session-ios/SignalServiceKit/src/Loki/LokiMessage.swift

import PromiseKit

@objc public final class LokiMessage : NSObject {
    /// The hex encoded public key of the receiver.
    let destination: String
    /// The content of the message.
    let data: LosslessStringConvertible
    /// The time to live for the message.
    let ttl: UInt64
    /// When the proof of work was calculated.
    let timestamp: UInt64
    /// The base 64 encoded proof of work.
    let nonce: String
    
    init(destination: String, data: LosslessStringConvertible, ttl: UInt64, timestamp: UInt64, nonce: String) {
        self.destination = destination
        self.data = data
        self.ttl = ttl
        self.timestamp = timestamp
        self.nonce = nonce
    }
    
    public static func fromSignalMessage(_ signalMessage: SignalMessage) -> Promise<LokiMessage> {
        return Promise<LokiMessage> { seal in
            DispatchQueue.global(qos: .default).async {
                let destination = signalMessage["destination"]!
                let data = signalMessage["content"]!
                let ttl = LokiMessagingAPI.defaultTTL
                let timestamp = UInt64(Date().timeIntervalSince1970)
                if let nonce = ProofOfWork.calculate(data: data, pubKey: destination, timestamp: timestamp, ttl: Int(ttl)) {
                    let result = LokiMessage(destination: destination, data: data, ttl: ttl, timestamp: timestamp, nonce: nonce)
                    seal.fulfill(result)
                } else {
                    seal.reject(LokiMessagingAPI.Error.proofOfWorkCalculationFailed)
                }
            }
        }
    }
    
    func toJSON() -> [String:String] {
        return [
            "destination" : destination,
            "data" : data.description,
            "ttl" : String(ttl),
            "timestamp" : String(timestamp),
            "nonce" : nonce
        ]
    }
}