stream-chat-flutter/example/ios/Notifications/NotificationService.swift

//
//  NotificationService.swift
//  Notifications
//
//  Created by Salvatore Giordano on 25/03/2020.
//  Copyright © 2020 The Chromium Authors. All rights reserved.
//

import UserNotifications
import StreamChatClient

class NotificationService: UNNotificationServiceExtension {

    var contentHandler: ((UNNotificationContent) -> Void)?
    var bestAttemptContent: UNMutableNotificationContent?
    
    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
        self.contentHandler = contentHandler
        bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
        
        let sharedDefaults = UserDefaults(suiteName: "group.io.stream.flutter")
        let apiKey = sharedDefaults!.string(forKey: "KEY_API_KEY")!
        let userId = sharedDefaults!.string(forKey: "KEY_USER_ID")!
        let token = sharedDefaults!.string(forKey: "KEY_TOKEN")!
        
        let messageId = bestAttemptContent?.userInfo["message_id"] as! String
        
        Client.config = .init(apiKey: apiKey, logOptions: .error)
        Client.shared.set(user: User(id: userId), token: token) { res in
            if res.isConnected {
                Client.shared.message(withId: messageId) { res in
                    if let message = res.value?.message,
                       let channel = res.value?.channel {
                        let messageWrapper = MessageWrapper(id: message.id, channel: ChannelWrapper(id: channel.id, cid: channel.cid, type: channel.type, name: channel.name, imageURL: channel.imageURL, lastMessageDate: channel.lastMessageDate, created: channel.created, deleted: channel.deleted, createdBy: channel.createdBy, config: channel.config, frozen: channel.frozen, extraData: channel.extraData), type: message.type, user: message.user, created: message.created, updated: message.updated, text: message.text, command: message.command, args: message.args, attachments: message.attachments, parentId: message.parentId, showReplyInChannel: message.showReplyInChannel, mentionedUsers: message.mentionedUsers, extraData: message.extraData)
                        if let encodedData = try? JSONEncoder.stream.encode(messageWrapper) {
                            let storedMessages = sharedDefaults?.stringArray(forKey: "messageQueue") ?? []
                            let encodedString = String(data: encodedData, encoding: .utf8)!
                            sharedDefaults?.setValue(storedMessages + [encodedString], forKey: "messageQueue")
                            
                            // Modify the notification content here...
                            self.bestAttemptContent?.title = "[modified] \(self.bestAttemptContent?.title ?? "<NoContent>")"
                            contentHandler(self.bestAttemptContent ?? request.content)
                        }
                        Client.shared.disconnect()
                    }
                }
            }
        }
    }
    
    override func serviceExtensionTimeWillExpire() {
        if let contentHandler = contentHandler, let bestAttemptContent =  bestAttemptContent {
            contentHandler(bestAttemptContent)
        }
    }
}

public struct MessageWrapper: Encodable {
    private enum CodingKeys: String, CodingKey {
        case id
        case channel
        case type
        case user
        case created = "created_at"
        case updated = "updated_at"
        case text
        case command
        case args
        case attachments
        case parentId = "parent_id"
        case showReplyInChannel = "show_in_channel"
        case mentionedUsers = "mentioned_users"
    }
    
    /// A message id.
    public let id: String
    /// The channel cid.
    public let channel: ChannelWrapper?
    /// A message type (see `MessageType`).
    public let type: MessageType
    /// A user (see `User`).
    public let user: User
    /// A created date.
    public let created: Date
    /// A updated date.
    public let updated: Date
    /// A text.
    public let text: String
    /// A used command name.
    public let command: String?
    /// A used command args.
    public let args: String?
    /// Attachments (see `Attachment`).
    public let attachments: [Attachment]
    /// A parent message id.
    public let parentId: String?
    /// Check if this reply message needs to show in the channel.
    public let showReplyInChannel: Bool
    /// Mentioned users (see `User`).
    public let mentionedUsers: [User]
    /// An extra data for the message.
    public let extraData: Codable?
}

public struct ChannelWrapper: Encodable {
    /// Coding keys for the encoding.
    private enum CodingKeys: String, CodingKey {
        case id
        case cid
        case type
        case name
        case imageURL = "image"
        case members
        case lastMessageDate = "last_message_at"
        case createdBy = "created_by"
        case created = "created_at"
        case deleted = "deleted_at"
    }

    /// A channel id.
    public let id: String
    /// A channel type + id.
    public let cid: ChannelId
    /// A channel type.
    public let type: ChannelType
    /// A channel name.
    public let name: String?
    /// An image of the channel.
    public let imageURL: URL?
    /// The last message date.
    public let lastMessageDate: Date?
    /// A channel created date.
    public let created: Date
    /// A channel deleted date.
    public let deleted: Date?
    /// A creator of the channel.
    public let createdBy: User?
    /// A config.
    public let config: Channel.Config
    /// Checks if the channel is frozen.
    public let frozen: Bool
    /// A list of user ids of the channel members.
    public let members = Set<Member>()
    /// An extra data for the channel.
    public let extraData: Codable?
}