(import scheme
        (chicken base)
        (chicken random)
        (only srfi-1 filter any)
        (only srfi-197 chain)
        (prefix sdl2 "sdl2:")
        (prefix sdl2-ttf "ttf:")
        (prefix sdl2-image "img:")
        downstroke-engine
        downstroke-world
        downstroke-physics
        downstroke-input
        downstroke-entity
        downstroke-assets
        downstroke-sound)

;; ── Constants ────────────────────────────────────────────────────────────────

(define +screen-width+  600)
(define +screen-height+ 400)
(define +spawn-interval+ 60)

;; ── State ────────────────────────────────────────────────────────────────────

(define *frame-count* 0)

;; ── Entity factories ─────────────────────────────────────────────────────────

(define (make-player)
  (list #:type 'player #:x 280 #:y 360
        #:width 16 #:height 16 #:vx 0 #:vy 0))

(define (make-bullet x y)
  (list #:type 'bullet #:x x #:y y
        #:width 4 #:height 8 #:vx 0 #:vy -6))

(define (make-enemy x)
  (list #:type 'enemy #:x x #:y 0
        #:width 16 #:height 16 #:vx 0 #:vy 2))

;; ── Collision ────────────────────────────────────────────────────────────────

(define (entities-overlap? a b)
  (aabb-overlap?
    (entity-ref a #:x 0) (entity-ref a #:y 0)
    (entity-ref a #:width 0) (entity-ref a #:height 0)
    (entity-ref b #:x 0) (entity-ref b #:y 0)
    (entity-ref b #:width 0) (entity-ref b #:height 0)))

(define (find-dead entities)
  (let ((bullets (filter (lambda (e) (eq? (entity-type e) 'bullet)) entities))
        (enemies (filter (lambda (e) (eq? (entity-type e) 'enemy))  entities)))
    (filter (lambda (e)
              (case (entity-type e)
                ((bullet) (any (lambda (en) (entities-overlap? e en)) enemies))
                ((enemy)  (any (lambda (b)  (entities-overlap? e b))  bullets))
                (else #f)))
            entities)))

(define (in-bounds? e)
  (let ((y (entity-ref e #:y 0)))
    (and (> y -20) (< y (+ +screen-height+ 20)))))

;; ── Update helpers ───────────────────────────────────────────────────────────

(define (player-vx input)
  (cond ((input-held? input 'left)  -4)
        ((input-held? input 'right)  4)
        (else 0)))

(define (clamp-player-x player)
  (entity-set player #:x
    (max 0 (min (- +screen-width+ 16) (entity-ref player #:x 0)))))

(define (update-player player input scene)
  (let ((updated (chain player
                        (entity-set _ #:vx (player-vx input))
                        (apply-velocity-x _)
                        (clamp-player-x _))))
    (when (input-pressed? input 'a)
      (play-sound 'shoot)
      (scene-add-entity scene
        (make-bullet (+ (entity-ref updated #:x 0) 6) 340)))
    updated))

(define (move-projectile e)
  (chain e
         (entity-set _ #:x (+ (entity-ref e #:x 0) (entity-ref e #:vx 0)))
         (entity-set _ #:y (+ (entity-ref e #:y 0) (entity-ref e #:vy 0)))))

(define (maybe-spawn-enemy! scene)
  (when (zero? (modulo *frame-count* +spawn-interval+))
    (scene-add-entity scene
      (make-enemy (+ 20 (* (pseudo-random-integer 28) 20))))))

;; ── Render ───────────────────────────────────────────────────────────────────

(define (entity-color type)
  (case type
    ((player) (sdl2:make-color 255 255 255 255))
    ((bullet) (sdl2:make-color 255 255   0 255))
    ((enemy)  (sdl2:make-color 255  50  50 255))
    (else     (sdl2:make-color 100 100 100 255))))

(define (draw-shmup-entity renderer e)
  (let ((x (inexact->exact (floor (entity-ref e #:x 0))))
        (y (inexact->exact (floor (entity-ref e #:y 0))))
        (w (entity-ref e #:width 16))
        (h (entity-ref e #:height 16)))
    (set! (sdl2:render-draw-color renderer) (entity-color (entity-type e)))
    (sdl2:render-fill-rect! renderer (sdl2:make-rect x y w h))))

;; ── Game ─────────────────────────────────────────────────────────────────────

(define *game*
  (make-game
    title: "Demo: Shoot-em-up"
    width: +screen-width+ height: +screen-height+

    preload: (lambda (game)
      (init-audio!)
      (load-sounds! '((shoot . "demo/assets/jump.wav"))))

    create: (lambda (game)
      (game-scene-set! game
        (make-scene
          entities:        (list (make-player))
          tilemap:         #f
          camera:          (make-camera x: 0 y: 0)
          tileset-texture: #f
          camera-target:   #f)))

    update: (lambda (game dt)
      (set! *frame-count* (+ *frame-count* 1))
      (let* ((input  (game-input game))
             (scene  (game-scene game))
             (player (car (scene-entities scene)))
             (player (update-player player input scene)))
        (maybe-spawn-enemy! scene)
        ;; Replace player, then move all projectiles
        (scene-entities-set! scene
          (cons player (filter (lambda (e) (not (eq? (entity-type e) 'player)))
                               (scene-entities scene))))
        (scene-update-entities scene
          (lambda (e) (if (eq? (entity-type e) 'player) e (move-projectile e))))
        ;; Remove bullet/enemy collisions, then out-of-bounds
        (let ((dead (find-dead (scene-entities scene))))
          (scene-filter-entities scene (lambda (e) (not (memq e dead)))))
        (scene-filter-entities scene
          (lambda (e) (or (eq? (entity-type e) 'player) (in-bounds? e))))))

    render: (lambda (game)
      (for-each (cut draw-shmup-entity (game-renderer game) <>)
                (scene-entities (game-scene game))))))

(game-run! *game*)