
+        
+        fn add(a, b) {
+            a + b
+        }
+        
+        fn multiply(a, b) {
+            a * b
+        }
+    "#;
+    fs::write(&script_path, modified_script).unwrap();
+    
+    // Call the hot reload callback
+    hot_reload_callback(&system, script_path.to_str().unwrap()).unwrap();
+    
+    // Test that the script was updated
+    let result: String = system.call_fn("greet", ("User",)).unwrap();
+    assert_eq!(result, "Hello, User! This is the MODIFIED script!");
+    
+    // Test that the new function is available
+    let multiply_result: i32 = system.call_fn("multiply", (6, 7)).unwrap();
+    assert_eq!(multiply_result, 42);
+}
+
+#[test]
+fn test_hot_reload_callback_with_syntax_error() {
+    // Create temporary script files
+    let temp_dir = tempfile::tempdir().unwrap();
+    let script_path = temp_dir.path().join("test_script.rhai");
+    
+    // Write initial script content
+    let initial_script = r#"
+        fn greet(name) {
+            "Hello, " + name + "! This is the original script."
+        }
+        
+        fn add(a, b) {
+            a + b
+        }
+    "#;
+    fs::write(&script_path, initial_script).unwrap();
+    
+    // Create engine and compile initial script
+    let engine = Engine::new();
+    let ast = engine.compile_file(script_path.clone()).unwrap();
+    let shared_ast = Arc::new(RwLock::new(ast));
+    
+    // Create a system with the initial script
+    let script_paths = vec![script_path.clone()];
+    let system = System::new(engine, shared_ast, script_paths);
+    
+    // Test initial script functionality
+    let result: String = system.call_fn("greet", ("User",)).unwrap();
+    assert_eq!(result, "Hello, User! This is the original script.");
+    
+    // Write modified script content with syntax error
+    let modified_script = r#"
+        fn greet(name) {
+            "Hello, " + name + "! This is the MODIFIED script!"
+        }
+        
+        fn add(a, b) {
+            a + b
+        }
+        
+        fn syntax_error() {
+            // Missing closing brace
+            if (true) {
+                "This will cause a syntax error"
+        }
+    "#;
+    fs::write(&script_path, modified_script).unwrap();
+    
+    // Call the hot reload callback - it should return an error
+    let result = hot_reload_callback(&system, script_path.to_str().unwrap());
+    assert!(result.is_err());
+    
+    // Test that the original script functionality is still available
+    let result: String = system.call_fn("greet", ("User",)).unwrap();
+    assert_eq!(result, "Hello, User! This is the original script.");
+}

rhai_system/tests/rhai_scripts/main.rhai

@@ -0,0 +1,9 @@
+// main.rhai - Main script that imports module1
+
+import "module1" as m1;
+
+// Call the calculate function from module1, which in turn calls multiply from module2
+let answer = m1::calculate();
+
+// Return the answer
+answer

rhai_system/tests/rhai_scripts/module1.rhai

@@ -0,0 +1,9 @@
+// module1.rhai - A simple module that imports module2
+
+import "module2" as m2;
+
+fn calculate() {
+    // Call the multiply function from module2
+    let result = m2::multiply(6, 7);
+    result
+}

rhai_system/tests/rhai_scripts/module2.rhai

@@ -0,0 +1,5 @@
+// module2.rhai - A simple module with a multiply function
+
+fn multiply(x, y) {
+    x * y
+}

rhai_system/tests/temp/hot_reload_error_test_1744044524811_2594/test_script.rhai

@@ -0,0 +1 @@
+fn get_value() { 84 ; ; }

rhai_system/tests/temp/hot_reload_error_test_1744044573273_54513/test_script.rhai

@@ -0,0 +1 @@
+fn get_value() { 84 ; ; }

rhai_system/tests/temp/hot_reload_multi_test_1744044365183_20187/main.rhai

@@ -0,0 +1,2 @@
+import "module" as m;
+fn calculate() { 21 * m::get_multiplier() }

rhai_system/tests/temp/hot_reload_multi_test_1744044365183_20187/module.rhai

@@ -0,0 +1 @@
+fn get_multiplier() { 4 }

rhai_system/tests/temp/hot_reload_multi_test_1744044402581_52748/main.rhai

@@ -0,0 +1,2 @@
+import "module" as m;
+fn calculate() { 21 * m::get_multiplier() }

rhai_system/tests/temp/hot_reload_multi_test_1744044402581_52748/module.rhai

@@ -0,0 +1 @@
+fn get_multiplier() { 4 }

rhai_system/tests/temp/hot_reload_multi_test_1744044524811_18731/main.rhai

@@ -0,0 +1,2 @@
+import "module" as m;
+fn calculate() { 21 * m::get_multiplier() }

rhai_system/tests/temp/hot_reload_multi_test_1744044524811_18731/module.rhai

@@ -0,0 +1 @@
+fn get_multiplier() { 4 }

rhai_system/tests/temp/hot_reload_multi_test_1744044592612_25679/main.rhai

@@ -0,0 +1,2 @@
+import "module" as m;
+fn calculate() { 21 * m::get_multiplier() }

rhai_system/tests/temp/hot_reload_multi_test_1744044592612_25679/module.rhai

@@ -0,0 +1 @@
+fn get_multiplier() { 4 }

rhai_system/tests/temp/hot_reload_multi_test_1744044639148_21519/main.rhai

@@ -0,0 +1,2 @@
+fn get_multiplier() { 4 }
+fn calculate() { 21 * get_multiplier() }

rhai_system/tests/temp/hot_reload_multi_test_1744044639148_21519/module.rhai

@@ -0,0 +1 @@
+// This is a secondary file that will be modified

rhai_system/tests/temp/hot_reload_multi_test_1744208365005_64464/main.rhai

@@ -0,0 +1,2 @@
+fn get_multiplier() { 4 }
+fn calculate() { 21 * get_multiplier() }

rhai_system/tests/temp/hot_reload_multi_test_1744208365005_64464/module.rhai

@@ -0,0 +1 @@
+// This is a secondary file that will be modified

rhai_system/tests/temp/hot_reload_test_1744044365183_6262/test_script.rhai

@@ -0,0 +1 @@
+fn get_value() { 84 }

rhai_system/tests/temp/hot_reload_test_1744044402581_43473/test_script.rhai

@@ -0,0 +1 @@
+fn get_value() { 84 }