implement add function

dsc_lib/src/functions/add.rs

@@ -0,0 +1,76 @@
+// 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 Add {}
+
+impl Function for Add {
+    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!("add function");
+        if let (Some(arg1), Some(arg2)) = (args[0].as_i64(), args[1].as_i64()) {
+            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("[add(2, 3)]", &Context::new()).unwrap();
+        assert_eq!(result, 5);
+    }
+
+    #[test]
+    fn nested() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[add(2, add(3, 4))]", &Context::new()).unwrap();
+        assert_eq!(result, 9);
+    }
+
+    #[test]
+    fn invalid_one_parameter() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[add(5)]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn overflow_result() {
+        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("[add(9223372036854775807, 2)]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn overflow_input() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[add(9223372036854775808, 2)]", &Context::new());
+        assert!(result.is_err());
+    }
+}

dsc_lib/src/functions/mod.rs

@@ -7,6 +7,7 @@ use crate::DscError;
 use crate::configure::context::Context;
 use serde_json::Value;
 
+pub mod add;
 pub mod base64;
 pub mod concat;
 pub mod create_array;
@@ -56,6 +57,7 @@ impl FunctionDispatcher {
     #[must_use]
     pub fn new() -> Self {
         let mut functions: HashMap<String, Box<dyn Function>> = HashMap::new();
+        functions.insert("add".to_string(), Box::new(add::Add{}));
         functions.insert("base64".to_string(), Box::new(base64::Base64{}));
         functions.insert("concat".to_string(), Box::new(concat::Concat{}));
         functions.insert("createArray".to_string(), Box::new(create_array::CreateArray{}));