import { describe, expect, it } from 'vitest'

import { upsert } from '../lib/messages.js'

describe('upsert', () => {
  it('appends when last role differs', () => {
    expect(upsert([{ role: 'user', text: 'hi' }], 'assistant', 'hello')).toHaveLength(2)
  })

  it('replaces when last role matches', () => {
    expect(upsert([{ role: 'assistant', text: 'partial' }], 'assistant', 'full')[0]!.text).toBe('full')
  })

  it('appends to empty', () => {
    expect(upsert([], 'user', 'first')).toEqual([{ role: 'user', text: 'first' }])
  })

  it('does not mutate', () => {
    const prev = [{ role: 'user' as const, text: 'hi' }]
    upsert(prev, 'assistant', 'yo')
    expect(prev).toHaveLength(1)
  })
})