feat(26-8923): generate src/applications/benefits/26-8923/utils/irrrlCalculations.js via Optimus

Author: tarratsco

src/applications/benefits/26-8923/utils/irrrlCalculations.js

@@ -0,0 +1,114 @@
+/**
+ * Computes all 18 lines of VA Form 26-8923 from raw inputs.
+ * Returns an object with all computed line values.
+ * All monetary values are rounded to 2 decimal places at each line.
+ * Line 18 is always rounded DOWN (Math.floor to cents) per form note.
+ *
+ * @param {Object} inputs
+ * @param {number} inputs.line1ExistingLoanBalance
+ * @param {number} inputs.line2CashPaymentFromVeteran
+ * @param {number} inputs.line5DiscountPercent
+ * @param {number} inputs.line6OriginationFeePercent
+ * @param {number} inputs.line7FundingFeePercent
+ * @param {number} inputs.line8OtherClosingCosts
+ * @returns {Object} computed line values
+ */
+export function computeIRRRLWorksheet(inputs) {
+  const {
+    line1ExistingLoanBalance = 0,
+    line2CashPaymentFromVeteran = 0,
+    line5DiscountPercent = 0,
+    line6OriginationFeePercent = 0,
+    line7FundingFeePercent = 0.5,
+    line8OtherClosingCosts = 0,
+  } = inputs;
+
+  // Section I
+  const line3Total = round2(line1ExistingLoanBalance - line2CashPaymentFromVeteran);
+
+  // Section II
+  const line4CarryForward = line3Total;
+  const line5DollarAmount = round2(line4CarryForward * (line5DiscountPercent / 100));
+  const line6DollarAmount = round2(line4CarryForward * (line6OriginationFeePercent / 100));
+  const line7DollarAmount = round2(line4CarryForward * (line7FundingFeePercent / 100));
+  const line9PreliminaryTotal = round2(
+    line4CarryForward +
+      line5DollarAmount +
+      line6DollarAmount +
+      line7DollarAmount +
+      line8OtherClosingCosts,
+  );
+
+  // Section III
+  const line10CarryForward = line9PreliminaryTotal;
+  const line11DiscountOnLine10 = round2(
+    line10CarryForward * (line5DiscountPercent / 100),
+  );
+  const line12Subtotal = round2(line10CarryForward + line11DiscountOnLine10);
+  const line13SubtractLine5 = line5DollarAmount;
+  const line14Subtotal = round2(line12Subtotal - line5DollarAmount);
+  const line15SubtractLine7 = line7DollarAmount;
+  const line16Subtotal = round2(line14Subtotal - line7DollarAmount);
+  const line17FinalFundingFee = round2(
+    line16Subtotal * (line7FundingFeePercent / 100),
+  );
+  const line18Raw = line16Subtotal + line17FinalFundingFee;
+
+  // Round DOWN always — never round up. Math.floor to nearest cent.
+  const line18MaxLoanAmount = floorToCents(line18Raw);
+
+  // Rounding differential for the $50 recomputation warning
+  const roundingDifferential = round2(line18Raw - line18MaxLoanAmount);
+
+  return {
+    line3Total,
+    line4CarryForward,
+    line5DollarAmount,
+    line6DollarAmount,
+    line7DollarAmount,
+    line9PreliminaryTotal,
+    line10CarryForward,
+    line11DiscountOnLine10,
+    line12Subtotal,
+    line13SubtractLine5,
+    line14Subtotal,
+    line15SubtractLine7,
+    line16Subtotal,
+    line17FinalFundingFee,
+    line18MaxLoanAmount,
+    roundingDifferential,
+  };
+}
+
+/**
+ * Rounds to 2 decimal places using banker-safe method.
+ * @param {number} value
+ * @returns {number}
+ */
+export function round2(value) {
+  return Math.round((value + Number.EPSILON) * 100) / 100;
+}
+
+/**
+ * Floors to nearest cent (always rounds DOWN per form note).
+ * @param {number} value
+ * @returns {number}
+ */
+export function floorToCents(value) {
+  return Math.floor(value * 100) / 100;
+}
+
+/**
+ * Formats a number as a US dollar currency string.
+ * @param {number|null} value
+ * @returns {string}
+ */
+export function formatCurrency(value) {
+  if (value === null || value === undefined || Number.isNaN(value)) {
+    return '$0.00';
+  }
+  return new Intl.NumberFormat('en-US', {
+    style: 'currency',
+    currency: 'USD',
+  }).format(value);
+}