// Public finances: revenue, spending, interest, debt and GDP. All flows are in
// % of GDP per year; debt and gdp are absolute (billions of the scenario currency).

import { TAX_IDS, clamp } from "./state.js";

// Laffer-style curve: revenue peaks at rate == peak, then falls.
export function taxRevenue(id, rate, bal) {
  const t = bal.tax[id];
  return t.coef * rate * (1 - rate / (2 * t.peak));
}

export function interestRate(debtRatio, bal) {
  const d = bal.debt;
  const excess = Math.max(0, debtRatio - d.premiumFrom);
  return d.baseRate + d.premiumCoef * excess * excess;
}

export function computeFiscal(state, bal) {
  const e = state.economy;
  let revenue = e.otherRevenue;
  for (const id of TAX_IDS) revenue += taxRevenue(id, e.taxes[id], bal);
  // Receipts follow the cycle: a slump costs revenue, a boom adds some.
  revenue += (bal.fiscal?.growthSens ?? 0) * (e.growth - state.ref.vars.growth);

  const debtRatio = (e.debt / e.gdp) * 100;
  const rate = interestRate(debtRatio, bal);
  const interest = (debtRatio * rate) / 100;

  let allocTotal = 0;
  for (const s of Object.values(state.sectors)) allocTotal += s.alloc;
  const spending = allocTotal + interest + e.extraSpending;

  return { revenue, allocTotal, interest, spending, deficit: spending - revenue, debtRatio, rate };
}

// Derived quantities that indicator/variable targets are written against.
// ref values are captured at game creation so the start is an equilibrium.
export function computeDevs(state, bal, fiscal) {
  const e = state.economy;
  let taxPressure = 0;
  let taxGrowthDrag = 0;
  for (const id of TAX_IDS) {
    const d = e.taxes[id] - state.ref.taxes[id];
    taxPressure += bal.tax[id].opinion * d;
    taxGrowthDrag += bal.tax[id].growth * d;
  }
  const start = bal.crackdown.unrestStart;
  return {
    growth: e.growth,
    unemployment: e.unemployment,
    inflation: e.inflation,
    debt: Math.max(0, fiscal.debtRatio - bal.debt.freeBelow),
    deficit: fiscal.deficit,
    taxPressure,
    taxGrowthDrag,
    // police sent in when unrest is high: 0..1
    crackdown: clamp((state.indicators.unrest - start) / (100 - start), 0, 1),
  };
}

export function advanceEconomy(state, fiscal) {
  const e = state.economy;
  e.debt = Math.max(0, e.debt + ((fiscal.deficit / 100) * e.gdp) / 365);
  e.gdp *= Math.pow(1 + e.growth / 100, 1 / 365);
}

// Player action, only allowed while the quarterly review is open.
export function setBudget(state, bal, { alloc = {}, taxes = {} } = {}) {
  if (!state.pending.review) return { ok: false, errors: ["budget_locked"] };

  const errors = [];
  for (const [id, v] of Object.entries(alloc)) {
    const s = state.sectors[id];
    if (!s) errors.push(`unknown_sector:${id}`);
    else if (!(v >= 0 && v <= s.need * bal.limits.allocMaxRatio)) errors.push(`alloc_out_of_range:${id}`);
  }
  for (const [id, v] of Object.entries(taxes)) {
    if (!TAX_IDS.includes(id)) errors.push(`unknown_tax:${id}`);
    else if (!(v >= 0 && v <= bal.tax[id].peak * bal.limits.taxMaxFactorOfPeak)) errors.push(`tax_out_of_range:${id}`);
  }
  if (errors.length) return { ok: false, errors };

  for (const [id, v] of Object.entries(alloc)) state.sectors[id].alloc = v;
  for (const [id, v] of Object.entries(taxes)) state.economy.taxes[id] = v;
  return { ok: true, errors: [] };
}

export function confirmBudget(state) {
  state.pending.review = false;
  state.risk.emergency = false;
}