import SwiftUI
import Foundation

struct BlockedCount: View {
    @State private var txtRecord: String = "..."

    var body: some View {
        Text(txtRecord)
        .onAppear {
            fetchTXTRecord()
        }
    }

    func parseResponse(data: Data) -> String? {
        // This is a DNS wire format response and we make a lot of assumptions
        // It is not critical functionality so just let it fail if it fails

        guard data.count > 44 else { return nil }

        let startIndex = 44
        let subData = data.suffix(from: startIndex)

        // Find the first space character (ASCII 32)
        var endIndex: Int?
        for (offset, byte) in subData.enumerated() {
            if byte == 32 { // Space character
                endIndex = offset
                break
            }
        }

        guard let foundEndIndex = endIndex else { return nil }

        // Extract bytes between start and space
        let numberData = subData.prefix(foundEndIndex)

        return String(decoding: numberData, as: UTF8.self)
    }
    
    func fetchTXTRecord() {
        let dohURL = URL(string: "https://dns.sr2.uk/dns-query?dns=DoQBAAABAAAAAAAABXN0YXRzB2ludmFsaWQAABAAAQ")!

        let request = URLRequest(url: dohURL)

        URLSession.shared.dataTask(with: request) { data, response, error in
            DispatchQueue.main.async {
                if error != nil {
                    txtRecord = "Error"
                    return
                }

                guard let data = data else {
                    txtRecord = "Error"
                    return
                }

                guard let count = parseResponse(data: data) else {
                    txtRecord = "Error"
                    return
                }

                txtRecord = count
            }
        }.resume()
    }
}

#Preview {
    BlockedCount()
}