Treat T&B hexes as equiv to underlying terrain

src/logic/shuffle.ts

@@ -1,8 +1,15 @@
-import { Hex, HexType, Port, PortOrientation, FishTile } from "../types/hexes";
+import {
+  Hex,
+  HexType,
+  Port,
+  PortOrientation,
+  FishTile,
+  FishTileOrientation,
+} from "../types/hexes";
 import { BinaryConstraints, NumericConstraints } from "../types/constraints";
 import { CatanBoard, Neighbors } from "../types/boards";
 import { HexGroups } from "./HexGroups";
-import { hexToPipCount } from "../utils/catan";
+import { compareHexType, hexToPipCount } from "../utils/catan";
 
 // structuredClone isn't available on older devices. use this as a polyfill
 if (typeof globalThis.structuredClone === "undefined") {
@@ -142,7 +149,7 @@ function getShuffledTerrain(
               // will still be shuffled, unless the lower neighbor is fixed
               if (
                 (neighbor > currentIndex || hexes[neighbor].fixed) &&
-                hexes[currentIndex].type === hexes[neighbor].type
+                compareHexType(hexes[currentIndex], hexes[neighbor])
               )
                 stack.push(neighbor);
             }

src/tests/utils.test.ts

@@ -1,4 +1,8 @@
-import { hexToPipCount, numberToPipCount } from "../utils/catan";
+import {
+  compareHexType,
+  hexToPipCount,
+  numberToPipCount,
+} from "../utils/catan";
 
 describe("Catan utils", () => {
   it("should return the correct number of pips for every valid number", () => {
@@ -25,4 +29,39 @@ describe("Catan utils", () => {
       hexToPipCount({ type: "mountains", number: 10, secondNumber: 10 })
     ).toBe(6);
   });
+
+  it("should correctly compare all hex type pairs", () => {
+    expect(
+      compareHexType({ type: "mountains" }, { type: "riverMountains" })
+    ).toBe(true);
+    expect(
+      compareHexType({ type: "riverMountains" }, { type: "riverMountains" })
+    ).toBe(true);
+    expect(compareHexType({ type: "hills" }, { type: "riverHills" })).toBe(
+      true
+    );
+    expect(compareHexType({ type: "riverHills" }, { type: "riverHills" })).toBe(
+      true
+    );
+    expect(compareHexType({ type: "pasture" }, { type: "riverPasture" })).toBe(
+      true
+    );
+    expect(
+      compareHexType({ type: "riverPasture" }, { type: "riverPasture" })
+    ).toBe(true);
+    expect(compareHexType({ type: "desert" }, { type: "oasis" })).toBe(true);
+    expect(
+      compareHexType({ type: "mountains" }, { type: "riverPasture" })
+    ).toBe(false);
+    expect(compareHexType({ type: "mountains" }, { type: "riverHills" })).toBe(
+      false
+    );
+    expect(compareHexType({ type: "hills" }, { type: "riverMountains" })).toBe(
+      false
+    );
+    expect(
+      compareHexType({ type: "pasture" }, { type: "riverMountains" })
+    ).toBe(false);
+    expect(compareHexType({ type: "fields" }, { type: "fields" })).toBe(true);
+  });
 });

src/utils/catan.ts

@@ -1,4 +1,4 @@
-import { NumberChitValue, Hex } from "../types/hexes";
+import { NumberChitValue, Hex, HexType } from "../types/hexes";
 
 /**
  * Given a valid `NumberChitValue` `num`, return the number of pips that appear
@@ -21,3 +21,21 @@ export function hexToPipCount(hex: Hex): number {
     res += numberToPipCount(hex.secondNumber!);
   return res;
 }
+
+/**
+ * Return `true` if `h1` and `h2` are the same terrain type and `false`
+ * otherwise. With the introduction of river hexes and the oasis from Traders &
+ * Barbarians, it is no longer sufficient to compare `Hex.type` directly
+ */
+export function compareHexType(h1: Hex, h2: Hex): boolean {
+  const mapping: Partial<Record<HexType, HexType>> = {
+    riverHills: "hills",
+    riverMountains: "mountains",
+    riverPasture: "pasture",
+    oasis: "desert",
+  };
+  let [t1, t2] = [h1.type, h2.type];
+  if (t1 in mapping) t1 = mapping[t1]!;
+  if (t2 in mapping) t2 = mapping[t2]!;
+  return t1 === t2;
+}