Gather general cycle-related functions in cycle module

lib/cycle.js

@@ -0,0 +1,65 @@
+import * as joda from 'js-joda'
+
+const LocalDate = joda.LocalDate
+
+export default function config(opts = {}) {
+  let bleedingDaysSortedByDate
+  if (!opts.bleedingDaysSortedByDate) {
+    // we only want to require (and run) the db module when not running the tests
+    bleedingDaysSortedByDate = require('../db').bleedingDaysSortedByDate
+  } else {
+    bleedingDaysSortedByDate = opts.bleedingDaysSortedByDate
+  }
+  const maxBreakInBleeding = opts.maxBreakInBleeding || 1
+
+  function getLastMensesStart(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))
+    })
+
+    function thereIsNoPreviousBleedingDayWithinTheThreshold(bleedingDay, previousBleedingDays) {
+      const periodThreshold = bleedingDay.wrappedDate.minusDays(maxBreakInBleeding + 1)
+      return !previousBleedingDays.some(({ wrappedDate }) => wrappedDate.equals(periodThreshold) || wrappedDate.isAfter(periodThreshold))
+    }
+
+    return lastPeriodStart
+  }
+
+  function getCycleDayNumber(targetDateString) {
+    const lastMensesStart = getLastMensesStart(targetDateString)
+    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 getPreviousDaysInCycle() {
+    return []
+  }
+
+  return {
+    getCycleDayNumber,
+    getLastMensesStart,
+    getPreviousDaysInCycle
+  }
+}