feat: add engine.scm — game struct, make-game constructor, convenience accessors

1 files changed, 78 insertions, 0 deletions

diff --git a/engine.scm b/engine.scm
new file mode 100644
index 0000000..5526e6c
--- /dev/null
+++ b/engine.scm
@@ -0,0 +1,78 @@
+(module downstroke/engine *
+
+(import scheme
+        (chicken base)
+        (chicken keyword)
+        (prefix sdl2 "sdl2:")
+        (prefix sdl2-ttf "ttf:")
+        (prefix sdl2-image "img:")
+        defstruct
+        downstroke/world
+        downstroke/input
+        downstroke/assets
+        downstroke/renderer)
+
+;; ── Game struct ────────────────────────────────────────────────────────────
+;; defstruct auto-generates make-game, which we'll wrap with default values
+
+(defstruct game
+  title width height
+  window renderer
+  input          ;; input-state record
+  input-config   ;; input-config record
+  assets         ;; asset registry (hash-table from assets.scm)
+  frame-delay
+  preload-hook   ;; (lambda (game) ...)
+  create-hook    ;; (lambda (game) ...)
+  update-hook    ;; (lambda (game dt) ...)
+  render-hook    ;; (lambda (game) ...) — post-render overlay
+  scene)         ;; current scene struct; #f until create: runs
+
+;; Store the auto-generated constructor
+(define make-game-raw make-game)
+
+;; ── Public constructor wrapper ─────────────────────────────────────────────
+
+(define (make-game #!key
+    (title "Downstroke Game")
+    (width 640) (height 480)
+    (frame-delay 16)
+    (input-config *default-input-config*)
+    (preload #f) (create #f) (update #f) (render #f))
+  (make-game-raw
+    title:        title
+    width:        width
+    height:       height
+    window:       #f
+    renderer:     #f
+    scene:        #f
+    input:        (create-input-state input-config)
+    input-config: input-config
+    assets:       (make-asset-registry)
+    frame-delay:  frame-delay
+    preload-hook: preload
+    create-hook:  create
+    update-hook:  update
+    render-hook:  render))
+
+;; ── Convenience accessors ──────────────────────────────────────────────────
+
+;; game-camera: derived from the current scene (only valid after create: runs)
+(define (game-camera game)
+  (scene-camera (game-scene game)))
+
+;; game-asset: retrieve an asset by key
+(define (game-asset game key)
+  (asset-ref (game-assets game) key))
+
+;; game-asset-set!: store an asset by key
+(define (game-asset-set! game key value)
+  (asset-set! (game-assets game) key value))
+
+;; ── game-run! ──────────────────────────────────────────────────────────────
+;; Stub — implemented in Task 4
+
+(define (game-run! game)
+  (error "game-run! not yet implemented"))
+
+) ;; end module