var Graphmitter = require('graphmitter')
var pull        = require('pull-stream')
var mlib        = require('ssb-msgs')
var memview     = require('level-memview')
var pushable    = require('pull-pushable')
var mdm         = require('mdmanifest')
var valid       = require('scuttlebot/lib/validators')
var apidoc      = require('scuttlebot/lib/apidocs').friends

// friends plugin
// methods to analyze the social graph
// maintains a 'follow' and 'flag' graph

function isFunction (f) {
  return 'function' === typeof f
}

function isString (s) {
  return 'string' === typeof s
}

function isFriend (friends, a, b) {
  return friends[a] && friends[b] && friends[a][b] && friends[b][a]
}

exports.name = 'friends'
exports.version = '1.0.0'
exports.manifest = mdm.manifest(apidoc)

exports.init = function (sbot, config) {

  var graphs = {
    follow: new Graphmitter(),
    flag: new Graphmitter()
  }

  // view processor
  var syncCbs = []
  function awaitSync (cb) {
    if (syncCbs) syncCbs.push(cb)
    else cb()
  }

  // read/watch the log for changes to the social graph
  pull(sbot.createLogStream({ live: true }), pull.drain(function (msg) {

    if (msg.sync) {
      syncCbs.forEach(function (cb) { cb() })
      syncCbs = null

      if (sbot.gossip) {
        // prioritize friends
        var friends = graphs['follow'].toJSON()
        sbot.gossip.peers().forEach(function(peer) {
          if (isFriend(friends, sbot.id, peer.key)) {
            sbot.gossip.add(peer, 'friends')
          }
        })
      }

      return
    }

    var c = msg.value.content
    if (c.type == 'contact') {
      mlib.asLinks(c.contact, 'feed').forEach(function (link) {
        if ('following' in c) {
          if (c.following)
            graphs.follow.edge(msg.value.author, link.link, true)
          else
            graphs.follow.del(msg.value.author, link.link)

        }
        if ('flagged' in c) {
          if (c.flagged)
            graphs.flag.edge(msg.value.author, link.link, c.flagged)
          else
            graphs.flag.del(msg.value.author, link.link)
        }
      })
    }
  }))

  return {

    get: valid.sync(function (opts) {
      var g = graphs[opts.graph || 'follow']
      if(!g) throw new Error('opts.graph must be provided')
      return g.get(opts.source, opts.dest)
    }, 'object?'),

    all: valid.async(function (graph, cb) {
      if (typeof graph == 'function') {
        cb = graph
        graph = null
      }
      if (!graph)
        graph = 'follow'
      awaitSync(function () {
        cb(null, graphs[graph] ? graphs[graph].toJSON() : null)
      })
    }, 'string?'),

    path: valid.sync(function (opts) {
      if(isString(opts))
        opts = {source: sbot.id, dest: opts}
      return graphs.follow.path(opts)

    }, 'string|object'),

    createFriendStream: valid.source(function (opts) {
      opts = opts || {}
      var live = opts.live === true
      var meta = opts.meta === true
      var start = opts.start || sbot.id
      var graph = graphs[opts.graph || 'follow']
      if(!graph)
        return pull.error(new Error('unknown graph:' + opts.graph))
      var cancel, ps = pushable(function () {
        cancel && cancel()
      })

      function push (to, hops) {
        return ps.push(meta ? {id: to, hops: hops} : to)
      }

      if (live) {
        awaitSync(function () {
          ps.push({sync: true})
        })
      }

      //by default, also emit your own key.
      if(opts.self !== false)
        push(start, 0)

      var conf = config.friends || {}
      cancel = graph.traverse({
        start: start,
        hops: opts.hops || conf.hops || 3,
        max: opts.dunbar || conf.dunbar || 150,
        each: function (_, to, hops) {
          if(to !== start) push(to, hops)
        }
      })

      if(!live) { cancel(); ps.end() }

      return ps
    }, 'createFriendStreamOpts?'),

    hops: valid.async(function (start, graph, opts, cb) {
      if (typeof opts == 'function') { // (start|opts, graph, cb)
        cb = opts
        opts = null
      } else if (typeof graph == 'function') { // (start|opts, cb)
        cb = graph
        opts = graph = null
      }
      opts = opts || {}
      if(isString(start)) { // (start, ...)
        // first arg is id string
        opts.start = start
      } else if (start && typeof start == 'object') { // (opts, ...)
        // first arg is opts
        for (var k in start)
          opts[k] = start[k]
      }

      var conf = config.friends || {}
      opts.start  = opts.start  || sbot.id
      opts.dunbar = opts.dunbar || conf.dunbar || 150
      opts.hops   = opts.hops   || conf.hops   || 3

      var g = graphs[graph || 'follow']
      if (!g)
        return cb(new Error('Invalid graph type: '+graph))

      awaitSync(function () {
        cb(null, g.traverse(opts))
      })
    }, ['feedId', 'string?', 'object?'], ['createFriendStreamOpts'])
  }
}