Battle-for-Tismo/shared/game_state/budget.js

// The monthly budget ledger. Money moves in and out of a nation's treasury all
// day; this keeps a running total for the calendar month, filed under the
// expense categories the budget screen shows, so the panel can report what the
// current month has cost so far and what each past month cost.
//
// Two figures are kept per category. `cash` is the money that actually left the
// treasury; `economic` is the market value of the materials the category
// consumed, whether they were drawn from the nation's stores or bought -- the
// upkeep rows consume stock for free, so their economic cost is the truer
// measure of what they took. Income and resource sales are the positive side.
//
// On every calendar-month rollover the live ledger is frozen into the history
// and a fresh one begins, so the panel can page back through the last two years.

import { BUDGET_EXPENSE_CATEGORIES } from "../data/economy.js";
import { MONTH_NAMES } from "../game_clock.js";

// How many completed months the history keeps. Two years is enough to compare a
// season with the one before it without growing the snapshot without bound.
export const BUDGET_HISTORY_MONTHS = 24;

function emptyBudgetLedger() {
  // Tax income is booked under the kind of trade tax that raised it; `income` is
  // kept as the running total the report reads.
  const cash = { income: 0, sell: 0, taxSales: 0, taxExport: 0, taxImport: 0 };
  const economic = {};
  for (const category of BUDGET_EXPENSE_CATEGORIES) {
    cash[category.id] = 0;
    economic[category.id] = 0;
  }
  // Money spent per category, broken down by the resource it bought, so an
  // expense row can expand to show what it consumed and what it paid.
  const resourceByCategory = {};
  for (const category of BUDGET_EXPENSE_CATEGORIES) resourceByCategory[category.id] = {};
  return { cash, economic, resourceBuy: {}, resourceSell: {}, resourceByCategory };
}

export const budgetMethods = {
  _initBudgetHistory() {
    this.budgetLedger = new Map();
    for (let civ = 0; civ < this.civilisations.length; civ++) {
      this.budgetLedger.set(civ, emptyBudgetLedger());
    }
    // Frozen months, oldest first: [{ monthIndex, records: [ledger, ...] }].
    this.budgetHistory = [];
  },

  _budgetRecord(civ) {
    if (!this.budgetLedger) this._initBudgetHistory();
    let record = this.budgetLedger.get(civ);
    if (!record) {
      record = emptyBudgetLedger();
      this.budgetLedger.set(civ, record);
    }
    return record;
  },

  // A signed cash movement for the month: positive is money into the treasury
  // (tax, a resource sale, a refund), negative is money spent. Recorded once per
  // category so the report can total them.
  _recordBudgetCash(civ, category, amount) {
    if (civ < 0 || !(amount !== 0)) return;
    const record = this._budgetRecord(civ);
    record.cash[category] = (record.cash[category] || 0) + amount;
  },

  // The market value of the materials one category consumed, whatever their
  // source, so an upkeep row can show what it cost even when the stores paid.
  _recordBudgetEconomic(civ, category, amount) {
    if (civ < 0 || !(amount > 0)) return;
    const record = this._budgetRecord(civ);
    record.economic[category] = (record.economic[category] || 0) + amount;
  },

  // The money one expense category spent on one resource, so the row can be
  // expanded to show what it bought. `source` names what consumed it -- a
  // building, unit, work or transport type -- and is optional.
  _recordBudgetCategoryResource(civ, category, resource, amount, source = null) {
    if (civ < 0 || !(amount > 0)) return;
    const record = this._budgetRecord(civ);
    const byResource = record.resourceByCategory[category]
      || (record.resourceByCategory[category] = {});
    let entry = byResource[resource];
    if (!entry || typeof entry === "number") {
      entry = { total: typeof entry === "number" ? entry : 0, sources: {} };
      byResource[resource] = entry;
    }
    entry.total += amount;
    if (source) entry.sources[source] = (entry.sources[source] || 0) + amount;
  },

  // The money a nation spent buying and earned selling one resource to the
  // world market or another country, for the month's resource-trade memo.
  _recordBudgetResource(civ, resource, bought, sold) {
    if (civ < 0) return;
    const record = this._budgetRecord(civ);
    if (bought > 0) record.resourceBuy[resource] = (record.resourceBuy[resource] || 0) + bought;
    if (sold > 0) record.resourceSell[resource] = (record.resourceSell[resource] || 0) + sold;
  },

  // Freezes the month that just ended and starts a new ledger. Called from the
  // monthly rollover with the month index that is being closed.
  _rolloverBudget(previousIndex) {
    if (!this.budgetLedger) return;
    const records = [];
    for (let civ = 0; civ < this.civilisations.length; civ++) {
      records.push(this.budgetLedger.get(civ) || emptyBudgetLedger());
    }
    this.budgetHistory.push({ monthIndex: previousIndex, records });
    while (this.budgetHistory.length > BUDGET_HISTORY_MONTHS) this.budgetHistory.shift();
    this.budgetLedger = new Map();
    for (let civ = 0; civ < this.civilisations.length; civ++) {
      this.budgetLedger.set(civ, emptyBudgetLedger());
    }
  },

  // Every month the panel may show, oldest first, with the live month last.
  budgetMonthReports(civ) {
    const reports = [];
    for (const entry of this.budgetHistory || []) {
      reports.push(this._budgetReport(civ, entry.monthIndex, entry.records[civ], false));
    }
    const currentIndex = this._monthIndexOf(this.totalHours);
    reports.push(this._budgetReport(
      civ,
      currentIndex,
      this.budgetLedger ? this.budgetLedger.get(civ) : null,
      true
    ));
    return reports;
  },

  _budgetReport(civ, monthIndex, record, isCurrent) {
    const cash = (record && record.cash) || {};
    const economic = (record && record.economic) || {};
    const expenses = [];
    let totalCash = 0;
    let totalEconomic = 0;
    const resourceByCategory = (record && record.resourceByCategory) || {};
    for (const category of BUDGET_EXPENSE_CATEGORIES) {
      const spent = Math.max(0, -(cash[category.id] || 0));
      const cost = Math.max(0, economic[category.id] || 0, spent);
      if (spent === 0 && cost === 0) continue;
      // Each buy is [resource, money, [[source, money], ...]]: what the
      // category bought and which buildings, units or works consumed it.
      const buys = Object.entries(resourceByCategory[category.id] || {})
        .map(([resource, detail]) => {
          if (typeof detail === "number") return [resource, detail, []];
          const sources = Object.entries(detail.sources || {})
            .filter(([, amount]) => amount > 0)
            .sort((a, b) => b[1] - a[1]);
          return [resource, detail.total || 0, sources];
        })
        .filter(([, amount]) => amount > 0)
        .sort((a, b) => b[1] - a[1]);
      expenses.push({
        id: category.id,
        label: category.label,
        group: category.group,
        cash: spent,
        economic: cost,
        buys,
      });
      totalCash += spent;
      totalEconomic += cost;
    }
    const resourceBuy = (record && record.resourceBuy) || {};
    const resourceSell = (record && record.resourceSell) || {};
    const resourceIds = new Set([...Object.keys(resourceBuy), ...Object.keys(resourceSell)]);
    const resourceTrade = Array.from(resourceIds)
      .map((id) => ({
        id,
        bought: Math.max(0, resourceBuy[id] || 0),
        sold: Math.max(0, resourceSell[id] || 0),
      }))
      .filter((entry) => entry.bought > 0 || entry.sold > 0);
    const taxes = {
      sales: cash.taxSales || 0,
      export: cash.taxExport || 0,
      import: cash.taxImport || 0,
    };
    const income = taxes.sales + taxes.export + taxes.import;
    const sales = cash.sell || 0;
    const year = Math.floor(monthIndex / 12);
    const month = monthIndex % 12;
    return {
      monthIndex,
      isCurrent,
      label: `${MONTH_NAMES[month]} ${year}`,
      income,
      taxes,
      sales,
      expenses,
      resourceTrade,
      totalCash,
      totalEconomic,
      net: income + sales - totalCash,
    };
  },
};