From 2abc577aca64cc7ba4bdb8c253e415da12dcb86c Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sun, 20 Mar 2022 20:37:22 +0100
Subject: [PATCH] implement topic matching

---
 haesli_messaging/src/routing.rs | 117 +++++++++++++++++++++++++++-----
 1 file changed, 99 insertions(+), 18 deletions(-)

diff --git a/haesli_messaging/src/routing.rs b/haesli_messaging/src/routing.rs
index d1cf35b..29c555e 100644
--- a/haesli_messaging/src/routing.rs
+++ b/haesli_messaging/src/routing.rs
@@ -40,26 +40,62 @@ pub fn route_message(exchange: &Exchange, routing_key: &str) -> Option<Vec<Queue
             Some(bindings.clone()) // see, this is actually Not That Bad I Hope
         }
         ExchangeType::Topic { bindings } => {
-            let topic = parse_topic(routing_key);
             // todo: optimizing this is a fun problem
 
-            Some(match_topic(bindings, topic))
+            Some(match_topic(bindings, routing_key))
         }
         ExchangeType::Headers => None, // unsupported
         ExchangeType::System => None,  // unsupported
     }
 }
 
-fn match_topic<Q: Clone>(
-    patterns: &[(Vec<TopicSegment>, Q)],
-    routing_key: Vec<TopicSegment>,
-) -> Vec<Q> {
+fn match_topic<Q: Clone>(patterns: &[(Vec<TopicSegment>, Q)], routing_key: &str) -> Vec<Q> {
     patterns
         .iter()
         .filter_map(|(pattern, value)| {
-            let mut queue_segments = routing_key.iter();
+            let mut key_segments = routing_key.split('.');
+            let mut pat_segments = pattern.iter();
 
-            for segment in pattern {}
+            loop {
+                let key = key_segments.next();
+                let pat = pat_segments.next();
+
+                match (pat, key) {
+                    (Some(TopicSegment::Word(pat)), Some(key)) if pat != key => return None,
+                    (Some(TopicSegment::Word(_)), Some(_)) => {}
+                    (Some(TopicSegment::SingleWildcard), Some(_)) => {}
+                    (Some(TopicSegment::MultiWildcard), _) => {
+                        let pat = pat_segments.next();
+                        match pat {
+                            Some(pat) => {
+                                // loop until we find the next pat segment in the key
+                                loop {
+                                    let key = key_segments.next();
+                                    match (pat, key) {
+                                        (_, None) => return None, // we are expecting something after the wildcard
+                                        (TopicSegment::Word(pat), Some(key)) if pat == key => {
+                                            break; // we matched all of the `#` and the segment afterwards
+                                        }
+                                        (TopicSegment::SingleWildcard, Some(_)) => {
+                                            break; // `#.*` is a cursed pattern, match `#` for 1
+                                        }
+                                        (TopicSegment::MultiWildcard, Some(_)) => {
+                                            break; // at this point I don't even care, who the fuck
+                                                   // would use `#.#`, just only match 2 which is
+                                                   // wrong so todo I guess lol
+                                        }
+                                        _ => continue,
+                                    }
+                                }
+                            }
+                            None => break, // pattern ends with `#`, it certainly matches
+                        }
+                    }
+                    (Some(_), None) => return None,
+                    (None, Some(_)) => return None,
+                    (None, None) => break,
+                }
+            }
 
             Some(value.clone())
         })
@@ -70,18 +106,63 @@ fn match_topic<Q: Clone>(
 mod tests {
     use crate::routing::{match_topic, parse_topic};
 
-    macro_rules! match_topics {
-        (patterns: $($pattern:expr),*) => {};
+    macro_rules! match_topics_test {
+        ($name:ident {
+            patterns: $($pattern:expr),*;
+            routing_key: $routing_key:expr;
+            expected: $($expected:expr),*;
+        }) => {
+            #[test]
+            fn $name() {
+                fn inc(x: &mut u64) -> u64 { let tmp = *x; *x += 1; tmp }
+
+                let mut n = 0;
+                let n = &mut n;
+
+                // assign each pattern a number
+                let patterns = [$((parse_topic($pattern), inc(n))),*];
+
+                let matched = match_topic(&patterns, $routing_key);
+                let expected = vec![$($expected),*];
+
+                assert_eq!(matched, expected);
+            }
+        };
     }
 
-    #[test]
-    #[ignore]
-    fn match_empty_topic() {
-        let patterns = [(parse_topic(""), 1), (parse_topic("BAD"), 2)];
-        let routing_key = parse_topic("");
+    match_topics_test!(match_spec_example_1 {
+        patterns: "*.stock.#";
+        routing_key: "usd.stock";
+        expected: 0;
+    });
 
-        let matched = match_topic(&patterns, routing_key);
+    match_topics_test!(match_spec_example_2 {
+        patterns: "*.stock.#";
+        routing_key: "eur.stock.db";
+        expected: 0;
+    });
 
-        assert_eq!(matched, vec![1])
-    }
+    match_topics_test!(match_spec_example_3 {
+        patterns: "*.stock.#";
+        routing_key: "stock.nasdaq";
+        expected: ;
+    });
+
+    match_topics_test!(match_no_wildcards {
+        patterns: "na.stock.usd", "sa.stock.peso", "stock.nasdaq", "usd.stock.na";
+        routing_key: "na.stock.usd";
+        expected: 0;
+    });
+
+    match_topics_test!(match_cursed_wildcards {
+        patterns: "*.*.*", "#.usd", "#.stock.*", "*.#", "#", "na.*";
+        routing_key: "na.stock.usd";
+        expected: 0, 1, 2, 3, 4;
+    });
+
+    match_topics_test!(match_empty_topic {
+        patterns: "", "bad";
+        routing_key: "";
+        expected: 0;
+    });
 }