refactor(acts): unify ACT_TOWNS and townLevelForAct single source of truth

TAG=agy
CONV=2a1934de-30ef-464e-b3f3-fcbcdbbc49f1

scripts/pack-act-assets.ts

@@ -30,7 +30,7 @@ import { join } from 'node:path'
 import { MpqArchive } from '../src/mpq/archive.ts'
 import { fileSource } from '../src/mpq/file-source.ts'
 import { MountedArchives } from '../src/mpq/mount.ts'
-import { cell, loadActTables, parseTable, resolveLevel, resolveLevelLibraries, tileMemberPath } from '../src/game/acts.ts'
+import { cell, loadActTables, parseTable, resolveLevel, resolveLevelLibraries, tileMemberPath, ACT_TOWNS } from '../src/game/acts.ts'
 import type { ActTables, LevelInfo, D2Table } from '../src/game/acts.ts'
 import { decodeDs1 } from '../src/formats/ds1.ts'
 import type { Ds1 } from '../src/formats/ds1.ts'
@@ -366,9 +366,6 @@ const monstersTable = {
  */
 const ACT_LAYOUT_SEED = 0x5eed_2000
 
-/** Where each act's town is, for working out which way is "up" in a dungeon. */
-const ACT_TOWNS: readonly number[] = [1, 40, 75, 103, 109]
-
 const worldGraph: WorldGraph = assignGateSides(
   buildWorldGraph(parseLevelRows(tables.levels)),
   ACT_LAYOUT_SEED,

scripts/verify-world-graph.ts

@@ -33,7 +33,7 @@ import { readFileSync } from 'node:fs'
 import { MountedArchives } from '../src/mpq/mount.ts'
 import { MpqArchive } from '../src/mpq/archive.ts'
 import { fileSource } from '../src/mpq/file-source.ts'
-import { loadActTables } from '../src/game/acts.ts'
+import { loadActTables, ACT_TOWNS } from '../src/game/acts.ts'
 import {
   parseLevelRows,
   buildWorldGraph,
@@ -56,8 +56,6 @@ const dir = process.argv[2] ?? 'samples/d2'
 const MOUNTS = ['d2data.mpq', 'd2exp.mpq', 'Patch_D2.mpq']
 /** The baked asset packs. */
 const PACK_INDEX = 'samples/d2-packs/index.json'
-/** The town of each act, keyed by the 0-based `Act` column. */
-const ACT_TOWNS: readonly number[] = [1, 40, 75, 103, 109]
 /** Waypoint ids run 0..38 with no gaps. */
 const WAYPOINT_COUNT = 39
 /** How many seeds to exercise the side solver with. */

src/game/acts.ts

@@ -183,6 +183,28 @@ export interface LevelInfo {
  */
 export type ActTown = LevelInfo
 
+/**
+ * Town level IDs for Acts 1..5 in order:
+ * Act 1: Rogue Encampment (1)
+ * Act 2: Lut Gholein (40)
+ * Act 3: Kurast Docks (75)
+ * Act 4: The Pandemonium Fortress (103)
+ * Act 5: Harrogath (109)
+ */
+export const ACT_TOWNS: readonly number[] = [1, 40, 75, 103, 109]
+
+/**
+ * Returns the town level ID for an act (1..5).
+ * Defaults to Act 5 Harrogath (109) for acts >= 5, or Act 1 Rogue Encampment (1) for acts <= 1.
+ */
+export function townLevelForAct(act: number): number {
+  if (act >= 1 && act <= 5) {
+    return ACT_TOWNS[act - 1]!
+  }
+  if (act <= 1) return ACT_TOWNS[0]!
+  return ACT_TOWNS[4]!
+}
+
 /** Turn a table-relative tile path into a member name. */
 export function tileMemberPath(relative: string): string {
   return `${TILES}${relative.replaceAll('/', '\\')}`

src/game/portal.ts

@@ -213,27 +213,4 @@ export class TownPortalSlot {
   }
 }
 
-/**
- * The town for an act.
- *
- * Hard-coded because `Levels.txt` does not mark towns: the Rogue Encampment's
- * row looks like any other preset. The ids are stable across every version of
- * the game.
- *
- * @param act - the act, 1..5.
- * @returns the town's level id.
- */
-export function townLevelForAct(act: number): number {
-  switch (act) {
-    case 1:
-      return 1
-    case 2:
-      return 40
-    case 3:
-      return 75
-    case 4:
-      return 103
-    default:
-      return 109
-  }
-}
+export { ACT_TOWNS, townLevelForAct } from './acts.ts'

src/game/wilderness.ts

@@ -4941,16 +4941,7 @@ export function generateWilderness(request: WildernessRequest): WildernessResult
   let floorLayers = 1
   let substitutionType = 0
   let version = 0
-  let inferredAct = 1
-  if (request.levelId >= 40 && request.levelId < 75) inferredAct = 2
-  else if (request.levelId >= 75 && request.levelId < 103) inferredAct = 3
-  else if (request.levelId >= 103 && request.levelId < 109) inferredAct = 4
-  else if (request.levelId >= 109) inferredAct = 5
-  else if (/Act 2/i.test(request.levelTypeName)) inferredAct = 2
-  else if (/Act 3/i.test(request.levelTypeName)) inferredAct = 3
-  else if (/Act 4/i.test(request.levelTypeName)) inferredAct = 4
-  else if (/Act 5/i.test(request.levelTypeName)) inferredAct = 5
-
+  const inferredAct = actOfLevel(request.levelId, request.levelTypeName)
   let act = inferredAct
   const allLevels: Ds1[] = []
   for (const piece of request.pieces) for (const level of piece.levels) allLevels.push(level)

tests/world-graph.test.ts

@@ -1,5 +1,7 @@
 import { describe, it, expect } from 'vitest'
 import type { D2Table } from '../src/game/acts.ts'
+import { ACT_TOWNS, townLevelForAct } from '../src/game/acts.ts'
+import { actOfLevel } from '../src/game/wilderness.ts'
 import {
   parseLevelRows,
   buildWorldGraph,
@@ -444,3 +446,37 @@ describe('seamArrivalSpot', () => {
     expect(Math.abs(spot.y - 0)).toBeGreaterThan(SEAM_TRIGGER_SUBTILES)
   })
 })
+
+describe('ACT_TOWNS and townLevelForAct single source of truth', () => {
+  it('defines the correct canonical town level IDs for Acts 1..5', () => {
+    expect(ACT_TOWNS).toEqual([1, 40, 75, 103, 109])
+  })
+
+  it('resolves townLevelForAct for all 5 acts correctly', () => {
+    expect(townLevelForAct(1)).toBe(1)
+    expect(townLevelForAct(2)).toBe(40)
+    expect(townLevelForAct(3)).toBe(75)
+    expect(townLevelForAct(4)).toBe(103)
+    expect(townLevelForAct(5)).toBe(109)
+  })
+
+  it('handles boundary / out-of-range acts gracefully', () => {
+    expect(townLevelForAct(0)).toBe(1)
+    expect(townLevelForAct(-5)).toBe(1)
+    expect(townLevelForAct(6)).toBe(109)
+    expect(townLevelForAct(99)).toBe(109)
+  })
+
+  it('actOfLevel correctly partitions level IDs matching ACT_TOWNS', () => {
+    expect(actOfLevel(1)).toBe(1)
+    expect(actOfLevel(39)).toBe(1)
+    expect(actOfLevel(40)).toBe(2)
+    expect(actOfLevel(74)).toBe(2)
+    expect(actOfLevel(75)).toBe(3)
+    expect(actOfLevel(102)).toBe(3)
+    expect(actOfLevel(103)).toBe(4)
+    expect(actOfLevel(108)).toBe(4)
+    expect(actOfLevel(109)).toBe(5)
+    expect(actOfLevel(136)).toBe(5)
+  })
+})