simplified code and added documentation

backend/formatter.js

@@ -1,3 +1,30 @@
+/**
+ * Formats the raw WebUntis JSON-RPC timetable response into a compact list of lessons.
+ *
+ * Output schema (per entry):
+ * - room: string
+ * - teacher: string
+ * - subject: string
+ * - startTime: "HH:MM" | "–"
+ * - endTime: "HH:MM" | "–"
+ * - weekday: German weekday name | "–"
+ * - date: "DD.MM.YYYY" | "–"
+ * - cancelled: boolean
+ *
+ * Business rules implemented here:
+ * 1) SZ normalization:
+ *    If multiple lessons share the same day + same start time and at least one subject starts
+ *    with "SZ" (e.g. "SZ1", "SZ10"), the whole slot becomes exactly ONE entry with:
+ *    subject="SZ", room="-", teacher="-".
+ * 2) Cancelled flag:
+ *    If the raw item contains code="cancelled", cancelled=true, otherwise cancelled=false.
+ * 3) Double-lesson merging:
+ *    Consecutive lessons with same (date, weekday, subject, teacher, room) are merged into one
+ *    block by extending endTime. A small gap (break) up to MERGE_GAP_MINUTES is allowed.
+ *
+ * @param {any} rawData WebUntis JSON-RPC response (expects rawData.result to be an array)
+ * @returns {Array<{room:string,teacher:string,subject:string,startTime:string,endTime:string,weekday:string,date:string,cancelled:boolean}>}
+ */
 export const formatData = (rawData) => {
   const weekdays = [
     "Sonntag",
@@ -9,8 +36,16 @@ export const formatData = (rawData) => {
     "Samstag",
   ];
 
+  /**
+   * Allowed gap (in minutes) between two blocks to still merge them into a double lesson.
+   * Example: 15:30 -> 15:35 (5 min break) will still merge.
+   */
   const MERGE_GAP_MINUTES = 15;
 
+  /**
+   * WebUntis times are typically numbers like 800, 855, 1435.
+   * Converts to "HH:MM". Returns "–" for missing/invalid values.
+   */
   function formatTime(time) {
     if (time === null || time === undefined) return "–";
     const n = Number(time);
@@ -19,6 +54,10 @@ export const formatData = (rawData) => {
     return str.slice(0, 2) + ":" + str.slice(2);
   }
 
+  /**
+   * WebUntis dates are typically numbers like 20260417.
+   * Converts to "DD.MM.YYYY". Returns "–" for missing/invalid values.
+   */
   function formatDate(date) {
     if (date === null || date === undefined) return "–";
     const str = String(date);
@@ -26,6 +65,10 @@ export const formatData = (rawData) => {
     return str.slice(6, 8) + "." + str.slice(4, 6) + "." + str.slice(0, 4);
   }
 
+  /**
+   * Returns German weekday name for a WebUntis date (YYYYMMDD).
+   * Returns "–" for missing/invalid values.
+   */
   function getWeekday(date) {
     if (date === null || date === undefined) return "–";
     const str = String(date);
@@ -35,6 +78,10 @@ export const formatData = (rawData) => {
     return weekdays[d.getDay()];
   }
 
+  /**
+   * Parses "HH:MM" into minutes since midnight.
+   * Returns null for "–" or invalid values.
+   */
   function parseTimeToMinutes(timeStr) {
     if (!timeStr || timeStr === "–") return null;
     const [h, m] = String(timeStr).split(":");
@@ -45,6 +92,10 @@ export const formatData = (rawData) => {
     return hh * 60 + mm;
   }
 
+  /**
+   * Converts a formatted date "DD.MM.YYYY" to a sortable numeric key YYYYMMDD.
+   * Returns null for "–" or invalid values.
+   */
   function dateKeyFromFormatted(dateStr) {
     if (!dateStr || dateStr === "–") return null;
     const [dd, mm, yyyy] = String(dateStr).split(".");
@@ -57,16 +108,19 @@ export const formatData = (rawData) => {
     return y * 10000 + m * 100 + d;
   }
 
+  /** @type {any[]} */
   const items = rawData?.result ?? [];
   const lessons = [];
 
   for (const item of items) {
     if (item?.activityType !== "Unterricht") continue;
 
+    // Subject name is typically in item.su[0].name.
     const subject = item?.su?.[0]?.name ?? "–";
     const normalizedSubject = String(subject).trimStart();
     const isSz = normalizedSubject.startsWith("SZ");
 
+    // WebUntis uses item.code === "cancelled" for cancelled lessons.
     const cancelled =
       String(item?.code ?? "")
         .trim()
@@ -97,8 +151,8 @@ export const formatData = (rawData) => {
     return a._endTimeRaw - b._endTimeRaw;
   });
 
-  // Group by same day + same start time.
+  // 1) Group by same day + same start time.
-  // If any subject in a group starts with "SZ", collapse the whole group into the SZ lesson.
+  //    If any subject in a group starts with "SZ", collapse the whole group into ONE SZ entry.
   const groups = new Map();
   for (const lesson of lessons) {
     const key = `${lesson._dateRaw}-${lesson._startTimeRaw}`;
@@ -126,6 +180,8 @@ export const formatData = (rawData) => {
       (max, l) => (l._endTimeRaw > max ? l._endTimeRaw : max),
       0,
     );
+    // SZ cancelled only if ALL underlying entries are cancelled.
+    // If at least one is not cancelled, the SZ block is considered not cancelled.
     const cancelled = group.every((l) => l.cancelled);
 
     timetable.push({
@@ -140,8 +196,8 @@ export const formatData = (rawData) => {
     });
   }
 
-  // Merge double lessons (same subject/teacher/room/day) that are consecutive
+  // 2) Merge double lessons: group by (date, weekday, subject, teacher, room)
-  // (allows a short gap, e.g. breaks).
+  //    and merge consecutive time blocks within each group.
   const bucketKey = (e) =>
     `${e.date}|${e.weekday}|${e.subject}|${e.teacher}|${e.room}`;
 

backend/server.js

@@ -163,10 +163,6 @@ app.get("/api/get-timetable/", async (req, res) => {
       console.error("formatData failed", formatError);
       res.status(500).json({ error: "Failed to format timetable data" });
     }
-
-    // respond to client
-    res.json(timetableResponse.data?.result ?? null);
-    return;
   } catch (error) {
     const status = error?.response?.status;
     const data = error?.response?.data;