From f73d0b2256f2afc05995929c930b2eeab6800ecf Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Sat, 3 Apr 2021 18:01:04 -0600
Subject: implement GNUish '%'-based inference rules

---
 src/makefile/inference_rules.rs | 55 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 6 deletions(-)

(limited to 'src/makefile/inference_rules.rs')

diff --git a/src/makefile/inference_rules.rs b/src/makefile/inference_rules.rs
index 3d18730..dfbb07c 100644
--- a/src/makefile/inference_rules.rs
+++ b/src/makefile/inference_rules.rs
@@ -1,19 +1,62 @@
 use std::fmt;
 
-use crate::makefile::command_line::CommandLine;
+use eyre::{eyre, Result};
+use regex::Captures;
+
+use super::command_line::CommandLine;
+use super::pattern::r#match;
 
 #[derive(PartialEq, Eq, Clone, Debug)]
 pub struct InferenceRule {
-    /// POSIX calls this ".s1" but that's not useful.
-    pub product: String,
-    /// POSIX calls this ".s2" but that's not useful.
-    pub prereq: String,
+    pub products: Vec<String>,
+    pub prerequisites: Vec<String>,
     pub commands: Vec<CommandLine>,
 }
 
+impl InferenceRule {
+    /// s1 is the product, s2 is the prereq
+    pub fn new_suffix(s1: String, s2: String, commands: Vec<CommandLine>) -> Self {
+        Self {
+            products: vec![format!("%.{}", s1)],
+            prerequisites: vec![format!("%.{}", s2)],
+            commands,
+        }
+    }
+
+    fn first_match<'s, 't: 's>(&'s self, target_name: &'t str) -> Result<Option<Captures<'t>>> {
+        self.products
+            .iter()
+            .map(|pattern| r#match(pattern, target_name))
+            .try_fold(None, |x, y| y.map(|y| x.or(y)))
+    }
+
+    pub fn matches(&self, target_name: &str) -> Result<bool> {
+        self.first_match(target_name).map(|x| x.is_some())
+    }
+
+    pub fn prereqs<'s>(
+        &'s self,
+        target_name: &'s str,
+    ) -> Result<impl Iterator<Item = String> + 's> {
+        let capture = self
+            .first_match(target_name)?
+            .ok_or_else(|| eyre!("asked non-matching inference rule for prerequisites"))?;
+        let percent_expansion = capture.get(1).expect("should've matched the %").as_str();
+        Ok(self
+            .prerequisites
+            .iter()
+            .map(move |p| p.replace('%', percent_expansion)))
+    }
+}
+
 impl fmt::Display for InferenceRule {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        writeln!(f, "{}{}:", &self.prereq, &self.product)?;
+        writeln!(
+            f,
+            "{}: {}",
+            self.products.join(" "),
+            self.prerequisites.join(" ")
+        )?;
         for command in &self.commands {
             writeln!(f, "\t{}", command)?;
         }
-- 
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