;;; Copyright (C) 2025 Gene Pasquet
;;;
;;; This program is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation, either version 3 of the License, or
;;; (at your option) any later version.
;;;
;;; 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 General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program.  If not, see <https://www.gnu.org/licenses/>.

(import utils [sub-points distance Direction])

;; Define systems here
(setv GRAVITY 5)

(defclass GoalHit [Exception])

(defn entities-by-type [entities types]
  (gfor ent entities
        :if (in ent.type types)
        ent))

(defmacro defsystem [name pred #* body]
  `(defn ~name [entity entities]
     (when ~pred
       ~@body)))

(defsystem apply-gravity
  (not entity.fixed)
  (.move entity #(0 GRAVITY)))

(defsystem apply-collisions
  (not entity.fixed)
  (for [ent (gfor enti entities
                  :if (!= enti.id entity.id)
                  enti)]
    (when (.colliderect entity.rect ent.rect)
      (if (= ent.type "goal")
          (raise (GoalHit))
          (let [collision-rect (.clip entity.rect ent.rect)
                move-x (get entity.total-move 0)
                move-y (get entity.total-move 1)]
            (when (!= move-x 0)
              (.move entity #((* (if (> move-x 0) -1 1) collision-rect.width) 0)))
            (when (!= move-y 0)
              (.move entity #(0 (* (if (> move-y 0) -1 1) collision-rect.height))))))
      (.ground entity))))

(defsystem run-enemies
  (= entity.type "enemy")
  ;; If the player is on the tile next to the enemy, attack.
  (let [player (next (entities-by-type entities ["player"]))
        delta (sub-points entity.pos player.pos)
        dist (distance entity.pos player.pos)
        direction (.x-from-move Direction delta)]
    ;; If facing the player and within reach, attack)
    (when (and (= direction entity.facing)
               (< (get delta 1) 1) ;; Same level
               (< (abs (get delta 0)) 2)
               (not entity.attacking))
      (.attack entity))
    ;; If not facing the player, turn to face
    (when (and (< dist 5)
               (!= direction entity.facing))
      (.move entity #((if (< (get delta 0) 0) -1 1) 0)))
    ))