/**
 * RED test stubs for expandOccurrences() — Wave 0 state.
 *
 * These tests encode the concrete behavioral contracts that Plan 02 (GREEN phase) must satisfy.
 * All tests reference the not-yet-built module apps/api/src/broker/expand.ts and are expected
 * to fail until that module is implemented.
 *
 * Contracts locked here:
 *  1. DST wall-clock correctness: occurrences in America/New_York must show 10:00 local time
 *     on BOTH sides of the March 2026 EST→EDT boundary (not shifted ±1h by UTC fallback).
 *  2. All-day events return allDay:true and start as 'YYYY-MM-DD' with no time component.
 *  3. EXDATE exclusions reduce the returned array by exactly one occurrence.
 */

import { describe, it, expect } from 'vitest'
import { readFileSync } from 'fs'
import { join, dirname } from 'path'
import { fileURLToPath } from 'url'

// Not yet built — import will fail (RED state) until Plan 02 implements expand.ts
import { expandOccurrences } from '../../src/broker/expand.js'

const __dirname = dirname(fileURLToPath(import.meta.url))
const FIXTURES = join(__dirname, '../fixtures')

function loadFixture(name: string): string {
  return readFileSync(join(FIXTURES, name), 'utf8')
}

describe('expandOccurrences — RED stubs (Wave 0)', () => {

  describe('DST correctness — weekly-dst.ics', () => {
    it('returns 10:00 America/New_York wall-clock time on BOTH sides of March 2026 DST boundary', () => {
      // The fixture has DTSTART;TZID=America/New_York:20260301T100000 RRULE:FREQ=WEEKLY.
      // March 8 2026 is the DST transition (clocks spring forward at 02:00).
      // Occurrences on 2026-03-01 (EST, UTC-5) and 2026-03-08 (DST transition day) and
      // 2026-03-15 (EDT, UTC-4) must ALL show hour === 10 in America/New_York.
      // A broken implementation that falls back to UTC would show hour === 10 UTC before
      // transition and hour === 11 local after transition — off by one DST hour.
      const rawVevent = loadFixture('weekly-dst.ics')
      const windowStart = new Date('2026-03-01T00:00:00Z')
      const windowEnd = new Date('2026-04-01T00:00:00Z')

      const occurrences = expandOccurrences(
        rawVevent,
        windowStart,
        windowEnd,
        1,          // calendarId
        'My Calendar', // calendarName
        1,          // ownerUserId
        '#4A90D9',  // color
        false,      // isShared
      )

      // Should return several weekly occurrences in March
      expect(occurrences.length).toBeGreaterThan(0)

      // The key contract: every occurrence must have local hour === 10 in America/New_York.
      // We verify this by checking the ISO string offset — before DST: offset is -05:00
      // (so 10:00-05:00 = 15:00 UTC); after DST: offset is -04:00 (10:00-04:00 = 14:00 UTC).
      // Both are valid as long as the LOCAL wall-clock hour is 10.
      for (const occ of occurrences) {
        expect(occ.allDay).toBe(false)
        // start must be an offset-aware ISO string: '2026-03-01T10:00:00-05:00' or similar
        expect(occ.start).toMatch(/T10:00:00/)
      }

      // Explicitly check one pre-transition occurrence (EST) and one post-transition (EDT)
      const preTransition = occurrences.find(o => o.start.includes('2026-03-01'))
      const postTransition = occurrences.find(o => o.start.includes('2026-03-15'))

      expect(preTransition).toBeDefined()
      expect(postTransition).toBeDefined()

      // Pre-transition occurrence: EST offset -05:00
      expect(preTransition!.start).toContain('T10:00:00')
      // Post-transition occurrence: EDT offset -04:00
      expect(postTransition!.start).toContain('T10:00:00')
    })
  })

  describe('All-day events — allday-birthday.ics', () => {
    it('returns allDay:true with start as YYYY-MM-DD and no time component', () => {
      // The fixture has DTSTART;VALUE=DATE:20260615 with RRULE:FREQ=YEARLY.
      // The all-day occurrence should have allDay:true and start === '2026-06-15' (DATE format).
      // A broken implementation returning '2026-06-15T00:00:00Z' would fail on date-shift.
      const rawVevent = loadFixture('allday-birthday.ics')
      const windowStart = new Date('2026-06-01T00:00:00Z')
      const windowEnd = new Date('2026-07-01T00:00:00Z')

      const occurrences = expandOccurrences(
        rawVevent,
        windowStart,
        windowEnd,
        1,
        'My Calendar',
        1,
        '#4A90D9',
        false,
      )

      expect(occurrences.length).toBe(1)

      const occ = occurrences[0]
      expect(occ.allDay).toBe(true)
      // start must be plain date string 'YYYY-MM-DD' — no 'T' time component
      expect(occ.start).toBe('2026-06-15')
      expect(occ.start).not.toContain('T')
    })
  })

  describe('EXDATE exclusions — exdate-series.ics', () => {
    it('omits the EXDATE-excluded occurrence (array length is one fewer than un-excluded)', () => {
      // The fixture has RRULE:FREQ=WEEKLY;COUNT=5 with EXDATE for the June 15 occurrence.
      // Without EXDATE: 5 occurrences (Jun 1, Jun 8, Jun 15, Jun 22, Jun 29).
      // With EXDATE on Jun 15: 4 occurrences returned.
      // ICAL.RecurExpansion handles EXDATE internally — no manual filtering needed.
      const rawVevent = loadFixture('exdate-series.ics')
      const windowStart = new Date('2026-06-01T00:00:00Z')
      const windowEnd = new Date('2026-07-01T00:00:00Z')

      const occurrences = expandOccurrences(
        rawVevent,
        windowStart,
        windowEnd,
        1,
        'My Calendar',
        1,
        '#4A90D9',
        false,
      )

      // 5 total occurrences minus 1 EXDATE = 4
      expect(occurrences.length).toBe(4)

      // The June 15 occurrence must be absent
      const june15 = occurrences.find(o => o.start.includes('2026-06-15'))
      expect(june15).toBeUndefined()
    })
  })
})