An Extension of Firebase Messaging To Get Topics

Firebase Topics

extension Messaging {
    
    static private let accessToken = "" //Server Web Key
    
    struct Topic : Decodable {
        var name : String?
        var addDate : String?
    }
    
    struct Rel : Decodable {
        var topics = [Topic]()
        
        init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: CodingKeys.self)
            let relContainer = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: .rel)
            let topicsContainer = try relContainer.nestedContainer(keyedBy: CodingKeys.self, forKey: .topics )
            
            for key in topicsContainer.allKeys {
                var topic = Topic()
                topic.name = key.stringValue
                
                let topicContainer = try? topicsContainer.nestedContainer(keyedBy: CodingKeys.self, forKey: key)
                topic.addDate = try! topicContainer?.decode(String.self, forKey: .addDate)
                
                self.topics.append(topic)
            }
        }

        struct CodingKeys : CodingKey {
            var stringValue: String
            init?(stringValue: String) {
                self.stringValue = stringValue
            }
            var intValue: Int? { return nil }
            init?(intValue: Int) { return nil }
            
            static let rel = CodingKeys(stringValue: "rel")!
            static let topics = CodingKeys(stringValue: "topics")!
            static let addDate = CodingKeys(stringValue: "addDate")!
        }
    }
    
    func loadTopics(block : @escaping (_ topics: [Messaging.Topic]?, _ error: Error?) -> Void ) {
        if let token = InstanceID.instanceID().token() {
            let url = URL(string: "https://iid.googleapis.com/iid/info/\(token)?details=true")!
            var request = URLRequest(url: url)
            request.addValue("key=\(Messaging.accessToken)", forHTTPHeaderField: "Authorization")
            let dataTask = URLSession.shared.dataTask(with: request) { (data, response, error) in
            DataManager.shared.make(request: urlRequest, block: { (data, error) in
                if let data = data {
                    let decoder = JSONDecoder()
                    let rel = try? decoder.decode(Rel.self, from: data)
                    block(rel?.topics, error)
                } else {
                    block(nil, error)
                }
            }
            
            dataTask.resume()
        }
    }
}

// Usage

Messaging.messaging().loadTopics { (topics, error) in
    topics?.forEach({ (topic) in
        print(topic.name)
    })
}