import { create } from 'xmlbuilder2'

export interface NzbFile {
  /** Name the downloader should use; the real name when it is known. */
  name: string
  poster: string
  /** Posting time in milliseconds. */
  date: number
  groups: string[]
  /** Segment number → message-id (without angle brackets) and article size. */
  segments: Record<string, { id: string; size: number }>
}

export interface NzbOptions {
  /** Shown by downloaders as the job name. */
  title?: string
  /** Archive password, when known. */
  password?: string
}

/**
 * Builds an NZB 1.1 document (newzbin DTD). The subject follows the common
 * `"name" yEnc (1/N)` form, which downloaders use to name the file.
 */
export function buildNzb(files: NzbFile[], options: NzbOptions = {}): string {
  const root = create({ version: '1.0', encoding: 'UTF-8' })
    .dtd({ pubID: '-//newzBin//DTD NZB 1.1//EN', sysID: 'http://www.newzbin.com/DTD/nzb/nzb-1.1.dtd' })
    .ele('nzb', { xmlns: 'http://www.newzbin.com/DTD/2003/nzb' })

  if (options.title || options.password) {
    const head = root.ele('head')
    if (options.title) head.ele('meta', { type: 'name' }).txt(options.title)
    if (options.password) head.ele('meta', { type: 'password' }).txt(options.password)
  }

  for (const file of files) {
    const numbers = Object.keys(file.segments)
      .map(Number)
      .sort((a, b) => a - b)
    const element = root.ele('file', {
      poster: file.poster,
      date: String(Math.floor(file.date / 1000)),
      subject: `"${file.name}" yEnc (1/${numbers.length})`,
    })
    const groups = element.ele('groups')
    for (const group of file.groups) groups.ele('group').txt(group)
    const segments = element.ele('segments')
    for (const number of numbers) {
      const segment = file.segments[String(number)]
      segments.ele('segment', { bytes: String(segment.size), number: String(number) }).txt(segment.id)
    }
  }
  return root.end({ prettyPrint: true })
}