add week selector

1 files changed, 60 insertions, 0 deletions

diff --git a/public/javascripts/weekSelector.js b/public/javascripts/weekSelector.js
new file mode 100644
index 0000000..7ce0d68
--- /dev/null
+++ b/public/javascripts/weekSelector.js
@@ -0,0 +1,60 @@
+const EventEmitter = require('events')
+
+const self = {}
+
+self.events = new EventEmitter()
+
+self._nodes = {
+  prevButton: document.querySelectorAll('#week-selector button')[0],
+  nextButton: document.querySelectorAll('#week-selector button')[1],
+  currentWeekText: document.querySelector('#week-selector .current')
+}
+
+self._weekOffset = 0
+
+// copied from http://www.meetingpointmco.nl/Roosters-AL/doc/dagroosters/untisscripts.js,
+// were using the same code as they do to be sure that we always get the same
+// week number.
+self.getCurrentWeek = function (target) {
+  const dayNr = (target.getDay() + 6) % 7
+  target.setDate(target.getDate() - dayNr + 3)
+  const firstThursday = target.valueOf()
+  target.setMonth(0, 1)
+  if (target.getDay() !== 4) {
+    target.setMonth(0, 1 + ((4 - target.getDay()) + 7) % 7)
+  }
+
+  return 1 + Math.ceil((firstThursday - target) / 604800000)
+}
+
+self.getSelectedWeek = function () {
+  const now = new Date()
+  const targetDate = new Date(now.getTime() + self._weekOffset * 604800 * 1000)
+  return self.getCurrentWeek(targetDate)
+}
+
+self.updateCurrentWeek = function () {
+  const selectedWeekNumber = self.getSelectedWeek()
+  self._nodes.currentWeekText.textContent = `Week ${selectedWeekNumber}`
+  if (self.getCurrentWeek(new Date()) !== selectedWeekNumber) {
+    self._nodes.currentWeekText.classList.add('changed')
+  } else {
+    self._nodes.currentWeekText.classList.remove('changed')
+  }
+  self.events.emit('weekChanged', selectedWeekNumber)
+}
+
+self._handlePrevButtonClick = function () {
+  self._weekOffset -= 1
+  self.updateCurrentWeek()
+}
+
+self._handleNextButtonClick = function () {
+  self._weekOffset += 1
+  self.updateCurrentWeek()
+}
+
+self._nodes.prevButton.addEventListener('click', self._handlePrevButtonClick)
+self._nodes.nextButton.addEventListener('click', self._handleNextButtonClick)
+
+module.exports = self