Improving cervix:

* adding tempEvalEnd value to cervix tests
* more comments in code for cervix sympto
* better description in cervix temp tests
* take out cervix.value

lib/sympto/cervix.js

@@ -1,15 +1,26 @@
 export default function (cycleDays, tempEvalEndIndex) {
-  const cervixDays = cycleDays.filter(day => day.cervix && !day.cervix.exclude)
+  const notDetected = { detected: false }
+  const cervixDays = cycleDays
+    .filter(day => day.cervix && !day.cervix.exclude)
+    .filter(day => typeof day.cervix.opening === 'number' && typeof day.cervix.firmness === 'number')
+
+  // we search for the day of cervix peak, which must:
+  // * have fertile cervix values
+  // * be followed by at least 3 days
+  // these 3 following days must all show infertile cervix values
+  // if everything applies we must check the days until the end of temperature evaluation
+  // during these relevantDays no fertile cervix must occur
 
   for (let i = 0; i < cervixDays.length; i++) {
     const day = cervixDays[i]
     if (isClosedAndHard(day.cervix)) continue
-    // the three following days must be with closed and hard cervix
-    // AND no other cervix value may occur until temperature evaluation has
-    // been completed
+
+    // the three following days must be with closed and hard cervix (indicating an infertile cervix)
     const threeFollowingDays = cervixDays.slice(i + 1, i + 4)
     if (threeFollowingDays.length < 3) continue
 
+    // no other fertile cervix value may occur until temperature evaluation has
+    // been completed
     const fertileCervixOccursIn3FollowingDays = threeFollowingDays.some(day => {
       return !isClosedAndHard(day.cervix)
     })
@@ -33,9 +44,9 @@ export default function (cycleDays, tempEvalEndIndex) {
     }
   }
 
-  return { detected: false }
+  return notDetected
 }
 
-function isClosedAndHard (cervix) {
-  return cervix.value.opening === 0 && cervix.value.firmness === 0
+function isClosedAndHard (cervixDay) {
+  return cervixDay.opening === 0 && cervixDay.firmness === 0
 }