Factor out generators

island/generators.ts

@@ -0,0 +1,74 @@
+import { BEACH, ICECAP, LIGHT_FOREST, MOUNTAIN, WATER } from "./data";
+import { IslandGrid } from "./grid";
+
+export type IsDone = boolean;
+export type LobeGenerator = () => IsDone;
+export type LobeGeneratorConstructor = (
+  islands: IslandGrid,
+  basePos: number
+) => LobeGenerator;
+
+/** form mountain with icecap */
+export const BIG_MOUNTAIN: LobeGeneratorConstructor =
+  (islands: IslandGrid, basePos: number) => () => {
+    const mountainTiles = islands.floodSearch(
+      basePos,
+      (tile) => tile > MOUNTAIN
+    );
+    islands.dropWithin(mountainTiles);
+
+    return mountainTiles.some((pos) => islands.data[pos] == ICECAP);
+  };
+
+/** form low-lying beach */
+export const BEACH_LOBE: LobeGeneratorConstructor =
+  (islands: IslandGrid, basePos: number) => () => {
+    const islandTiles = islands.floodSearch(basePos, (tile) => tile > WATER);
+
+    const shoreTiles = islandTiles.filter((pos) => islands.data[pos] == WATER);
+    islands.dropWithin(shoreTiles);
+
+    return true;
+  };
+
+/** form forested zone */
+export const FOREST_LOBE: LobeGeneratorConstructor =
+  (islands: IslandGrid, basePos: number) => () => {
+    const islandTiles = islands.floodSearch(basePos, (tile) => tile > WATER);
+
+    // grow shore
+    const shoreTiles = islandTiles.filter((pos) => islands.data[pos] == WATER);
+    islands.dropWithin(shoreTiles);
+
+    // seed beach
+    const beachTiles = islandTiles.filter((pos) => islands.data[pos] == BEACH);
+    islands.dropWithin(beachTiles);
+
+    // expand forest
+    const forestLobe = islands.floodSearch(basePos, (tile) => tile > BEACH);
+    const forestTiles = forestLobe.filter(
+      (pos) => islands.data[pos] == LIGHT_FOREST
+    );
+    islands.dropWithin(forestTiles);
+    islands.dropWithin(forestTiles);
+    islands.dropWithin(forestTiles);
+
+    return true;
+  };
+
+/** form low-lying beach with eroded sections */
+export const ERODED_LOBE: LobeGeneratorConstructor =
+  (islands: IslandGrid, basePos: number) => () => {
+    const islandTiles = islands.floodSearch(basePos, (tile) => tile > WATER);
+
+    const shoreTiles = islandTiles.filter((pos) => islands.data[pos] == WATER);
+    islands.dropWithin(shoreTiles);
+
+    // erode
+    if (islandTiles.length > 1) {
+      const erodePos = islandTiles[islands.rng() % islandTiles.length];
+      islands.data[erodePos] = Math.max(islands.data[erodePos] - 1, WATER);
+    }
+
+    return true;
+  };

island/grid.ts

@@ -1,13 +1,17 @@
 import { Prng, mulberry32 } from "../lib/prng";
 import { BEACH, ICECAP, LIGHT_FOREST, MOUNTAIN, WATER } from "./data";
+import {
+  BEACH_LOBE,
+  BIG_MOUNTAIN,
+  FOREST_LOBE,
+  LobeGenerator,
+} from "./generators";
 
 export class IslandGrid {
   data: number[];
   rng: Prng;
 
-  basePos: number;
-  lobePos1: number;
-  lobePos2: number;
+  generators: LobeGenerator[] = [];
 
   done = false;
 
@@ -15,14 +19,24 @@ export class IslandGrid {
     this.data = Array(width * height).fill(0);
     this.rng = mulberry32(seed);
 
-    this.basePos = this.data.length >> 1;
-    this.lobePos1 = this.xy(
-      (width >> 1) + (this.rng() % 48) - 24,
-      (height >> 1) + (this.rng() % 48) - 24
+    this.generators.push(BIG_MOUNTAIN(this, this.data.length >> 1));
+    this.generators.push(
+      FOREST_LOBE(
+        this,
+        this.xy(
+          (width >> 1) + (this.rng() % 48) - 24,
+          (height >> 1) + (this.rng() % 48) - 24
+        )
+      )
     );
-    this.lobePos2 = this.xy(
-      (width >> 1) + (this.rng() % 48) - 24,
-      (height >> 1) + (this.rng() % 48) - 24
+    this.generators.push(
+      BEACH_LOBE(
+        this,
+        this.xy(
+          (width >> 1) + (this.rng() % 48) - 24,
+          (height >> 1) + (this.rng() % 48) - 24
+        )
+      )
     );
   }
 
@@ -112,44 +126,8 @@ export class IslandGrid {
   }
 
   public step() {
-    const lowlandTiles1 = this.floodSearch(
-      this.lobePos1,
-      (tile) => tile > WATER
-    );
-    const lowlandTiles2 = this.floodSearch(
-      this.lobePos2,
-      (tile) => tile > WATER
-    );
-
-    // grow shore
-    const shoreTiles1 = lowlandTiles1.filter((pos) => this.data[pos] == WATER);
-    this.dropWithin(shoreTiles1);
-    const shoreTiles2 = lowlandTiles2.filter((pos) => this.data[pos] == WATER);
-    this.dropWithin(shoreTiles2);
-
-    // seed beach
-    const beachTiles = lowlandTiles1.filter((pos) => this.data[pos] == BEACH);
-    this.dropWithin(beachTiles);
-
-    // expand forest
-    const forestLobe = this.floodSearch(this.lobePos1, (tile) => tile > BEACH);
-    const forestTiles = forestLobe.filter(
-      (pos) => this.data[pos] == LIGHT_FOREST
-    );
-    this.dropWithin(forestTiles);
-    this.dropWithin(forestTiles);
-    this.dropWithin(forestTiles);
-
-    // form mountain
-    const mountainTiles = this.floodSearch(
-      this.basePos,
-      (tile) => tile > MOUNTAIN
-    );
-    this.dropWithin(mountainTiles); // GENERATOR
-
-    if (lowlandTiles2.length > 1) {
-      const erodePos = lowlandTiles2[this.rng() % lowlandTiles2.length];
-      this.data[erodePos] = Math.max(this.data[erodePos] - 1, 0);
-    }
+    this.done = this.generators
+      .map((generator) => generator())
+      .every((done) => done);
   }
 }