// Investments: nine societies in three risk tiers. Every `intervalSeconds` each
// price moves by a random percentage within the tier's swing (low ±5 %, mid
// ±15 %, high ±50 %), then drifts back towards its fair value (more weakly for the wilder tiers), and
// holdings pay a small dividend. Buying and selling carries a small fee.

import { clamp } from './formulas.js';

export function holdingValue(state, id) {
  return state.invest.holdings[id] * state.invest.prices[id];
}

export function portfolio(state, ctx) {
  let value = 0;
  let basis = 0;
  for (const s of ctx.investments.societies) {
    value += holdingValue(state, s.id);
    basis += state.invest.basis[s.id];
  }
  return { value, basis, profit: value - basis };
}

function repriceAll(state, ctx, rng, dividendMultiplier) {
  const cfg = ctx.investments;
  const inv = state.invest;
  for (const s of cfg.societies) {
    const tier = cfg.tiers[s.tier];
    const before = inv.prices[s.id];
    let price = before * (1 + (rng() * 2 - 1) * tier.swing);
    price += (s.basePrice - price) * tier.reversion;
    price = clamp(price, s.basePrice * cfg.minRatio, s.basePrice * cfg.maxRatio);
    inv.prices[s.id] = price;
    inv.change[s.id] = price / before - 1;
    state.funds += inv.holdings[s.id] * price * tier.dividend * dividendMultiplier;
  }
}

export function stepInvestments(state, ctx, dt, rng, mods) {
  state.investTimer += dt;
  while (state.investTimer >= ctx.investments.intervalSeconds) {
    state.investTimer -= ctx.investments.intervalSeconds;
    repriceAll(state, ctx, rng, mods.dividend);
  }
}

/** Spend `fraction` of the current funds on society `id`. */
export function buyShares(state, ctx, id, fraction) {
  if (!ctx.societiesById.has(id)) return false;
  const spend = state.funds * clamp(fraction, 0, 1);
  if (!(spend >= 0.01)) return false;
  state.funds -= spend;
  state.invest.holdings[id] += (spend * (1 - ctx.investments.fee)) / state.invest.prices[id];
  state.invest.basis[id] += spend;
  return true;
}

/** Sell `fraction` of what is held in society `id`. */
export function sellShares(state, ctx, id, fraction) {
  if (!ctx.societiesById.has(id)) return false;
  const inv = state.invest;
  const share = clamp(fraction, 0, 1);
  if (!(inv.holdings[id] > 0) || share <= 0) return false;

  const proceeds = inv.holdings[id] * share * inv.prices[id] * (1 - ctx.investments.fee);
  const basisPart = inv.basis[id] * share;
  state.funds += proceeds;
  state.stats.investProfit += proceeds - basisPart;
  if (share >= 1) {
    inv.holdings[id] = 0;
    inv.basis[id] = 0;
  } else {
    inv.holdings[id] -= inv.holdings[id] * share;
    inv.basis[id] -= basisPart;
  }
  return true;
}