diff -r abe0a561005e -r 831ecafd74c6 rust/chat_sanitizer/src/bad_words.rs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/chat_sanitizer/src/bad_words.rs	Thu Dec 27 23:43:54 2018 +0100
@@ -0,0 +1,54 @@
+use crate::{normalized_message, MessageChecker, Severity};
+
+use std::marker::PhantomData;
+
+struct BadWordsChecker<T> {
+    blacklist: Vec<String>,
+    whitelist: Vec<String>,
+    player_id_type: PhantomData<T>,
+}
+
+impl<T> BadWordsChecker<T> {
+    pub fn new(blacklist: &[&str], whitelist: &[&str]) -> Self {
+        Self {
+            blacklist: blacklist.iter().map(|s| normalized_message(*s)).collect(),
+            whitelist: whitelist.iter().map(|s| normalized_message(*s)).collect(),
+            player_id_type: PhantomData,
+        }
+    }
+}
+
+impl<T> MessageChecker<T> for BadWordsChecker<T> {
+    fn check(&self, player_id: T, message: &str) -> Severity {
+        let msg = normalized_message(message);
+
+        // silly implementation, allows bad messages with a single good word
+        for badword in &self.blacklist {
+            if msg.contains(badword) {
+                if !self.whitelist.iter().any(|goodword| msg.contains(goodword)) {
+                    return Severity::Warn;
+                }
+            }
+        }
+
+        Severity::Pass
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn it_works() {
+        let checker = BadWordsChecker::new(&["fsck", "poop"], &["fsck -y"]);
+        assert_eq!(checker.check(0, "group hug"), Severity::Pass);
+        assert_eq!(checker.check(0, "fpoopf"), Severity::Warn);
+        assert_eq!(checker.check(0, "PooP"), Severity::Warn);
+
+        // this one fails
+        //assert_eq!(checker.check(0, "poop 'fsck -y' poop"), Severity::Warn);
+
+        // ideally this one shouldn't fail
+        // assert_eq!(checker.check(0, "P00P"), Severity::Warn);
+    }
+}