const VALUE_SCALE = 18;
const VALUE_FACTOR = 10n ** BigInt(VALUE_SCALE);

export function computePortfolioMetric({
  baseline = null,
  currentInventory,
  currentPrice,
  btcAsset,
  eureAsset,
  commandCount = 0,
  resultCount = 0,
} = {}) {
  if (!currentInventory || !currentPrice || !btcAsset?.assetId || !eureAsset?.assetId) {
    return null;
  }

  const currentBtcUnits = String(currentInventory.spendable?.[btcAsset.assetId] || '0');
  const currentEureUnits = String(currentInventory.spendable?.[eureAsset.assetId] || '0');
  const currentBtc = unitsToScaledDecimal(currentBtcUnits, btcAsset.decimals);
  const currentEure = unitsToScaledDecimal(currentEureUnits, eureAsset.decimals);
  const currentPriceScaled = parseScaledDecimal(currentPrice.eure_per_btc);
  const currentBtcMarkValue = multiplyScaled(currentBtc, currentPriceScaled);
  const currentPortfolioValue = currentEure + currentBtcMarkValue;

  const payload = {
    metric_version: 1,
    baseline_status: baseline ? 'active' : 'awaiting_first_execution',
    command_count: commandCount,
    result_count: resultCount,
    current_price: {
      price_id: currentPrice.price_id || null,
      observed_at: currentPrice.observed_at || null,
      eure_per_btc: String(currentPrice.eure_per_btc),
    },
    current_inventory: buildInventoryView({
      inventory: currentInventory,
      btcAsset,
      eureAsset,
    }),
    current_portfolio_value_eure: formatScaledDecimal(currentPortfolioValue),
    current_btc_mark_value_eure: formatScaledDecimal(currentBtcMarkValue),
    current_eure_cash_value_eure: formatScaledDecimal(currentEure),
    trade_pnl_eure: null,
    mark_to_market_pnl_eure: null,
    price_move_pnl_eure: null,
    baseline_portfolio_value_eure_at_baseline_price: null,
    baseline_portfolio_value_eure_at_current_price: null,
    current_portfolio_value_eure_at_baseline_price: null,
    inventory_delta: null,
    baseline: null,
  };

  if (!baseline?.inventory || !baseline?.price) {
    return payload;
  }

  const baselineBtcUnits = String(baseline.inventory.spendable?.[btcAsset.assetId] || '0');
  const baselineEureUnits = String(baseline.inventory.spendable?.[eureAsset.assetId] || '0');
  const baselineBtc = unitsToScaledDecimal(baselineBtcUnits, btcAsset.decimals);
  const baselineEure = unitsToScaledDecimal(baselineEureUnits, eureAsset.decimals);
  const baselinePriceScaled = parseScaledDecimal(baseline.price.eure_per_btc);
  const baselinePortfolioAtBaselinePrice = baselineEure + multiplyScaled(baselineBtc, baselinePriceScaled);
  const baselinePortfolioAtCurrentPrice = baselineEure + multiplyScaled(baselineBtc, currentPriceScaled);
  const currentPortfolioAtBaselinePrice = currentEure + multiplyScaled(currentBtc, baselinePriceScaled);
  const tradePnl = currentPortfolioAtBaselinePrice - baselinePortfolioAtBaselinePrice;
  const markToMarketPnl = currentPortfolioValue - baselinePortfolioAtCurrentPrice;
  const priceMovePnl = markToMarketPnl - tradePnl;

  payload.trade_pnl_eure = formatScaledDecimal(tradePnl);
  payload.mark_to_market_pnl_eure = formatScaledDecimal(markToMarketPnl);
  payload.price_move_pnl_eure = formatScaledDecimal(priceMovePnl);
  payload.baseline_portfolio_value_eure_at_baseline_price = formatScaledDecimal(
    baselinePortfolioAtBaselinePrice,
  );
  payload.baseline_portfolio_value_eure_at_current_price = formatScaledDecimal(
    baselinePortfolioAtCurrentPrice,
  );
  payload.current_portfolio_value_eure_at_baseline_price = formatScaledDecimal(
    currentPortfolioAtBaselinePrice,
  );
  payload.inventory_delta = {
    btc_units: (BigInt(currentBtcUnits) - BigInt(baselineBtcUnits)).toString(),
    btc: formatScaledDecimal(currentBtc - baselineBtc),
    eure_units: (BigInt(currentEureUnits) - BigInt(baselineEureUnits)).toString(),
    eure: formatScaledDecimal(currentEure - baselineEure),
  };
  payload.baseline = {
    anchor: baseline.anchor || 'latest_inventory_before_first_command',
    command_at: baseline.command_at || null,
    price: {
      price_id: baseline.price.price_id || null,
      observed_at: baseline.price.observed_at || null,
      eure_per_btc: String(baseline.price.eure_per_btc),
    },
    inventory: buildInventoryView({
      inventory: baseline.inventory,
      btcAsset,
      eureAsset,
    }),
  };

  return payload;
}

export function buildPortfolioMetricId({ baselineInventoryId, currentInventoryId, currentPriceId }) {
  return [
    'portfolio-metric',
    baselineInventoryId || 'no-baseline',
    currentInventoryId || 'no-current-inventory',
    currentPriceId || 'no-current-price',
  ].join(':');
}

function buildInventoryView({ inventory, btcAsset, eureAsset }) {
  const spendable = inventory?.spendable || {};
  const btcUnits = String(spendable[btcAsset.assetId] || '0');
  const eureUnits = String(spendable[eureAsset.assetId] || '0');

  return {
    inventory_id: inventory?.inventory_id || null,
    synced_at: inventory?.synced_at || null,
    btc_units: btcUnits,
    btc: formatAssetUnits(btcUnits, btcAsset.decimals),
    eure_units: eureUnits,
    eure: formatAssetUnits(eureUnits, eureAsset.decimals),
  };
}

function unitsToScaledDecimal(units, decimals) {
  return BigInt(units || '0') * 10n ** BigInt(VALUE_SCALE - decimals);
}

function formatAssetUnits(units, decimals) {
  return formatScaledDecimal(BigInt(units || '0') * 10n ** BigInt(VALUE_SCALE - decimals));
}

function parseScaledDecimal(value) {
  const normalized = String(value ?? '0').trim();
  const negative = normalized.startsWith('-');
  const unsigned = normalized.replace(/^[+-]/, '');
  const [wholePart, fractionalPart = ''] = unsigned.split('.');
  const whole = BigInt(wholePart || '0');
  const fractional = BigInt((fractionalPart.padEnd(VALUE_SCALE, '0')).slice(0, VALUE_SCALE) || '0');
  const scaled = (whole * VALUE_FACTOR) + fractional;
  return negative ? -scaled : scaled;
}

function multiplyScaled(left, right) {
  return (left * right) / VALUE_FACTOR;
}

function formatScaledDecimal(value) {
  const negative = value < 0n;
  const absolute = negative ? -value : value;
  const whole = absolute / VALUE_FACTOR;
  const fractional = absolute % VALUE_FACTOR;
  if (fractional === 0n) {
    return `${negative ? '-' : ''}${whole}`;
  }
  const fractionalText = fractional.toString().padStart(VALUE_SCALE, '0').replace(/0+$/, '');
  return `${negative ? '-' : ''}${whole}.${fractionalText}`;
}