//
//  NoticeMessage.swift
//  sdlan
//
//  Created by 安礼成 on 2024/6/3.
//

import Foundation
import NIOCore

struct NoticeMessage {
    enum InboundMessage {
        case none
        case upgradeMessage(prompt: String, address: String)
        case alertMessage(alert: String)
        case ip(ip: String)
    }
    
    static func decodeMessage(buffer: inout ByteBuffer) -> InboundMessage {
        guard let type = buffer.readInteger(as: UInt8.self) else {
            return .none
        }
        
        switch type {
        case 0x01:
            if let len0 = buffer.readInteger(as: UInt16.self),
               let prompt = buffer.readString(length: Int(len0)),
               let len1 = buffer.readInteger(as: UInt16.self),
               let address = buffer.readString(length: Int(len1)) {
                return .upgradeMessage(prompt: prompt, address: address)
            }
        case 0x02:
            if let len0 = buffer.readInteger(as: UInt16.self),
               let alert = buffer.readString(length: Int(len0)) {
                return .alertMessage(alert: alert)
            }
            
        case 0x03:
            if let len0 = buffer.readInteger(as: UInt16.self),
               let ipAddress = buffer.readString(length: Int(len0)) {
                return .ip(ip: ipAddress)
            }
        default:
            return .none
        }
        
        return .none
    }
    
    static func upgrade(prompt: String, address: String) -> Data {
        var data = Data()
        data.append(contentsOf: [0x01])
        
        data.append(contentsOf: lenBytes(UInt16(prompt.count)))
        data.append(prompt.data(using: .utf8)!)
        
        data.append(contentsOf: lenBytes(UInt16(address.count)))
        data.append(address.data(using: .utf8)!)
        
        return data
    }
    
    static func alert(alert: String) -> Data {
        var data = Data()
        data.append(contentsOf: [0x02])
        
        data.append(contentsOf: lenBytes(UInt16(alert.count)))
        data.append(alert.data(using: .utf8)!)
        
        return data
    }
    
    static func ipAdress(ip: String) -> Data {
        var data = Data()
        data.append(contentsOf: [0x03])
        
        data.append(contentsOf: lenBytes(UInt16(ip.count)))
        data.append(ip.data(using: .utf8)!)
        
        return data
    }
    
    private static func lenBytes(_ value: UInt16) -> [UInt8] {
        let byte1 = UInt8((value >> 8) & 0xFF)
        let bytes2 = UInt8(value & 0xFF)
        
        return [byte1, bytes2]
    }
    
}