const nest = require('depnest')
const { computed, Value } = require('mutant')
const { title } = require('markdown-summary')
const { isMsg } = require('ssb-ref')

exports.gives = nest('message.html.subject')

exports.needs = nest({
  'message.html.markdown': 'first',
  'message.sync.unbox': 'first',
  'sbot.async.get': 'first'
})

exports.create = function (api) {
  var subjectCache = {}

  return nest('message.html.subject', subject)

  function subject (msg) {
    if (msg === undefined) debugger
    // test if it's a message ref, or a full message object
    // a message ref is generally passed in if we're fetching the subject of a root message
    if (isMsg(msg)) {
      if (subjectCache[msg]) return subjectCache[msg]

      var subject = Value()

      api.sbot.async.get(msg, (err, value) => {
        if (err) throw err

        var _subject = getMsgSubject({ key: msg, value: api.message.sync.unbox(value) })
        subject.set(_subject)
        subjectCache[msg] = _subject
      })

      return subject
    } else { return getMsgSubject(msg) }
  }

  function getMsgSubject (msg) {
    const { subject, text } = msg.value.content
    if (!(subject || text)) return

    return subject
      ? api.message.html.markdown(subject)
      : api.message.html.markdown(title(text))
  }
}