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

lib/game/world.ts

@@ -123,3 +123,105 @@ export function generateRing(
   const systems = placeRing(rng, anchorX, anchorY, EXPAND_RING, takenNames, takenPositions)
   return { systems, edges: ringEdges(systems.length) }
 }
+
+// --- Bodies (planets + moons) and exploration -------------------------------
+
+export interface WorldMoon {
+  name: string
+  type: string
+  hazard: boolean
+}
+
+export interface WorldPlanet {
+  name: string
+  type: string
+  hazard: boolean
+  moons: WorldMoon[]
+}
+
+// Derive an independent PRNG stream for one entity from the save seed, so a system's bodies
+// and a planet's exploration haul are reproducible offline (tests recompute them directly).
+export function bodyRng(seed: string, systemId: number): () => number {
+  return mulberry32((Number(seed) + Math.imul(systemId, 0x9e3779b1)) >>> 0)
+}
+
+export function explorationRng(seed: string, planetId: number): () => number {
+  return mulberry32((Number(seed) + Math.imul(planetId, 0x85ebca6b)) >>> 0)
+}
+
+const BODY_NAMES = [
+  'AURELLE', 'BRIMSTONE', 'CINDERROCK', 'DRIFTBAND', 'PALEMOON', 'ASHFALL', 'VESPERINE', 'KORR',
+  'MIRELLA', 'SABLET', 'EMBERLING', 'FROSTHOLD', 'GALEN', 'IRONVEIN', 'JUNO', 'KESTREL',
+  'LUMEN', 'NADIR', 'OPALINE', 'PYRE', 'QUILL', 'RUSTBARK', 'SIROCCO', 'TARN',
+  'UMBRA', 'VELVETINE', 'WYRM', 'ZEPHYR', 'HALCYON', 'MORROW', 'ONYX', 'THALASSA',
+]
+
+const PLANET_TYPES = ['TERRESTRIAL', 'GAS GIANT', 'ROCKY', 'ICE WORLD', 'VOLCANIC', 'OCEAN', 'ASTEROID FIELD']
+const MOON_TYPES = ['MOON', 'ICE MOON', 'VOLCANIC MOON']
+
+const HAZARD_CHANCE = 0.25
+const MOON_CHANCE = 0.6 // a planet has any moons at all
+const PLANET_COUNT_MIN = 2
+const PLANET_COUNT_SPREAD = 4 // 2..5 planets per system
+
+// A body name unique within its system (planets and moons share one pool). Max bodies per
+// system is 5 + 5*3 = 20 < BODY_NAMES.length, so the loop always terminates.
+function makeBodyName(rng: () => number, taken: Set<string>): string {
+  for (;;) {
+    const name = title(BODY_NAMES[Math.floor(rng() * BODY_NAMES.length)])
+    if (!taken.has(name)) {
+      taken.add(name)
+      return name
+    }
+  }
+}
+
+function pick<T>(rng: () => number, arr: T[]): T {
+  return arr[Math.floor(rng() * arr.length)]
+}
+
+// The bodies of one system: 2–5 planets, some with 1–3 moons. Pure — the caller derives the
+// rng from (save seed, system id) so a given system always gets the same bodies.
+export function generatePlanets(rng: () => number): WorldPlanet[] {
+  const taken = new Set<string>()
+  const planets: WorldPlanet[] = []
+  for (let i = 0; i < PLANET_COUNT_MIN + Math.floor(rng() * PLANET_COUNT_SPREAD); i++) {
+    const name = makeBodyName(rng, taken)
+    const type = pick(rng, PLANET_TYPES)
+    const hazard = rng() < HAZARD_CHANCE
+    const moons: WorldMoon[] = []
+    if (rng() < MOON_CHANCE) {
+      for (let m = 0; m < 1 + Math.floor(rng() * 3); m++) {
+        moons.push({ name: makeBodyName(rng, taken), type: pick(rng, MOON_TYPES), hazard: rng() < HAZARD_CHANCE })
+      }
+    }
+    planets.push({ name, type, hazard, moons })
+  }
+  return planets
+}
+
+export interface FoundItem {
+  kind: 'resource' | 'part'
+  name: string
+  qty: number
+}
+
+const RESOURCE_NAMES = ['IRON ORE', 'CRYSTAL SHARDS', 'GAS CELLS', 'WATER ICE', 'RARE EARTH']
+const PART_NAMES = ['NAV MODULE', 'HULL PLATE', 'REACTOR CORE', 'COMMS ARRAY', 'ENGINE TUNING']
+
+const RESOURCE_CHANCE = 0.7
+const PART_CHANCE = 0.3 // parts are rarer than resources
+
+// The haul from scanning one body: a resource and/or a part, or nothing (~21% of scans).
+// Pure — the caller derives the rng from (save seed, planet id), so the same save+planet
+// always yields the same outcome.
+export function rollExploration(rng: () => number): FoundItem[] {
+  const found: FoundItem[] = []
+  if (rng() < RESOURCE_CHANCE) {
+    found.push({ kind: 'resource', name: pick(rng, RESOURCE_NAMES), qty: 1 + Math.floor(rng() * 4) }) // 1..4
+  }
+  if (rng() < PART_CHANCE) {
+    found.push({ kind: 'part', name: pick(rng, PART_NAMES), qty: 1 })
+  }
+  return found
+}