Battle-for-Tismo/shared/resources.js

// Pure resource maths shared by the server (which simulates the economy) and
// the browser (which explains it). Everything here is framework-free and takes
// plain numbers, so both sides derive identical figures from the same rules in
// shared/data/resources.js.

import {
  RESOURCE_IDS,
  RESOURCE_RULES,
  RESOURCE_MARKET,
  RESOURCE_MARKET_BASE,
  formatEnergy,
  formatResourceAmount,
} from "./data/resources.js";
import { EFFECT_RESEARCH } from "./data/effects.js";

const DAYS_PER_YEAR = 365;

// The amount formatters live with the resource catalogue so its descriptions
// can quote the same figures; re-exported here for the existing callers.
export { formatEnergy, formatResourceAmount };

// --------------------------------------------------------------- per-person --

export function foodNeedPerDay(population) {
  return Math.max(0, population) * RESOURCE_RULES.foodPerPersonPerDay;
}

// The food a unit eats in a day from its carried stores. Aircraft and ships do
// not: they live on endurance and range instead. Every land unit fields a
// company of `population` (or the rule's default), fed like the civilians of
// that size. Mirrors GameState._tickUnitSupply so the card and the tick agree.
export function unitFoodPerDay(proto) {
  if (!proto || proto.air || proto.naval) return 0;
  if (!(proto.traversableTerrains || []).includes("Land")) return 0;
  return foodNeedPerDay(proto.population || RESOURCE_RULES.unitPopulation);
}

export function steelNeedPerDay(population) {
  return Math.max(0, population) * RESOURCE_RULES.steelPerPersonPerDay;
}

export function luxuryNeedPerDay(population) {
  return Math.max(0, population) * RESOURCE_RULES.luxuryPerPersonPerDay;
}

// What one worked land tile grows in a day. Food comes from the land, not from
// how many people live on it: a farm feeds whoever works it, so moving people
// between regions changes only the income per head, never the harvest. A tile
// feeds roughly `ECONOMY.basePopulation` people at factor 1.
export function tileFoodOutput(tile) {
  const factor = RESOURCE_RULES.tileFoodFactor[tile.terrainType] ?? 1;
  return RESOURCE_RULES.foodPerTilePerDay * factor;
}

// The reserve a region wants to hold of a material it consumes: a month at the
// current appetite. Every storable good is buffered to the same horizon, so the
// same figure sizes food, steel, luxury and high-tech reserves alike.
export function stockpileTarget(needPerDay) {
  return Math.max(0, needPerDay) * RESOURCE_RULES.stockpileDays;
}

// How much food a city wants in store before the coming month: a month at the
// current appetite.
export function foodMonthlyTarget(population) {
  return stockpileTarget(foodNeedPerDay(population));
}

// The energy a region spends to force `extraFood` tonnes a day from the land
// beyond its harvest. Quadratic in the extra food, so the marginal tonne gets
// dearer the harder the land is pushed.
export function foodSynthesisEnergy(extraFood) {
  const x = Math.max(0, extraFood);
  return RESOURCE_RULES.foodSynthesisQuadratic * x * x;
}

// The marginal energy for one more tonne of synthesised food, the slope of
// `foodSynthesisEnergy`.
export function foodSynthesisMarginalEnergy(extraFood) {
  return 2 * RESOURCE_RULES.foodSynthesisQuadratic * Math.max(0, extraFood);
}

// How much extra food a region grows for a `shortfall` it can cover. Growing is
// always cheapest for the first tonnes (its marginal energy starts near zero)
// and buying is a flat price, so the region grows while the marginal energy is
// cheaper than the market, up to the break-even. Then it completes with the
// dearer option: what the reachable market cannot actually supply -- `buyable`
// tonnes -- it must grow itself, even past the break-even. With an unreachable
// or bottomless market the default `buyable = Infinity` gives the plain
// break-even result.
//
// `shortfall` is how much the region would *like* to grow -- the day's meal
// plus whatever it must add to refill an empty reserve. `mustGrow` is the part
// it cannot avoid: the ration it must force because it cannot buy that much. It
// defaults to the whole shortfall, which is the old single-target behaviour.
export function synthesisedFoodFor(
  foodPrice, energyPrice, shortfall, buyable = Infinity, mustGrow = shortfall
) {
  const gap = Math.max(0, shortfall);
  if (!(gap > 0)) return 0;
  const forced = Math.max(0, Math.max(0, mustGrow) - Math.max(0, buyable));
  const quadratic = RESOURCE_RULES.foodSynthesisQuadratic;
  if (!(energyPrice > 0) || !(quadratic > 0) || !(foodPrice > 0)) {
    return Math.min(gap, forced);
  }
  const breakEven = foodPrice / (2 * quadratic * energyPrice);
  if (!(breakEven > 0)) return Math.min(gap, forced);
  return Math.min(gap, Math.max(breakEven, forced));
}

// A city's baseline electric appetite, kWh a day, from its yearly GDP.
export function cityEnergyPerDay(gdp) {
  return Math.max(0, gdp) * RESOURCE_RULES.gdpEnergyIntensity / DAYS_PER_YEAR;
}

// What one building level, unit or tile work wears out in a day, from its money
// value. Advanced things also burn high-tech. Buildings pass their level's cost
// (so upkeep grows with the level), units their training cost.
export function upkeepResources(value, advanced = false) {
  const amount = Math.max(0, value);
  return {
    steel: amount * RESOURCE_RULES.upkeepSteelPerEuro,
    energy: amount * RESOURCE_RULES.upkeepEnergyPerEuro,
    hightech: advanced ? amount * RESOURCE_RULES.upkeepHighTechPerEuro : 0,
  };
}

// The daily upkeep of a catalogue entry. An explicit `materialUpkeep` override
// wins -- guns and aircraft are cheap parked and costly when fired, so their
// standing bill is set by hand -- otherwise it scales with the entry's value.
export function protoUpkeep(proto, value) {
  if (proto && proto.materialUpkeep) {
    return {
      steel: proto.materialUpkeep.steel || 0,
      energy: proto.materialUpkeep.energy || 0,
      hightech: proto.materialUpkeep.hightech || 0,
    };
  }
  return upkeepResources(value, !!(proto && proto.advanced));
}

// The materials and power a tile improvement spends to be built: steel in
// proportion to its money cost, the electricity that steel embodies, and
// high-tech for an advanced work. Shared so the server's bill and the browser's
// cost buttons agree on the same figures.
export function tileImprovementResourceCost(proto, buildCost = null) {
  const cost = Math.max(0, buildCost !== null ? buildCost : ((proto && proto.buildCost) || 0));
  return {
    steel: cost * RESOURCE_RULES.steelPerBudgetEuro,
    energy: cost * RESOURCE_RULES.constructionEnergyPerBudgetEuro,
    hightech: proto && proto.advanced ? RESOURCE_RULES.constructionHighTechPerLevel : 0,
  };
}

// The steel and high-tech a building or unit spends to be built: steel in
// proportion to its money cost, high-tech for an advanced item (more with every
// level). Mirrors the server's construction bill so the browser can quote it at
// today's prices.
export function constructionResourceCost(proto, level = 0, buildCost = null) {
  const cost = buildCost !== null ? buildCost : ((proto && (proto.buildCost || proto.baseCost)) || 0);
  const advanced = !!(proto && (proto.advanced ||
    (proto.effects || []).some((e) => e.stat === EFFECT_RESEARCH)));
  return {
    steel: Math.max(0, cost) * RESOURCE_RULES.steelPerBudgetEuro,
    hightech: advanced ? RESOURCE_RULES.constructionHighTechPerLevel * (level + 1) : 0,
  };
}

// Today's global price index: the average ratio of each resource's current
// price to its base. One figure lets a money cost with no material bill of its
// own be quoted at the market.
export function marketPriceIndex(prices) {
  let total = 0;
  let count = 0;
  for (const id of RESOURCE_IDS) {
    const base = RESOURCE_MARKET_BASE[id];
    if (!(base > 0)) continue;
    const price = prices && prices[id] !== undefined ? prices[id] : base;
    total += price / base;
    count += 1;
  }
  return count > 0 ? total / count : 1;
}

// The market value of a resource bill at the given prices, a resource at a time.
export function resourceMarketValue(resources, prices) {
  let total = 0;
  for (const id of RESOURCE_IDS) {
    const amount = (resources && resources[id]) || 0;
    if (!(amount > 0)) continue;
    const price = prices && prices[id] !== undefined ? prices[id] : RESOURCE_MARKET_BASE[id];
    total += amount * (price || 0);
  }
  return total;
}

// The energy a material producer burns to make its output: the energy-per-unit
// ratio from the rules, whichever resource it makes.
export function producerEnergyPerDay(id, outputPerDay) {
  if (id === "steel") return outputPerDay * RESOURCE_RULES.energyPerSteelTonne;
  if (id === "food") return outputPerDay * RESOURCE_RULES.energyPerFoodTonne;
  if (id === "hightech") return outputPerDay * RESOURCE_RULES.energyPerHighTechUnit;
  return 0;
}

// ----------------------------------------------------------------- market --

// Eases a price toward the equilibrium the day's world-wide supply and demand
// imply: the price that clears supply against demand is `base * demand/supply`,
// and the price travels a fixed share of the way there each day. A sustained
// shortage therefore lifts a good above its base and a glut cheapens it, but the
// price settles at the equilibrium instead of compounding without bound, so no
// price band is needed to keep it sane. A day with no supply at all is treated as
// the sharpest shortage the ratio may read, and the ratio is capped so a
// rounding-error supply cannot run the equilibrium away.
export function nextMarketPrice(basePrice, price, supply, demand) {
  if (!(demand > 0)) return basePrice;
  const ratio = supply > 0 ? demand / supply : RESOURCE_MARKET.maxRatio;
  const equilibrium = basePrice * Math.min(ratio, RESOURCE_MARKET.maxRatio);
  return price + (equilibrium - price) * RESOURCE_MARKET.adjustment;
}