Clojure script to count number of chats per person from WhatsApp export

script.clj

(ns user
  (:require [clojure.string :refer [lower-case includes? trim]]))

(defn parse-line
  "Returns the name of the message, or nil if it can't be found"
  [l]
  (->> l
       trim
       (re-find #"\[.{19}\].(.[A-Za-z\ \-]+):")
       second))

(defn chats-by-user
  ([in-file]
   (chats-by-user in-file parse-line))
  ([in-file filter-fn]
   (with-open [rdr (clojure.java.io/reader in-file)]
     (let [lines     (line-seq rdr)
           histogram (reduce
                      (fn [acc l]
                        (if-let [n (filter-fn l)]
                          (update acc n (fnil inc 0))
                          ;;else ignore
                          acc))
                      {}
                      lines)]
       (->> histogram
            (sort-by second)
            reverse
            (map (fn [[name amount]]
                   {:name   name
                    :amount amount}))
            clojure.pprint/print-table)))))

;;Usage
(chats-by-user "export.txt")