From 66fcd6a3cf7d26be1440586470af09d2064ea040 Mon Sep 17 00:00:00 2001
From: Jeremy Penner <jeremy@sporktania.com>
Date: Tue, 13 Apr 2021 19:56:23 -0400
Subject: [PATCH] Pacman movement! Basically.

---
 game/entities/pacman.fnl | 68 +++++++++++++++++++++++++++++++++++-----
 game/helpers.fnl         | 10 ++++--
 2 files changed, 68 insertions(+), 10 deletions(-)

diff --git a/game/entities/pacman.fnl b/game/entities/pacman.fnl
index 71c2f84..b411ee6 100644
--- a/game/entities/pacman.fnl
+++ b/game/entities/pacman.fnl
@@ -2,7 +2,7 @@
 (local dim (require :game.dim))
 (local {: defmethod} (util.require :lib.multimethod))
 (local {: direct : draw : update} (util.require :game.entity))
-(local {: vec*} (util.require :game.helpers))
+(local {: vec* : vec+ : edge : edge-crosses} (util.require :game.helpers))
 (local map (require :game.tilemap))
 
 (local pacman (util.hot-table ...))
@@ -37,13 +37,67 @@
 ; their edges filed off!)
 ; I think Bomberman actually does this too
 
-(defmethod update :pacman (fn [entity dt rules]
+(fn tile-at [x y rules]
+  (-?> [x y]
+    (map.world-to-tile)
+    (rules.tile-at)))
+
+(fn collides? [[x y] rules]
+  (let [tile (tile-at x y rules)]
+    (and tile (or tile.bomb tile.wall))))
+
+(fn horizontal [c copp] [c copp])
+(fn vertical   [c copp] [copp c])
+(fn perp-move? [dprev doppnext] (and (not= dprev 0) (not= doppnext 0)))
+(fn try-perp-turn [entity d make-xy rules]
+  (let [[c copp] (make-xy (table.unpack entity.pos))
+        posperp (vec+ entity.pos (make-xy (if (> d 0) dim.tilesize (- dim.tilesize)) 0))
+        [xcenter ycenter] (vec+ (vec* (map.world-to-tile posperp) dim.tilesize) dim.halftile)
+        [ccenter coppcenter] (make-xy xcenter ycenter)
+        turn-allowed? (and (> copp (- coppcenter (/ dim.tilesize 4)))
+                           (< copp (+ coppcenter (/ dim.tilesize 4))))]
+    (when (and turn-allowed? (not (collides? posperp rules)))
+      (set entity.vel (make-xy d 0))
+      (set entity.opp-target coppcenter))))
+
+(fn rev-move? [dprev dprevopp dnext]
+       ; currently moving on this axis or not moving at all
+  (and (or (not= dprev 0) (and (= dprev 0) (= dprevopp 0)))
+       ; attempting to move in a new direction
+       (not= dnext 0) (not= dprev dnext)))
+
+(fn update-direction [entity rules]
   (let [[dx dy] entity.vel
-        [dxkey dykey] (direct pacman.keymap (* dim.tilesize 4))
-        turn-attempted (and (or (not= dxkey 0) (not= dykey 0))
-                            (or (not= dxkey dx) (not= dykey dy)))]
-    (when turn-attempted
-      (set entity.vel [dxkey dykey])))))
+        [dxkey dykey] (direct pacman.keymap (* dim.tilesize 4))]
+        ; two possible movement cases:
+        ; 1. Pacman wants to change direction perpendicular to how he is currently moving
+        ; 2. Pacman wants to change direction on the axis he is currently moving on
+        ; Case 1 takes priority over case 2
+    (if (perp-move? dy dxkey) (try-perp-turn entity dxkey horizontal rules)
+        (perp-move? dx dykey) (try-perp-turn entity dykey vertical rules)
+        (rev-move? dx dy dxkey) (set entity.vel [dxkey 0])
+        (rev-move? dy dx dykey) (set entity.vel [0 dykey]))))
+
+(fn move [entity dt rules]
+  (let [[dx dy] (vec* entity.vel dt)
+        make-xy (if (= dy 0) horizontal vertical)
+        [c copp] (make-xy (table.unpack entity.pos))
+        [dc _] (make-xy dx dy)
+        (edge-prev edge-next) (edge c dc dim.halftile)
+        (crosses? edge-snap) (edge-crosses edge-prev edge-next dim.tilesize)
+        _ (print edge-prev edge-next edge-snap)
+        cnext (if (and crosses? (collides? (make-xy edge-next copp) rules))
+                (+ c (- edge-snap edge-prev))
+                (+ c dc))
+        dcopp (if (= entity.opp-target nil) 0
+                (-> (- entity.opp-target copp)
+                  (math.min (* dt dim.tilesize 4))
+                  (math.max (* dt dim.tilesize -4))))]
+    (set entity.pos (make-xy cnext (+ copp dcopp)))))
+
+(defmethod update :pacman (fn [entity dt rules]
+  (update-direction entity rules)
+  (move entity dt rules)))
 
 (fn pacman.new [pos]
   {: pos :vel [0 0] :entity :pacman})
diff --git a/game/helpers.fnl b/game/helpers.fnl
index 7e902c3..622d1ce 100644
--- a/game/helpers.fnl
+++ b/game/helpers.fnl
@@ -39,8 +39,12 @@
     (values (+ c pos-offset) (+ c dc pos-offset))))
 
 (fn edge-crosses [c1 c2 width]
-  (if (= c1 c2) false
-      (or (= (% c1 width) 0) (= (% c2 width) 0)) true
-    (not= (math.floor (/ c1 width)) (math.floor (/ c2 width)))))
+  (let [t1 (math.floor (/ c1 width))
+        t2 (math.floor (/ c2 width))]
+    (if (= c1 c2) false
+        (= (% c1 width) 0) (values true c1)
+        (= (% c2 width) 0) (values true c2)
+        (not= t1 t2)       (values true (* (math.max t1 t2) width))
+      false)))
 
 {: dir-from-key : vec* : vec+ : vec-op : all-coordinates : edge : edge-crosses}