import Foundation
import Observation

@Observable
@MainActor
final class TTLManager {
    private(set) var currentTTL: Int = 64
    private(set) var currentIPv6HopLimit: Int = 64
    private(set) var isProtected: Bool = false
    private(set) var lastError: String?
    
    var onStatusChanged: (() -> Void)?
    
    let defaultTTL: Int = 64
    let targetTTL: Int = 65
    
    init() {
        refreshStatus()
    }
    
    /// Reads the current system IPv4 TTL value using sysctlbyname (no root required)
    func readCurrentTTL() -> Int {
        var ttl: Int32 = 0
        var size = MemoryLayout<Int32>.size
        let result = sysctlbyname("net.inet.ip.ttl", &ttl, &size, nil, 0)
        if result == 0 {
            return Int(ttl)
        }
        return defaultTTL
    }
    
    /// Reads the current system IPv6 Hop Limit value using sysctlbyname (no root required)
    func readCurrentIPv6HopLimit() -> Int {
        var hlim: Int32 = 0
        var size = MemoryLayout<Int32>.size
        let result = sysctlbyname("net.inet6.ip6.hlim", &hlim, &size, nil, 0)
        if result == 0 {
            return Int(hlim)
        }
        return defaultTTL
    }
    
    /// Refreshes current IPv4 TTL, IPv6 Hop Limit, and protection status
    func refreshStatus() {
        currentTTL = readCurrentTTL()
        currentIPv6HopLimit = readCurrentIPv6HopLimit()
        isProtected = (currentTTL == targetTTL) && (currentIPv6HopLimit == targetTTL)
        lastError = nil
        onStatusChanged?()
    }
    
    func didSetTTL(_ value: Int) {
        currentTTL = value
        currentIPv6HopLimit = value
        isProtected = value == targetTTL
        lastError = nil
        onStatusChanged?()
    }

    func setError(_ message: String) {
        lastError = message
        onStatusChanged?()
    }
}