import { describe, expect, it } from 'vitest'
import { computeSplit } from './split'

describe('computeSplit', () => {
  it('divides evenly when amount divides cleanly', () => {
    expect(computeSplit(1000, [1, 2, 4])).toEqual({ 1: 334, 2: 333, 4: 333 })
  })

  it('sums back exactly to the original amount', () => {
    const shares = computeSplit(1001, [1, 2, 3, 4, 5, 6, 7])
    const total = Object.values(shares).reduce((sum, share) => sum + share, 0)
    expect(total).toBe(1001)
  })

  it('distributes remainder cents one-each to the first participants in order', () => {
    expect(computeSplit(10, [1, 2, 3])).toEqual({ 1: 4, 2: 3, 3: 3 })
  })

  it('gives the full amount to a single participant', () => {
    expect(computeSplit(1234, [9])).toEqual({ 9: 1234 })
  })

  it('handles a zero amount', () => {
    expect(computeSplit(0, [1, 2])).toEqual({ 1: 0, 2: 0 })
  })

  it('throws when given no participants', () => {
    expect(() => computeSplit(1000, [])).toThrow()
  })
})