// -----------------------------------------------------------------------
// Ajax object
// -----------------------------------------------------------------------
// 
// This provides simple functions for making Ajax calls easily.

(
  function(window) {
    var Ajax = window.Ajax = {
      getJSON: function getJSON(path, obj, cb) {
        if (obj)
          path += "?" + queryString(obj);
        var req = new XMLHttpRequest();
        req.open("GET", path);
        prepare(req, cb);
        req.send(null);
        return req;
      },
      postJSON: function postJSON(path, obj, cb) {
        var body = JSON.stringify(obj);
        var req = new XMLHttpRequest();
        req.open("POST", path);
        req.setRequestHeader("Content-Type", "application/json");
        prepare(req, cb);
        req.send(body);
        return req;
      }
    };

    function queryString(data) {
      var parts = [];
      for (name in data) {
        var values = data[name];
        if (!values.forEach)
          values = [values];
        values.forEach(
          function(value) {
            parts.push(encodeURI(name) + "=" + encodeURI(value));
          });
      }
      return parts.join("&");
    }

    function prepare(req, cb) {
      function onLoad(event) {
        var data = null;
        try {
          data = JSON.parse(req.responseText);
        } catch (e) {}
        if (req.status >= 200 && req.status < 300)
          cb(true, data);
        else
          cb(false, data);
      }

      function onError(event) {
        var data = null;
        try {
          data = JSON.parse(req.responseText);
        } catch (e) {}
        cb(false, data);
      }

      req.addEventListener("load", onLoad, false);
      req.addEventListener("error", onError, false);
      req.addEventListener("abort", onError, false);
      req.overrideMimeType("application/json");
    }
  }
)(window);

// -----------------------------------------------------------------------
// Config object
// -----------------------------------------------------------------------
// 
// This manages interactions with client-side persistent storage and the
// current login state of the app.

(
  function(window) {
    // Amount of time, in milliseconds, that pass before we check
    // to see if another instance of this page changed our persistent
    // storage.
    const REFRESH_INTERVAL = 2000;

    var Config = window.Config = {
      get value() {
        var val = localStorage.getItem("SUMMIT_CFG");
        if (val)
          return JSON.parse(val);
        return {};
      },
      get lastChanged() {
        var ts = localStorage.getItem("SUMMIT_CFG_TIMESTAMP");
        if (ts)
          return new Date(ts);
        return new Date(0);
      },
      setValue: function Config_setValue(val) {
        localStorage.setItem("SUMMIT_CFG", JSON.stringify(val));
        localStorage.setItem("SUMMIT_CFG_TIMESTAMP",
                             (new Date()).toString());
        this.observers.forEach(function(cb) { cb(); });
      },
      wipe: function Config_wipe() {
        localStorage.removeItem("SUMMIT_CFG");
        localStorage.removeItem("SUMMIT_CFG_TIMESTAMP");
        this.observers.forEach(function(cb) { cb(); });
      },
      observers: []
    };

    function ensureStateIsValid() {
      if (!('state' in Config.value))
        Config.setValue({state: "login"});
    }

    Config.observers.push(ensureStateIsValid);

    // This is useful for finding out whether our configuration has
    // been changed by another instance of our same window.
    function setupConfigWatcher() {
      var lastChanged = Config.lastChanged;

      function onConfigChanged() {
        lastChanged = Config.lastChanged;
      };

      Config.observers.push(onConfigChanged);

      window.setInterval(
        function() {
          if (Config.lastChanged > lastChanged)
            Config.observers.forEach(function(cb) { cb(); });
        },
        REFRESH_INTERVAL
      );
    }

    function initConfig() {
      ensureStateIsValid();
      setupConfigWatcher();
    }

    window.addEventListener("DOMContentLoaded", initConfig, false);
  }
)(window);

// -----------------------------------------------------------------------
// Attendees object
// -----------------------------------------------------------------------
// 
// This manages the list of Summit attendees and their shared metadata.

(
  function(window) {
    var req;

    var Attendees = window.Attendees = {
      refresh: function refresh() {
        if (req)
          return;
        var self = this;
        if (Config.value.token) {
          req = Ajax.getJSON(
            "api/profile",
            {token: Config.value.token},
            function(success, data) {
              req = null;
              if (success) {
                self.all = data.contents;
                self.currentUser = self.all[Config.value.userID];
                self.observers.forEach(function(cb) { cb(); });
              } else {
                // TODO: Raise an error?
              }
            });
        }
      },
      currentUser: null,
      all: null,
      observers: []
    };

    function refreshAttendees() {
      if (Config.value.state == "logged-in" && !Attendees.all)
        Attendees.refresh();
    }

    Config.observers.push(refreshAttendees);
    window.addEventListener("DOMContentLoaded", refreshAttendees, false);
  }
)(window);