RouterOS/RouterOSAssistant/Core/Networking/RestTransport.swift

import Foundation

/// REST-API transport for RouterOS >= 7.1 (JSON over HTTPS, `/rest/...`).
final class RestTransport: NSObject, RouterOSTransport {
    let kind: RouterOSTransportKind = .rest

    private let credentials: RouterOSCredentials
    private let certificateTrust: CertificateTrustStore
    private var lastRejectedFingerprint: String?

    private lazy var session: URLSession = URLSession(
        configuration: .ephemeral,
        delegate: self,
        delegateQueue: nil
    )

    init(credentials: RouterOSCredentials, certificateTrust: CertificateTrustStore) {
        self.credentials = credentials
        self.certificateTrust = certificateTrust
    }

    private var baseURL: URL {
        URL(string: "https://\(credentials.host):\(credentials.httpsPort)/rest")!
    }

    func connect() async throws {
        _ = try await fetchDeviceInfo()
    }

    func fetchDeviceInfo() async throws -> RouterDeviceInfo {
        let json = try await getJSONObject(path: "system/resource")
        guard
            let boardName = json["board-name"] as? String,
            let version = json["version"] as? String,
            let arch = json["architecture-name"] as? String
        else {
            throw RouterOSError.invalidResponse("system/resource")
        }
        let uptime = json["uptime"] as? String ?? "-"
        return RouterDeviceInfo(boardName: boardName, routerOSVersion: version, architecture: arch, uptime: uptime)
    }

    func fetchInterfaces() async throws -> [NetworkInterface] {
        let array = try await getJSONArray(path: "interface")
        return array.compactMap { item in
            guard let name = item["name"] as? String, let type = item["type"] as? String else {
                return nil
            }
            return NetworkInterface(
                name: name,
                type: type,
                running: (item["running"] as? String) == "true",
                disabled: (item["disabled"] as? String) == "true",
                macAddress: item["mac-address"] as? String
            )
        }
    }

    /// Creates or modifies the item described by `command`. `.add` is a plain
    /// `POST /rest/<restPath>`. `.set` has no CLI-style inline lookup on REST, so it first
    /// `GET`s the collection to find the item whose `matchField` equals `matchValue`, reads
    /// its RouterOS-internal `.id`, then `PATCH`es `restPath/<id>`.
    func apply(_ command: RouterOSCommand) async throws {
        switch command.operation {
        case .add:
            _ = try await send(path: command.restPath, method: "POST", jsonBody: command.arguments)
        case .set(let matchField, let matchValue):
            let itemID = try await findItemID(path: command.restPath, matchField: matchField, matchValue: matchValue)
            _ = try await send(path: "\(command.restPath)/\(itemID)", method: "PATCH", jsonBody: command.arguments)
        }
    }

    private func findItemID(path: String, matchField: String, matchValue: String) async throws -> String {
        let items = try await getJSONArray(path: path)
        guard let match = items.first(where: { ($0[matchField] as? String) == matchValue }) else {
            throw RouterOSError.invalidResponse("Kein Eintrag mit \(matchField)=\(matchValue) unter \(path) gefunden")
        }
        guard let id = match[".id"] as? String else {
            throw RouterOSError.invalidResponse("Eintrag unter \(path) hat keine .id")
        }
        return id
    }

    func disconnect() async {
        session.invalidateAndCancel()
    }

    private func getJSONObject(path: String) async throws -> [String: Any] {
        let data = try await send(path: path, method: "GET", jsonBody: nil)
        guard let object = try JSONSerialization.jsonObject(with: data) as? [String: Any] else {
            throw RouterOSError.invalidResponse(path)
        }
        return object
    }

    private func getJSONArray(path: String) async throws -> [[String: Any]] {
        let data = try await send(path: path, method: "GET", jsonBody: nil)
        guard let array = try JSONSerialization.jsonObject(with: data) as? [[String: Any]] else {
            throw RouterOSError.invalidResponse(path)
        }
        return array
    }

    private func send(path: String, method: String, jsonBody: [String: String]?) async throws -> Data {
        var request = URLRequest(url: baseURL.appendingPathComponent(path))
        request.httpMethod = method

        let authString = "\(credentials.username):\(credentials.password)"
        guard let authData = authString.data(using: .utf8) else {
            throw RouterOSError.invalidResponse("credentials")
        }
        request.setValue("Basic \(authData.base64EncodedString())", forHTTPHeaderField: "Authorization")
        request.timeoutInterval = 5

        if let jsonBody {
            request.httpBody = try JSONSerialization.data(withJSONObject: jsonBody)
            request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        }

        lastRejectedFingerprint = nil
        do {
            let (data, response) = try await session.data(for: request)
            guard let httpResponse = response as? HTTPURLResponse else {
                throw RouterOSError.invalidResponse(path)
            }
            if httpResponse.statusCode == 401 {
                throw RouterOSError.authenticationFailed
            }
            guard (200...299).contains(httpResponse.statusCode) else {
                throw RouterOSError.invalidResponse("HTTP \(httpResponse.statusCode)")
            }
            return data
        } catch let error as RouterOSError {
            throw error
        } catch {
            if let fingerprint = lastRejectedFingerprint {
                throw RouterOSError.untrustedCertificate(fingerprint: fingerprint)
            }
            throw RouterOSError.transportUnavailable("REST-Verbindung fehlgeschlagen: \(error.localizedDescription)")
        }
    }
}

extension RestTransport: URLSessionDelegate {
    func urlSession(
        _ session: URLSession,
        didReceive challenge: URLAuthenticationChallenge,
        completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void
    ) {
        guard
            challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust,
            let serverTrust = challenge.protectionSpace.serverTrust
        else {
            completionHandler(.performDefaultHandling, nil)
            return
        }

        let fingerprint = CertificateFingerprint.sha256(of: serverTrust)
        if certificateTrust.isTrusted(host: credentials.host, fingerprint: fingerprint) {
            completionHandler(.useCredential, URLCredential(trust: serverTrust))
        } else {
            lastRejectedFingerprint = fingerprint
            completionHandler(.cancelAuthenticationChallenge, nil)
        }
    }
}