From 917fdc033a08c314aa91b533728172a6f5bd458c Mon Sep 17 00:00:00 2001
From: Tess Gauthier <tessgauthier@microsoft.com>
Date: Fri, 29 Mar 2024 13:30:09 -0400
Subject: [PATCH] add max function

---
 dsc_lib/src/functions/max.rs | 115 +++++++++++++++++++++++++++++++++++
 dsc_lib/src/functions/mod.rs |   2 +
 2 files changed, 117 insertions(+)
 create mode 100644 dsc_lib/src/functions/max.rs

diff --git a/dsc_lib/src/functions/max.rs b/dsc_lib/src/functions/max.rs
new file mode 100644
index 00000000..f9a5177b
--- /dev/null
+++ b/dsc_lib/src/functions/max.rs
@@ -0,0 +1,115 @@
+// 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 Max {}
+
+impl Function for Max {
+    fn min_args(&self) -> usize {
+        1
+    }
+
+    fn max_args(&self) -> usize {
+        usize::MAX
+    }
+
+    fn accepted_arg_types(&self) -> Vec<AcceptedArgKind> {
+        vec![AcceptedArgKind::Number, AcceptedArgKind::Array]
+    }
+
+    fn invoke(&self, args: &[Value], _context: &Context) -> Result<Value, DscError> {
+        debug!("max function");
+        if args.len() == 1 {
+            if let Some(array) = args[0].as_array() {
+                find_max(array)
+            }
+            else {
+                Err(DscError::Parser("Array cannot be empty".to_string()))
+            }
+        }
+        else {
+            find_max(args)
+        }
+    }
+}
+
+fn find_max(args: &[Value]) -> Result<Value, DscError> {
+    let array = args.iter().map(|v| v.as_i64().ok_or(DscError::Parser("Input must only contain integers".to_string()))).collect::<Result<Vec<i64>, DscError>>()?;
+    let value = array.iter().max().ok_or(DscError::Parser("Unable to find max value".to_string()))?;
+    Ok(Value::Number((*value).into()))
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::configure::context::Context;
+    use crate::parser::Statement;
+
+    #[test]
+    fn list() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(3,2,5,4)]", &Context::new()).unwrap();
+        assert_eq!(result, 5);
+    }
+
+    #[test]
+    fn list_with_spaces() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(3, 2, 5, 4)]", &Context::new()).unwrap();
+        assert_eq!(result, 5);
+    }
+
+    #[test]
+    fn array() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(createArray(0, 3, 2, 7, 4)]", &Context::new()).unwrap();
+        assert_eq!(result, 7);
+    }
+
+    #[test]
+    fn array_single_value() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(createArray(0)]", &Context::new()).unwrap();
+        assert_eq!(result, 0);
+    }
+
+    #[test]
+    fn arrays() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(createArray(0, 3), createArray(2, 5))]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn string_and_numbers() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max('a', 1)]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn nested() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(-10, max(-2, -9), -5)]", &Context::new()).unwrap();
+        assert_eq!(result, -2);
+    }
+
+    #[test]
+    fn int_and_array() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(1, createArray(0,2))]", &Context::new());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn array_and_int() {
+        let mut parser = Statement::new().unwrap();
+        let result = parser.parse_and_execute("[max(createArray(0,2), 1)]", &Context::new());
+        assert!(result.is_err());
+    }
+}
diff --git a/dsc_lib/src/functions/mod.rs b/dsc_lib/src/functions/mod.rs
index d838a88a..3e88d2aa 100644
--- a/dsc_lib/src/functions/mod.rs
+++ b/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 max;
 pub mod min;
 pub mod mod_function;
 pub mod mul;
@@ -67,6 +68,7 @@ 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("max".to_string(), Box::new(max::Max{}));
         functions.insert("min".to_string(), Box::new(min::Min{}));
         functions.insert("mod".to_string(), Box::new(mod_function::Mod{}));
         functions.insert("mul".to_string(), Box::new(mul::Mul{}));