DnsUpdater/Sources/App/Model/DNSChangeResponse.swift

import Foundation

enum DNSChangeResponse: RawRepresentable, Codable {

    /**
     The update was successful. You should not attempt another update until your IP address changes.

     The response is followed by a list of the user’s IP addresses
     */
    case success

    /**
     The supplied IP address is already set for this host. You should not attempt another update until your IP address changes.

     The response is followed by a list of the user’s IP addresses
     */
    case noChange

    /**
     The hostname doesn't exist, or doesn't have Dynamic DNS enabled.
     */
    case invalidHostname

    /**
     The username/password combination isn't valid for the specified host.
     */
    case badAuthentication

    /**
     The supplied hostname isn't a valid fully-qualified domain name.
     */
    case notFullyQualifiedDomainName

    /**
     Your Dynamic DNS client makes bad requests. Ensure the user agent is set in the request.
     */
    case badUserAgent

    /**
     Too many hosts (more than 20) specified in an update. Also returned if trying to update a round robin (which is not allowed).
     */
    case tooManyHosts

    /**
     Dynamic DNS access for the hostname has been blocked due to failure to interpret previous responses correctly.
     */
    case abuse

    /**
     An error happened on the server end. Wait 5 minutes and retry.
     */
    case unexpectedServerError

    /**
     A custom A or AAAA resource record conflicts with the update. Delete the indicated resource record within the DNS settings page and try the update again.
     */
    case conflict

    case noResponseString

    case unknown(String)

    /// The IP addresses reported after update are not the same as the requested
    case ipMismatch

    init(rawValue: String) {
        switch rawValue {
        case "good": self = .success
        case "nochg": self = .noChange
        case "nohost": self = .invalidHostname
        case "badauth": self = .badAuthentication
        case "notfqdn": self = .notFullyQualifiedDomainName
        case "badagent": self = .badUserAgent
        case "abuse": self = .abuse
        case "numhost": self = .tooManyHosts
        case "911": self = .unexpectedServerError
        case "conflict": self = .conflict
        case "nostring": self = .noResponseString
        case "mismatch": self = .ipMismatch
        default: self = .unknown(rawValue)
        }
    }

    var rawValue: String {
        switch self {
        case .success: return "good"
        case .noChange: return "nochg"
        case .invalidHostname: return "nohost"
        case .badAuthentication: return "badauth"
        case .notFullyQualifiedDomainName: return "notfqdn"
        case .badUserAgent: return "badagent"
        case .abuse: return "abuse"
        case .tooManyHosts: return "numhost"
        case .unexpectedServerError: return "911"
        case .conflict: return "conflict"
        case .noResponseString: return "nostring"
        case .ipMismatch: return "mismatch"
        case .unknown(let string): return string
        }
    }

    init(line: String, expecting addresses: Set<String>) {
        let parts = line.components(separatedBy: " ").compactMap { $0.trimmed }
        self.init(rawValue: parts[0])
        if case .unknown = self {
            // Insert full response for better logging
            self = .unknown(line)
            return
        }
        guard isSuccessStatus else {
            return
        }
        guard Set(parts.dropFirst()) != addresses else {
            return
        }
        self = .ipMismatch
    }

    var isSuccessStatus: Bool {
        switch self {
        case .success, .noChange, .noResponseString, .ipMismatch:
            // Treat no response and ip mismatch as success,
            // otherwise we risk spamming the server
            return true
        default:
            return false
        }
    }

    var isServerError: Bool {
        switch self {
        case .invalidHostname, .badAuthentication, .notFullyQualifiedDomainName, .badUserAgent, .abuse, .unexpectedServerError, .conflict, .tooManyHosts:
            return true
        default: return false
        }
    }

    var isClientError: Bool {
        switch self {
        case .noResponseString, .unknown, .ipMismatch:
            return true
        default: return false
        }
    }

    func delayTime(previous time: TimeInterval) -> TimeInterval {
        switch self {
        case .invalidHostname, .badAuthentication, .notFullyQualifiedDomainName, .badUserAgent, .conflict, .noChange:
            // Increase wait time by 10 minutes, up to 24 hours
            return min(86400, time + 600)
        case .abuse:
            // Increase wait time by one hour, until abuse is lifted
            return time + 3600
        case .unknown:
            // Don't spam on unknown errors
            return time + 3600
        default:
            // Try again next time
            return 0
        }
    }
}

extension DNSChangeResponse: CustomStringConvertible {

    var description: String {
        switch self {
        case .success: return "success"
        case .noChange: return "No change"
        case .invalidHostname: return "Invalid hostname"
        case .badAuthentication: return "Bad authentication"
        case .notFullyQualifiedDomainName: return "Not FQDN"
        case .badUserAgent: return "Bad user agent"
        case .tooManyHosts: return "Too many hosts"
        case .abuse: return "Abuse"
        case .unexpectedServerError: return "Server error"
        case .conflict: return "Conflict"
        case .noResponseString: return "No response string"
        case .unknown(let string): return string
        case .ipMismatch: return "IP mismatch"
        }
    }
}