Extract getLastMensesStart

lib/get-cycle-day-number.js

 import * as joda from 'js-joda'
-
-const LocalDate = joda.LocalDate
+import getLastMensesStart from './get-last-menses-start'
 
 export default function config(opts = {}) {
   let bleedingDaysSortedByDate
@@ -12,37 +11,13 @@ export default function config(opts = {}) {
   }
   const maxBreakInBleeding = opts.maxBreakInBleeding || 1
 
-  return function getCycleDayNumber(targetDateString) {
-    const targetDate = LocalDate.parse(targetDateString)
-    const withWrappedDates = bleedingDaysSortedByDate
-      .filter(day => !day.bleeding.exclude)
-      .map(day => {
-        day.wrappedDate = LocalDate.parse(day.date)
-        return day
-      })
-
-    const firstBleedingDayBeforeTargetDayIndex = withWrappedDates.findIndex(day => {
-      return (
-        day.wrappedDate.isEqual(targetDate) ||
-        day.wrappedDate.isBefore(targetDate)
-      )
-    })
-
-    if (firstBleedingDayBeforeTargetDayIndex < 0) return null
-    const previousBleedingDays = withWrappedDates.slice(firstBleedingDayBeforeTargetDayIndex)
-
-    const lastPeriodStart = previousBleedingDays.find((day, i) => {
-      return thereIsNoPreviousBleedingDayWithinTheThreshold(day, previousBleedingDays.slice(i + 1), maxBreakInBleeding)
-    })
-
-    const diffInDays = lastPeriodStart.wrappedDate.until(targetDate, joda.ChronoUnit.DAYS)
+  return function(targetDateString) {
+    const lastMensesStart = getLastMensesStart(targetDateString, bleedingDaysSortedByDate, maxBreakInBleeding)
+    if (!lastMensesStart) return null
+    const targetDate = joda.LocalDate.parse(targetDateString)
+    const diffInDays = lastMensesStart.wrappedDate.until(targetDate, joda.ChronoUnit.DAYS)
 
     // cycle starts at day 1
     return diffInDays + 1
   }
-}
-
-function thereIsNoPreviousBleedingDayWithinTheThreshold(bleedingDay, earlierCycleDays, allowedBleedingBreak) {
-  const periodThreshold = bleedingDay.wrappedDate.minusDays(allowedBleedingBreak + 1)
-  return !earlierCycleDays.some(({ wrappedDate }) => wrappedDate.equals(periodThreshold) || wrappedDate.isAfter(periodThreshold))
 }
\ No newline at end of file

lib/get-last-menses-start.js

+import * as joda from 'js-joda'
+
+const LocalDate = joda.LocalDate
+
+export default function getLastMensesStart(targetDateString, bleedingDaysSortedByDate, maxBreakInBleeding) {
+  const targetDate = LocalDate.parse(targetDateString)
+  const withWrappedDates = bleedingDaysSortedByDate
+    .filter(day => !day.bleeding.exclude)
+    .map(day => {
+      day.wrappedDate = LocalDate.parse(day.date)
+      return day
+    })
+
+  const firstBleedingDayBeforeTargetDayIndex = withWrappedDates.findIndex(day => {
+    return (
+      day.wrappedDate.isEqual(targetDate) ||
+      day.wrappedDate.isBefore(targetDate)
+    )
+  })
+
+  if (firstBleedingDayBeforeTargetDayIndex < 0) return null
+  const previousBleedingDays = withWrappedDates.slice(firstBleedingDayBeforeTargetDayIndex)
+
+  const lastPeriodStart = previousBleedingDays.find((day, i) => {
+    return thereIsNoPreviousBleedingDayWithinTheThreshold(day, previousBleedingDays.slice(i + 1), maxBreakInBleeding)
+  })
+
+  return lastPeriodStart
+}
+
+function thereIsNoPreviousBleedingDayWithinTheThreshold(bleedingDay, earlierCycleDays, allowedBleedingBreak) {
+  const periodThreshold = bleedingDay.wrappedDate.minusDays(allowedBleedingBreak + 1)
+  return !earlierCycleDays.some(({ wrappedDate }) => wrappedDate.equals(periodThreshold) || wrappedDate.isAfter(periodThreshold))
+}
\ No newline at end of file