feat(mensa): load menus from the Studierendenwerk Oldenburg

App/AppContainer.swift

@@ -56,7 +56,7 @@ final class AppContainer {
         studIPService = studIPClient
         studIPAnnouncementService = studIPClient
         studIPScheduleService = studIPClient
-        canteenService = OpenMensaClient()
+        canteenService = StudierendenwerkOldenburgClient()
         if inMemory {
             preferences = InMemoryStudyPreferences()
             studIPAccountStore = InMemoryStudIPAccountStore()

Data/Mensa/StudierendenwerkMenuParser.swift

@@ -0,0 +1,103 @@
+import Foundation
+
+/// Reads the menu HTML of the Studierendenwerk Oldenburg (`func=make_spl` of its menu system).
+///
+/// The page lists a heading per serving counter (`.gruppenname`, e.g. „AUSGABE EINS“, „SUPPEN“)
+/// followed by its meals (`.splMeal`). Each meal shows its name, the prices
+/// „Studierende / Bedienstete / Gäste“ and icons such as „vegan“. A closed day is a single `.nodata` row.
+enum StudierendenwerkMenuParser {
+    /// Heading for meals listed before the first counter heading.
+    static let defaultCategory = "Gerichte"
+
+    static func isClosed(_ html: String) -> Bool {
+        html.contains("class='row nodata'") || html.contains("class=\"row nodata\"")
+    }
+
+    static func meals(_ html: String) -> [Meal] {
+        var meals: [Meal] = []
+        var category = defaultCategory
+        // Headings and meals in page order; each meal's HTML runs up to the next marker.
+        let markers = matches(of: #"col-xs-4 gruppenname'>([^<]*)<|<div class='row splMeal'"#, in: html)
+        for (index, marker) in markers.enumerated() {
+            if let heading = marker.group(1) {
+                category = categoryTitle(heading)
+                continue
+            }
+            let end = index + 1 < markers.count ? markers[index + 1].range.lowerBound : html.endIndex
+            let block = String(html[marker.range.lowerBound..<end])
+            guard let name = mealName(in: block) else { continue }
+            meals.append(Meal(
+                id: meals.count,
+                name: name,
+                category: category,
+                studentPrice: studentPrice(in: block),
+                notes: notes(in: block)
+            ))
+        }
+        return meals
+    }
+
+    // MARK: Parts of a meal
+
+    /// The name in the wide layout, without the allergen codes that follow it.
+    static func mealName(in block: String) -> String? {
+        guard let raw = matches(of: #"<div class='col-md-5[^>]*>\s*<span[^>]*>(.*?)(?:<div|</span>)"#, in: block)
+            .first?.group(1) else { return nil }
+        let name = plainText(raw)
+        return name.isEmpty ? nil : name
+    }
+
+    /// First amount of „2,50 / 4,40 / 4,60 €“; „max. 2,50*“ counts as 2,50.
+    static func studentPrice(in block: String) -> Double? {
+        guard let prices = matches(of: #"<div class='preise'><span>(.*?)</span>"#, in: block).first?.group(1),
+              let amount = matches(of: #"(\d+),(\d{2})"#, in: prices).first,
+              let euros = amount.group(1), let cents = amount.group(2) else { return nil }
+        return Double("\(euros).\(cents)")
+    }
+
+    /// Icon titles such as „vegan“ or „mit Rindfleisch“, each once.
+    static func notes(in block: String) -> [String] {
+        var notes: [String] = []
+        for match in matches(of: #"class='iconLarge' title='([^']*)'"#, in: block) {
+            guard let title = match.group(1).map(plainText), !title.isEmpty, !notes.contains(title) else { continue }
+            notes.append(title)
+        }
+        return notes
+    }
+
+    /// „AUSGABE EINS“ → „Ausgabe Eins“; an empty heading keeps the default.
+    static func categoryTitle(_ heading: String) -> String {
+        let text = plainText(heading)
+        return text.isEmpty ? defaultCategory : text.lowercased().capitalized
+    }
+
+    // MARK: Helpers
+
+    private static func plainText(_ html: String) -> String {
+        var text = html.replacingOccurrences(of: #"<[^>]+>"#, with: "", options: .regularExpression)
+        let entities = ["&nbsp;": " ", "&amp;": "&", "&euro;": "€", "&quot;": "\"", "&#39;": "'", "&lt;": "<", "&gt;": ">"]
+        for (entity, replacement) in entities {
+            text = text.replacingOccurrences(of: entity, with: replacement)
+        }
+        return text.replacingOccurrences(of: #"\s+"#, with: " ", options: .regularExpression)
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+
+    private struct Match {
+        let range: Range<String.Index>
+        let groups: [String?]
+
+        func group(_ index: Int) -> String? { index <= groups.count ? groups[index - 1] : nil }
+    }
+
+    private static func matches(of pattern: String, in text: String) -> [Match] {
+        guard let regex = try? NSRegularExpression(pattern: pattern, options: [.dotMatchesLineSeparators]) else { return [] }
+        return regex.matches(in: text, range: NSRange(text.startIndex..., in: text)).compactMap { result in
+            guard let range = Range(result.range, in: text) else { return nil }
+            let groups = (1..<max(result.numberOfRanges, 1)).map { index in
+                Range(result.range(at: index), in: text).map { String(text[$0]) }
+            }
+            return Match(range: range, groups: groups)
+        }
+    }
+}

Data/Mensa/StudierendenwerkOldenburgClient.swift

@@ -0,0 +1,70 @@
+import Foundation
+
+/// Loads the menus of the University of Oldenburg's canteens from the Studierendenwerk Oldenburg.
+///
+/// The Studierendenwerk's menu pages (studierendenwerk-oldenburg.de/essen/speiseplaene-mensen) embed its
+/// menu system, which returns a day's menu as HTML for a `POST` with `func=make_spl`. No account is needed.
+struct StudierendenwerkOldenburgClient: CanteenService {
+    static let endpoint = URL(string: "https://sw-oldenburg-spl56.maxmanager.xyz/inc/ajax-php_konnektor.inc.php")!
+
+    /// The canteens of the university; the IDs are the menu system's location IDs.
+    static let universityCanteens = [
+        Canteen(id: 2, name: "Mensa Uhlhornsweg", city: "Oldenburg", address: "Campus Haarentor"),
+        Canteen(id: 3, name: "Mensa Wechloy", city: "Oldenburg", address: "Campus Wechloy"),
+    ]
+
+    var session: URLSession = .shared
+    var calendar: Calendar = .current
+
+    func canteens() async throws -> [Canteen] {
+        Self.universityCanteens
+    }
+
+    func menu(canteenID: Int, on date: Date) async throws -> CanteenMenu {
+        var request = URLRequest(url: Self.endpoint)
+        request.httpMethod = "POST"
+        request.timeoutInterval = 20
+        request.setValue("application/x-www-form-urlencoded; charset=utf-8", forHTTPHeaderField: "Content-Type")
+        request.httpBody = Data(Self.formBody(locationID: canteenID, date: date, calendar: calendar).utf8)
+        let data: Data
+        let response: URLResponse
+        do {
+            (data, response) = try await session.data(for: request)
+        } catch {
+            throw MensaError.offline
+        }
+        guard let http = response as? HTTPURLResponse, (200...299).contains(http.statusCode),
+              let html = String(data: data, encoding: .utf8) ?? String(data: data, encoding: .isoLatin1)
+        else { throw MensaError.unavailable }
+        let isClosed = StudierendenwerkMenuParser.isClosed(html)
+        let meals = isClosed ? [] : StudierendenwerkMenuParser.meals(html)
+        return CanteenMenu(canteenID: canteenID, date: date, isClosed: isClosed, meals: meals)
+    }
+
+    /// The menu system also needs the Mondays of the day's week and of the following week.
+    static func formBody(locationID: Int, date: Date, calendar: Calendar) -> String {
+        let monday = weekStart(of: date, calendar: calendar)
+        let nextMonday = calendar.date(byAdding: .day, value: 7, to: monday) ?? monday
+        return [
+            "func=make_spl",
+            "locId=\(locationID)",
+            "date=\(dayString(date, calendar: calendar))",
+            "lang=de",
+            "startThisWeek=\(dayString(monday, calendar: calendar))",
+            "startNextWeek=\(dayString(nextMonday, calendar: calendar))",
+        ].joined(separator: "&")
+    }
+
+    /// Monday of the week containing `date`, also for Sundays.
+    static func weekStart(of date: Date, calendar: Calendar) -> Date {
+        var mondayFirst = calendar
+        mondayFirst.firstWeekday = 2
+        return mondayFirst.dateInterval(of: .weekOfYear, for: date)?.start ?? calendar.startOfDay(for: date)
+    }
+
+    /// `yyyy-MM-dd` in the canteen's (German) time zone.
+    static func dayString(_ date: Date, calendar: Calendar) -> String {
+        let components = calendar.dateComponents([.year, .month, .day], from: date)
+        return String(format: "%04d-%02d-%02d", components.year ?? 0, components.month ?? 0, components.day ?? 0)
+    }
+}

Domain/Entities/Mensa.swift

@@ -1,6 +1,6 @@
 import Foundation
 
-/// A canteen listed by OpenMensa.
+/// A canteen whose menu the app can show.
 struct Canteen: Identifiable, Hashable, Codable, Sendable {
     let id: Int
     var name: String

Domain/Repositories/CanteenService.swift

@@ -1,10 +1,10 @@
 import Foundation
 
-/// Port to a canteen menu source (OpenMensa).
+/// Port to a canteen menu source (the Studierendenwerk Oldenburg).
 @MainActor
 protocol CanteenService {
-    /// Canteens within `radius` kilometres of a coordinate.
-    func canteens(nearLatitude latitude: Double, longitude: Double, radius: Double) async throws -> [Canteen]
+    /// The canteens the source offers menus for, the default one first.
+    func canteens() async throws -> [Canteen]
     /// The menu of a canteen on a day. Throws `MensaError.unavailable` when the canteen publishes nothing for it.
     func menu(canteenID: Int, on date: Date) async throws -> CanteenMenu
 }

Domain/Repositories/StudyPreferences.swift

@@ -20,7 +20,7 @@ protocol StudySettingsStore: AnyObject {
     var automaticBackups: Bool { get set }
     /// Import the dates of linked Stud.IP courses into the calendar during a Stud.IP sync.
     var importsStudIPTimetable: Bool { get set }
-    /// OpenMensa canteen shown on „Heute“; `nil` hides the menu.
+    /// Canteen shown on „Heute“; `nil` hides the menu.
     var canteenID: Int? { get set }
     var notificationSettings: NotificationSettings { get set }
     var studyTimerSettings: StudyTimerSettings { get set }

Domain/UseCases/MensaUseCases.swift

@@ -12,14 +12,6 @@ enum MensaSchedule {
     }
 }
 
-/// Canteens of the Studierendenwerk Oldenburg area, nearest first.
-enum MensaLocation {
-    /// University of Oldenburg, campus Haarentor.
-    static let oldenburgLatitude = 53.1478
-    static let oldenburgLongitude = 8.1814
-    static let searchRadius = 15.0
-}
-
 /// Loads a menu and keeps it for the rest of the day, so „Heute“ does not ask the server on every visit.
 @MainActor
 final class LoadCanteenMenuUseCase {

Presentation/Mensa/MensaCard.swift

@@ -106,7 +106,7 @@ struct MensaSettingsSection: View {
         } header: {
             Text("Mensa")
         } footer: {
-            Text("Der Speiseplan kommt von OpenMensa. Nach dem Mittagessen zeigt „Heute“ schon den Plan für morgen.")
+            Text("Der Speiseplan kommt vom Studierendenwerk Oldenburg. Nach dem Mittagessen zeigt „Heute“ schon den Plan für morgen.")
         }
         .task { await viewModel.loadCanteens() }
     }

Presentation/Mensa/MensaViewModel.swift

@@ -53,6 +53,7 @@ final class MensaViewModel {
     }
 
     func refresh() async {
+        await loadCanteens()
         guard let canteenID else {
             state = .off
             return
@@ -68,16 +69,19 @@ final class MensaViewModel {
         }
     }
 
-    /// Canteens around Oldenburg for the settings, nearest first.
+    /// The canteens for the settings, the default one first.
     func loadCanteens() async {
         guard canteens.isEmpty, !isLoadingCanteens else { return }
         isLoadingCanteens = true
         defer { isLoadingCanteens = false }
-        canteens = (try? await service.canteens(
-            nearLatitude: MensaLocation.oldenburgLatitude,
-            longitude: MensaLocation.oldenburgLongitude,
-            radius: MensaLocation.searchRadius
-        )) ?? []
+        canteens = (try? await service.canteens()) ?? []
+        adoptSupportedCanteen()
+    }
+
+    /// A canteen chosen from an earlier source (OpenMensa) is no longer offered; the default one replaces it.
+    private func adoptSupportedCanteen() {
+        guard let canteenID, let fallback = canteens.first, !canteens.contains(where: { $0.id == canteenID }) else { return }
+        settings.canteenID = fallback.id
     }
 
     static func priceText(_ price: Double?) -> String? {