var nest = require('depnest')
var { Dict, Set } = require('mutant')

exports.gives = nest({
  'unread.sync.isUnread': true,
  'unread.sync.markRead': true,
  'unread.obs.userMessages': true
})

// load current state of unread messages.

exports.create = function (api) {
  var unread = null
  if (localStorage.unread) {
    try {
      unread = JSON.parse(localStorage.unread)
    } catch (err) {}
  }
  if (!unread) { unread = {timestamp: Date.now()} }

  unread.timestamp = unread.timestamp || Date.now()

  if (!unread.filter) { unread.filter = {} }

  var timer
  function save () {
    if (timer) return

    timer = setTimeout(function () {
      timer = null
      localStorage.unread = JSON.stringify(unread)
    }, 2e3)
  }

  function isUnread (msg) {
    if (msg.timestamp && msg.timestamp < unread.timestamp) return false
    return !unread.filter[msg.key]
  }

  function markRead (msg) {
    if (msg && typeof msg.key === 'string') {
      // note: there is a quirk where some messages don't have a timestamp
      if (isUnread(msg)) {
        var userUser
        unread.filter[msg.key] = true
        save()
        return true
      }
    }
  }

  function userMessages (feedId) {

  }

  document.body.onunload = save

  return nest({
    'unread.sync.isUnread': isUnread,
    'unread.sync.markRead': markRead,
    'unread.obs.userMessages': userMessages
  })
}