titlegen/titlegen.coffee

Generate plausible titles from a list of example titles.

defaults =
  min_word_count: 2
  max_word_count: 16
  max_attempts: 20
  splitter: /(\s|'s|[:!?]\s)/
  joiner: ' '
  transform: (title) ->
    title.replace /\s('s|[:!?])/g, '$1'

create = (config={}) ->
  for own k,v of defaults
    config[k] ?= defaults[k]

  titles = []
  states = {}

  feed = (_titles) ->
    states =
      __BEGIN__:
        t:1
        p: '__END__': 1
      __END__:
        t:0
        p: {}

    titles = _titles

    for title,i in titles
      title = titles[i] = title.trim()
      continue  if title.length is 0

      words = (word.trim() for word in title.split(config.splitter) when word.trim().length > 0)

      first = true
      for word,i in words
        if first
          ++states.__BEGIN__.t
          states.__BEGIN__.p[word] ?= 0
          ++states.__BEGIN__.p[word]
          first = false

        next = words[i+1] ? '__END__'
        if not states.hasOwnProperty(word)
          states[word] = {p:{}}
        state = states[word]
        state.t ?= 0
        ++state.t
        state.p[next] ?= 0
        ++state.p[next]

    return

  _next = (depth=0) ->
    title = ''
    state = states.__BEGIN__
    n = 0
    while n < config.max_word_count
      rnd = Math.round(Math.random() * state.t)
      tot = 0
      for own next,count of state.p
        tot += count
        break  if tot >= rnd

      break  if next is '__END__'

      state = states[next]
      next = config.joiner + next  unless n is 0
      title += next
      ++n

    title = config.transform title

    if depth < config.max_attempts and (n < config.min_word_count or title in titles)
      return _next(depth+1)

    return title

  generate =
    feed: feed
    config: config
    next: _next
  
  generate.feed []

  return generate

titlegen =
  create: create

module.exports = titlegen  if module?
window.titlegen = titlegen  if window?
global.titlegen = titlegen  if global?