// ==UserScript==
// @name        TVMaze: add "Watched" button to calendar
// @description Add add "Watched" button to calendar at TVMaze
// @namespace   BlackNullerNS
// @include     http://www.tvmaze.com/calendar*
// @version     1.0
// @grant       GM_xmlhttpRequest
// @downloadURL none
// ==/UserScript==

var btn = document.createElement('button');
btn.innerHTML = '✓';
btn.style.border = 0;
btn.style.padding = '2px';
btn.style.background = 'transparent';
btn.style.color = '#3C948B';
btn.style.cursor = 'pointer';

var handler = function (e) {
    e.preventDefault();

    if (!confirm('Mark the episode as watched?')) {
        return false;
    }

    var self = this,
        entry = this.parentNode,
        link = this.previousElementSibling;

    if (link.getAttribute('href').indexOf('episodes/') === -1) {
        return false;
    }

    var eid = link.getAttribute('href').split('episodes/')[1].split('/')[0];
    var url = '/watch/set?episode_id=' + eid;
    var csrf = document.querySelector('meta[name="csrf-token"]').getAttribute('content');

    GM_xmlhttpRequest({
      method: "POST",
      url: url,
      data: "type=0",
      headers: {
        "Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",
        "X-CSRF-Token": csrf
      },
      onload: function(response) {
        entry.classList.add('watched');
        self.remove();
      }
    });
};

var cloned;
var episodes = document.querySelectorAll(".entry:not(.watched)");

for (var i = 0, l = episodes.length; i < l; i++) {
    cloned = btn.cloneNode(true);
    cloned.addEventListener('click', handler);
    episodes.item(i).appendChild(cloned);
}