feat: player knowledge layer - aging price intel and seen ships

src/sim/knowledge.js

@@ -1 +1,27 @@
-export function markSeen() {}
+import { playerSystem } from './player.js';
+import { shipsIn } from './npc.js';
+
+// Best price intel the player has for a planet: personal dock visit
+// vs. news that has reached the player's current location. Caches the
+// winner in the price book so intel never gets worse.
+export function playerKnownPrices(world, planetId) {
+  const p = world.player;
+  const sys = playerSystem(world);
+  if (sys == null) return p.priceBook[planetId] ?? null;
+  const planet = world.galaxy.planets[planetId];
+  const news = world.news.knownPrices(planetId, world.hops[sys][planet.systemId], world.t);
+  const book = p.priceBook[planetId] ?? null;
+  let best = book;
+  if (news && (!best || news.time > best.time)) best = news;
+  if (best && (!book || best.time > book.time)) p.priceBook[planetId] = best;
+  return best ? { time: best.time, prices: best.prices, ageDays: world.t - best.time } : null;
+}
+
+// Called by the world's observe heartbeat: every concrete ship sharing
+// the player's system becomes "seen" — its cloud is now player-visible forever.
+export function markSeen(world) {
+  if (!world.player.alive) return;
+  const sys = playerSystem(world);
+  if (sys == null) return;
+  for (const { npc } of shipsIn(world, sys)) world.player.seenNpcs.add(npc.id);
+}

tests/knowledge.test.js

@@ -0,0 +1,42 @@
+import { describe, it, expect } from 'vitest';
+import { createWorld, advance } from '../src/sim/world.js';
+import { playerKnownPrices } from '../src/sim/knowledge.js';
+import { playerSystem } from '../src/sim/player.js';
+
+describe('knowledge', () => {
+  it('knows every planet at game start via the day-0 snapshot', () => {
+    const w = createWorld('know-test', { systemCount: 10, npcCount: 5 });
+    for (const planet of w.galaxy.planets) {
+      const known = playerKnownPrices(w, planet.id);
+      expect(known).not.toBeNull();
+      expect(known.time).toBe(0);
+      expect(known.ageDays).toBe(0);
+    }
+  });
+
+  it('intel ages and refreshes as news travels', () => {
+    const w = createWorld('know-test', { systemCount: 10, npcCount: 5 });
+    const sys = playerSystem(w);
+    const far = w.galaxy.planets.find((p) => w.hops[sys][p.systemId] >= 2);
+    advance(w, 5);
+    const known = playerKnownPrices(w, far.id);
+    const hops = w.hops[sys][far.systemId];
+    // freshest possible news is `hops` days old
+    expect(known.ageDays).toBeGreaterThanOrEqual(hops - 1e-9);
+    expect(known.ageDays).toBeLessThanOrEqual(hops + 1 + 1e-9);
+  });
+
+  it('local planet intel is near-live', () => {
+    const w = createWorld('know-test', { systemCount: 10, npcCount: 5 });
+    advance(w, 5);
+    const local = w.galaxy.planets.find((p) => p.systemId === playerSystem(w));
+    expect(playerKnownPrices(w, local.id).ageDays).toBeLessThanOrEqual(1);
+  });
+
+  it('the observe heartbeat marks co-located NPCs as seen', () => {
+    const w = createWorld('know-test', { systemCount: 10, npcCount: 40 });
+    advance(w, 10);
+    // with 40 NPCs over 10 days, some must have passed through the player's system
+    expect(w.player.seenNpcs.size).toBeGreaterThan(0);
+  });
+});