(function (context, $) {

  "use strict";

  context.JK = context.JK || {};
  context.JK.FindSessionScreen = function (app) {
    var CATEGORY = {
      INVITATION: {index: 0, id: "table#sessions-invitations"},
      FRIEND: {index: 1, id: "table#sessions-friends"},
      OTHER: {index: 2, id: "table#sessions-other"}
    };

    var logger = context.JK.logger;
    var rest = context.JK.Rest();
    var sessionLatency;
    var sessions = {};
    var invitationSessionGroup = {};
    var friendSessionGroup = {};
    var otherSessionGroup = {};
    var sessionCounts = [0, 0, 0];
    var sessionList;
    var currentQuery = defaultQuery();
    var currentPage = 0;
    var LIMIT = 20;
    var $next = null;
    var $scroller = null;
    var $noMoreSessions = null;


    function defaultQuery() {
      return {offset:currentPage * LIMIT, limit:LIMIT, page:currentPage};
    }
    // for unit tests
    function getCategoryEnum() {
      return CATEGORY;
    }

    function removeSpinner() {
      $('div[layout-id=findSession] .content .spinner').remove();// remove any existing spinners

    }

    function addSpinner() {
      removeSpinner();
      $('div[layout-id=findSession] .content').append('<div class="spinner spinner-large"></div>')
    }

    function loadSessionsOriginal() {
      addSpinner();

      rest.findSessions(currentQuery)
        .done(afterLoadSessions)
        .fail(app.ajaxError)
        .always(removeSpinner)
    }

    function loadSessionsNew() {

      addSpinner();

      rest.findScoredSessions(app.clientId, currentQuery)
        .done(function(response) { afterLoadScoredSessions(response); })
        .always(function(){ removeSpinner(); })
        .fail(app.ajaxError)
    }

    function loadSessions() {


      if (gon.use_cached_session_scores) {
        loadSessionsNew();
      }
      else {
        loadSessionsOriginal();
      }

    }

    function buildQuery() {
      currentQuery = defaultQuery();

      // genre filter
      var genres = context.JK.GenreSelectorHelper.getSelectedGenres('#find-session-genre');
      if (genres !== null && genres.length > 0) {
        currentQuery.genres = genres.join(',');
      }

      // keyword filter
      var keyword = $('#session-keyword-srch').val();
      if (keyword !== null && keyword.length > 0 && keyword !== 'Search by Keyword') {
        currentQuery.keyword = $('#session-keyword-srch').val();
      }

      return currentQuery;
    }

    function search() {
      logger.debug("Searching for sessions...");
      clearResults();
      buildQuery();
      refreshDisplay();
      loadSessions();
    }

    function refreshDisplay() {
      var priorVisible;

      var INVITATION = 'div#sessions-invitations';
      var FRIEND = 'div#sessions-friends';
      var OTHER = 'div#sessions-other';

      // INVITATION
      //logger.debug("sessionCounts[CATEGORY.INVITATION.index]=" + sessionCounts[CATEGORY.INVITATION.index]);
      if (sessionCounts[CATEGORY.INVITATION.index] === 0) {
        priorVisible = false;
        $(INVITATION).hide();
      }
      else {
        priorVisible = true;
        $(INVITATION).show();
      }

      // FRIEND
      if (!priorVisible) {
        $(FRIEND).removeClass('mt35');
      }

      //logger.debug("sessionCounts[CATEGORY.FRIEND.index]=" + sessionCounts[CATEGORY.FRIEND.index]);
      if (sessionCounts[CATEGORY.FRIEND.index] === 0) {
        priorVisible = false;
        $(FRIEND).hide();
      }
      else {
        priorVisible = true;
        $(FRIEND).show();
      }

      // OTHER
      if (!priorVisible) {
        $(OTHER).removeClass('mt35');
      }

      //logger.debug("sessionCounts[CATEGORY.OTHER.index]=" + sessionCounts[CATEGORY.OTHER.index]);
      if (sessionCounts[CATEGORY.OTHER.index] === 0) {
        $(OTHER).hide();
      }
      else {
        $(OTHER).show();
      }
    }

    function afterLoadScoredSessions(sessionList) {

      // display the 'no sessions' banner if appropriate
      var $noSessionsFound = $('#sessions-none-found');
      if (currentPage == 0 && sessionList.length == 0) {
        $noSessionsFound.show();
      }
      else {
        $noSessionsFound.hide();
      }

      // update pager so infinitescroll can do it's thing
      //$next.attr('href', '/api/sessions/nindex/' + app.clientId + '?' + $.param(currentQuery))

      /**
      // XXX
      if(sessionList.length > 0) {
        for(var i = 0; i < 20; i++) {
          var copied =  $.extend(true, {}, sessionList[0]);
          copied.id = 'session_' + i;
          sessionList.push(copied);
        }
      }
       */

      $.each(sessionList, function (i, session) {
        sessions[session.id] = session;
      });

      $.each(sessionList, function (i, session) {
        renderSession(session.id);
      });

      if(sessionList.length < LIMIT) {
        // if we less results than asked for, end searching
        $scroller.infinitescroll('pause');

        if(currentPage > 0) {
          $noMoreSessions.show();
        }

      }else {
        currentPage++;
        buildQuery();
        registerInfiniteScroll();
      }

      context.JK.GA.trackFindSessions(sessionList.length);
    }


    function afterLoadSessions(sessionList) {

      // display the 'no sessions' banner if appropriate
      var $noSessionsFound = $('#sessions-none-found');
      if (sessionList.length == 0) {
        $noSessionsFound.show();
      }
      else {
        $noSessionsFound.hide();
      }

      startSessionLatencyChecks(sessionList);

      context.JK.GA.trackFindSessions(sessionList.length);
    }

    function startSessionLatencyChecks(sessionList) {
      logger.debug("Starting latency checks on " + sessionList.length + " sessions");

      sessionLatency.subscribe(app.clientId, latencyResponse);
      $.each(sessionList, function (index, session) {
        sessions[session.id] = session;
        sessionLatency.sessionPings(session);
      });
    }

    function containsInvitation(session) {
      var i, invitation = null;

      if (session !== undefined) {
        if ("invitations" in session) {
          // user has invitations for this session
          for (i = 0; i < session.invitations.length; i++) {
            invitation = session.invitations[i];
            // session contains an invitation for this user
            if (invitation.receiver_id == context.JK.currentUserId) {
              return true;
            }
          }
        }
      }

      return false;
    }

    function containsFriend(session) {
      var i, participant = null;

      if (session !== undefined) {
        if ("participants" in session) {
          for (i = 0; i < session.participants.length; i++) {
            participant = session.participants[i];
            // this session participant is a friend
            if (participant !== null && participant !== undefined && participant.user.is_friend) {
              return true;
            }
          }
        }
      }
      return false;
    }

    function latencyResponse(sessionId) {
      logger.debug("Received latency response for session " + sessionId);
      renderSession(sessionId);
    }

    /**
     * Not used normally. Allows modular unit testing
     * of the renderSession method without having to do
     * as much heavy setup.
     */
    function setSession(session) {
      invitationSessionGroup[session.id] = session;
    }

    /**
     * Render a single session line into the table.
     * It will be inserted at the appropriate place according to the
     * sortScore in sessionLatency.
     */
    function renderSession(sessionId) {
      // store session in the appropriate bucket and increment category counts
      var session = sessions[sessionId];
      if (containsInvitation(session)) {
        invitationSessionGroup[sessionId] = session;
        sessionCounts[CATEGORY.INVITATION.index]++;
      }
      else if (containsFriend(session)) {
        friendSessionGroup[sessionId] = session;
        sessionCounts[CATEGORY.FRIEND.index]++;
      }
      else {
        otherSessionGroup[sessionId] = session;
        sessionCounts[CATEGORY.OTHER.index]++;
      }

      // hack to prevent duplicate rows from being rendered when filtering
      var sessionAlreadyRendered = false;
      var $tbGroup;

      logger.debug('Rendering session ID = ' + sessionId);

      if (invitationSessionGroup[sessionId] != null) {
        $tbGroup = $(CATEGORY.INVITATION.id);

        if ($("table#sessions-invitations tr[id='" + sessionId + "']").length > 0) {
          sessionAlreadyRendered = true;
        }
      }
      else if (friendSessionGroup[sessionId] != null) {
        ;
        $tbGroup = $(CATEGORY.FRIEND.id);

        if ($("table#sessions-friends tr[id='" + sessionId + "']").length > 0) {
          sessionAlreadyRendered = true;
        }
      }
      else if (otherSessionGroup[sessionId] != null) {
        $tbGroup = $(CATEGORY.OTHER.id);

        if ($("table#sessions-other tr[id='" + sessionId + "']").length > 0) {
          sessionAlreadyRendered = true;
        }
      }
      else {
        logger.debug('ERROR: No session with ID = ' + sessionId + ' found.');
        return;
      }

      if (!sessionAlreadyRendered) {
        var row = sessionList.renderSession(session, sessionLatency, $tbGroup, $('#template-session-row').html(), $('#template-musician-info').html());
      }

      refreshDisplay();
    }

    function beforeShow(data) {
      context.JK.GenreSelectorHelper.render('#find-session-genre');
    }

    function afterShow(data) {
      if(!context.JK.JamServer.connected) {
        app.notifyAlert("Not Connected", 'To create or join a session, you must be connected to the server.');
        window.location = '/client#/home'
        return;
      }

      clearResults();
      buildQuery();
      refreshDisplay();
      loadSessions();
      context.JK.guardAgainstBrowser(app);
    }

    function clearResults() {
      currentPage = 0;
      $noMoreSessions.hide();
      $scroller.infinitescroll('resume');
      $('table#sessions-invitations').children(':not(:first-child)').remove();
      $('table#sessions-friends').children(':not(:first-child)').remove();
      $('table#sessions-other').children(':not(:first-child)').remove();

      sessionCounts = [0, 0, 0];

      sessions = {};
      invitationSessionGroup = {};
      friendSessionGroup = {};
      otherSessionGroup = {};
    }

    function deleteSession(evt) {
      var sessionId = $(evt.currentTarget).attr("action-id");
      if (sessionId) {
        $.ajax({
          type: "DELETE",
          url: "/api/sessions/" + sessionId,
          error: app.ajaxError
        }).done(loadSessions);
      }
    }
    function tempDebugStuff() {
      if (gon.allow_both_find_algos && context.JK.currentUserAdmin) {
        // show extra Refresh button, and distinguish between them
        $('#btn-refresh-other').show().click(function() {
          clearResults();
          buildQuery();
          refreshDisplay();
          if(gon.use_cached_session_scores) {
            loadSessionsOriginal();
          }
          else {
            loadSessionsNew();
          }
        });
        $('#btn-refresh').find('.extra').text(gon.use_cached_session_scores ? ' (new way)' : ' (old way)')
        $('#btn-refresh-other').find('.extra').text(gon.use_cached_session_scores ? ' (old way)' : ' (new way)')
      }
    }

    function registerInfiniteScroll() {

      if(gon.use_cached_session_scores) {

        $scroller.infinitescroll({

          behavior: 'local',
          navSelector: '#findSession .btn-next-wrapper',
          nextSelector: '#findSession .btn-next',
          binder: $scroller,
          dataType: 'json',
          appendCallback: false,
          debug: true,
          prefill: false,
          bufferPx:100,
          loading: {
            msg: $('<div class="infinite-scroll-loader">Loading ...</div>'),
            img: '/assets/shared/spinner.gif'
          },
          path: function(page) {
            return '/api/sessions/nindex/' + app.clientId + '?' + $.param(buildQuery());
          }
        },function(json, opts) {
          // Get current page
          //currentPage = opts.state.currPage;
          // Do something with JSON data, create DOM elements, etc ..
          afterLoadScoredSessions(json);
        });
      }
    }

    function events() {

      $('#session-keyword-srch').focus(function () {
        $(this).val('');
      });

      $("#session-keyword-srch").keypress(function (evt) {
        if (evt.which === 13) {
          evt.preventDefault();
          search();
        }
      });

      $('#btn-refresh').on("click", search);

      tempDebugStuff();
    }

    /**
     * Initialize, providing an instance of the SessionLatency class.
     */
    function initialize(latency) {

      var screenBindings = {
        'beforeShow': beforeShow,
        'afterShow': afterShow
      };
      app.bindScreen('findSession', screenBindings);

      if (latency) {
        sessionLatency = latency;
      }
      else {
        logger.warn("No sessionLatency provided.");
      }

      sessionList = new context.JK.SessionList(app);

      $next = $('#findSession .btn-next')
      $scroller = $('#findSession .content-body-scroller');
      $noMoreSessions = $('#end-of-session-list');
      events();
    }

    this.initialize = initialize;
    this.renderSession = renderSession;
    this.afterShow = afterShow;

    // Following exposed for easier testing.
    this.setSession = setSession;
    this.clearResults = clearResults;
    this.getCategoryEnum = getCategoryEnum;

    return this;
  };

})(window, jQuery);