import test from 'brittle'
import { readFile } from 'node:fs/promises'
import { dirname, join } from 'node:path'
import { fileURLToPath } from 'node:url'
import { createContext, runInContext } from 'node:vm'

const __dirname = dirname(fileURLToPath(import.meta.url))
const composePath = join(__dirname, '../lib/baretop/baretop-compose.js')

test('incremental line-diff patch is smaller than full frame when one line changes', async (t) => {
  const compose = await readFile(composePath, 'utf8')
  const ctx = createContext({})
  runInContext(compose, ctx)
  const n = 48
  const prev = Array.from({ length: n }, (_, i) => 'row-' + i + ' ' + 'x'.repeat(40))
  const next = prev.slice()
  next[22] = 'row-22 ' + 'CHANGED'.repeat(6)
  const full = next.join('\r\n') + '\r\n'
  const cup = (r, c) => '\x1b[' + r + ';' + c + 'H'
  const { patch, nch } = ctx.bareTopBuildLinePatch(prev, next, cup, {
    useLineHash: false
  })
  t.is(nch, 1)
  t.ok(
    patch.length < full.length,
    'expected patch bytes < full frame (' +
      patch.length +
      ' vs ' +
      full.length +
      ')'
  )
})