Added Section 179 Limits

server/depreciation.js

@@ -1,6 +1,7 @@
 const { parseJson } = require('./db');
 const { buildDepreciationMethods } = require('./rule-catalog');
 const { getZone } = require('./services/zones');
+const { getLimit: getSection179Limit } = require('./services/section179Limits');
 
 // Built-in method catalog, used as a fallback so codes like MF200/DB200 always resolve
 // even if a particular rule set hasn't been re-expanded to include them.
@@ -47,7 +48,45 @@ function salvageValue(asset, book, methodRule) {
 }
 
 function section179Amount(asset, book) {
-  return Math.min(grossBasis(asset, book), Number(book.section_179_amount || 0));
+  return Math.min(grossBasis(asset, book), Number(book.section_179_amount || 0), section179Limit(asset, book));
+}
+
+// Enterprise/empowerment-zone Section 179 treatment for the federal book: an increased dollar
+// limit and a reduced (e.g. 50%) share of cost counting toward the phaseout threshold. Applies
+// only when the asset is flagged for such a zone and placed in service within the date window.
+function zoneSection179(asset, book) {
+  if (!asset.special_zone || String(book.book_type) !== 'FEDERAL') return null;
+  const zone = getZone(asset.special_zone);
+  if (!zone) return null;
+  const increase = Number(zone.section_179_increase || 0);
+  const costFactor = Number(zone.section_179_cost_factor || 0) || 1;
+  if (!increase && costFactor === 1) return null;
+  const pis = asset.in_service_date || asset.acquired_date || '';
+  if (pis && zone.pis_start && pis < zone.pis_start) return null;
+  if (pis && zone.pis_end && pis > zone.pis_end) return null;
+  return { increase, costFactor };
+}
+
+// Applicable §179 dollar cap for an asset's placed-in-service year: the configured base limit
+// (plus any enterprise-zone increase) less the dollar-for-dollar investment phaseout. Returns
+// Infinity when no limit is configured for the year, leaving the entered §179 amount uncapped.
+function section179Limit(asset, book) {
+  const pisYear = yearFromDate(asset.in_service_date || asset.acquired_date);
+  const limitRow = getSection179Limit(pisYear);
+  if (!limitRow) return Infinity;
+  let limit = Number(limitRow.base_limit) || 0;
+  const threshold = Number(limitRow.phaseout_threshold) || 0;
+  let costFactor = 1;
+  const zone = zoneSection179(asset, book);
+  if (zone) {
+    limit += zone.increase;
+    costFactor = zone.costFactor;
+  }
+  if (threshold > 0) {
+    const investment = grossBasis(asset, book) * costFactor;
+    limit -= Math.max(0, investment - threshold);
+  }
+  return Math.max(0, limit);
 }
 
 // Special-zone §168 allowance (e.g. New York Liberty Zone): applies to the federal tax book