;;;; 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 `once` 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.
;;;;
;;;; `ball.x = ...` works on a struct field of a global: a field of an
;;;; assignable place is itself one.

import rl "vendor:raylib"

const screen-width = 800
const screen-height = 450

once ball: rl/Vector2

fn main() -> ()
  rl/init-window(screen-width, screen-height,
                 "raylib [core] example - input keys")
  defer rl/close-window()
  ball = rl/Vector2{.x f32(screen-width / 2) .y f32(screen-height / 2)}
  rl/set-target-fps(60)
  until rl/window-should-close()
    ;; Update. is-key-down and not is-key-pressed: this is meant to repeat for as
    ;; long as the key is held, which is the whole difference between the two.
    if rl/is-key-down(:key-right)
      ball.x += 2.0
    if rl/is-key-down(:key-left)
      ball.x -= 2.0
    if rl/is-key-down(:key-up)
      ball.y -= 2.0
    if rl/is-key-down(:key-down)
      ball.y += 2.0
    ;; Draw
    rl/with-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)