Adds test and fixes getCycleByStartDate method of cycle module

lib/cycle.js

@@ -51,7 +51,7 @@ export default function config(opts) {
     const i = cycleStartsSortedByDate.indexOf(cycleStart)
     const earlierCycleStart = cycleStartsSortedByDate[i + 1]
     if (!earlierCycleStart) return null
-    return getCycleForCycleStartDay(earlierCycleStart)
+    return getCycleByStartDay(earlierCycleStart)
   }
 
   function getCyclesBefore(targetCycleStartDay) {
@@ -61,40 +61,70 @@ export default function config(opts) {
     if (startFromHere < 0) return null
     return cycleStartsSortedByDate
       .slice(startFromHere)
-      .map(start => getCycleForCycleStartDay(start))
+      .map(start => getCycleByStartDay(start))
       // filter the ones exceeding maxCycleLength, those are null
       .filter(cycle => cycle)
   }
 
-  function getCycleForCycleStartDay(startDay, todayDate) {
-    const todayAsLocalDate = todayDate
-      ? LocalDate.parse(todayDate)
-      : LocalDate.now()
-    const cycleStartIndex = cycleDaysSortedByDate.indexOf(startDay)
-    const i = cycleStartsSortedByDate.indexOf(startDay)
-    const startLocalDate = LocalDate.parse(startDay.date)
-    const nextMensesStart = cycleStartsSortedByDate[i - 1]
-    let cycle
-    let cycleLength
-    if (nextMensesStart) {
-      cycle = cycleDaysSortedByDate.slice(
-        cycleDaysSortedByDate.indexOf(nextMensesStart) + 1,
-        cycleStartIndex + 1,
+  function findIndexOfDay(day, daysSortedByDate) {
+    return daysSortedByDate.findIndex(d => d.date === day.date)
+  }
+
+  function getNextCycleStartDay(startDay, cycleStartsSortedByDate) {
+    const cycleStartIndex = findIndexOfDay(
+      startDay,
+      cycleStartsSortedByDate)
+    return cycleStartsSortedByDate[cycleStartIndex - 1]
+  }
+
+  function getTodayDate() {
+    return new Date().toISOString().slice(0, 10)
+  }
+
+  function getCycleLength(startDate, endDate) {
+    return LocalDate.parse(startDate)
+      .until(LocalDate.parse(endDate), DAYS)
+  }
+
+  function isValidCycle(startDate, endDate) {
+    return getCycleLength(startDate, endDate) <= maxCycleLength
+  }
+
+  function getCycleByStartDay(startDay, todayDate) {
+    let cycleEndDate = todayDate || getTodayDate()
+    let cycleEndIndex = 0
+
+    const nextCycleStart = getNextCycleStartDay(
+      startDay,
+      cycleStartsSortedByDate
+    )
+
+    if (nextCycleStart) {
+      const nextCycleIndex = findIndexOfDay(
+        nextCycleStart,
+        cycleDaysSortedByDate
       )
-      const nextLocalDate = LocalDate.parse(nextMensesStart.date)
-      cycleLength = startLocalDate.until(nextLocalDate, DAYS)
-    } else {
-      cycle = cycleDaysSortedByDate.slice(0, cycleStartIndex + 1)
-      cycleLength = startLocalDate.until(todayAsLocalDate, DAYS)
+      cycleEndIndex = nextCycleIndex + 1
+      cycleEndDate = nextCycleStart.date
     }
-    return cycleLength > maxCycleLength ? null : cycle
+
+    if (isValidCycle(startDay.date, cycleEndDate)) {
+      const cycleStartIndex = findIndexOfDay(
+        startDay,
+        cycleDaysSortedByDate
+      )
+      return cycleDaysSortedByDate
+        .slice(cycleEndIndex, cycleStartIndex + 1)
+    }
+
+    return null
   }
 
   function getCycleForDay(dayOrDate, todayDate) {
     const dateString = typeof dayOrDate === 'string' ? dayOrDate : dayOrDate.date
     const cycleStart = getLastMensesStartForDay(dateString)
     if (!cycleStart) return null
-    return getCycleForCycleStartDay(cycleStart, todayDate)
+    return getCycleByStartDay(cycleStart, todayDate)
   }
 
   function isMensesStart(cycleDay) {
@@ -201,6 +231,7 @@ export default function config(opts) {
     getAllCycleLengths,
     getPredictedMenses,
     isMensesStart,
-    getMensesDaysRightAfter
+    getMensesDaysRightAfter,
+    getCycleByStartDay,
   }
 }