(use-modules (chickadee)
             (chickadee math vector)
             (chickadee math rect)
             (chickadee graphics color)
             (chickadee graphics font)
             (chickadee graphics tiled)
             (ice-9 format)
             (ice-9 match)
             (srfi srfi-11))

(define map #f)
(define prev-camera (vec2 0.0 0.0))
(define camera (vec2 0.0 0.0))
(define render-camera (vec2 0.0 0.0))
(define text-position (vec2 4.0 4.0))
(define text "0, 0")
(define (stats-message)
  (format #f "fps: ~1,2f"
          (/ 1.0 avg-frame-time)))
(define start-time 0.0)
(define avg-frame-time 16)
(define stats-text (stats-message))
(define stats-text-pos (vec2 4.0 464.0))
(define last-update start-time)
(define scroll-speed 6.0)

(define (load)
  (set! map (load-tile-map "maps/example.tmx")))

(define (draw alpha)
  ;; Linearly interpolate between the current camera position and the
  ;; previous camera position based on the alpha value.  This makes
  ;; the scrolling appear much smoother because the Chickadee game
  ;; loop does not render in lock-step with updates.
  (let ((beta (- 1.0 alpha)))
    (set-vec2-x! render-camera
                 (+ (* (vec2-x camera) alpha)
                    (* (vec2-x prev-camera) beta)))
    (set-vec2-y! render-camera
                 (+ (* (vec2-y camera) alpha)
                    (* (vec2-y prev-camera) beta))))
  (draw-tile-map map #:camera render-camera)
  (draw-text text text-position #:color black)
  (draw-text stats-text stats-text-pos #:color black)
  (let ((current-time (elapsed-time)))
    (set! avg-frame-time
          (+ (* (- current-time start-time) 0.1)
             (* avg-frame-time 0.9)))
    (set! start-time current-time)
    (when (>= (- current-time last-update) 1000)
      (set! stats-text (stats-message))
      (set! last-update current-time))))

(define (update dt)
  (vec2-copy! camera prev-camera)
  (set-vec2-x! camera
               (+ (vec2-x camera)
                  (if (key-pressed? 'right) scroll-speed 0.0)
                  (if (key-pressed? 'left) (- scroll-speed) 0.0)))
  (set-vec2-y! camera
               (+ (vec2-y camera)
                  (if (key-pressed? 'up) scroll-speed 0.0)
                  (if (key-pressed? 'down) (- scroll-speed) 0.0))))

(define (key-press key modifiers repeat?)
  (match key
    ((or 'escape 'q) (abort-game))
    (_ #t)))

(define (mouse-move x y x-rel y-rel buttons)
  (let-values (((tx ty) (point->tile map (- x (vec2-x camera)) (- y (vec2-y camera)))))
    (set! text (format #f "~d, ~d" tx ty))))

(run-game #:window-width 640
          #:window-height 480
          #:window-title "tile map demo"
          #:load load
          #:draw draw
          #:update update
          #:key-press key-press
          #:mouse-move mouse-move)