var pull = require('pull-stream')
var multicb = require('multicb')
var cat = require('pull-cat')
var u = require('./util')

module.exports = About

function About(app, myId, follows) {
  this.app = app
  this.myId = myId
  this.follows = follows
}

About.prototype.createAboutOpStream = function (id) {
  return pull(
    this.app.sbot.links({dest: id, rel: 'about', values: true, reverse: true}),
    pull.map(function (msg) {
      var c = msg.value.content || {}
      return Object.keys(c).filter(function (key) {
        return key !== 'about'
          && key !== 'type'
          && key !== 'recps'
          && key !== 'reason'
      }).map(function (key) {
        var value = c[key]
        return {
          id: msg.key,
          author: msg.value.author,
          timestamp: msg.value.timestamp,
          prop: key,
          value: value,
          remove: value && value.remove,
        }
      })
    }),
    pull.flatten()
  )
}

About.prototype.createAboutStreams = function (id) {
  var ops = this.createAboutOpStream(id)
  var scalars = {/* author: {prop: value} */}
  var sets = {/* author: {prop: {link}} */}

  var setsDone = multicb({pluck: 1, spread: true})
  setsDone()(null, pull.values([]))
  return {
    scalars: pull(
      ops,
      pull.unique(function (op) {
        return op.author + '-' + op.prop + '-'
      }),
      pull.filter(function (op) {
        return !op.remove
      })
    ),
    sets: u.readNext(setsDone)
  }
}

function computeTopAbout(aboutByFeed) {
  var propValueCounts = {/* prop: {value: count} */}
  var topValues = {/* prop: value */}
  var topValueCounts = {/* prop: count */}
  for (var feed in aboutByFeed) {
    var feedAbout = aboutByFeed[feed]
    for (var prop in feedAbout) {
      var value = feedAbout[prop]
      var valueCounts = propValueCounts[prop] || (propValueCounts[prop] = {})
      var count = (valueCounts[value] || 0) + 1
      valueCounts[value] = count
      if (count > (topValueCounts[prop] || 0)) {
        topValueCounts[prop] = count
        topValues[prop] = value
      }
    }
  }
  return topValues
}

About.prototype.get = function (dest, cb) {
  var self = this
  var myAbout = []
  var aboutByFeed = {}
  var aboutByFeedFollowed = {}
  this.follows.getFollows(this.myId, function (err, follows) {
    if (err) return cb(err)
    pull(
      cat([
        dest[0] === '%' && self.app.pullGetMsg(dest),
        self.app.sbot.links({
          rel: 'about',
          dest: dest,
          values: true,
        })
      ]),
      self.app.unboxMessages(),
      pull.drain(function (msg) {
        var author = msg.value.author
        var c = msg.value.content
        if (!c) return
        if (msg.key === dest && c.type === 'about') {
          // don't describe an about message with itself
          return
        }
        var about = author === self.myId ? myAbout :
          follows[author] ?
            aboutByFeedFollowed[author] || (aboutByFeedFollowed[author] = {}) :
            aboutByFeed[author] || (aboutByFeed[author] = {})

        if (c.name) about.name = c.name
        if (c.title) about.title = c.title
        if (c.image) {
          about.image = u.linkDest(c.image)
          about.imageLink = u.toLink(c.image)
        }
        if (c.description) about.description = c.description
        if (c.publicWebHosting) about.publicWebHosting = c.publicWebHosting
      }, function (err) {
        if (err) return cb(err)
        var destAbout = aboutByFeedFollowed[dest] || aboutByFeed[dest]
        // bias the author's choices by giving them an extra vote
        if (destAbout) {
          if (follows[dest]) aboutByFeedFollowed._author = destAbout
          else aboutByFeed._author = destAbout
        }
        var about = {}
        var followedAbout = computeTopAbout(aboutByFeedFollowed)
        var topAbout = computeTopAbout(aboutByFeed)
        for (var k in topAbout) about[k] = topAbout[k]
        // prefer followed feeds' choices
        for (var k in followedAbout) about[k] = followedAbout[k]
        // if we follow the destination/author feed, prefer its choices
        if (follows[dest]) for (var k in destAbout) about[k] = destAbout[k]
        // always prefer own choices
        for (var k in myAbout) about[k] = myAbout[k]
        cb(null, about)
      })
    )
  })
}