fix deterministic authoritative RNG fallbacks

packages/logic/src/world/bootstrap.ts

@@ -1,3 +1,4 @@
+import { LiteHashDRBG, RandUtil } from '@sammo-ts/common';
 import type {
     City,
     General,
@@ -18,6 +19,7 @@ import type {
     WorldSeedPayload,
     WorldSnapshot,
 } from './types.js';
+import { simpleSerialize } from '../war/utils.js';
 
 export interface ScenarioBootstrapOptions {
     includeNeutralNation?: boolean;
@@ -144,16 +146,38 @@ const resolveKillturnFromDeathYear = (
     currentYear: number | null,
     currentMonth: number,
     deathYear: number,
+    deathMonth: number,
     fallback: number
 ): number => {
     if (currentYear === null || !Number.isFinite(deathYear) || deathYear <= 0) {
         return fallback;
     }
-    const deathMonth = Math.floor(Math.random() * 12) + 1;
     const diff = (deathYear - currentYear) * 12 + (deathMonth - currentMonth);
     return Math.max(diff, 0);
 };
 
+export const resolveScenarioGeneralDeathMonth = (input: {
+    scenarioTitle: string;
+    startYear: number | null;
+    contextLabel: string;
+    generalId: number;
+    generalName: string;
+    deathYear: number;
+}): number =>
+    new RandUtil(
+        new LiteHashDRBG(
+            simpleSerialize(
+                input.scenarioTitle,
+                input.startYear ?? 0,
+                input.contextLabel,
+                input.generalId,
+                input.generalName,
+                input.deathYear,
+                'deathMonth'
+            )
+        )
+    ).nextRangeInt(1, 12);
+
 const resolveAge = (startYear: number | null, birthYear: number): number => {
     if (startYear === null || birthYear <= 0) {
         return 20;
@@ -309,6 +333,14 @@ const buildGeneralSeeds = (
         const cityId = resolveCityId(row.city, cityByName, warnings, row.name);
         const birthYear = resolveBirthYear(row.birthYear, scenario.startYear);
         const deathYear = resolveDeathYear(row.deathYear, birthYear, scenario.startYear);
+        const deathMonth = resolveScenarioGeneralDeathMonth({
+            scenarioTitle: scenario.title,
+            startYear: scenario.startYear,
+            contextLabel,
+            generalId: id,
+            generalName: row.name,
+            deathYear,
+        });
         const officerLevel = resolveOfficerLevel(row.officerLevel, nationId);
         const age = resolveAge(scenario.startYear, birthYear);
         const stats = {
@@ -319,6 +351,7 @@ const buildGeneralSeeds = (
 
         const seedMeta: Record<string, unknown> = {
             source: contextLabel,
+            deathMonth,
             specage: buildSpecialityAge(retirementYear, age, 12),
             specage2: buildSpecialityAge(retirementYear, age, 6),
         };
@@ -379,7 +412,14 @@ const buildGeneralSeeds = (
         seeds.push(seed);
 
         const generalMeta: GeneralMeta = {
-            killturn: resolveKillturnFromDeathYear(scenario.startYear, 1, deathYear, DEFAULT_GENERAL_KILLTURN),
+            killturn: resolveKillturnFromDeathYear(
+                scenario.startYear,
+                1,
+                deathYear,
+                deathMonth,
+                DEFAULT_GENERAL_KILLTURN
+            ),
+            deathMonth,
             npcType,
             crewTypeId: defaultCrewTypeId,
             specage: buildSpecialityAge(retirementYear, age, 12),

packages/logic/test/worldBootstrap.test.ts

@@ -1,10 +1,20 @@
-import { describe, expect, it } from 'vitest';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import type { ScenarioDefinition } from '../src/scenario/types.js';
 import type { MapDefinition, UnitSetDefinition } from '../src/world/types.js';
 import { buildScenarioBootstrap } from '../src/world/bootstrap.js';
 
 describe('scenario bootstrap', () => {
+    beforeEach(() => {
+        vi.spyOn(Math, 'random').mockImplementation(() => {
+            throw new Error('scenario bootstrap must not use Math.random');
+        });
+    });
+
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
     it('builds snapshot and seed from scenario/map inputs', () => {
         const scenario: ScenarioDefinition = {
             title: 'Test Scenario',
@@ -120,7 +130,14 @@ describe('scenario bootstrap', () => {
         expect(result.snapshot.generals[0]?.role.specialDomestic).toBe('Special');
         expect(result.snapshot.generals[0]?.role.specialWar).toBeNull();
         expect(result.snapshot.generals[0]?.meta).toMatchObject({ specage: 25, specage2: 30 });
-        expect(result.seed.generals[0]?.meta).toMatchObject({ specage: 25, specage2: 30 });
+        expect(result.seed.generals[0]?.meta).toMatchObject({
+            deathMonth: expect.any(Number),
+            specage: 25,
+            specage2: 30,
+        });
+        expect(buildScenarioBootstrap({ scenario, map, unitSet }).snapshot.generals[0]?.meta).toEqual(
+            result.snapshot.generals[0]?.meta
+        );
         expect(result.seed.generals[0]?.npcType).toBe(2);
         expect(result.snapshot.scenarioMeta?.title).toBe('Test Scenario');
     });