game: seeded planet/moon generation per system + deterministic exploration roll

lib/game/world.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { generateRing, generateStartRegion, makeName, mulberry32 } from './world'
+import { bodyRng, explorationRng, generatePlanets, generateRing, generateStartRegion, makeName, mulberry32, rollExploration } from './world'
 
 describe('generateStartRegion', () => {
   const region = generateStartRegion(mulberry32(42))
@@ -77,3 +77,58 @@ describe('generateRing (expansion)', () => {
     expect(taken.size).toBe(40)
   })
 })
+
+describe('generatePlanets', () => {
+  it('gives every system 2–5 planets and keeps body names unique within the system', () => {
+    for (const seed of [1, 7, 42, 999]) {
+      const planets = generatePlanets(bodyRng(String(seed), seed))
+      expect(planets.length).toBeGreaterThanOrEqual(2)
+      expect(planets.length).toBeLessThanOrEqual(5)
+
+      const names: string[] = []
+      for (const p of planets) {
+        names.push(p.name, ...p.moons.map((m) => m.name))
+        expect(['TERRESTRIAL', 'GAS GIANT', 'ROCKY', 'ICE WORLD', 'VOLCANIC', 'OCEAN', 'ASTEROID FIELD']).toContain(p.type)
+        for (const m of p.moons) {
+          expect(['MOON', 'ICE MOON', 'VOLCANIC MOON']).toContain(m.type)
+        }
+      }
+      expect(new Set(names).size).toBe(names.length) // planets + moons share one name pool per system
+    }
+  })
+
+  it('is deterministic per (seed, system id) and differs across systems', () => {
+    const a = generatePlanets(bodyRng('42', 7))
+    expect(generatePlanets(bodyRng('42', 7))).toEqual(a) // same save+system → same bodies
+    const b = generatePlanets(bodyRng('43', 7))
+    expect(JSON.stringify(b)).not.toBe(JSON.stringify(a)) // different seed → different world
+  })
+})
+
+describe('rollExploration', () => {
+  it('is deterministic for the same save+planet and yields valid items', () => {
+    const first = rollExploration(explorationRng('42', 13))
+    expect(rollExploration(explorationRng('42', 13))).toEqual(first)
+
+    for (const item of first) {
+      expect(['resource', 'part']).toContain(item.kind)
+      if (item.kind === 'resource') {
+        expect(item.qty).toBeGreaterThanOrEqual(1)
+        expect(item.qty).toBeLessThanOrEqual(4)
+      } else {
+        expect(item.qty).toBe(1)
+      }
+    }
+  })
+
+  it('across many planets produces every outcome shape: resource, part, both, or nothing', () => {
+    const shapes = new Set<string>()
+    for (let planetId = 1; planetId <= 200; planetId++) {
+      const found = rollExploration(explorationRng('42', planetId))
+      const hasResource = found.some((f) => f.kind === 'resource')
+      const hasPart = found.some((f) => f.kind === 'part')
+      shapes.add(`${hasResource ? 'r' : '-'}${hasPart ? 'p' : '-'}`)
+    }
+    expect(shapes).toEqual(new Set(['rp', 'r-', '-p', '--']))
+  })
+})