;;;; raylib [core] example - 2d camera
;;;;
;;;; examples/core/core_2d_camera.c. Needed no new binding at all, which is
;;;; the reason to port it: Camera2D, begin-mode-2d and end-mode-2d have been
;;;; in vendor/raylib/raylib.flan since the beginning and nothing in the
;;;; corpus had ever passed a whole Camera2D across the FFI on a frame's path.
;;;; Two Vector2s, a float and a float, by value, sixty times a second — the
;;;; acceptance table pins that layout with get-screen-to-world-2d, and this
;;;; is the same struct going into the call that actually draws with it.
;;;;
;;;; The hundred buildings are a `defvar` of fixed arrays rather than a Vec:
;;;; a global cannot hold a Vec (PORTING.md §3) and does not need to here,
;;;; because the count is a constant in the C too. `(array n T)` is the zeroed
;;;; fixed array, and the C's `= { 0 }` is exactly that.
;;;;
;;;; get-random-value comes from the generated half of the bindings. It is on
;;;; no frame's path — it runs once, before the loop — and its Flan face is
;;;; the C one, so PORTING.md §1's rule does not reach it.
;;;;
;;;; One deliberate difference from the C: `(- camera.rotation 1.0)` and the
;;;; clamp after it are written with the prelude's `clamp` macro rather than
;;;; two ifs. It is the same arithmetic; the C spells it out because C has no
;;;; clamp.

(import rl "vendor:raylib")

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

(defconst max-buildings 100)

(defvar buildings     [100 rl/Rectangle])
(defvar build-colors  [100 rl/Color])
(defvar player        rl/Rectangle)
(defvar camera        rl/Camera2D)

(defn main [] ()
  (rl/init-window screen-width screen-height
                  "raylib [core] example - 2d camera")
  (defer (rl/close-window))

  (set player (rl/Rectangle {.x 400.0 .y 280.0 .width 40.0 .height 40.0}))
  (set buildings (array max-buildings rl/Rectangle))
  (set build-colors (array max-buildings rl/Color))

  ;; The skyline: each building is as wide as the last one left room for, so
  ;; the spacing accumulates and the row starts 6000 units to the left.
  (let [spacing 0]
    (dotimes [i max-buildings]
      (let [w (f32 (rl/get-random-value 50 200))
            h (f32 (rl/get-random-value 100 800))]
        (set (at buildings i)
             (rl/Rectangle {.x (+ -6000.0 (f32 spacing))
                            .y (- (- (f32 screen-height) 130.0) h)
                            .width w
                            .height h}))
        (set spacing (+ spacing (i32 w)))
        (set (at build-colors i)
             (rl/Color {.r (u8 (rl/get-random-value 200 240))
                        .g (u8 (rl/get-random-value 200 240))
                        .b (u8 (rl/get-random-value 200 250))
                        .a 255})))))

  ;; A fresh Camera2D is all zeroes and a zoom of 0 makes the transform
  ;; singular, so the zoom is the one field that must be set — raylib.flan's
  ;; own comment on the struct says so.
  (set camera (rl/Camera2D {.offset (rl/Vector2 {.x (/ (f32 screen-width) 2.0)
                                                 .y (/ (f32 screen-height) 2.0)})
                            .target (rl/Vector2 {.x (+ (.x player) 20.0)
                                                 .y (+ (.y player) 20.0)})
                            .rotation 0.0
                            .zoom 1.0}))

  (rl/set-target-fps 60)

  (until (rl/window-should-close?)
    ;; Update
    ;; The C's `if (RIGHT) ... else if (LEFT) ...`: both held cancels to the
    ;; right, which is the else-if and not an accident.
    (if (rl/key-down? :right)
      (set (.x player) (+ (.x player) 2.0))
      (when (rl/key-down? :left) (set (.x player) (- (.x player) 2.0))))

    ;; The camera follows the player's centre.
    (set (.target camera) (rl/Vector2 {.x (+ (.x player) 20.0)
                                       .y (+ (.y player) 20.0)}))

    (if (rl/key-down? :a)
      (set (.rotation camera) (- (.rotation camera) 1.0))
      (when (rl/key-down? :s)
        (set (.rotation camera) (+ (.rotation camera) 1.0))))
    (set (.rotation camera) (clamp (.rotation camera) -40.0 40.0))

    (set (.zoom camera) (+ (.zoom camera) (* (rl/get-mouse-wheel-move) 0.05)))
    (set (.zoom camera) (clamp (.zoom camera) 0.1 3.0))

    (when (rl/key-pressed? :r)
      (set (.zoom camera) 1.0)
      (set (.rotation camera) 0.0))

    ;; Draw
    (rl/begin-drawing)
    (rl/clear-background rl/raywhite)

    ;; Everything between these two is in world space and goes through the
    ;; camera. The ground and the crosshair lines are drawn far outside the
    ;; window on purpose: at zoom 0.1 they still have to reach the edges.
    (rl/begin-mode-2d camera)

    (rl/draw-rectangle -6000 320 13000 8000 rl/darkgray)

    (dotimes [i max-buildings]
      (rl/draw-rectangle-rec (at buildings i) (at build-colors i)))

    (rl/draw-rectangle-rec player rl/red)

    (rl/draw-line (i32 (.x (.target camera))) (* screen-height -10)
                  (i32 (.x (.target camera))) (* screen-height 10) rl/green)
    (rl/draw-line (* screen-width -10) (i32 (.y (.target camera)))
                  (* screen-width 10) (i32 (.y (.target camera))) rl/green)

    (rl/end-mode-2d)

    ;; And everything after it is in screen space again — the frame drawn
    ;; around the window is how the example shows the difference.
    (rl/draw-text "SCREEN AREA" 640 10 20 rl/red)

    (rl/draw-rectangle 0 0 screen-width 5 rl/red)
    (rl/draw-rectangle 0 5 5 (- screen-height 10) rl/red)
    (rl/draw-rectangle (- screen-width 5) 5 5 (- screen-height 10) rl/red)
    (rl/draw-rectangle 0 (- screen-height 5) screen-width 5 rl/red)

    (rl/draw-rectangle 10 10 250 113 (rl/fade rl/skyblue 0.5))
    (rl/draw-rectangle-lines 10 10 250 113 rl/blue)

    (rl/draw-text "Free 2d camera controls:" 20 20 10 rl/black)
    (rl/draw-text "- Right/Left to move Offset" 40 40 10 rl/darkgray)
    (rl/draw-text "- Mouse Wheel to Zoom in-out" 40 60 10 rl/darkgray)
    (rl/draw-text "- A / S to Rotate" 40 80 10 rl/darkgray)
    (rl/draw-text "- R to reset Zoom and Rotation" 40 100 10 rl/darkgray)

    (rl/end-drawing)))