fix nextTopic calculation for today

src/components/nextTopic.js

@@ -10,7 +10,7 @@ export default () => {
   // because it would be outdated rather quickly
   const isSSR = typeof window === "undefined"
   if (isSSR) {
-    testNextTopic()
+    test()
     return "unbekannt"
   }
 
@@ -21,11 +21,7 @@ export default () => {
 
 function getNextTopicDate() {
   // first thursday and third tuesday in month
-  const nextTopic = new Date(today)
+  const nextTopic = zeroizeTime(today)
-  nextTopic.setHours(0)
-  nextTopic.setMinutes(0)
-  nextTopic.setSeconds(0)
-  nextTopic.setMilliseconds(0)
 
   // first thursday
   if (calculatePriorWeekdays(THURSDAY) === 0) {
@@ -119,9 +115,11 @@ function formatDateInfo(date) {
 }
 
 /**
- * how many sunday to monday transitions are between the two daysTillTuesday
+ * how many sunday to monday transitions are between the two dates
  */
-function weeksBetween(date1, date2) {
+function weeksBetween(datetime1, datetime2) {
+  const date1 = zeroizeTime(datetime1)
+  const date2 = zeroizeTime(datetime2)
   const MILLISECONDS_IN_WEEK = 7 * 24 * 60 * 60 * 1000
   var weeks = Math.floor((date2 - date1) / MILLISECONDS_IN_WEEK)
   // if there is a sunday to monday transition between
@@ -140,9 +138,37 @@ function getISODateString(date) {
   return `${year}-${monthPadded}-${dayPadded}`
 }
 
-// test, becuase this is complicated
+function zeroizeTime(date) {
+  const copy = new Date(date)
+  copy.setHours(0)
+  copy.setMinutes(0)
+  copy.setSeconds(0)
+  copy.setMilliseconds(0)
+  return copy
+}
 
-function testNextTopic() {
+// test, because this is complicated
+
+function test() {
+  testLateSunday()
+  testYear2020()
+
+  // reset to correct value
+  today = new Date()
+}
+
+function testLateSunday() {
+  today = new Date("2020-01-19T23:59:59+01:00")
+  const result = formatDateInfo(getNextTopicDate())
+  console.assert(
+    result === "Nächste Woche Dienstag, 2020-01-21",
+    `starting at ${getISODateString(
+      today
+    )}: was ${result}, expected "Nächste Woche Dienstag, 2020-01-21"`
+  )
+}
+
+function testYear2020() {
   const topicsIn2020 = [
     "2020-01-02",
     "2020-01-21",
@@ -169,20 +195,21 @@ function testNextTopic() {
     "2020-12-03",
     "2020-12-15",
   ]
-  today = new Date("2020-01-01")
+  today = zeroizeTime(new Date("2020-01-01"))
+  let currentIndex = 0
 
-  for (const nextTopic of topicsIn2020) {
+  while (today <= new Date("2020-12-15")) {
     const result = getISODateString(getNextTopicDate())
+    const expect = topicsIn2020[currentIndex]
     console.assert(
-      result === nextTopic,
+      result === expect,
       `starting at ${getISODateString(
         today
-      )}: was ${result}, expected ${nextTopic}`
+      )}: was ${result}, expected ${expect}`
     )
-    today = new Date(result)
+    if (getISODateString(today) === result) {
-    today.setDate(today.getDate() + 1)
+      currentIndex++
+    }
+    addDays(today, 1)
   }
-
-  // reset to correct value
-  today = new Date()
 }