From 9267fb0387a87edc4b059dbbdf0258ec6b7cc62d Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Mon, 5 Apr 2021 11:30:21 -0600
Subject: implement function `findstring`

---
 src/makefile/functions.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/makefile/functions.rs b/src/makefile/functions.rs
index 6e04b7a..6dacd10 100644
--- a/src/makefile/functions.rs
+++ b/src/makefile/functions.rs
@@ -20,6 +20,10 @@ pub fn expand_call(
             assert_eq!(args.len(), 1);
             text::strip(macros, &args[0])
         }
+        "findstring" => {
+            assert_eq!(args.len(), 2);
+            text::findstring(macros, &args[0], &args[1])
+        }
         "filter" => {
             assert_eq!(args.len(), 2);
             text::filter(macros, &args[0], &args[1])
@@ -110,6 +114,20 @@ mod text {
         Ok(words.join(" "))
     }
 
+    pub fn findstring(
+        macros: &MacroSet,
+        needle: &TokenString,
+        haystack: &TokenString,
+    ) -> Result<String> {
+        let needle = macros.expand(needle)?;
+        let haystack = macros.expand(haystack)?;
+        if haystack.contains(&needle) {
+            Ok(needle)
+        } else {
+            Ok(String::new())
+        }
+    }
+
     pub fn filter(macros: &MacroSet, patterns: &TokenString, text: &TokenString) -> Result<String> {
         let patterns = macros.expand(patterns)?;
         let patterns = patterns.split_whitespace().collect::<Vec<_>>();
@@ -379,6 +397,13 @@ mod test {
         Ok(())
     }
 
+    #[test]
+    fn findstring() -> R {
+        assert_eq!(call!(findstring "hi", "thighs"), "hi");
+        assert_eq!(call!(findstring "hey", "hello there"), "");
+        Ok(())
+    }
+
     #[test]
     fn filter() -> R {
         let result = call!(filter "word", "this contains a word inside it");
-- 
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