TheLadder/test/fixtures/strategies.js

// Player archetypes for content probing.
//
// "Is this content reachable?" is not the same question as "does random play
// reach it?" — a random player is not a plausible player, and several things
// in a pack exist precisely for a player pursuing something. Coverage is
// therefore the union across archetypes, and each one is a rough caricature of
// a way somebody actually plays.
//
// NOTE: seed the chooser differently from the game. Both draw one number per
// turn from the same generator, so a shared seed correlates the choice with
// the event draw and silently makes combinations unreachable.

import { startGame, currentTurn, takeTurn } from '../../src/engine/game.js';
import { createRng } from '../../src/engine/rng.js';

/**
 * What an effect is worth to a bot. An amount read from state (DECISIONS #38)
 * is scored at its cap: the most it could be, which is what a player weighing
 * the option sees on the label.
 */
const amountOf = (effect) => {
  if (typeof effect.value === 'number') return effect.value;
  if (typeof effect.value?.cap === 'number') return effect.value.cap * (effect.value.times ?? 1);
  return 0;
};

/**
 * Every effect an option can have, with the weight a player reading the odds
 * would give it: plain effects count in full, a check's success and failure by
 * their chance (DECISIONS #41). An option with no check is just its effects.
 */
export const weightedEffects = (resolved) => {
  const { option, odds } = resolved;
  const plain = (option.effects ?? []).map((effect) => ({ effect, weight: 1 }));
  if (!option.check) return plain;
  const p = (odds?.chance ?? 50) / 100;
  return [
    ...plain,
    ...(option.success?.effects ?? []).map((effect) => ({ effect, weight: p })),
    ...(option.failure?.effects ?? []).map((effect) => ({ effect, weight: 1 - p })),
  ];
};

const moneyGain = (resolved) => weightedEffects(resolved)
  .filter(({ effect }) => effect.path === 'money' && effect.op === 'add')
  .reduce((sum, { effect, weight }) => sum + amountOf(effect) * weight, 0);

const relationshipGain = (resolved) => weightedEffects(resolved)
  .filter(({ effect }) => effect.path.startsWith('relationships.'))
  .reduce((sum, { effect, weight }) => sum + amountOf(effect) * weight, 0);

const best = (options, score) => [...options].sort((a, b) => score(b) - score(a))[0];

export const strategies = {
  /** No plan at all. */
  random: (options, rng) => rng.pick(options),
  /** Takes the money every time. */
  thrifty: (options) => best(options, moneyGain),
  /** Spends it every time. */
  spendthrift: (options) => best(options, (o) => -moneyGain(o)),
  /** Chases standing with people. */
  sociable: (options) => best(options, relationshipGain),
  /**
   * Broke but well-liked — the state the "ask a friend for money" options were
   * written for, and one no single-axis strategy ever reaches.
   */
  desperate: (options, rng) => (rng.next() < 0.25
    ? rng.pick(options)
    : best(options, (o) => relationshipGain(o) - moneyGain(o) / 40)),
  /**
   * Never leaves the first rung — refuses anything that would change stage,
   * and otherwise plays for people. Added after a real 182-turn session that
   * stayed in the mailroom the whole way and spent 30% of it below zero: every
   * other archetype either optimised money or got promoted out of the problem,
   * so none of them could see it.
   */
  lifer: (options) => {
    const stays = options.filter(
      (o) => !weightedEffects(o).some(({ effect }) => effect.path === 'stage'),
    );
    return best(stays.length ? stays : options, relationshipGain);
  },
};

/** Play one run to `turns`, calling `visit` before each choice. */
export function play(pack, { strategy = 'random', seed = 'run', turns = 200, visit } = {}) {
  const choose = strategies[strategy];
  const rng = createRng(`chooser-${strategy}-${seed}`);
  let state = startGame(pack, { seed: `game-${strategy}-${seed}` });

  for (let t = 0; t < turns; t++) {
    const turn = currentTurn(pack, state);
    const available = turn.options.filter((o) => o.available);
    if (available.length === 0) throw new Error(`no available option on "${turn.event.id}"`);
    const chosen = choose(available, rng);
    visit?.({ turn, state, chosen });
    state = takeTurn(pack, state, chosen.option.id).state;
  }
  return state;
}

/** Play every archetype across several seeds, reporting what was reached. */
export function sweep(pack, { seeds = 12, turns = 200 } = {}) {
  const firedEvents = new Set();
  const takenOptions = new Set();
  // What a player *could* have picked. This, not what a bot happened to pick,
  // is what "is this content reachable" means — a real player chooses freely,
  // and an archetype's preferences are an artefact of the harness.
  const offeredOptions = new Set();
  const byStrategy = {};

  for (const strategy of Object.keys(strategies)) {
    const finals = [];
    for (let seed = 0; seed < seeds; seed++) {
      const state = play(pack, {
        strategy,
        seed,
        turns,
        visit: ({ turn, chosen }) => {
          firedEvents.add(turn.event.id);
          takenOptions.add(`${turn.event.id}.${chosen.option.id}`);
          for (const resolved of turn.options) {
            if (resolved.available) offeredOptions.add(`${turn.event.id}.${resolved.option.id}`);
          }
        },
      });
      finals.push(state);
    }
    byStrategy[strategy] = finals;
  }
  return { firedEvents, takenOptions, offeredOptions, byStrategy };
}

export const median = (values) =>
  [...values].sort((a, b) => a - b)[Math.floor(values.length / 2)];