Change the handling

website/src/components/TimetableDisplay.vue

@@ -78,19 +78,46 @@ function filterForTargetDay(lessonsTime: MergedLesson[][]) {
 }
 
 function handleSubstitutionsSpacialCase(lessonsTimeDay: MergedLesson[]) {
-  if (lessonsTimeDay.length > 1) {
-    for (const lesson of lessonsTimeDay) {
-      if (lesson.isSubstitution && lesson.substitutionSubject !== lesson.subject) {
-        const sharedSubstitutionLesson = lesson
-
-        sharedSubstitutionLesson.subject = ''
-        sharedSubstitutionLesson.teacher = ''
-        sharedSubstitutionLesson.classroom = ''
-        sharedSubstitutionLesson.notes ??= 'ves razred'
+  // Important: this can cause breaking changes when multiple entities have overlapping times
+
+  // Special cases occur only when multiple lessons happen at the same time (only in class view).
+  // This counts for ŠVM/ŠVŽ, INFV/INF and language lessons happening at the same time (FRA/ITA/NEM/ŠPA)
+  if (currentEntityType.value === EntityType.Class && lessonsTimeDay.length > 1) {
+    // If subjects that are not in the timetable originally appear,
+    // we replace the original subjects with them
+    if (lessonsTimeDay.find(l => l.subject === null)) {
+      return lessonsTimeDay.filter(l => l.subject === null)
+    }
 
-        lessonsTimeDay = [sharedSubstitutionLesson]
+    // A subject change needs to be present as this is the breaking point
+    const lesson: MergedLesson | undefined = lessonsTimeDay.find(
+      l => l.isSubstitution && l.substitutionSubject !== l.subject,
+    )
+
+    if (!lesson) return lessonsTimeDay
+
+    // We need to treat ŠVM/ŠVŽ and INFV/INF as the same subject,
+    // so what happens to one happens to another
+    if (['ŠVM', 'ŠVŽ', 'INFV', 'INF'].includes(lesson.subject!)) {
+      if (lessonsTimeDay.length > 2) {
+        // When there are more than 2 subject it means a new subject has appeared.
+        // We need to delete the original subjects then
+        return lessonsTimeDay.filter(l => !['ŠVM', 'ŠVŽ', 'INFV', 'INF'].includes(l.subject || ''))
+      } else {
+        // We keep only the element of the subject pair that changed
+        return lessonsTimeDay.filter(l => l === lesson)
       }
     }
+
+    // At this point we are left only with languages
+    const LanguageLesson: MergedLesson | undefined = lessonsTimeDay.find(
+      l => l.isSubstitution && !['FRA', 'ITA', 'NEM', 'ŠPA', null].includes(l.substitutionSubject),
+    )
+
+    if (!LanguageLesson) return lessonsTimeDay
+
+    // If a subject was changed for another then all the languages are substituted with the new subject
+    return [LanguageLesson!]
   }
 
   return lessonsTimeDay