use std::net::IpAddr;
use async_recursion::async_recursion;
use packet::{PacketType, Packet, Result, PacketQuestion, PacketBuffer, ResultCode};
use tokio::net::UdpSocket;

use crate::config::Config;


async fn lookup(qname: &str, qtype: PacketType, server: (IpAddr, u16)) -> Result<Packet> {
    let socket = UdpSocket::bind("0.0.0.0:43210").await?;

    let mut packet = Packet::new();

    packet.header.id = 6666;
    packet.header.questions = 1;
    packet.header.recursion_desired = true;
    packet
        .questions
        .push(PacketQuestion::new(qname.to_string(), qtype));

    let mut req_buffer = PacketBuffer::new();
    packet.write(&mut req_buffer)?;
    socket.send_to(&req_buffer.buf[0..req_buffer.pos], server).await?;

    let mut res_buffer = PacketBuffer::new();
    socket.recv_from(&mut res_buffer.buf).await?;

    Packet::from_buffer(&mut res_buffer)
}

#[async_recursion]
async fn recursive_lookup(qname: &str, qtype: PacketType, config: &Config) -> Result<Packet> {

    let mut ns = config.get_fallback_ns().clone();

    loop {
        println!("attempting lookup of {:?} {} with ns {}", qtype, qname, ns);

        let ns_copy = ns;

        let server = (ns_copy, 53);
        let response = lookup(qname, qtype, server).await?;

        if !response.answers.is_empty() && response.header.rescode == ResultCode::NOERROR {
            return Ok(response);
        }

        if response.header.rescode == ResultCode::NXDOMAIN {
            return Ok(response);
        }

        if let Some(new_ns) = response.get_resolved_ns(qname) {
            ns = new_ns;

            continue;
        }

        let new_ns_name = match response.get_unresolved_ns(qname) {
            Some(x) => x,
            None => return Ok(response),
        };

        let recursive_response = recursive_lookup(&new_ns_name, PacketType::A, config).await?;

        if let Some(new_ns) = recursive_response.get_random_a() {
            ns = new_ns;
        } else {
            return Ok(response);
        }
    }
}

pub async fn handle_query(socket: &UdpSocket, config: &Config) -> Result<()> {
    let mut req_buffer = PacketBuffer::new();

    let (_, src) = socket.recv_from(&mut req_buffer.buf).await?;

    let mut request = Packet::from_buffer(&mut req_buffer)?;

    let mut packet = Packet::new();
    packet.header.id = request.header.id;
    packet.header.recursion_desired = true;
    packet.header.recursion_available = true;
    packet.header.response = true;

    if let Some(question) = request.questions.pop() {
        println!("Received query: {:?}", question);

        if let Ok(result) = recursive_lookup(&question.name, question.qtype, config).await {
            packet.questions.push(question.clone());
            packet.header.rescode = result.header.rescode;

            for rec in result.answers {
                println!("Answer: {:?}", rec);
                packet.answers.push(rec);
            }
            for rec in result.authorities {
                println!("Authority: {:?}", rec);
                packet.authorities.push(rec);
            }
            for rec in result.resources {
                println!("Resource: {:?}", rec);
                packet.resources.push(rec);
            }
        } else {
            packet.header.rescode = ResultCode::SERVFAIL;
        }
    } else {
        packet.header.rescode = ResultCode::FORMERR;
    }

    let mut res_buffer = PacketBuffer::new();
    packet.write(&mut res_buffer)?;

    let len = res_buffer.pos();
    let data = res_buffer.get_range(0, len)?;

    socket.send_to(data, src).await?;

    Ok(())
}