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

export function computePortfolioMetric({
  baseline = null,
  currentInventory,
  currentPrice,
  externalFlows = [],
  btcAsset,
  btcAssets = null,
  eureAsset,
  commandCount = 0,
  resultCount = 0,
} = {}) {
  const effectiveBtcAssets = normalizeBtcAssets({ btcAsset, btcAssets });
  const displayBtcAsset = effectiveBtcAssets[0];
  if (!currentInventory || !currentPrice || !displayBtcAsset?.assetId || !eureAsset?.assetId) {
    return null;
  }

  const currentBtcUnits = sumAssetUnits(currentInventory, effectiveBtcAssets).toString();
  const currentEureUnits = String(currentInventory.spendable?.[eureAsset.assetId] || '0');
  const currentBtc = sumAssetScaled(currentInventory, effectiveBtcAssets);
  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: 2,
    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: displayBtcAsset,
      btcAssets: effectiveBtcAssets,
      eureAsset,
    }),
    current_portfolio_value_eure: formatScaledDecimal(currentPortfolioValue),
    current_btc_mark_value_eure: formatScaledDecimal(currentBtcMarkValue),
    current_eure_cash_value_eure: formatScaledDecimal(currentEure),
    portfolio_vs_simple_hold_eure: null,
    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,
    initial_baseline_portfolio_value_eure_at_baseline_price: null,
    initial_baseline_portfolio_value_eure_at_current_price: null,
    external_cash_flows: {
      flow_count: 0,
      deposit_count: 0,
      withdrawal_count: 0,
      latest_effective_at: null,
      net_btc_units: '0',
      net_btc: '0',
      net_eure_units: '0',
      net_eure: '0',
      net_value_eure_at_flow_time: '0',
      net_value_eure_at_current_price: '0',
    },
    inventory_delta: null,
    baseline: null,
  };

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

  const baselineBtcUnits = sumAssetUnits(baseline.inventory, effectiveBtcAssets).toString();
  const baselineEureUnits = String(baseline.inventory.spendable?.[eureAsset.assetId] || '0');
  const baselineBtc = sumAssetScaled(baseline.inventory, effectiveBtcAssets);
  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 externalFlowSummary = summarizeExternalFlows({
    externalFlows,
    currentPriceScaled,
    btcAsset: displayBtcAsset,
    btcAssets: effectiveBtcAssets,
    eureAsset,
  });
  const fundedPortfolioAtFlowTime = baselinePortfolioAtBaselinePrice
    + externalFlowSummary.netValueEureAtFlowTime;
  const simpleHoldAtCurrentPrice = baselinePortfolioAtCurrentPrice
    + externalFlowSummary.netValueEureAtCurrentPrice;
  const portfolioVsSimpleHold = currentPortfolioValue - simpleHoldAtCurrentPrice;
  const markToMarketPnl = currentPortfolioValue - fundedPortfolioAtFlowTime;
  const priceMovePnl = simpleHoldAtCurrentPrice - fundedPortfolioAtFlowTime;

  payload.portfolio_vs_simple_hold_eure = formatScaledDecimal(portfolioVsSimpleHold);
  payload.trade_pnl_eure = null;
  payload.mark_to_market_pnl_eure = formatScaledDecimal(markToMarketPnl);
  payload.price_move_pnl_eure = formatScaledDecimal(priceMovePnl);
  payload.baseline_portfolio_value_eure_at_baseline_price = formatScaledDecimal(
    fundedPortfolioAtFlowTime,
  );
  payload.baseline_portfolio_value_eure_at_current_price = formatScaledDecimal(
    simpleHoldAtCurrentPrice,
  );
  payload.current_portfolio_value_eure_at_baseline_price = formatScaledDecimal(
    currentPortfolioAtBaselinePrice,
  );
  payload.initial_baseline_portfolio_value_eure_at_baseline_price = formatScaledDecimal(
    baselinePortfolioAtBaselinePrice,
  );
  payload.initial_baseline_portfolio_value_eure_at_current_price = formatScaledDecimal(
    baselinePortfolioAtCurrentPrice,
  );
  payload.external_cash_flows = {
    flow_count: externalFlowSummary.flowCount,
    deposit_count: externalFlowSummary.depositCount,
    withdrawal_count: externalFlowSummary.withdrawalCount,
    latest_effective_at: externalFlowSummary.latestEffectiveAt,
    net_btc_units: externalFlowSummary.netBtcUnits.toString(),
    net_btc: formatScaledDecimal(unitsToScaledDecimal(
      externalFlowSummary.netBtcUnits.toString(),
      displayBtcAsset.decimals,
    )),
    net_eure_units: externalFlowSummary.netEureUnits.toString(),
    net_eure: formatScaledDecimal(unitsToScaledDecimal(
      externalFlowSummary.netEureUnits.toString(),
      eureAsset.decimals,
    )),
    net_value_eure_at_flow_time: formatScaledDecimal(externalFlowSummary.netValueEureAtFlowTime),
    net_value_eure_at_current_price: formatScaledDecimal(externalFlowSummary.netValueEureAtCurrentPrice),
  };
  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: displayBtcAsset,
      btcAssets: effectiveBtcAssets,
      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, btcAssets = null, eureAsset }) {
  const effectiveBtcAssets = normalizeBtcAssets({ btcAsset, btcAssets });
  const spendable = inventory?.spendable || {};
  const btcUnits = sumAssetUnits(inventory, effectiveBtcAssets).toString();
  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),
    btc_assets: effectiveBtcAssets.map((asset) => {
      const units = String(spendable[asset.assetId] || '0');
      return {
        asset_id: asset.assetId,
        label: asset.label || asset.symbol,
        units,
        amount: formatAssetUnits(units, asset.decimals),
      };
    }),
    eure_units: eureUnits,
    eure: formatAssetUnits(eureUnits, eureAsset.decimals),
  };
}

function summarizeExternalFlows({
  externalFlows,
  currentPriceScaled,
  btcAsset,
  btcAssets = null,
  eureAsset,
}) {
  const effectiveBtcAssets = normalizeBtcAssets({ btcAsset, btcAssets });
  let flowCount = 0;
  let depositCount = 0;
  let withdrawalCount = 0;
  let latestEffectiveAt = null;
  let netBtcUnits = 0n;
  let netEureUnits = 0n;
  let netValueEureAtFlowTime = 0n;
  let netValueEureAtCurrentPrice = 0n;

  for (const flow of externalFlows || []) {
    if (!flow?.asset_id || !flow?.signed_units) continue;

    const signedUnits = BigInt(flow.signed_units);
    if (signedUnits === 0n) continue;

    flowCount += 1;
    if (flow.kind === 'deposit') depositCount += 1;
    if (flow.kind === 'withdrawal') withdrawalCount += 1;
    if (timestampValue(flow.effective_at) > timestampValue(latestEffectiveAt)) {
      latestEffectiveAt = flow.effective_at || null;
    }

    const flowBtcAsset = effectiveBtcAssets.find((asset) => asset.assetId === flow.asset_id);
    if (flowBtcAsset) {
      netBtcUnits += signedUnits;
      const btcAmount = unitsToScaledDecimal(signedUnits.toString(), flowBtcAsset.decimals);
      const flowPriceScaled = parseScaledDecimal(
        flow.reference_price_eure_per_btc_at_flow_time || '0',
      );
      netValueEureAtFlowTime += multiplyScaled(btcAmount, flowPriceScaled);
      netValueEureAtCurrentPrice += multiplyScaled(btcAmount, currentPriceScaled);
    } else if (flow.asset_id === eureAsset.assetId) {
      netEureUnits += signedUnits;
      const eureAmount = unitsToScaledDecimal(signedUnits.toString(), eureAsset.decimals);
      netValueEureAtFlowTime += eureAmount;
      netValueEureAtCurrentPrice += eureAmount;
    }
  }

  return {
    flowCount,
    depositCount,
    withdrawalCount,
    latestEffectiveAt,
    netBtcUnits,
    netEureUnits,
    netValueEureAtFlowTime,
    netValueEureAtCurrentPrice,
  };
}

function normalizeBtcAssets({ btcAsset, btcAssets = null }) {
  const assets = btcAssets?.length ? btcAssets : [btcAsset];
  const byId = new Map();
  for (const asset of assets) {
    if (!asset?.assetId) continue;
    byId.set(asset.assetId, asset);
  }
  return [...byId.values()];
}

function sumAssetUnits(inventory, assets) {
  const spendable = inventory?.spendable || {};
  return assets.reduce(
    (total, asset) => total + BigInt(spendable[asset.assetId] || '0'),
    0n,
  );
}

function sumAssetScaled(inventory, assets) {
  const spendable = inventory?.spendable || {};
  return assets.reduce((total, asset) => (
    total + unitsToScaledDecimal(String(spendable[asset.assetId] || '0'), asset.decimals)
  ), 0n);
}

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}`;
}

function timestampValue(value) {
  const parsed = Date.parse(value || '');
  return Number.isFinite(parsed) ? parsed : -Infinity;
}