// Endless upgrades: once a family of upgrades is complete (its `requires`
// milestone is owned), it continues forever as a repeatable line. Every level
// multiplies the effect once more and costs exponentially more, up to
// `maxLevel` levels, which nobody will ever reach.

import { bulkCost, maxAffordable } from './formulas.js';

export const lineLevel = (state, id) => state.endless[id] ?? 0;

export function lineAvailable(state, line) {
  return !line.requires || state.upgrades.includes(line.requires);
}

/** How many levels `amount` ("max" or a number) buys right now, and what they cost. */
export function endlessQuote(state, ctx, id, amount) {
  const line = ctx.endlessById.get(id);
  const level = lineLevel(state, id);
  const wanted =
    amount === 'max' ? maxAffordable(line.baseCost, line.costGrowth, level, state.funds) : amount;
  const count = Math.max(0, Math.min(wanted, line.maxLevel - level));
  return { count, cost: bulkCost(line.baseCost, line.costGrowth, level, count) };
}

export function buyEndless(state, ctx, id, amount = 1) {
  const line = ctx.endlessById.get(id);
  if (!line || !lineAvailable(state, line)) return false;
  const { count, cost } = endlessQuote(state, ctx, id, amount);
  if (count <= 0 || !(state.funds >= cost)) return false; // an infinite cost is never affordable
  state.funds -= cost;
  state.endless[id] = lineLevel(state, id) + count;
  return true;
}