gun/sea/user.js

    var SEA = require('./sea');
    var Gun = SEA.Gun;
    var then = require('./then');

    function User(root){ 
      this._ = {$: this};
    }
    User.prototype = (function(){ function F(){}; F.prototype = Gun.chain; return new F() }()) // Object.create polyfill
    User.prototype.constructor = User;

    // let's extend the gun chain with a `user` function.
    // only one user can be logged in at a time, per gun instance.
    Gun.chain.user = function(pub){
      var gun = this, root = gun.back(-1), user;
      if(pub){ return root.get('~'+pub) }
      if(user = root.back('user')){ return user }
      var root = (root._), at = root, uuid = at.opt.uuid || Gun.state.lex;
      (at = (user = at.user = gun.chain(new User))._).opt = {};
      at.opt.uuid = function(cb){
        var id = uuid(), pub = root.user;
        if(!pub || !(pub = pub.is) || !(pub = pub.pub)){ return id }
        id = id + '~' + pub + '/';
        if(cb && cb.call){ cb(null, id) }
        return id;
      }
      return user;
    }
    Gun.User = User;
    module.exports = User;