frontend/src/pages/GekanatorPage.tsx

@@ -674,6 +674,120 @@ const isQuestionRedundantAfterAnswers = (
 })
 
 
+const isSourceFactBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  if (candidate.type !== 'source' || previous.type !== 'source')
+    return false
+
+  switch (answer)
+  {
+  case 'yes':
+    return true
+  case 'no':
+    return candidate.host === previous.host
+  default:
+    return false
+  }
+}
+
+
+const isOriginalYearFactBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  if (candidate.type !== 'original-year' || previous.type !== 'original-year')
+    return false
+
+  switch (answer)
+  {
+  case 'yes':
+    return true
+  case 'no':
+    return candidate.year === previous.year
+  default:
+    return false
+  }
+}
+
+
+const isOriginalMonthFactBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  switch (answer)
+  {
+  case 'yes':
+    if (previous.type === 'original-month')
+      {
+	if (candidate.type === 'original-month')
+	  return true
+
+	if (candidate.type === 'original-month-day')
+	  return monthForCondition (candidate) !== previous.month
+
+	return false
+      }
+
+    if (previous.type === 'original-month-day')
+      return candidate.type === 'original-month'
+	  || candidate.type === 'original-month-day'
+
+    return false
+  case 'no':
+    if (previous.type === 'original-month')
+      {
+	if (candidate.type === 'original-month')
+	  return candidate.month === previous.month
+
+	if (candidate.type === 'original-month-day')
+	  return monthForCondition (candidate) === previous.month
+
+	return false
+      }
+
+    if (previous.type === 'original-month-day')
+      return candidate.type === 'original-month-day'
+	  && candidate.monthDay === previous.monthDay
+
+    return false
+  default:
+    return false
+  }
+}
+
+
+const isFactQuestionBlocked = (
+    candidate:  GekanatorQuestion['condition'],
+    previous:   GekanatorQuestion['condition'],
+    answer:     GekanatorAnswerValue,
+): boolean => {
+  if (!(answer === 'yes' || answer === 'no'))
+    return false
+
+  return isSourceFactBlocked (candidate, previous, answer)
+      || isOriginalYearFactBlocked (candidate, previous, answer)
+      || isOriginalMonthFactBlocked (candidate, previous, answer)
+}
+
+
+const isQuestionHardFilteredAfterAnswers = (
+    question:  GekanatorQuestion,
+    answers:   GekanatorAnswerLog[],
+): boolean => answers.some (answer => {
+  const previous = answer.questionCondition
+  if (previous === undefined)
+    return false
+
+  return isQuestionRedundantAfterAnswers (question, [answer])
+      || isFactQuestionBlocked (question.condition, previous, answer.answer)
+})
+
+
 const isMonthCrossMatch = (
     candidate:  GekanatorQuestion['condition'],
     previous:   GekanatorQuestion['condition'],
@@ -808,7 +922,7 @@ const chooseQuestion = ({
 
     return questionsToRank
       .map (question => {
-	if (isQuestionRedundantAfterAnswers (question, answers))
+	if (isQuestionHardFilteredAfterAnswers (question, answers))
 	  return null
 
 	const signature = signatureFor (question, candidates)