feat(smart-proxy): add typed Rust config serialization and regex header contract coverage

rust/crates/rustproxy-routing/src/matchers/header.rs

@@ -1,5 +1,42 @@
-use std::collections::HashMap;
 use regex::Regex;
+use std::collections::HashMap;
+
+fn compile_regex_pattern(pattern: &str) -> Option<Regex> {
+    if !pattern.starts_with('/') {
+        return None;
+    }
+
+    let last_slash = pattern.rfind('/')?;
+    if last_slash == 0 {
+        return None;
+    }
+
+    let regex_body = &pattern[1..last_slash];
+    let flags = &pattern[last_slash + 1..];
+
+    let mut inline_flags = String::new();
+    for flag in flags.chars() {
+        match flag {
+            'i' | 'm' | 's' | 'u' => {
+                if !inline_flags.contains(flag) {
+                    inline_flags.push(flag);
+                }
+            }
+            'g' => {
+                // Global has no effect for single header matching.
+            }
+            _ => return None,
+        }
+    }
+
+    let compiled = if inline_flags.is_empty() {
+        regex_body.to_string()
+    } else {
+        format!("(?{}){}", inline_flags, regex_body)
+    };
+
+    Regex::new(&compiled).ok()
+}
 
 /// Match HTTP headers against a set of patterns.
 ///
@@ -24,16 +61,15 @@ pub fn headers_match(
             None => return false, // Required header not present
         };
 
-        // Check if pattern is a regex (surrounded by /)
-        if pattern.starts_with('/') && pattern.ends_with('/') && pattern.len() > 2 {
-            let regex_str = &pattern[1..pattern.len() - 1];
-            match Regex::new(regex_str) {
-                Ok(re) => {
+        // Check if pattern is a regex literal (/pattern/ or /pattern/flags)
+        if pattern.starts_with('/') && pattern.len() > 2 {
+            match compile_regex_pattern(pattern) {
+                Some(re) => {
                     if !re.is_match(header_value) {
                         return false;
                     }
                 }
-                Err(_) => {
+                None => {
                     // Invalid regex, fall back to exact match
                     if header_value != pattern {
                         return false;
@@ -85,6 +121,24 @@ mod tests {
         assert!(headers_match(&patterns, &headers));
     }
 
+    #[test]
+    fn test_regex_header_match_with_flags() {
+        let patterns: HashMap<String, String> = {
+            let mut m = HashMap::new();
+            m.insert(
+                "Content-Type".to_string(),
+                "/^application\\/json$/i".to_string(),
+            );
+            m
+        };
+        let headers: HashMap<String, String> = {
+            let mut m = HashMap::new();
+            m.insert("content-type".to_string(), "Application/JSON".to_string());
+            m
+        };
+        assert!(headers_match(&patterns, &headers));
+    }
+
     #[test]
     fn test_missing_header() {
         let patterns: HashMap<String, String> = {