Add mod function

dsc_lib/src/functions/mod.rs

@@ -13,6 +13,7 @@ pub mod concat;
 pub mod create_array;
 pub mod div;
 pub mod envvar;
+pub mod mod_function;
 pub mod mul;
 pub mod parameters;
 pub mod resource_id;
@@ -64,6 +65,7 @@ impl FunctionDispatcher {
         functions.insert("createArray".to_string(), Box::new(create_array::CreateArray{}));
         functions.insert("div".to_string(), Box::new(div::Div{}));
         functions.insert("envvar".to_string(), Box::new(envvar::Envvar{}));
+        functions.insert("mod".to_string(), Box::new(mod_function::Mod{}));
         functions.insert("mul".to_string(), Box::new(mul::Mul{}));
         functions.insert("parameters".to_string(), Box::new(parameters::Parameters{}));
         functions.insert("resourceId".to_string(), Box::new(resource_id::ResourceId{}));

dsc_lib/src/functions/mod_function.rs

@@ -0,0 +1,79 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use crate::DscError;
+use crate::configure::context::Context;
+use crate::functions::{AcceptedArgKind, Function};
+use serde_json::Value;
+use tracing::debug;
+
+#[derive(Debug, Default)]
+pub struct Mod {}
+
+impl Function for Mod {
+    fn min_args(&self) -> usize {
+        2
+    }
+
+    fn max_args(&self) -> usize {
+        2
+    }
+
+    fn accepted_arg_types(&self) -> Vec<AcceptedArgKind> {
+        vec![AcceptedArgKind::Number]
+    }
+
+    fn invoke(&self, args: &[Value], _context: &Context) -> Result<Value, DscError> {
+        debug!("mod function");
+        if let (Some(arg1), Some(arg2)) = (args[0].as_i64(), args[1].as_i64()) {
+            if arg2 == 0 {
+                return Err(DscError::Parser("Cannot divide by zero".to_string()));
+            }
+            Ok(Value::Number((arg1 % arg2).into()))
+        } else {
+            Err(DscError::Parser("Invalid argument(s)".to_string()))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::configure::context::Context;
+    use crate::parser::Statement;
+
+    #[test]
+    fn numbers() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[mod(7, 3)]", &Context::new()).unwrap();
+        assert_eq!(result, 1);
+    }
+
+    #[test]
+    fn nested() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[mod(18, mod(8, 3))]", &Context::new()).unwrap();
+        assert_eq!(result, 0);
+    }
+
+    #[test]
+    fn invalid_one_parameter() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[mod(5)]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn invalid_div_by_zero() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[mod(5, 0)]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn overflow_input() {
+        let mut parser = Statement::new().unwrap();
+        // max value for i64 is 2^63 -1 (or 9,223,372,036,854,775,807)
+        let result = parser.parse_and_execute("[mod(9223372036854775808, 2)]", &Context::new());
+        assert!(result.is_err());
+    }
+}