Add electron warp terminals.

modules/game/actors.scm

@@ -13,6 +13,7 @@
             ^xor-gate
             ^or-gate
             ^electric-switch
+            ^electron-warp
             ^player
             ^level))
 
@@ -31,9 +32,6 @@
     ((new-val)
      (bcom (^cell bcom new-val)))))
 
-;; TODO: Add layer info to 'describe' output for sorting sprites when
-;; rendering.
-
 ;; TODO: Port actor-lib methods and use it.
 (define (^exit bcom x y)
   (define position (vector x y 1))
@@ -211,6 +209,47 @@
     (('describe) `(electric-switch ,position ,($ on?)))
     (('collide other offset grid-info) #f)))
 
+(define (^electron-warp bcom x y target-x target-y)
+  (define position (vector x y 0))
+  (define state (spawn ^cell 'copper))
+  (define electron? (spawn ^cell))
+  (define (find-receiver grid-info)
+    (let lp ((objs ($ grid-info 'occupants target-x target-y)))
+      (match objs
+        (() (error "no electron receiver at tile" target-x target-y))
+        ((obj . rest)
+         (if (eq? ($ obj 'type) 'electron-warp)
+             obj
+             (lp rest))))))
+  (match-lambda*
+    (('type) 'electron-warp)
+    (('position) position)
+    (('tick grid-info) #f)
+    (('post-tick grid-info) #f)
+    (('enter obj grid-info) #f)
+    (('exit obj grid-info) #f)
+    (('wire-state grid-info) ($ state))
+    (('update-wire-state grid-info)
+     (match ($ state)
+       ('electron-head ($ state 'electron-tail))
+       ('electron-tail ($ state 'copper))
+       ('copper
+        (if ($ electron?)
+            (begin
+              ($ state 'electron-head)
+              ($ electron? #f))
+            (let ((neighbors ($ grid-info 'wireworld-neighbor-count x y)))
+              (if (<= 1 neighbors 2)
+                  (begin
+                    ($ state 'electron-head)
+                    ;; Forward an electron head to the receiver.
+                    ($ (find-receiver grid-info) 'give-electron))
+                  ($ state 'copper)))))))
+    (('give-electron) ($ electron? #t))
+    (('alive?) #t)
+    (('describe) `(electron-warp ,position ,($ state)))
+    (('collide other offset grid-info) #f)))
+
 (define (^gem bcom x y)
   (define position (vector x y 1))
   (define picked-up? (spawn ^cell))
@@ -403,7 +442,6 @@
     (('enter obj grid-info) #f)
     (('exit obj grid-info) #f)
     (('wire-state grid-info) #f)
-    (('update-wire-state grid-info) #f)
     (('alive?) ($ alive?))
     (('describe) `(player ,($ position)))
     (('collide other offset grid-info)
@@ -468,7 +506,9 @@
          (match ($ obj-cell)
            (() #f)
            ;; TODO: Handle tiles with many occupants.  Might not be
-           ;; necessary in practice.
+           ;; necessary in practice.  Actually this *WILL* cause
+           ;; problems for electron warps, at least, since they are
+           ;; invisible and the player can stand over them.
            ((refr . _)
             ($ wire-cell ($ refr 'wire-state grid-info))))))))
   (define (wire-state-at x y)