structure placement order (#1833)

It is more intuitive in scenario design for "later" things to be placed "on top of" earlier things.

There were only a small number of scenarios for which placement order was relevant, so I fixed them.

data/scenarios/Testing/1138-structures/sibling-precedence.yaml

@@ -68,11 +68,11 @@ world:
           xx
           xx
   placements:
-    - src: tiny rectangle
-    - src: small rectangle
-    - src: medium rectangle
-    - src: big rectangle
     - src: huge rectangle
+    - src: big rectangle
+    - src: medium rectangle
+    - src: small rectangle
+    - src: tiny rectangle
   map: |
     ............
     ............

data/scenarios/Testing/1356-portals/portals-and-waypoints.yaml

@@ -10,6 +10,7 @@ attrs:
   - name: portal_out
     fg: "#00a2ff"
     bg: "#0065ff"
+solution: turn left; move; move; turn left; move; move; move; turn left; move; move; move; move; move;
 entities:
   - name: telepad entrance
     display:

data/scenarios/Testing/1575-structure-recognizer/1575-placement-occlusion.yaml

@@ -67,8 +67,6 @@ world:
     'B': [grass, null, base]
   upperleft: [-97, 17]
   placements:
-    - src: green_jewel
-      offset: [3, -3]
     - src: red_jewel
       offset: [1, -1]
     - src: red_jewel
@@ -77,6 +75,8 @@ world:
       offset: [5, -1]
     - src: red_jewel
       offset: [5, -5]
+    - src: green_jewel
+      offset: [3, -3]
   map: |
     .........
     .........

data/scenarios/Vignettes/roadway.yaml

@@ -89,14 +89,6 @@ world:
           SSSSSS
           SSSSSS
   placements:
-    - src: tunnel
-      offset: [3, -21]
-      orient:
-        up: west
-    - src: tunnel
-      offset: [71, -21]
-      orient:
-        up: east
     - src: road segment
       offset: [6, -22]
       orient:
@@ -161,6 +153,14 @@ world:
       orient:
         up: west
         flip: true
+    - src: tunnel
+      offset: [3, -21]
+      orient:
+        up: west
+    - src: tunnel
+      offset: [71, -21]
+      orient:
+        up: east
   upperleft:
     - -18
     - 30

src/swarm-scenario/Swarm/Game/Scenario/Topography/Structure/Assembly.hs

@@ -15,7 +15,7 @@ import Control.Arrow (left, (&&&))
 import Control.Monad (when)
 import Data.Coerce
 import Data.Either.Extra (maybeToEither)
-import Data.Foldable (foldrM)
+import Data.Foldable (foldlM)
 import Data.Map qualified as M
 import Data.Set qualified as Set
 import Data.Text (Text)
@@ -53,8 +53,8 @@ overlaySingleStructure
       offsetLoc (coerce loc)
         . modifyLoc (reorientLandmark orientation $ getGridDimensions overArea)
 
--- | Overlays all of the "child placements", such that the children encountered earlier
--- in the YAML file supersede the later ones (due to use of 'foldr' instead of 'foldl').
+-- | Overlays all of the "child placements", such that the children encountered later
+-- in the YAML file supersede the earlier ones (dictated by using 'foldl' instead of 'foldr').
 mergeStructures ::
   M.Map StructureName (NamedStructure (Maybe a)) ->
   Parentage Placement ->
@@ -77,8 +77,8 @@ mergeStructures inheritedStrucDefs parentPlacement (Structure origArea subStruct
         map wrapPlacement $
           filter (\(Placed _ ns) -> isRecognizable ns) overlays
 
-  foldrM
-    (overlaySingleStructure structureMap)
+  foldlM
+    (flip $ overlaySingleStructure structureMap)
     (MergedStructure origArea wrappedOverlays originatedWaypoints)
     overlays
  where