Add option for minimum cycle length

get-cycle-day-number.js

@@ -1,46 +1,44 @@
-export default function (cycleDays, targetDay) {
-  const lastFirstBleedingday = findLastFirstBleedingDay(cycleDays)
+import moment from 'moment'
 
-  if (!lastFirstBleedingday) return
+export default function config(opts) {
+  opts = opts || {
+    // at the very minimum, a cycle can be a bleeding day
+    // followed by a non-bleeding day, thus a length of 2
+    minCycleLengthInDays: 2
+  }
 
-  const diffInDays = targetDay.diff(lastFirstBleedingday.date, 'days')
+  return function getCycleDayNumber(unsorted, targetDate) {
+    // sort the cycle days in descending order so we travel into
+    // the past as we iterate over the array
+    const cycleDays = [...unsorted].sort((a, b) => b.date.isAfter(a.date))
 
-  // cycle starts at day 1
-  return diffInDays + 1
-}
+    const lastPeriodStart = cycleDays.find((day, i) => {
+      if (
+        isBleedingDay(day) &&
+        thereIsNoPreviousBleedingDayWithinTheThreshold(day, cycleDays.slice(i + 1), opts.minCycleLengthInDays)) {
+        return true
+      }
+    })
 
-function findLastFirstBleedingDay(cycleDays) {
-  // sort the cycle days in descending order
-  // so we travel into the past as we iterate
-  // over the array
-  cycleDays.sort((a,b) => b.date - a.date)
+    if (!lastPeriodStart) return null
 
-  let sawBleeding = false
+    // by default, moment.diff rounds down, so we get the decimal number
+    // and round it ourselves
+    const diffInDays = Math.round(targetDate.diff(lastPeriodStart.date, 'days', true))
 
-  for (let i = 0; i < cycleDays.length; i++) {
-    const cycleDay = cycleDays[i]
-
-    // we have detected the day before the beginning
-    // of a bleeding period, so the previous cycle day in the array
-    // was the first day of bleeding
-    if (sawBleeding && (!isBleedingDay(cycleDay))) {
-      return cycleDays[i - 1]
-    }
-
-    // if we get to the earliest cycle day and there was
-    // bleeding on that day, it's the first bleeding day for us
-    if (i === cycleDays.length - 1 && isBleedingDay(cycleDay)) {
-      return cycleDay
-    }
-
-    if (isBleedingDay(cycleDay)) {
-      sawBleeding = true
-    }
+    // cycle starts at day 1
+    return diffInDays + 1
   }
 }
 
-function isBleedingDay(cycleDay) {
-  return cycleDay.bleeding
-    && cycleDay.bleeding.value
-    && !cycleDay.bleeding.exclude
+function thereIsNoPreviousBleedingDayWithinTheThreshold(bleedingDay, earlierCycleDays, threshold) {
+  // the bleeding day itself is included in the threshold, thus we subtract 1
+  const minCycleThresholdDate = moment(bleedingDay.date).subtract(threshold - 1, 'days')
+  return !earlierCycleDays.some(day => {
+    return day.date.isSameOrAfter(minCycleThresholdDate, 'day') && isBleedingDay(day)
+  })
+}
+
+function isBleedingDay(day) {
+  return day.bleeding && day.bleeding.value && !day.bleeding.exclude
 }