elysium/apps/api/src/services/offlineProgress.ts

/**
 * @file Offline earnings calculator for gold and essence accrued while logged out.
 * @copyright nhcarrigan
 * @license Naomi's Public License
 * @author Naomi Carrigan
 */
/* eslint-disable max-lines-per-function -- Offline earnings calculation requires iterating all adventurers with multi-step math */
import type { GameState } from "@elysium/types";

/**
 * Maximum offline accrual cap: 8 hours.
 */
const maxOfflineSeconds = 8 * 60 * 60;

/**
 * Calculates the gold and essence earned whilst the player was offline.
 * Capped at 8 hours to prevent exploit via system clock manipulation.
 * Applies the same multipliers as the client-side tick engine.
 * @param state - The current game state to calculate offline earnings from.
 * @param nowMs - The current timestamp in milliseconds.
 * @returns The gold, essence, and elapsed seconds earned offline.
 */
const calculateOfflineEarnings = (
  state: GameState,
  nowMs: number,
): { offlineGold: number; offlineEssence: number; offlineSeconds: number } => {
  const elapsedSeconds = Math.min(
    (nowMs - state.lastTickAt) / 1000,
    maxOfflineSeconds,
  );

  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- Defensive check for runtime nullable fields
  const equipmentGoldMultiplier = (state.equipment ?? []).
    filter((item) => {
      return item.equipped;
    }).
    reduce((mult, item) => {
      return mult * (item.bonus.goldMultiplier ?? 1);
    }, 1);

  const runestonesIncome = state.prestige.runestonesIncomeMultiplier ?? 1;
  const runestonesEssence = state.prestige.runestonesEssenceMultiplier ?? 1;

  let goldPerSecond = 0;
  let essencePerSecond = 0;

  for (const adventurer of state.adventurers) {
    if (!adventurer.unlocked || adventurer.count === 0) {
      continue;
    }

    const upgradeMultiplier = state.upgrades.
      filter((upgrade) => {
        const isGlobal = upgrade.target === "global";
        const isForAdventurer
          = upgrade.target === "adventurer"
          && upgrade.adventurerId === adventurer.id;
        const affectsAdventurer = isGlobal || isForAdventurer;
        return upgrade.purchased && affectsAdventurer;
      }).
      reduce((mult, upgrade) => {
        return mult * upgrade.multiplier;
      }, 1);

    const prestige = state.prestige.productionMultiplier;

    const goldContribution
      = adventurer.goldPerSecond
      * adventurer.count
      * upgradeMultiplier
      * prestige
      * runestonesIncome
      * equipmentGoldMultiplier;
    goldPerSecond = goldPerSecond + goldContribution;

    const essenceContribution
      = adventurer.essencePerSecond
      * adventurer.count
      * upgradeMultiplier
      * prestige
      * runestonesEssence;
    essencePerSecond = essencePerSecond + essenceContribution;
  }

  return {
    offlineEssence: essencePerSecond * elapsedSeconds,
    offlineGold:    goldPerSecond * elapsedSeconds,
    offlineSeconds: elapsedSeconds,
  };
};

export { calculateOfflineEarnings };