feat(forms): add useMaskedField and useMaskedInput composables for input masking

core/encoding/src/index.ts

@@ -1,2 +1,3 @@
+export * from './luhn';
 export * from './reed-solomon';
 export * from './qr';

core/encoding/src/luhn/index.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it } from 'vitest';
+import { luhn } from './index';
+
+describe(luhn, () => {
+  it('passes valid checksums (separators ignored)', () => {
+    expect(luhn('4111 1111 1111 1111')).toBe(true);
+    expect(luhn('5500005555555559')).toBe(true);
+    expect(luhn('371449635398431')).toBe(true);
+    expect(luhn('79927398713')).toBe(true); // classic Luhn example
+  });
+
+  it('fails bad checksums', () => {
+    expect(luhn('4111 1111 1111 1112')).toBe(false);
+    expect(luhn('79927398710')).toBe(false);
+  });
+
+  it('returns false for empty input', () => {
+    expect(luhn('')).toBe(false);
+    expect(luhn('----')).toBe(false);
+  });
+});

core/encoding/src/luhn/index.ts

@@ -0,0 +1,39 @@
+const NON_DIGIT = /\D/g;
+const ASCII_ZERO = 0x30;
+
+/**
+ * @name luhn
+ * @category Encoding
+ * @description Validate a number string against the Luhn (mod 10) checksum — the
+ * check digit used by payment cards, IMEIs, SIM ICCIDs, and more. Non-digits are
+ * ignored; an empty input is `false`.
+ *
+ * @param {string} value The number (separators allowed)
+ * @returns {boolean} Whether the Luhn checksum passes
+ *
+ * @example
+ * luhn('4111 1111 1111 1111'); // true
+ * luhn('4111 1111 1111 1112'); // false
+ *
+ * @since 0.0.2
+ */
+export function luhn(value: string): boolean {
+  const digits = value.replaceAll(NON_DIGIT, '');
+  if (!digits)
+    return false;
+
+  let sum = 0;
+  let double = false;
+  for (let i = digits.length - 1; i >= 0; i--) {
+    let digit = digits.charCodeAt(i) - ASCII_ZERO;
+    if (double) {
+      digit *= 2;
+      if (digit > 9)
+        digit -= 9;
+    }
+    sum += digit;
+    double = !double;
+  }
+
+  return sum % 10 === 0;
+}