initial commit

shared/lessons.js

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+// Lesson identity and schedule comparison, shared by the browser and the tests.
+// Lesson ids depend on the table row, so they change whenever the university
+// republishes a file; these keys describe what a student would call "the same lesson".
+
+const norm = (s) => (s || "").toLowerCase().replace(/\s+/g, " ").trim();
+const subgroupOf = (lesson, group) =>
+  lesson.subgroups?.find((s) => s.group === group)?.label || "";
+
+/** Same day, time, subject, row colour and subgroup: survives republishing. */
+export function lessonKey(lesson, group) {
+  return [
+    lesson.date || lesson.day,
+    lesson.start,
+    norm(lesson.subject),
+    lesson.variant,
+    subgroupOf(lesson, group),
+    norm(lesson.condition),
+  ].join("|");
+}
+// Looser identity for pairing a lesson whose time or week mark changed.
+const looseKey = (lesson, group) =>
+  [norm(lesson.subject), lesson.variant, subgroupOf(lesson, group), norm(lesson.type)].join("|");
+
+const FIELDS = [
+  ["start", "Начало"],
+  ["end", "Окончание"],
+  ["day", "День"],
+  ["date", "Дата"],
+  ["room", "Аудитория"],
+  ["teacher", "Преподаватель"],
+  ["condition", "Недели"],
+  ["type", "Вид занятия"],
+];
+
+/**
+ * What changed for one group between two versions of the same document.
+ * Returns { added, removed, changed } where changed items list field differences.
+ */
+export function diffSchedules(before, after, group) {
+  const pick = (s) => (s?.lessons || []).filter((l) => l.groups.includes(group));
+  const removed = [],
+    added = [],
+    changed = [];
+  const old = new Map();
+  for (const lesson of pick(before)) {
+    const key = lessonKey(lesson, group);
+    old.set(key, [...(old.get(key) || []), lesson]);
+  }
+  const unmatched = [];
+  for (const lesson of pick(after)) {
+    const key = lessonKey(lesson, group),
+      list = old.get(key);
+    if (list?.length) {
+      const was = list.shift();
+      const fields = differences(was, lesson);
+      if (fields.length) changed.push({ before: was, after: lesson, fields });
+    } else unmatched.push(lesson);
+  }
+  const left = [...old.values()].flat();
+  // Pair the rest by subject on the same day first, then by subject alone (a lesson moved to another day).
+  for (const sameDay of [true, false])
+    for (const lesson of [...unmatched]) {
+      const index = left.findIndex(
+        (l) =>
+          looseKey(l, group) === looseKey(lesson, group) &&
+          (!sameDay || (l.date || l.day) === (lesson.date || lesson.day)),
+      );
+      if (index < 0) continue;
+      const [was] = left.splice(index, 1);
+      unmatched.splice(unmatched.indexOf(lesson), 1);
+      changed.push({ before: was, after: lesson, fields: differences(was, lesson) });
+    }
+  added.push(...unmatched);
+  removed.push(...left);
+  const order = (l) => `${l.date || ""}${l.day}${l.start}`;
+  added.sort((a, b) => order(a).localeCompare(order(b)));
+  removed.sort((a, b) => order(a).localeCompare(order(b)));
+  changed.sort((a, b) => order(a.after).localeCompare(order(b.after)));
+  return { added, removed, changed };
+}
+function differences(before, after) {
+  return FIELDS.filter(([field]) => (before[field] ?? "") !== (after[field] ?? "")).map(
+    ([field, label]) => ({ field, label, from: before[field] ?? "", to: after[field] ?? "" }),
+  );
+}
+export const changeCount = (diff) =>
+  diff ? diff.added.length + diff.removed.length + diff.changed.length : 0;
+
+/** Applies the student's own choices: their subgroup and the lessons they hid. */
+export function personalFilter(lesson, group, prefs) {
+  const own = subgroupOf(lesson, group);
+  if (prefs?.subgroup && own && own !== prefs.subgroup) return "other-subgroup";
+  if (prefs?.hidden?.includes(lessonKey(lesson, group))) return "hidden";
+  return "shown";
+}
+/** Subgroup labels present for a group, in column order. */
+export function subgroupsOf(schedule, group) {
+  const labels = new Set();
+  for (const lesson of schedule?.lessons || [])
+    if (lesson.groups.includes(group)) {
+      const label = subgroupOf(lesson, group);
+      if (label) labels.add(label);
+    }
+  return [...labels].sort((a, b) => a.localeCompare(b, "ru", { numeric: true }));
+}