feat: add recurrence grid expansion

test/recur.test.js

@@ -0,0 +1,69 @@
+import { describe, it, expect } from 'vitest'
+import { expandOccurrences, intervalDays } from '../src/lib/recur.js'
+
+describe('intervalDays', () => {
+  it('returns 7 for WEEKLY interval=1', () => {
+    const ev = { rrule: { freq: 'WEEKLY', interval: 1 } }
+    expect(intervalDays(ev)).toBe(7)
+  })
+
+  it('returns 14 for WEEKLY interval=2', () => {
+    const ev = { rrule: { freq: 'WEEKLY', interval: 2 } }
+    expect(intervalDays(ev)).toBe(14)
+  })
+
+  it('returns interval for DAILY', () => {
+    const ev = { rrule: { freq: 'DAILY', interval: 3 } }
+    expect(intervalDays(ev)).toBe(3)
+  })
+})
+
+describe('expandOccurrences', () => {
+  it('returns single occurrence for non-recurring event', () => {
+    const ev = { dtstartDate: '2026-07-27', rrule: null, exdates: [] }
+    const occs = expandOccurrences(ev)
+    expect(occs).toHaveLength(1)
+    expect(occs[0]).toEqual({ date: '2026-07-27', skipped: false })
+  })
+
+  it('expands weekly event from Jul 27 to Oct 19', () => {
+    const ev = {
+      dtstartDate: '2026-07-27',
+      rrule: { freq: 'WEEKLY', interval: 1, byday: 'MO', untilDate: '2026-10-19' },
+      exdates: ['2026-09-21'],
+    }
+    const occs = expandOccurrences(ev)
+    // Jul 27 + 12 weeks = Oct 19 -> 13 occurrences
+    expect(occs).toHaveLength(13)
+    expect(occs[0].date).toBe('2026-07-27')
+    expect(occs[12].date).toBe('2026-10-19')
+    // Sep 21 is skipped
+    const sep21 = occs.find(o => o.date === '2026-09-21')
+    expect(sep21.skipped).toBe(true)
+    // Others not skipped
+    expect(occs[0].skipped).toBe(false)
+  })
+
+  it('respects exdates set', () => {
+    const ev = {
+      dtstartDate: '2026-07-27',
+      rrule: { freq: 'WEEKLY', interval: 1, byday: 'MO', untilDate: '2026-08-24' },
+      exdates: ['2026-08-03', '2026-08-17'],
+    }
+    const occs = expandOccurrences(ev)
+    expect(occs).toHaveLength(5) // Jul27, Aug3, Aug10, Aug17, Aug24
+    expect(occs[1].skipped).toBe(true)  // Aug 3
+    expect(occs[2].skipped).toBe(false) // Aug 10
+    expect(occs[3].skipped).toBe(true)  // Aug 17
+  })
+
+  it('caps at 500 occurrences', () => {
+    const ev = {
+      dtstartDate: '2020-01-01',
+      rrule: { freq: 'DAILY', interval: 1, untilDate: '2030-12-31' },
+      exdates: [],
+    }
+    const occs = expandOccurrences(ev)
+    expect(occs.length).toBeLessThanOrEqual(500)
+  })
+})