import { createHash } from 'node:crypto'

/**
 * Upload signatures (CONCEPT.md D42): which tool posted an article, read from
 * its Message-ID, and the group it was posted to first. Together they predict
 * whether a random-named upload will ever get a name: ngPost uploads in
 * a.b.ath almost never do, nyuu uploads in a.b.friends always do (LOG.md
 * 2026-10-08 (5)).
 */
const TOOLS: [string, RegExp][] = [
  // FmFwIaTpGgUiSfYcMwFlMeRo-1790637260478@nyuu: 12 random capital+small letter pairs, a ms timestamp
  ['nyuu', /^(?:[A-Z][a-z]){12}-\d{13}@nyuu$/],
  ['nyuu-host', /^(?:[A-Z][a-z]){12}-\d{13}@.+$/],
  // b94268bc702040f7b811d5318f727e4f@ngPost: a UUID's hex
  ['ngPost', /^[0-9a-f]{32}@ngPost$/],
  ['yuun', /^[0-9a-f]{32}@[0-9a-f]{32}\.yuun$/],
  ['hex32', /^[0-9a-f]{32}@[A-Za-z0-9.-]+$/],
  ['JBinUp', /@JBin(?:Up|Down)\.local$/],
  // part1of69.lOlWzvSHabJCBTVrs0ts@AdultPoster.local
  ['partNofM', /^part\d+of\d+\./i],
  // 1790923856877$1729905757859$1@localhost
  ['ts-dollar', /^\d{13}\$\d+\$\d+@localhost$/],
  // t3Y4mV92YCp0McxDc5@zLZlsw.RYqes: random local part and random host
  ['random', /^[A-Za-z0-9]{10,40}@[A-Za-z0-9]{3,12}\.[A-Za-z0-9]{2,6}$/],
]

/** The posting tool of a Message-ID (without angle brackets), or 'other'. */
export function uploadTool(messageId: string | null | undefined): string {
  if (!messageId) return 'other'
  for (const [tool, pattern] of TOOLS) if (pattern.test(messageId)) return tool
  return 'other'
}

/** The group of a signature: the first the upload was posted to, as stored in `groups`. */
export function signatureGroup(groups: unknown): string {
  return Array.isArray(groups) && typeof groups[0] === 'string' ? groups[0] : ''
}

/** The key of a signature in a Set. */
export function signatureKey(tool: string, group: string) {
  return `${tool}\t${group}`
}

/**
 * Whether an upload is in the share of dropped signatures that is still kept
 * (and probed), so their rates keep being measured. Decided per release key,
 * so a release is kept or dropped as a whole.
 */
export function explored(key: string, percent: number): boolean {
  if (percent <= 0) return false
  return createHash('md5').update(key).digest().readUInt32BE(0) % 10_000 < percent * 100
}