From 1479b2b9a2d5d00e2799a05c3af3bef1508a3e80 Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Tue, 6 Apr 2021 16:28:24 -0600
Subject: implement function `patsubst`

---
 src/makefile/functions.rs | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/makefile/functions.rs b/src/makefile/functions.rs
index e6efd1c..2192d26 100644
--- a/src/makefile/functions.rs
+++ b/src/makefile/functions.rs
@@ -20,6 +20,10 @@ pub fn expand_call(
             assert_eq!(args.len(), 3);
             text::subst(macros, &args[0], &args[1], &args[2])
         }
+        "patsubst" => {
+            assert_eq!(args.len(), 3);
+            text::patsubst(macros, &args[0], &args[1], &args[2])
+        }
         "strip" => {
             assert_eq!(args.len(), 1);
             text::strip(macros, &args[0])
@@ -148,6 +152,29 @@ mod text {
         Ok(text.replace(&from, &to))
     }
 
+    pub fn patsubst(
+        macros: &MacroSet,
+        from: &TokenString,
+        to: &TokenString,
+        text: &TokenString,
+    ) -> Result<String> {
+        let from = macros.expand(from)?;
+        let to = macros.expand(to)?;
+        let text = macros.expand(text)?;
+        let words = text
+            .split_whitespace()
+            .map(|word| {
+                let pattern_match = r#match(&from, word)?.and_then(|x| x.get(1));
+                Ok(if let Some(pm) = pattern_match {
+                    to.replace('%', pm.as_str())
+                } else {
+                    word.to_owned()
+                })
+            })
+            .collect::<Result<Vec<_>>>()?;
+        Ok(words.join(" "))
+    }
+
     pub fn strip(macros: &MacroSet, text: &TokenString) -> Result<String> {
         let text = macros.expand(text)?;
         // TODO don't allocate this vec
-- 
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