Implement zap notification support for push notifications

The code paths for generating zap notifications were very different from
the paths used by most other notifications. In this commit, I include
the logic and data structures necessary for formatting zap notifications
in the same fashion as local notifications.

A good amount of refactoring and moving functions/structures around was
necessary to reuse zap local notification logic. I also attempted to
make the notification generation process more consistent between zaps
and other notifications, without changing too much of existing logic to
avoid even more regression risk.

General push notifications + local notifications test
-----------------------------------------------------

PASS

Device: iPhone 15 Pro simulator
iOS: 17.0.1
Damus: This commit
Setup:
- Two phones running Damus on different accounts
- Local relay with strfry-push-notify test setup
- Apple push notification test tool

Coverage:
1. Mention notifications
2. DM notifications
3. Reaction notifications
4. Repost notifications

Steps for each notification type:
1. Trigger a notification (local and then push)
2. Ensure that the notification is received on the other device
3. Ensure that the notification is formatted correctly
4. Ensure that DMs are decrypted correctly
5. Ensure that profile names are unfurled correctly
6. Click on the notification and ensure that the app opens to the correct screen

Result: PASS (all notifications received and formatted correctly)

Notes:
- For some reason my relay is not receiving zap events, so I could not
  test zap notifications yet.

- Reply notifications do not seem to be implemented yet

- These apply to the tests below as well

Changelog-Added: Zap notification support for push notifications
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
Signed-off-by: William Casarin <jb55@jb55.com>

DamusNotificationService/NotificationFormatter.swift

@@ -49,7 +49,7 @@ struct NotificationFormatter {
     
     // MARK: - Formatting with LocalNotification
     
-    func format_message(displayName: String, notify: LocalNotification) -> (content: UNMutableNotificationContent, identifier: String) {
+    func format_message(displayName: String, notify: LocalNotification) -> (content: UNMutableNotificationContent, identifier: String)? {
         let content = UNMutableNotificationContent()
         var title = ""
         var identifier = ""
@@ -68,8 +68,8 @@ struct NotificationFormatter {
                 title = displayName
                 identifier = "myDMNotification"
             case .zap, .profile_zap:
-                // not handled here
-                break
+                // not handled here. Try `format_message(displayName: String, notify: LocalNotification, state: HeadlessDamusState) async -> (content: UNMutableNotificationContent, identifier: String)?`
+                return nil
         }
         content.title = title
         content.body = notify.content
@@ -78,4 +78,59 @@ struct NotificationFormatter {
 
         return (content, identifier)
     }
+    
+    func format_message(displayName: String, notify: LocalNotification, state: HeadlessDamusState) async -> (content: UNMutableNotificationContent, identifier: String)? {
+        // Try sync method first and return if it works
+        if let sync_formatted_message = self.format_message(displayName: displayName, notify: notify) {
+            return sync_formatted_message
+        }
+        
+        // If it does not work, try async formatting methods
+        let content = UNMutableNotificationContent()
+        
+        switch notify.type {
+            case .zap, .profile_zap:
+                guard let zap = await get_zap(from: notify.event, state: state) else {
+                    return nil
+                }
+                content.title = Self.zap_notification_title(zap)
+                content.body = Self.zap_notification_body(profiles: state.profiles, zap: zap)
+                content.sound = UNNotificationSound.default
+                content.userInfo = LossyLocalNotification(type: .zap, mention: .note(notify.event.id)).to_user_info()
+                return (content, "myZapNotification")
+            default:
+                // The sync method should have taken care of this.
+                return nil
+        }
+    }
+    
+    // MARK: - Formatting zap utility notifications
+
+    static func zap_notification_title(_ zap: Zap) -> String {
+        if zap.private_request != nil {
+            return NSLocalizedString("Private Zap", comment: "Title of notification when a private zap is received.")
+        } else {
+            return NSLocalizedString("Zap", comment: "Title of notification when a non-private zap is received.")
+        }
+    }
+
+    static func zap_notification_body(profiles: Profiles, zap: Zap, locale: Locale = Locale.current) -> String {
+        let src = zap.request.ev
+        let pk = zap.is_anon ? ANON_PUBKEY : src.pubkey
+
+        let name = profiles.lookup(id: pk).map { profile in
+            Profile.displayName(profile: profile, pubkey: pk).displayName.truncate(maxLength: 50)
+        }.value
+
+        let sats = NSNumber(value: (Double(zap.invoice.amount) / 1000.0))
+        let formattedSats = format_msats_abbrev(zap.invoice.amount)
+
+        if src.content.isEmpty {
+            let format = localizedStringFormat(key: "zap_notification_no_message", locale: locale)
+            return String(format: format, locale: locale, sats.decimalValue as NSDecimalNumber, formattedSats, name)
+        } else {
+            let format = localizedStringFormat(key: "zap_notification_with_message", locale: locale)
+            return String(format: format, locale: locale, sats.decimalValue as NSDecimalNumber, formattedSats, name, src.content)
+        }
+    }
 }