import { describe, it, expect } from 'vitest'
import { moonName, illumination, nextMoonPhase, interpolateDate, diffDays } from '../../../src/lib/api/moon.js'

describe('moonName', () => {
  it('names the four principal phases', () => {
    expect(moonName(0.0)).toBe('New Moon')
    expect(moonName(0.25)).toBe('First Quarter')
    expect(moonName(0.5)).toBe('Full Moon')
    expect(moonName(0.75)).toBe('Last Quarter')
  })

  it('names the intermediate phases', () => {
    expect(moonName(0.125)).toBe('Waxing Crescent')
    expect(moonName(0.375)).toBe('Waxing Gibbous')
    expect(moonName(0.625)).toBe('Waning Gibbous')
    expect(moonName(0.875)).toBe('Waning Crescent')
  })

  it('wraps 1.0 back to new moon', () => {
    expect(moonName(1.0)).toBe('New Moon')
    expect(moonName(0.98)).toBe('Waning Crescent')
  })
})

describe('illumination', () => {
  it('is 0 at new moon and 1 at full', () => {
    expect(illumination(0)).toBeCloseTo(0, 5)
    expect(illumination(0.5)).toBeCloseTo(1, 5)
  })

  it('is symmetric about full: quarter both ~0.5', () => {
    expect(illumination(0.25)).toBeCloseTo(0.5, 5)
    expect(illumination(0.75)).toBeCloseTo(0.5, 5)
  })

  it('near new gives small illumination', () => {
    expect(illumination(0.912)).toBeLessThan(0.1)
  })
})

describe('interpolateDate / diffDays', () => {
  it('interpolates dates', () => {
    expect(interpolateDate('2026-09-10', '2026-09-12', 0.5)).toBe('2026-09-11')
    expect(interpolateDate('2026-09-10', '2026-09-12', 0)).toBe('2026-09-10')
    expect(interpolateDate('2026-09-10', '2026-09-12', 1)).toBe('2026-09-12')
  })

  it('computes whole days between dates', () => {
    expect(diffDays('2026-09-08', '2026-09-10')).toBe(2)
    expect(diffDays('2026-09-08', '2026-09-08')).toBe(0)
  })
})

describe('nextMoonPhase', () => {
  const mk = (arr) => arr.map(([date, phase]) => ({ date, phase }))

  it('finds next new moon from a waning-crescent sample', () => {
    const days = mk([
      ['2026-09-08', 0.912], ['2026-09-09', 0.948], ['2026-09-10', 0.985],
      ['2026-09-11', 0.020], ['2026-09-12', 0.054], ['2026-09-13', 0.088],
      ['2026-09-14', 0.121], ['2026-09-15', 0.153],
    ])
    const r = nextMoonPhase(days)
    expect(r.name).toBe('New Moon')
    expect(r.daysUntil).toBe(2)
    expect(r.date).toBe('2026-09-10')
  })

  it('finds next first quarter from a new-moon sample', () => {
    const days = mk([
      ['2026-09-11', 0.020], ['2026-09-12', 0.054], ['2026-09-13', 0.088],
      ['2026-09-14', 0.121], ['2026-09-15', 0.153], ['2026-09-16', 0.184],
      ['2026-09-17', 0.215], ['2026-09-18', 0.245], ['2026-09-19', 0.276],
    ])
    const r = nextMoonPhase(days)
    expect(r.name).toBe('First Quarter')
    expect(r.daysUntil).toBe(7)
  })

  it('returns null with too few samples', () => {
    expect(nextMoonPhase(null)).toBeNull()
    expect(nextMoonPhase(mk([['2026-09-08', 0.5]]))).toBeNull()
  })
})