Negated filters

Resolves #92

src/bot/deliver_job.rs

@@ -181,9 +181,27 @@ async fn deliver_subscription_updates(
                     }
                 },
                 Some(words) => {
-                    let mtch = words
-                        .iter()
-                        .any(|word| message.to_lowercase().contains(word));
+                    let (negated_words, regular_words): (Vec<String>, Vec<String>) =
+                        words.into_iter().partition(|word| word.starts_with("!"));
+
+                    let mut mtch = true;
+
+                    if regular_words.len() > 0 {
+                        let regular_mtch = regular_words
+                            .iter()
+                            .any(|word| message.to_lowercase().contains(word));
+
+                        mtch = regular_mtch;
+                    }
+
+                    if negated_words.len() > 0 {
+                        let negated_mtch = regular_words.iter().all(|neg_word| {
+                            let word = neg_word.replace("!", "");
+                            !message.to_lowercase().contains(&word)
+                        });
+
+                        mtch = mtch && negated_mtch;
+                    }
 
                     if mtch {
                         match api::send_message(chat_id, message).await {

src/bot/logic.rs

@@ -164,6 +164,10 @@ pub fn set_filter(db_connection: &PgConnection, chat_id: i64, params: String) ->
         .map(|s| s.trim().to_lowercase().to_string())
         .collect();
 
+    if filter_words.len() > 7 {
+        return "The number of filter words is limited by 7".to_string();
+    }
+
     match telegram::set_filter(db_connection, &subscription, Some(filter_words.clone())) {
         Ok(_) => format!("The filter was updated:\n\n{}", filter_words.join(", ")).to_string(),
         Err(_) => "Failed to update the filter".to_string(),