Add Civ Lite barbarian camps and events

demo/civ-lite/barbarian-model.js

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+const EVENT_CADENCE = 4;
+
+const EVENT_TABLE = [
+  {
+    id: 'ancient_ruins',
+    title: 'Ancient ruins',
+    description: 'Scouts uncover a buried archive near your border.',
+    choices: [
+      { id: 'study', label: 'Study the tablets', effects: { science: 5, cityProd: 1 } },
+      { id: 'salvage', label: 'Salvage the stonework', effects: { prod: 4, cityProd: 2 } },
+    ],
+  },
+  {
+    id: 'bumper_harvest',
+    title: 'Bumper harvest',
+    description: 'A mild season gives your capital surplus grain.',
+    choices: [
+      { id: 'store', label: 'Store grain', effects: { food: 4, cityFood: 4 } },
+      { id: 'trade', label: 'Trade surplus', effects: { prod: 2, science: 2 } },
+    ],
+  },
+  {
+    id: 'frontier_plague',
+    title: 'Frontier sickness',
+    description: 'A caravan brings illness and rumors from the frontier.',
+    choices: [
+      { id: 'quarantine', label: 'Quarantine quickly', effects: { prod: -1, cityFood: 2 } },
+      { id: 'research', label: 'Fund healers', effects: { science: 4, food: -1 } },
+    ],
+  },
+];
+
+function hashSeed(seed) {
+  let hash = 2166136261;
+  for (const char of String(seed)) {
+    hash ^= char.codePointAt(0);
+    hash = Math.imul(hash, 16777619);
+  }
+  return hash >>> 0;
+}
+
+export function createSeededRng(seed) {
+  let state = hashSeed(seed) || 1;
+  return () => {
+    state = Math.imul(state, 1664525) + 1013904223;
+    return (state >>> 0) / 4294967296;
+  };
+}
+
+function distance(a, b) {
+  return Math.abs(a.x - b.x) + Math.abs(a.y - b.y);
+}
+
+function isSafeTile(tile, safeZones, minDistance) {
+  return safeZones.every(zone => distance(tile, zone) > minDistance);
+}
+
+export function planBarbarianCamps({
+  map,
+  seed,
+  count = 3,
+  safeZones = [],
+  minDistance = 3,
+}) {
+  const rng = createSeededRng(seed);
+  const candidates = [];
+
+  for (let y = 0; y < map.length; y++) {
+    for (let x = 0; x < map[y].length; x++) {
+      const tile = { x, y };
+      if (map[y][x] !== 'water' && isSafeTile(tile, safeZones, minDistance)) {
+        candidates.push({ ...tile, score: rng() });
+      }
+    }
+  }
+
+  const sortedCandidates = [...candidates];
+  sortedCandidates.sort((a, b) => a.score - b.score);
+
+  return sortedCandidates
+    .slice(0, count)
+    .map((tile, index) => ({
+      id: `camp-${index + 1}`,
+      name: `Camp ${index + 1}`,
+      x: tile.x,
+      y: tile.y,
+      hp: 40,
+      lastSpawnTurn: 1,
+      cleared: false,
+    }));
+}
+
+export function shouldSpawnFromCamp(camp, turn, cadence = 3) {
+  return !camp.cleared && turn - camp.lastSpawnTurn >= cadence;
+}
+
+export function createBarbarianUnit(camp, id, turn) {
+  return {
+    id,
+    owner: 'barbarian',
+    x: camp.x,
+    y: camp.y,
+    hp: 70,
+    atk: 22,
+    def: 10,
+    mov: 1,
+    movLeft: 1,
+    type: 'raider',
+    campId: camp.id,
+    spawnedTurn: turn,
+  };
+}
+
+export function buildRandomEvent({ seed, turn, cadence = EVENT_CADENCE }) {
+  if (turn <= 1 || turn % cadence !== 0) return null;
+  const rng = createSeededRng(`${seed}:${turn}`);
+  const event = EVENT_TABLE[Math.floor(rng() * EVENT_TABLE.length)];
+
+  return {
+    id: event.id,
+    title: event.title,
+    description: event.description,
+    turn,
+    choices: event.choices.map(choice => ({
+      id: choice.id,
+      label: choice.label,
+      effects: { ...choice.effects },
+    })),
+  };
+}
+
+export function applyEventChoice(empire, event, choiceId) {
+  const choice = event.choices.find(item => item.id === choiceId);
+  if (!choice) return { ...empire };
+
+  const next = { ...empire };
+  for (const [key, value] of Object.entries(choice.effects)) {
+    next[key] = (next[key] ?? 0) + value;
+  }
+  return next;
+}
+
+export function formatEventEffects(effects) {
+  return Object.entries(effects)
+    .map(([key, value]) => `${value > 0 ? '+' : ''}${value} ${key}`)
+    .join(', ');
+}

demo/civ-lite/barbarian-model.test.mjs

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+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import {
+  applyEventChoice,
+  buildRandomEvent,
+  createBarbarianUnit,
+  planBarbarianCamps,
+  shouldSpawnFromCamp,
+} from './barbarian-model.js';
+
+const map = [
+  ['plains', 'forest', 'hill', 'plains', 'desert', 'plains'],
+  ['plains', 'water', 'plains', 'forest', 'hill', 'plains'],
+  ['hill', 'plains', 'desert', 'plains', 'forest', 'plains'],
+  ['plains', 'forest', 'plains', 'hill', 'plains', 'desert'],
+  ['desert', 'plains', 'hill', 'plains', 'water', 'plains'],
+  ['plains', 'hill', 'forest', 'plains', 'desert', 'plains'],
+];
+
+test('places deterministic barbarian camps on valid land away from capitals', () => {
+  const first = planBarbarianCamps({
+    map,
+    seed: 'barbarians-21',
+    count: 3,
+    safeZones: [{ x: 0, y: 0 }, { x: 5, y: 5 }],
+  });
+  const again = planBarbarianCamps({
+    map,
+    seed: 'barbarians-21',
+    count: 3,
+    safeZones: [{ x: 0, y: 0 }, { x: 5, y: 5 }],
+  });
+
+  assert.deepEqual(first, again);
+  assert.equal(first.length, 3);
+  for (const camp of first) {
+    assert.notEqual(map[camp.y][camp.x], 'water');
+    assert.ok(Math.abs(camp.x - 0) + Math.abs(camp.y - 0) > 3);
+    assert.ok(Math.abs(camp.x - 5) + Math.abs(camp.y - 5) > 3);
+    assert.match(camp.name, /^Camp /);
+  }
+});
+
+test('creates reproducible hostile units and throttles camp spawns by cadence', () => {
+  const camp = { id: 'camp-1', x: 3, y: 2, lastSpawnTurn: 1 };
+
+  assert.equal(shouldSpawnFromCamp(camp, 2, 3), false);
+  assert.equal(shouldSpawnFromCamp(camp, 4, 3), true);
+
+  const unit = createBarbarianUnit(camp, 12, 5);
+  assert.deepEqual(unit, {
+    id: 12,
+    owner: 'barbarian',
+    x: 3,
+    y: 2,
+    hp: 70,
+    atk: 22,
+    def: 10,
+    mov: 1,
+    movLeft: 1,
+    type: 'raider',
+    campId: 'camp-1',
+    spawnedTurn: 5,
+  });
+});
+
+test('selects deterministic random events only on event turns', () => {
+  assert.equal(buildRandomEvent({ seed: 'events', turn: 3 }), null);
+
+  const event = buildRandomEvent({ seed: 'events', turn: 4 });
+  const again = buildRandomEvent({ seed: 'events', turn: 4 });
+
+  assert.deepEqual(event, again);
+  assert.ok(event.id);
+  assert.equal(event.turn, 4);
+  assert.ok(event.choices.length >= 2);
+  assert.ok(event.choices.every(choice => choice.id && choice.label));
+});
+
+test('applies event choices without mutating the original empire snapshot', () => {
+  const empire = {
+    food: 2,
+    prod: 3,
+    science: 1,
+    cityFood: 4,
+    cityProd: 5,
+  };
+  const event = {
+    id: 'ancient_ruins',
+    choices: [
+      { id: 'study', effects: { science: 5, cityProd: 1 } },
+      { id: 'salvage', effects: { prod: 4 } },
+    ],
+  };
+
+  const result = applyEventChoice(empire, event, 'study');
+
+  assert.deepEqual(empire, {
+    food: 2,
+    prod: 3,
+    science: 1,
+    cityFood: 4,
+    cityProd: 5,
+  });
+  assert.deepEqual(result, {
+    food: 2,
+    prod: 3,
+    science: 6,
+    cityFood: 4,
+    cityProd: 6,
+  });
+});