import type { Holding, PortfolioSummary } from '@/lib/types';

function asFiniteNumber(value: string | number | null | undefined) {
  if (value === null || value === undefined) {
    return 0;
  }

  const parsed = typeof value === 'number' ? value : Number(value);
  return Number.isFinite(parsed) ? parsed : 0;
}

function toDecimalString(value: number, digits = 4) {
  return value.toFixed(digits);
}

export function recalculateHolding(base: Holding): Holding {
  const shares = asFiniteNumber(base.shares);
  const avgCost = asFiniteNumber(base.avg_cost);
  const price = base.current_price === null
    ? avgCost
    : asFiniteNumber(base.current_price);

  const marketValue = shares * price;
  const costBasis = shares * avgCost;
  const gainLoss = marketValue - costBasis;
  const gainLossPct = costBasis > 0 ? (gainLoss / costBasis) * 100 : 0;

  return {
    ...base,
    shares: toDecimalString(shares, 6),
    avg_cost: toDecimalString(avgCost, 6),
    current_price: toDecimalString(price, 6),
    market_value: toDecimalString(marketValue, 2),
    gain_loss: toDecimalString(gainLoss, 2),
    gain_loss_pct: toDecimalString(gainLossPct, 2)
  };
}

export function buildPortfolioSummary(holdings: Holding[]): PortfolioSummary {
  const positions = holdings.length;

  const totals = holdings.reduce(
    (acc, holding) => {
      const shares = asFiniteNumber(holding.shares);
      const avgCost = asFiniteNumber(holding.avg_cost);
      const marketValue = asFiniteNumber(holding.market_value);
      const gainLoss = asFiniteNumber(holding.gain_loss);

      acc.totalValue += marketValue;
      acc.totalGainLoss += gainLoss;
      acc.totalCostBasis += shares * avgCost;

      return acc;
    },
    { totalValue: 0, totalGainLoss: 0, totalCostBasis: 0 }
  );

  const avgReturnPct = totals.totalCostBasis > 0
    ? (totals.totalGainLoss / totals.totalCostBasis) * 100
    : 0;

  return {
    positions,
    total_value: toDecimalString(totals.totalValue, 2),
    total_gain_loss: toDecimalString(totals.totalGainLoss, 2),
    total_cost_basis: toDecimalString(totals.totalCostBasis, 2),
    avg_return_pct: toDecimalString(avgReturnPct, 2)
  };
}