protohackers challenge4

challenge4.lisp

(defpackage :challenge4
  (:use cl usocket)
  (:export main)
  (:import-from flexi-streams
                :string-to-octets
                :octets-to-string)
  (:import-from serapeum
                :fmt
                :@
                :dict))

(in-package :challenge4)

(defvar *db* (dict "version" "Ken's Key-Value Store 1.0"))

(defun handler (msg)
  (destructuring-bind (key &optional value)
      (str:split "=" (octets-to-string msg) :limit 2)
    (if value
        (unless (string= key "version")
          (setf (@ *db* key) value)
          nil)
        (string-to-octets (fmt "~a=~a" key (@ *db* key))))))

(socket-server "0.0.0.0" 1234 'handler nil :protocol :datagram)