feat(mobile/ios): add NIP-PL notification service foundation

Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>
Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

mobile/ios/NotificationService/NotificationService.swift

@@ -0,0 +1,221 @@
+import Foundation
+import UserNotifications
+
+final class NotificationService: UNNotificationServiceExtension {
+  private var contentHandler: ((UNNotificationContent) -> Void)?
+  private var bestAttemptContent: UNMutableNotificationContent?
+  private var resolver: BuzzPushNotificationResolving = BuzzPushNotificationResolver()
+
+  override func didReceive(
+    _ request: UNNotificationRequest,
+    withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void
+  ) {
+    self.contentHandler = contentHandler
+    guard let content = request.content.mutableCopy() as? UNMutableNotificationContent else {
+      contentHandler(request.content)
+      return
+    }
+    bestAttemptContent = content
+
+    resolver.resolve { [weak self] resolution in
+      guard let self else { return }
+      if let resolution {
+        content.title = resolution.title
+        content.body = resolution.body
+        if let subtitle = resolution.subtitle {
+          content.subtitle = subtitle
+        }
+        if let threadIdentifier = resolution.threadIdentifier {
+          content.threadIdentifier = threadIdentifier
+        }
+      }
+      self.finish(content)
+    }
+  }
+
+  override func serviceExtensionTimeWillExpire() {
+    if let bestAttemptContent {
+      finish(bestAttemptContent)
+    }
+  }
+
+  private func finish(_ content: UNNotificationContent) {
+    guard let contentHandler else { return }
+    self.contentHandler = nil
+    contentHandler(content)
+  }
+}
+
+struct BuzzPushResolution: Decodable {
+  let title: String
+  let body: String
+  let subtitle: String?
+  let threadIdentifier: String?
+}
+
+protocol BuzzPushNotificationResolving {
+  func resolve(completion: @escaping (BuzzPushResolution?) -> Void)
+}
+
+final class BuzzPushNotificationResolver: BuzzPushNotificationResolving {
+  private let snapshotFile = "push-communities.json"
+  private let session: URLSession
+  private let appGroupIdentifier: String?
+
+  init(
+    session: URLSession = .shared,
+    appGroupIdentifier: String? = Bundle.main.object(forInfoDictionaryKey: "BuzzAppGroupIdentifier")
+      as? String
+  ) {
+    self.session = session
+    self.appGroupIdentifier = appGroupIdentifier
+  }
+
+  func resolve(completion: @escaping (BuzzPushResolution?) -> Void) {
+    guard let community = loadCommunities().first(where: { $0.pubkey?.isEmpty == false }) else {
+      completion(nil)
+      return
+    }
+
+    // The NIP-PL APNs payload intentionally carries no relay or event id. The
+    // service extension therefore performs a bounded catch-up against locally
+    // configured origins and only replaces the fixed placeholder if authoritative
+    // relay data is available before the NSE deadline.
+    let filters: [[String: Any]] = [
+      [
+        "kinds": [9, 40002, 45001, 45003],
+        "#p": [community.pubkey!],
+        "limit": 10,
+      ]
+    ]
+    guard let body = try? JSONSerialization.data(withJSONObject: filters) else {
+      completion(nil)
+      return
+    }
+    let url = URL(string: "/query", relativeTo: community.relayURL)!
+    var request = URLRequest(url: url)
+    request.httpMethod = "POST"
+    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+    request.httpBody = body
+
+    session.dataTask(with: request) { data, response, _ in
+      guard let httpResponse = response as? HTTPURLResponse,
+        (200..<300).contains(httpResponse.statusCode),
+        let data,
+        let events = try? JSONSerialization.jsonObject(with: data) as? [[String: Any]],
+        !events.isEmpty
+      else {
+        completion(nil)
+        return
+      }
+      let resolution = Self.decodeResolution(
+        events: events,
+        community: community
+      )
+      completion(resolution)
+    }.resume()
+  }
+
+  private static func decodeResolution(events: [[String: Any]], community: BuzzPushCommunity)
+    -> BuzzPushResolution?
+  {
+    guard let myPubkey = community.pubkey?.lowercased() else { return nil }
+    let candidates = events.compactMap(BuzzPushEvent.init(json:)).filter { event in
+      event.pubkey.lowercased() != myPubkey && [9, 40002, 45001, 45003].contains(event.kind)
+    }
+    guard
+      let event = candidates.sorted(by: { left, right in
+        if left.createdAt != right.createdAt { return left.createdAt > right.createdAt }
+        return left.id < right.id
+      }).first
+    else { return nil }
+    let body = previewBody(event.content)
+    guard !body.isEmpty else { return nil }
+    return BuzzPushResolution(
+      title: shortPubkey(event.pubkey),
+      body: body,
+      subtitle: community.name,
+      threadIdentifier: event.channelId ?? community.id
+    )
+  }
+
+  private static func previewBody(_ content: String) -> String {
+    var result = content.replacingOccurrences(
+      of: #"```[\s\S]*?```"#,
+      with: "[code]",
+      options: .regularExpression
+    )
+    result = result.replacingOccurrences(of: #"`([^`]*)`"#, with: "$1", options: .regularExpression)
+    result = result.replacingOccurrences(
+      of: #"!\[([^\]]*)\]\([^)]*\)"#, with: "$1", options: .regularExpression)
+    result = result.replacingOccurrences(
+      of: #"\[([^\]]+)\]\([^)]*\)"#, with: "$1", options: .regularExpression)
+    result = result.replacingOccurrences(
+      of: #"https?://\S+"#, with: "[link]", options: .regularExpression)
+    result = result.replacingOccurrences(of: #"\s+"#, with: " ", options: .regularExpression)
+      .trimmingCharacters(in: .whitespacesAndNewlines)
+    guard result.count > 180 else { return result }
+    return String(result.prefix(177)).trimmingCharacters(in: .whitespacesAndNewlines) + "…"
+  }
+
+  private static func shortPubkey(_ pubkey: String) -> String {
+    guard pubkey.count > 8 else { return pubkey }
+    return String(pubkey.prefix(8)) + "…"
+  }
+
+  private func loadCommunities() -> [BuzzPushCommunity] {
+    guard let appGroupIdentifier,
+      let container = FileManager.default.containerURL(
+        forSecurityApplicationGroupIdentifier: appGroupIdentifier)
+    else { return [] }
+    let url = container.appendingPathComponent(snapshotFile)
+    guard let data = try? Data(contentsOf: url),
+      let decoded = try? JSONDecoder().decode(BuzzPushSnapshot.self, from: data)
+    else { return [] }
+    return decoded.communities
+  }
+}
+
+struct BuzzPushEvent {
+  let id: String
+  let pubkey: String
+  let createdAt: Int
+  let kind: Int
+  let tags: [[String]]
+  let content: String
+
+  init?(json: [String: Any]) {
+    guard let id = json["id"] as? String,
+      let pubkey = json["pubkey"] as? String,
+      let createdAt = json["created_at"] as? Int,
+      let kind = json["kind"] as? Int,
+      let tags = json["tags"] as? [[String]],
+      let content = json["content"] as? String
+    else { return nil }
+    self.id = id
+    self.pubkey = pubkey
+    self.createdAt = createdAt
+    self.kind = kind
+    self.tags = tags
+    self.content = content
+  }
+
+  var channelId: String? {
+    tags.first { $0.count >= 2 && $0[0] == "h" }?[1]
+  }
+}
+
+struct BuzzPushSnapshot: Decodable {
+  let communities: [BuzzPushCommunity]
+}
+
+struct BuzzPushCommunity: Decodable {
+  let id: String
+  let name: String
+  let relayUrl: String
+  let pubkey: String?
+
+  var relayURL: URL {
+    URL(string: relayUrl) ?? URL(string: "http://127.0.0.1")!
+  }
+}