session-ios/SignalServiceKit/src/Loki/API/Multi Device/LokiDeviceLinkingSession.swift

import PromiseKit

@objc (LKDeviceLinkingSession)
public final class LokiDeviceLinkingSession : NSObject {
    private let delegate: LokiDeviceLinkingSessionDelegate
    private var timer: Timer?
    @objc public var isListeningForLinkingRequests = false
    
    // MARK: Lifecycle
    @objc public init(delegate: LokiDeviceLinkingSessionDelegate) {
        self.delegate = delegate
    }
    
    // MARK: Settings
    private let listeningTimeout: TimeInterval = 60

    // MARK: Public API
    @objc public func startListeningForLinkingRequests() {
        isListeningForLinkingRequests = true
        timer = Timer.scheduledTimer(withTimeInterval: listeningTimeout, repeats: false) { [weak self] timer in
            guard let self = self else { return }
            self.stopListeningForLinkingRequests()
            self.delegate.handleDeviceLinkingSessionTimeout()
        }
    }
    
    @objc public func processLinkingRequest(from slaveHexEncodedPublicKey: String, with slaveSignature: Data) {
        guard isListeningForLinkingRequests else { return }
        stopListeningForLinkingRequests()
        let master = LokiDeviceLink.Device(hexEncodedPublicKey: OWSIdentityManager.shared().identityKeyPair()!.hexEncodedPublicKey)
        let slave = LokiDeviceLink.Device(hexEncodedPublicKey: slaveHexEncodedPublicKey, signature: slaveSignature)
        let deviceLink = LokiDeviceLink(between: master, and: slave)
        guard isValid(deviceLink) else { return }
        delegate.requestUserAuthorization(for: deviceLink)
    }
    
    @objc public func authorizeDeviceLink(_ deviceLink: LokiDeviceLink) {
        // TODO: Send a device link authorized message
    }
    
    @objc public func stopListeningForLinkingRequests() {
        timer?.invalidate()
        timer = nil
        isListeningForLinkingRequests = false
    }
    
    // MARK: Private API
    private func isValid(_ deviceLink: LokiDeviceLink) -> Bool {
        return true // TODO: Implement
    }
}