/* global window, document, fetch, URLSearchParams */

(function () {
  'use strict';

  var Luxtools = window.Luxtools || (window.Luxtools = {});

  function findCalendarRoot(target) {
    var el = target;
    while (el && el !== document) {
      if (el.classList && el.classList.contains('luxtools-calendar') && el.getAttribute('data-luxtools-calendar') === '1') {
        return el;
      }
      el = el.parentNode;
    }
    return null;
  }

  function getNextMonth(year, month, direction) {
    var cursor = new Date(year, month - 1, 1);
    cursor.setMonth(cursor.getMonth() + direction);
    return {
      year: cursor.getFullYear(),
      month: cursor.getMonth() + 1
    };
  }

  function parseCalendarFromHtml(html) {
    if (!html) return null;

    var wrapper = document.createElement('div');
    wrapper.innerHTML = html;

    return wrapper.querySelector('div.luxtools-calendar[data-luxtools-calendar="1"]');
  }

  function setCalendarBusy(calendar, busy) {
    if (!calendar) return;

    if (busy) {
      calendar.setAttribute('data-luxtools-loading', '1');
    } else {
      calendar.removeAttribute('data-luxtools-loading');
    }

    var buttons = calendar.querySelectorAll('button.luxtools-calendar-nav-button');
    for (var i = 0; i < buttons.length; i++) {
      buttons[i].disabled = !!busy;
    }
  }

  function fetchCalendarMonth(calendar, year, month) {
    var ajaxUrl = calendar.getAttribute('data-luxtools-ajax-url') || '';
    if (!ajaxUrl) return Promise.reject(new Error('Missing calendar ajax url'));

    var baseNs = calendar.getAttribute('data-base-ns') || 'chronological';
    var params = new URLSearchParams({
      call: 'luxtools_calendar_month',
      year: String(year),
      month: String(month),
      base: baseNs
    });

    var url = ajaxUrl + (ajaxUrl.indexOf('?') >= 0 ? '&' : '?') + params.toString();

    return fetch(url, {
      method: 'GET',
      credentials: 'same-origin',
      headers: {
        'X-Requested-With': 'XMLHttpRequest'
      }
    }).then(function (response) {
      if (!response.ok) {
        throw new Error('Calendar request failed: ' + response.status);
      }
      return response.text();
    });
  }

  function navigateCalendarMonth(calendar, direction) {
    var year = parseInt(calendar.getAttribute('data-current-year') || '', 10);
    var month = parseInt(calendar.getAttribute('data-current-month') || '', 10);
    if (!year || !month) return;

    var next = getNextMonth(year, month, direction);
    setCalendarBusy(calendar, true);

    fetchCalendarMonth(calendar, next.year, next.month)
      .then(function (html) {
        var replacement = parseCalendarFromHtml(html);
        if (!replacement) {
          throw new Error('Calendar markup missing in response');
        }

        calendar.replaceWith(replacement);
      })
      .catch(function () {
        var fallbackLink = calendar.querySelector('a.luxtools-calendar-month-link');
        if (fallbackLink && fallbackLink.href) {
          window.location.href = fallbackLink.href;
        }
      })
      .finally(function () {
        setCalendarBusy(calendar, false);
      });
  }

  function onCalendarClick(event) {
    var target = event.target;
    if (!target || !target.classList || !target.classList.contains('luxtools-calendar-nav-button')) return;

    var calendar = findCalendarRoot(target);
    if (!calendar) return;

    var direction = parseInt(target.getAttribute('data-luxtools-dir') || '0', 10);
    if (direction !== -1 && direction !== 1) return;

    event.preventDefault();
    navigateCalendarMonth(calendar, direction);
  }

  function initCalendarWidgets() {
    document.addEventListener('click', onCalendarClick, false);
  }

  Luxtools.CalendarWidget = {
    init: initCalendarWidgets
  };
})();