ntfy-ios/ntfy/Utils/NotificationContent.swift

import Foundation
import UserNotifications

private let actionsCategory = "ntfyActions" // It seems ok to re-use the same category

extension UNMutableNotificationContent {
    func modify(message: Message, baseUrl: String) {
        // Body and title
        if let body = message.message {
            self.body = body
        }
        
        // Set notification title to short URL if there is no title. The title is always set
        // by the server, but it may be empty.
        if let title = message.title, title != "" {
            self.title = title
        } else {
            self.title = topicShortUrl(baseUrl: baseUrl, topic: message.topic)
        }
        
        // Emojify title or message
        let emojiTags = parseEmojiTags(message.tags)
        if !emojiTags.isEmpty {
            if let title = message.title, title != "" {
                self.title = emojiTags.joined(separator: "") + " " + self.title
            } else {
                self.body = emojiTags.joined(separator: "") + " " + self.body
            }
        }
        
        // Add custom actions
        //
        // We re-define the categories every time here, which is weird, but it works. When tapped, the action sets the
        // actionIdentifier in the application(didReceive) callback. This logic is handled in the AppDelegate. This approach
        // is described in a comment in https://stackoverflow.com/questions/30103867/changing-action-titles-in-interactive-notifications-at-run-time#comment122812568_30107065
        //
        // We also must set the .foreground flag, which brings the notification to the foreground and avoids an error about
        // permissions. This is described in https://stackoverflow.com/a/44580916/1440785
        if let actions = message.actions, !actions.isEmpty {
            self.categoryIdentifier = actionsCategory
            
            let center = UNUserNotificationCenter.current()
            let notificationActions = actions.map { UNNotificationAction(identifier: $0.id, title: $0.label, options: [.foreground]) }
            let category = UNNotificationCategory(identifier: actionsCategory, actions: notificationActions, intentIdentifiers: [])
            center.setNotificationCategories([category])
        }
        
        // Play a sound, and group by topic
        self.sound = .default
        self.threadIdentifier = topicUrl(baseUrl: baseUrl, topic: message.topic)
        
        // Map priorities to interruption level (light up screen, ...) and relevance (order)
        if #available(iOS 15.0, *) {
            switch message.priority {
            case 1:
                self.interruptionLevel = .passive
                self.relevanceScore = 0
            case 2:
                self.interruptionLevel = .passive
                self.relevanceScore = 0.25
            case 4:
                self.interruptionLevel = .timeSensitive
                self.relevanceScore = 0.75
            case 5:
                self.interruptionLevel = .critical
                self.relevanceScore = 1
            default:
                self.interruptionLevel = .active
                self.relevanceScore = 0.5
            }
        }
        
        // Make sure the userInfo matches, so that when the notification is tapped, the AppDelegate
        // can properly navigate to the right topic and re-assemble the message.
        self.userInfo = message.toUserInfo()
        self.userInfo["base_url"] = baseUrl
    }
}