diff --git a/src/rss_thread_watch/filters.clj b/src/rss_thread_watch/filters.clj
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+++ b/src/rss_thread_watch/filters.clj
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+;; Copyright (C) 2024  Felisp
+;;
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU Affero General Public License as published by
+;; the Free Software Foundation, version 3 of the License.
+;;
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU Affero General Public License for more details.
+;;
+;; You should have received a copy of the GNU Affero General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+(ns rss-thread-watch.filters
+  "Functions filtering posts"
+  (:require [clojure.string :as cs]
+            [rss-thread-watch.utils :as u])
+  (:gen-class))
+
+(defn case-sensitive-filter
+  "Returns true if string [s] is matched by any query. It's case insensitive"
+  [s queries]
+  (some (fn [querry]
+          (cs/includes? s querry))
+        queries))
+
+(defn case-insensitive-filter
+  "Returns true if string [s] is case-matched by query"
+  [s queries]
+  (basic-filter (cs/lower-case s) (cs/lower-case s)))
+