feat: algorithm module with unit tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/algorithm.test.mjs

@@ -0,0 +1,102 @@
+import assert from 'node:assert/strict';
+import { getWorkdays, generatePlan } from '../js/algorithm.js';
+
+const fixed = () => 0.5; // deterministic random for tests
+
+function emp(id, constraints = {}) {
+  return {
+    id, name: id,
+    constraints: {
+      neverDays: [], lowPriorityDays: [], onlyDays: [],
+      maxPerMonth: null, minGapDays: 0, vacations: [],
+      ...constraints
+    }
+  };
+}
+
+// getWorkdays
+{
+  const days = getWorkdays(2026, 4, [], []);
+  assert.equal(days.length, 22, 'April 2026: 22 workdays');
+  assert.equal(days[0], '2026-04-01', 'First workday = 2026-04-01');
+  assert.equal(days.at(-1), '2026-04-30', 'Last workday = 2026-04-30');
+}
+{
+  const days = getWorkdays(2026, 4, ['2026-04-01'], []);
+  assert.equal(days.length, 21, 'Holiday reduces count by 1');
+  assert.ok(!days.includes('2026-04-01'), 'Holiday excluded');
+}
+{
+  const days = getWorkdays(2026, 4, [], []);
+  assert.ok(!days.includes('2026-04-04'), '2026-04-04 Saturday excluded');
+  assert.ok(!days.includes('2026-04-05'), '2026-04-05 Sunday excluded');
+}
+
+// generatePlan — basic assignment
+{
+  const result = generatePlan(['2026-04-01'], [emp('alice'), emp('bob')], [], fixed);
+  assert.equal(result.length, 1, 'One workday → one assignment');
+  assert.ok(['alice','bob'].includes(result[0].employeeId), 'Assigned to alice or bob');
+}
+
+// neverDays blocks employee
+{
+  // 2026-04-01 is Wednesday (3)
+  const result = generatePlan(['2026-04-01'], [emp('alice', {neverDays:[3]}), emp('bob')], [], fixed);
+  assert.equal(result[0].employeeId, 'bob', 'alice blocked on Wednesday → bob assigned');
+}
+
+// onlyDays restricts to specific days
+{
+  // 2026-04-01 = Wednesday (3), 2026-04-02 = Thursday (4)
+  const employees = [emp('alice', {onlyDays:[3]}), emp('bob')];
+  const result = generatePlan(['2026-04-01','2026-04-02'], employees, [], fixed);
+  const aliceOnThursday = result.find(r => r.date === '2026-04-02' && r.employeeId === 'alice');
+  assert.ok(!aliceOnThursday, 'alice with onlyDays:[3] not assigned on Thursday');
+}
+
+// vacation blocks employee
+{
+  const employees = [
+    emp('alice', {vacations:[{from:'2026-04-01', to:'2026-04-03'}]}),
+    emp('bob')
+  ];
+  const result = generatePlan(['2026-04-01'], employees, [], fixed);
+  assert.equal(result[0].employeeId, 'bob', 'alice on vacation → bob assigned');
+}
+
+// maxPerMonth cap
+{
+  const days = ['2026-04-01','2026-04-02','2026-04-03'];
+  const employees = [emp('alice', {maxPerMonth:1}), emp('bob'), emp('clara')];
+  const result = generatePlan(days, employees, [], fixed);
+  const aliceCount = result.filter(r => r.employeeId === 'alice').length;
+  assert.ok(aliceCount <= 1, 'alice maxPerMonth=1 → assigned at most once');
+}
+
+// minGapDays
+{
+  // 2026-04-06 = Monday, alice last assigned 2026-04-02 (Thu) = 4 days ago, gap=5 → blocked
+  const history = [{date:'2026-04-02', employeeId:'alice', manual:false}];
+  const employees = [emp('alice', {minGapDays:5}), emp('bob')];
+  const result = generatePlan(['2026-04-06'], employees, history, fixed);
+  assert.equal(result[0].employeeId, 'bob', 'alice within minGap (4<5) → bob assigned');
+}
+
+// No candidates → day skipped
+{
+  // 2026-04-01 = Wednesday (3), only employee blocked
+  const result = generatePlan(['2026-04-01'], [emp('alice', {neverDays:[3]})], [], fixed);
+  assert.equal(result.length, 0, 'No candidate → day skipped');
+}
+
+// Fairness: less history = higher priority
+{
+  const history = [1,2,3,4,5].map(i => ({
+    date: '2026-04-0' + i, employeeId: 'alice', manual: false
+  }));
+  const result = generatePlan(['2026-05-04'], [emp('alice'), emp('bob')], history, fixed);
+  assert.equal(result[0].employeeId, 'bob', 'bob (0 history) beats alice (5 history)');
+}
+
+console.log('All algorithm tests passed.');