Improve financial statement value formatting

lib/format.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it } from 'bun:test';
-import { formatCurrencyByScale, formatScaledNumber } from './format';
+import {
+  formatCurrencyByScale,
+  formatFinancialStatementValue,
+  formatScaledNumber
+} from './format';
 
 describe('formatScaledNumber', () => {
   it('keeps values below one thousand unscaled', () => {
@@ -45,3 +49,59 @@ describe('formatCurrencyByScale', () => {
     expect(formatCurrencyByScale(-2_500_000, 'millions')).toBe('-$2.5M');
   });
 });
+
+describe('formatFinancialStatementValue', () => {
+  it('renders null statement values as em dashes', () => {
+    expect(formatFinancialStatementValue({
+      value: null,
+      unit: 'currency',
+      scale: 'millions',
+      rowKey: 'revenue',
+      surfaceKind: 'income_statement'
+    })).toBe('—');
+  });
+
+  it('formats scaled currency values without a currency symbol', () => {
+    expect(formatFinancialStatementValue({
+      value: 15_940_899_000,
+      unit: 'currency',
+      scale: 'millions',
+      rowKey: 'revenue',
+      surfaceKind: 'income_statement'
+    })).toBe('15,940.9');
+    expect(formatFinancialStatementValue({
+      value: 1_100_000_000,
+      unit: 'currency',
+      scale: 'millions',
+      rowKey: 'long_term_debt_issued',
+      surfaceKind: 'cash_flow_statement'
+    })).toBe('1,100');
+  });
+
+  it('keeps extra precision for per-share rows', () => {
+    expect(formatFinancialStatementValue({
+      value: 14.64,
+      unit: 'currency',
+      scale: 'millions',
+      rowKey: 'diluted_eps',
+      surfaceKind: 'income_statement'
+    })).toBe('14.64');
+  });
+
+  it('formats statement percents and ratios with trimmed precision', () => {
+    expect(formatFinancialStatementValue({
+      value: 0.233,
+      unit: 'percent',
+      scale: 'millions',
+      rowKey: 'effective_tax_rate',
+      surfaceKind: 'income_statement'
+    })).toBe('23.3%');
+    expect(formatFinancialStatementValue({
+      value: 1.5,
+      unit: 'ratio',
+      scale: 'millions',
+      rowKey: 'debt_to_equity',
+      surfaceKind: 'ratios'
+    })).toBe('1.5x');
+  });
+});