From 3b4ed9869de4645c54f470a2d1a5681f35408e64 Mon Sep 17 00:00:00 2001
From: Tyler McMullen <tyler@fastly.com>
Date: Thu, 5 Dec 2024 19:07:37 +0000
Subject: [PATCH] Implement 'lower' function in library

---
 esi/src/error.rs      |  1 -
 esi/src/expression.rs | 27 +++++++++++++++------------
 esi/src/lib.rs        |  6 +++++-
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/esi/src/error.rs b/esi/src/error.rs
index 44bf393..2122a6f 100644
--- a/esi/src/error.rs
+++ b/esi/src/error.rs
@@ -1,7 +1,6 @@
 use thiserror::Error;
 
 use fastly::http::request::SendError;
-use regex::Error;
 
 /// Describes an error encountered during ESI parsing or execution.
 #[derive(Error, Debug)]
diff --git a/esi/src/expression.rs b/esi/src/expression.rs
index adbd53a..e3f8e5a 100644
--- a/esi/src/expression.rs
+++ b/esi/src/expression.rs
@@ -74,6 +74,16 @@ fn eval_expr(expr: Expr, ctx: &EvalContext) -> Result<Value> {
 fn call_dispatch(identifier: String, args: Vec<Value>) -> Result<Value> {
     let result = match identifier.as_str() {
         "ping" => Value::String("pong".to_string()),
+        "lower" => {
+            if args.len() != 1 {
+                Value::Error("wrong number of arguments to 'lower'".to_string())
+            } else {
+                match &args[0] {
+                    Value::String(s) => Value::String(s.to_lowercase()),
+                    _ => Value::Error("incorrect type passed to 'lower'".to_string()),
+                }
+            }
+        }
         _ => Value::Error(format!("unknown function: {}", identifier)),
     };
     Ok(result)
@@ -106,7 +116,6 @@ fn parse(tokens: Vec<Token>) -> Result<Expr> {
     Ok(expr)
 }
 fn parse_expr(cur: &mut Peekable<Iter<Token>>) -> Result<Expr> {
-    println!("peek: {:?}", cur.peek());
     let node = if let Some(token) = cur.next() {
         match token {
             Token::String(s) => Expr::String(s.clone()),
@@ -157,7 +166,6 @@ fn parse_call(identifier: String, cur: &mut Peekable<Iter<Token>>) -> Result<Exp
     match cur.next() {
         Some(Token::OpenParen) => {
             let mut args = Vec::new();
-            let mut first_arg = true;
             loop {
                 match cur.peek() {
                     Some(&&Token::CloseParen) => {
@@ -625,18 +633,13 @@ mod tests {
         assert_eq!(result, Value::String("pong".to_string()));
         Ok(())
     }
-
-    // TODO: more negative tests
-    // #[test]
-    fn test_evaluation_error() -> Result<()> {
+    #[test]
+    fn test_eval_lower_call() -> Result<()> {
         let result = evaluate_expression(
-            "$hello".to_string(),
-            EvalContext::new(&Variables::from([(
-                "hello".to_string(),
-                Value::String("goodbye".to_string()),
-            )])),
+            "$lower('FOO')".to_string(),
+            EvalContext::new(&Variables::new()),
         )?;
-        assert_eq!(result, Value::Error("$hello".to_string()));
+        assert_eq!(result, Value::String("foo".to_string()));
         Ok(())
     }
 }
diff --git a/esi/src/lib.rs b/esi/src/lib.rs
index 976c5dc..c548f3f 100644
--- a/esi/src/lib.rs
+++ b/esi/src/lib.rs
@@ -486,7 +486,11 @@ fn event_receiver(
         }) => {
             let mut chose_branch = false;
             for (when, events) in when_branches {
-                if let Tag::When { test, match_name } = when {
+                if let Tag::When {
+                    test,
+                    match_name: _,
+                } = when
+                {
                     let result = evaluate_expression(test, EvalContext::new(&variables))?;
                     if result.to_bool() {
                         chose_branch = true;