feat: add change alerts for schedule updates with notifications

ios/PSUSchedule/AppModel.swift

@@ -192,6 +192,8 @@ final class AppModel {
         afterChange()
     }
 
+    func setChangeAlerts(_ on: Bool) { change { $0.changeAlerts = on } }
+
     func setReminderMinutes(_ minutes: Int) {
         change { $0.reminderMinutes = minutes }
         afterChange()

ios/PSUSchedule/ChangeAlerts.swift

@@ -0,0 +1,37 @@
+import Foundation
+import UserNotifications
+
+/**
+ * A notification when the background refresh finds that the university republished the group's
+ * document and something changed. Local, like the reminders: the refresh itself notices it, when
+ * iOS lets it run, without a push server. Opening it shows the overview with the changes card.
+ */
+enum ChangeAlerts {
+    /// "Проектирование общественных зданий: аудитория 374 → 375", up to `max` lines.
+    static func summary(_ record: ScheduleChanges, max: Int = 4) -> [String] {
+        let changed = record.changed.map { c in
+            let fields = c.fields.map { "\($0.label.lowercased()) \($0.from) → \($0.to)" }.joined(separator: ", ")
+            return c.after.lesson.subject + ": " + (fields.isEmpty ? "изменилась запись Word" : fields)
+        }
+        let added = record.added.map { row in
+            let when = row.date.flatMap { CivilDate($0) }?.longLabel ?? dayName(row.day).lowercased()
+            return "Добавлено: \(row.lesson.subject), \(when) \(row.lesson.start)"
+        }
+        let removed = record.removed.map { "Удалено: \($0.lesson.subject)" }
+        let lines = changed + added + removed
+        return lines.count > max ? Array(lines.prefix(max - 1)) + ["И ещё \(lines.count - max + 1)"] : lines
+    }
+
+    static func show(_ record: ScheduleChanges) async {
+        let center = UNUserNotificationCenter.current()
+        let status = await center.notificationSettings().authorizationStatus
+        guard status == .authorized || status == .provisional else { return }
+        let content = UNMutableNotificationContent()
+        content.title = "Расписание \(record.group) изменилось"
+        let head = changesLabel(record.count) + (fileDateLabel(record.to).map { " · файл от \($0)" } ?? "")
+        content.body = ([head] + summary(record)).joined(separator: "\n")
+        content.sound = .default
+        content.threadIdentifier = "changes"
+        try? await center.add(UNNotificationRequest(identifier: "changes-\(record.document)-\(record.group)", content: content, trigger: nil))
+    }
+}

ios/PSUSchedule/PSUScheduleApp.swift

@@ -58,8 +58,16 @@ enum Background {
         try? BGTaskScheduler.shared.submit(request)
     }
 
+    @MainActor
     static func refresh() async {
         schedule()
-        await AppModel().refresh()
+        let model = AppModel()
+        let known = Set(model.allChanges.map(\.at))
+        await model.refresh()
+        // A change found by this run, for the open group: tell the student without waiting for
+        // them to open the app. The overview's card shows the same record.
+        if model.settings.changeAlerts, let record = model.changes, !record.seen, !known.contains(record.at) {
+            await ChangeAlerts.show(record)
+        }
     }
 }

ios/PSUSchedule/Views/SettingsView.swift

@@ -1,9 +1,12 @@
 import SwiftUI
+import UserNotifications
 
 struct SettingsView: View {
     @Environment(AppModel.self) private var model
     @Environment(\.dismiss) private var dismiss
     @State private var changes: ScheduleChanges?
+    /** Whether iOS lets the app notify; nil until asked. */
+    @State private var notificationsAllowed: Bool?
 
     var body: some View {
         let s = model.settings
@@ -52,6 +55,24 @@ struct SettingsView: View {
                                 .font(.footnote).foregroundStyle(.secondary)
                         }
                     }
+                    // On by default; the permission is asked when switched on (or for the reminders).
+                    Toggle(isOn: Binding(get: { s.changeAlerts && notificationsAllowed != false }, set: { on in
+                        if on {
+                            Task {
+                                let granted = await Reminders.authorize()
+                                notificationsAllowed = granted
+                                model.setChangeAlerts(granted)
+                            }
+                        } else { model.setChangeAlerts(false) }
+                    })) {
+                        VStack(alignment: .leading, spacing: 2) {
+                            Text("Изменения в расписании")
+                            Text(notificationsAllowed == false
+                                 ? "Уведомления для приложения выключены в настройках iOS: включите их там."
+                                 : "Уведомление, когда университет перезалил документ и у группы что-то поменялось. Приходит при фоновом обновлении, когда iOS его разрешит.")
+                                .font(.footnote).foregroundStyle(.secondary)
+                        }
+                    }
                     if s.reminders {
                         Picker("За сколько минут", selection: Binding(get: { s.reminderMinutes }, set: { model.setReminderMinutes($0) })) {
                             ForEach([5, 10, 15, 30], id: \.self) { Text("\($0)").tag($0) }
@@ -68,8 +89,8 @@ struct SettingsView: View {
                     if let record = model.changes {
                         Button { changes = record } label: {
                             LabeledContent("Последние изменения", value: changesLabel(record.count) + " · " + CivilDate(record.at).longLabel)
-                                .foregroundStyle(.primary)
                         }
+                        .tint(.primary)
                     }
                     LabeledContent("Сервер", value: model.api.base.absoluteString)
                 } header: {
@@ -82,6 +103,10 @@ struct SettingsView: View {
             .navigationBarTitleDisplayMode(.inline)
             .toolbar { ToolbarItem(placement: .confirmationAction) { Button("Готово", systemImage: "checkmark") { dismiss() } } }
             .sheet(item: $changes) { ChangesSheet(record: $0).presentationDetents([.medium, .large]) }
+            .task {
+                let status = await UNUserNotificationCenter.current().notificationSettings().authorizationStatus
+                notificationsAllowed = status == .notDetermined ? nil : status == .authorized || status == .provisional
+            }
         }
     }