;;;; raylib [core] example - input keys
;;;;
;;;; examples/core/core_input_keys.c. Faithful, and the only thing worth noting
;;;; is a Flan rule rather than a raylib one.
;;;;
;;;; The C moves the ball by writing `ballPosition.x += 2.0f` on a local
;;;; struct. Flan has the same thing — a local IS an assignable place
;;;; (spec-memory.md) — but the local has to be a `defvar` here rather than a
;;;; `let` inside the loop, because a `let` binding is rebound every iteration
;;;; and the position has to survive between frames. The C's variable is
;;;; outside its while loop for the same reason; this is that, spelled with the
;;;; storage the language has.
;;;;
;;;; `(set (.x ball) ...)` works on a struct field of a global: a field of an
;;;; assignable place is itself one.

(import rl "vendor:raylib")

(defconst screen-width  800)
(defconst screen-height 450)

(defvar ball rl/Vector2)

(defn main []
  (rl/init-window screen-width screen-height
                  "raylib [core] example - input keys")
  (defer (rl/close-window))

  (set ball (rl/Vector2 {.x (f32 (/ screen-width 2))
                         .y (f32 (/ screen-height 2))}))

  (rl/set-target-fps 60)

  (until (rl/window-should-close?)
    ;; Update. key-down? and not key-pressed?: this is meant to repeat for as
    ;; long as the key is held, which is the whole difference between the two.
    (when (rl/key-down? :right) (set (.x ball) (+ (.x ball) 2.0)))
    (when (rl/key-down? :left)  (set (.x ball) (- (.x ball) 2.0)))
    (when (rl/key-down? :up)    (set (.y ball) (- (.y ball) 2.0)))
    (when (rl/key-down? :down)  (set (.y ball) (+ (.y ball) 2.0)))

    ;; Draw
    (rl/begin-drawing)
    (rl/clear-background rl/raywhite)
    (rl/draw-text "move the ball with arrow keys" 10 10 20 rl/darkgray)
    (rl/draw-circle-v ball 50.0 rl/maroon)
    (rl/end-drawing)))