# Event loop
# SPDX-FileCopyrightText: 2025 Nguyễn Gia Phong
# SPDX-License-Identifier: GPL-3.0-or-later

(defn kay/select/move
  [buf direction]
  (let [selection (buf :selection)]
    (struct ;(kvs buf)
            :selection (match selection
                         {:head head :tail tail}
                         (struct ;(kvs selection)
                                 :head (direction head buf)
                                 :tail (direction tail buf))))))

(defn kay/select/head
  [buf direction]
  (let [selection (buf :selection)]
    (struct ;(kvs buf)
            :selection (match selection
                         {:head head :tail tail}
                         (struct ;(kvs selection)
                                 :head (direction head buf)
                                 :tail tail)))))

(defn kay/select/flip
  [buf]
  (struct ;(kvs buf)
          :selection (match (buf :selection)
                       {:head head :tail tail} {:head tail :tail head})))

(defn handle
  [event buf]
  (match event
    {:winsize ws} (do (:resize kay/env ws)
                      [[] buf])
    {:key-press key}
    (cond
      (:matches key (chr "c") {:ctrl true}) [[:quit] buf]
      (:matches key (chr "y") {}) (do (:yank kay/env buf)
                                      [[] buf])
      (:matches key (chr "i") {}) (do (:request-paste kay/env)
                                      [[] buf])
      (:matches key (chr "p") {}) [[] (struct ;(kvs buf)
                                              :scroll-row (max 0 (dec (buf :scroll-row))))]
      (:matches key (chr "n") {}) [[] (struct ;(kvs buf)
                                              :scroll-row (inc (buf :scroll-row)))]
      (:matches key (chr "h") {}) [[] (kay/select/move buf :up)]
      (:matches key (chr "j") {}) [[] (kay/select/move buf :right)]
      (:matches key (chr "k") {}) [[] (kay/select/move buf :left)]
      (:matches key (chr "l") {}) [[] (kay/select/move buf :down)]
      (:matches key (chr "h") {:shift true}) [[] (kay/select/head buf :up)]
      (:matches key (chr "j") {:shift true}) [[] (kay/select/head buf :right)]
      (:matches key (chr "k") {:shift true}) [[] (kay/select/head buf :left)]
      (:matches key (chr "l") {:shift true}) [[] (kay/select/head buf :down)]
      (:matches key (chr ";") {}) [[] (kay/select/flip buf)]
      [[] buf])
    {:paste paste} [[] (:paste kay/env buf paste)]))

(defn run
  [events buf]
  (if-let [event (array/pop events)]
    (unless (= :quit event)
      (let [[next-events next-buf] (handle event buf)]
        (:render kay/env next-buf)
        (run (array/join events next-events)
             next-buf)))
    (run @[(:next-event kay/env)]
         buf)))

(with [buf (kay/open (if-with [f (file/open (string kay/path))]
                       (buffer (:read f :all))
                       @"\n")
                     kay/path)]
  (run @[] buf))