probability/src/sim/galaxy.js

import { makeRng, hash32 } from './rng.js';

const SYSTEM_NAMES = [
  'Arcadia', 'Boreas', 'Cygni', 'Drakon', 'Eridu', 'Fenrir', 'Gorgon', 'Helix',
  'Icarus', 'Juno', 'Kepler', 'Lyra', 'Mira', 'Nyx', 'Orion', 'Pavo',
  'Quasar', 'Rigel', 'Sirius', 'Talos', 'Umbra', 'Vega', 'Wraith', 'Xandar',
  'Yara', 'Zenith', 'Altair', 'Bellatrix', 'Castor', 'Deneb',
];
const PLANET_SUFFIX = ['Prime', 'II', 'III'];

const PROFILES = [
  { kind: 'agri', produces: { food: 10, meds: 3 }, consumes: { fuel: 4, tech: 3 } },
  { kind: 'mining', produces: { ore: 12, fuel: 6 }, consumes: { food: 6, meds: 2 } },
  { kind: 'industrial', produces: { tech: 6 }, consumes: { ore: 8, fuel: 5, food: 5 } },
  { kind: 'refinery', produces: { fuel: 10 }, consumes: { ore: 6, food: 4 } },
  { kind: 'resort', produces: { luxury: 5 }, consumes: { food: 7, meds: 4, fuel: 3 } },
];
const ALL_GOODS = ['ore', 'food', 'fuel', 'tech', 'meds', 'luxury'];

export function otherEnd(lane, systemId) {
  return lane.a === systemId ? lane.b : lane.a;
}

export function generateGalaxy(seed, { systemCount = 25 } = {}) {
  const rng = makeRng(hash32('galaxy:' + seed));

  // 1. Place systems with minimum spacing (relaxes if placement gets tight).
  const systems = [];
  let minDist = 95, attempts = 0;
  while (systems.length < systemCount) {
    const x = 60 + rng() * 880, y = 50 + rng() * 600;
    if (systems.every((s) => Math.hypot(s.x - x, s.y - y) > minDist)) {
      systems.push({ id: systems.length, name: SYSTEM_NAMES[systems.length % SYSTEM_NAMES.length], x, y, planets: [], lanes: [] });
    }
    if (++attempts > 2000) { minDist *= 0.9; attempts = 0; }
  }

  // 2. Lanes: each system to its 2 nearest neighbors, deduplicated.
  const laneKeys = new Set();
  const key = (a, b) => (a < b ? `${a}-${b}` : `${b}-${a}`);
  for (const s of systems) {
    const near = systems
      .filter((o) => o.id !== s.id)
      .sort((p, q) => Math.hypot(p.x - s.x, p.y - s.y) - Math.hypot(q.x - s.x, q.y - s.y));
    laneKeys.add(key(s.id, near[0].id));
    laneKeys.add(key(s.id, near[1].id));
  }

  // 3. Connectivity repair: link closest pair across components until one component.
  const parent = systems.map((_, i) => i);
  const find = (i) => (parent[i] === i ? i : (parent[i] = find(parent[i])));
  const union = (a, b) => { parent[find(a)] = find(b); };
  for (const k of laneKeys) { const [a, b] = k.split('-').map(Number); union(a, b); }
  for (;;) {
    const roots = new Set(systems.map((s) => find(s.id)));
    if (roots.size === 1) break;
    let best = null;
    for (const s of systems) for (const o of systems) {
      if (find(s.id) === find(o.id)) continue;
      const d = Math.hypot(s.x - o.x, s.y - o.y);
      if (!best || d < best.d) best = { a: s.id, b: o.id, d };
    }
    laneKeys.add(key(best.a, best.b));
    union(best.a, best.b);
  }

  // 4. Materialize lanes with travel time and hazard.
  const lanes = [...laneKeys].sort().map((k, i) => {
    const [a, b] = k.split('-').map(Number);
    const dist = Math.hypot(systems[a].x - systems[b].x, systems[a].y - systems[b].y);
    const days = Math.min(4, Math.max(1, Math.round(dist / 80)));
    const hazard = rng() < 0.2 ? +(0.3 + rng() * 0.4).toFixed(3) : +(rng() * 0.15).toFixed(3);
    return { id: i, a, b, days, hazard };
  });
  for (const lane of lanes) {
    systems[lane.a].lanes.push(lane.id);
    systems[lane.b].lanes.push(lane.id);
  }

  // 5. Planets with economy profiles and a render orbit.
  const planets = [];
  for (const s of systems) {
    const n = 1 + Math.floor(rng() * 3);
    for (let i = 0; i < n; i++) {
      const profile = PROFILES[Math.floor(rng() * PROFILES.length)];
      const stock = {};
      for (const g of ALL_GOODS) {
        if (profile.produces[g]) stock[g] = Math.floor(150 + rng() * 150);
        else if (profile.consumes[g]) stock[g] = Math.floor(40 + rng() * 80);
        else stock[g] = Math.floor(80 + rng() * 70);
      }
      const planet = {
        id: planets.length, systemId: s.id,
        name: `${s.name} ${PLANET_SUFFIX[i]}`, kind: profile.kind,
        produces: { ...profile.produces }, consumes: { ...profile.consumes },
        stock, stockTime: 0,
        orbit: { r: 90 + i * 55, a: rng() * Math.PI * 2 },
      };
      planets.push(planet);
      s.planets.push(planet.id);
    }
  }

  return { systems, lanes, planets };
}

// All-pairs hop counts (BFS per system). hops[a][b] = lanes to cross.
export function hopMatrix(galaxy) {
  const n = galaxy.systems.length;
  const m = Array.from({ length: n }, () => Array(n).fill(Infinity));
  for (let src = 0; src < n; src++) {
    m[src][src] = 0;
    const queue = [src];
    while (queue.length) {
      const cur = queue.shift();
      for (const laneId of galaxy.systems[cur].lanes) {
        const next = otherEnd(galaxy.lanes[laneId], cur);
        if (m[src][next] === Infinity) {
          m[src][next] = m[src][cur] + 1;
          queue.push(next);
        }
      }
    }
  }
  return m;
}

// Dijkstra by travel days. Returns { lanes: [laneId...], days } or null.
export function findRoute(galaxy, fromSys, toSys) {
  if (fromSys === toSys) return { lanes: [], days: 0 };
  const dist = new Map([[fromSys, 0]]);
  const prevLane = new Map();
  const visited = new Set();
  for (;;) {
    let cur = null, best = Infinity;
    for (const [s, d] of dist) if (!visited.has(s) && d < best) { best = d; cur = s; }
    if (cur === null) return null;
    if (cur === toSys) break;
    visited.add(cur);
    for (const laneId of galaxy.systems[cur].lanes) {
      const lane = galaxy.lanes[laneId];
      const next = otherEnd(lane, cur);
      const nd = best + lane.days;
      if (nd < (dist.get(next) ?? Infinity)) {
        dist.set(next, nd);
        prevLane.set(next, laneId);
      }
    }
  }
  const laneIds = [];
  let s = toSys;
  while (s !== fromSys) {
    const laneId = prevLane.get(s);
    laneIds.unshift(laneId);
    s = otherEnd(galaxy.lanes[laneId], s);
  }
  return { lanes: laneIds, days: dist.get(toSys) };
}