//
//  TetheringHiderApp.swift
//
//
//  Created by Jesús David Chapman Vélez on 12/08/26.
//

import Foundation

enum SystemCommandError: LocalizedError {
    case executionFailed(String)
    case userCancelledAuth
    case scriptError(String)
    
    var errorDescription: String? {
        switch self {
        case .executionFailed(let reason):
            return "Command failed: \(reason)"
        case .userCancelledAuth:
            return "Administrator authentication was cancelled."
        case .scriptError(let detail):
            return "Script error: \(detail)"
        }
    }
}

struct SystemCommandService: Sendable {
    
    /// Sets IPv4 TTL, IPv6 Hop Limit, and flushes system DNS cache with administrator privileges.
    func setTTL(_ value: Int) async throws {
        let command = "sysctl -w net.inet.ip.ttl=\(value) && sysctl -w net.inet6.ip6.hlim=\(value) && dscacheutil -flushcache && killall -HUP mDNSResponder"
        try await executeWithAdminPrivileges(command)
    }
    
    /// Resets IPv4 TTL and IPv6 Hop Limit to default (64) and flushes DNS cache.
    func resetTTL() async throws {
        try await setTTL(64)
    }
    
    /// Executes a shell command with administrator privileges via NSAppleScript
    @MainActor
    private func executeWithAdminPrivileges(_ command: String) async throws {
        let scriptSource = "do shell script \"\(command)\" with administrator privileges"
        
        guard let script = NSAppleScript(source: scriptSource) else {
            throw SystemCommandError.scriptError("Failed to create AppleScript.")
        }
        
        var errorDict: NSDictionary?
        script.executeAndReturnError(&errorDict)
        
        if let error = errorDict {
            let errorNumber = error[NSAppleScript.errorNumber] as? Int ?? -1
            let errorMessage = error[NSAppleScript.errorMessage] as? String ?? "Unknown error"
            
            if errorNumber == -128 {
                throw SystemCommandError.userCancelledAuth
            }
            
            throw SystemCommandError.executionFailed(errorMessage)
        }
    }
}