Shuffle and group lines in a text file using deno

shuffle.ts

// ! deno run -A shuffle.ts
// Shuffle and group lines in a text file.
// Groups are created by adding two newlines between each group.

const filename = 'items.txt'

const txt = Deno.readTextFileSync(filename)

const nonEmpty = (i: string) => i.trim() !== ''

const groupSeparator = '\n\n'
const numberOfGroups = txt.split(groupSeparator).filter(nonEmpty).length

const shuffled = txt.split('\n').filter(nonEmpty)
  .map(value => ({ sort: Math.random(), value }))
  .sort((a, b) => a.sort - b.sort)
  .map(i => i.value)

const grouped = Object.values(Object.groupBy(shuffled, (_, index) => Math.round(index % numberOfGroups)))
const sorted = grouped.length > 1 ? grouped.map(i => i.sort((a, b) => a.localeCompare(b))) : grouped
const stringified = sorted.flatMap(i => i.join('\n')).join(groupSeparator)

Deno.writeTextFileSync(filename, stringified)