use core::fmt::Debug;

use embassy_net::tcp::TcpSocket;
use embassy_net::{dns::Error as DnsError, tcp::ConnectError};
use embassy_time::{with_timeout, Duration, Instant, TimeoutError, Timer};
use embedded_tls::{
    Aes128GcmSha256, NoVerify, TlsConfig, TlsConnection, TlsContext, TlsError, UnsecureProvider,
    TLS_RECORD_OVERHEAD,
};
use esp_backtrace as _;
use log::{debug, error, info};
use rand::rngs::StdRng;
use rand::{CryptoRng, RngCore, SeedableRng};
use rust_mqtt::client::client::MqttClient;
use rust_mqtt::client::client_config::ClientConfig;
use rust_mqtt::packet::v5::reason_codes::ReasonCode;
use rust_mqtt::utils::rng_generator::CountingRng;

use crate::{NetworkStack, WifiHandle, DATA};

#[derive(Debug)]
pub enum SendError {
    Dns(DnsError),
    NXDomain(&'static str),
    Tls(TlsError),
    Connect(ConnectError),
    MqttConnect(ReasonCode),
    MqttPublish(ReasonCode),
    Timeout(TimeoutError),
}

#[derive(Debug)]
pub struct ErrorLocation<E: Debug> {
    pub error: E,
    pub location: Option<(&'static str, u32)>,
}

impl<E: Debug> ErrorLocation<E> {
    pub fn from_result<T>(
        result: Result<T, E>,
        location: (&'static str, u32),
    ) -> Result<T, ErrorLocation<E>> {
        result.map_err(|error| Self {
            error,
            location: Some(location),
        })
    }
}

macro_rules! with_line {
    ($result:expr) => {
        ErrorLocation::from_result($result, (file!(), line!()))
    };
}

macro_rules! from_impl {
    ($err:ty, $var:ident) => {
        impl From<$err> for SendError {
            fn from(value: $err) -> Self {
                Self::$var(value)
            }
        }
    };
}

from_impl!(DnsError, Dns);
from_impl!(TlsError, Tls);
from_impl!(ConnectError, Connect);
from_impl!(ReasonCode, MqttConnect);
from_impl!(TimeoutError, Timeout);

const MQTT_SERVER_HOSTNAME: &str = "mqtt.shimun.net";
#[cfg(feature = "tls")]
const MQTT_SERVER_PORT: u16 = 8883;
#[cfg(not(feature = "tls"))]
const MQTT_SERVER_PORT: u16 = 1883;

pub async fn send_message(
    stack: NetworkStack,
    messages: impl Iterator<Item = (&str, &[u8])>,
    rng: impl CryptoRng + RngCore,
) -> core::result::Result<(), SendError> {
    async fn inner(
        stack: NetworkStack,
        messages: impl Iterator<Item = (&str, &[u8])>,
        mut rng: impl CryptoRng + RngCore,
    ) -> core::result::Result<(), SendError> {
        let begin = Instant::now();
        let dns_resp = stack
            .dns_query(MQTT_SERVER_HOSTNAME, embassy_net::dns::DnsQueryType::A)
            .await?;
        let after_dns = Instant::now();
        const TCP_BUFLEN: usize = 2048 << 2;
        let mut rx_buffer = [0; TCP_BUFLEN];
        let mut tx_buffer = [0; TCP_BUFLEN];
        let mut socket = TcpSocket::new(stack, &mut rx_buffer, &mut tx_buffer);
        socket.set_timeout(Some(Duration::from_secs(30)));
        socket.set_keep_alive(Some(Duration::from_secs(5)));
        let socket_addr = dns_resp
            .into_iter()
            .map(|addr| (addr, MQTT_SERVER_PORT))
            .next()
            .ok_or(SendError::NXDomain(MQTT_SERVER_HOSTNAME))?;

        debug!("got address {socket_addr:?}");

        // establish TCP connection
        socket.connect(socket_addr).await?;
        let after_tcp = Instant::now();
        debug!("connected to {socket_addr:?}");

        // seed mqtt rng from rng
        let mut mqtt_config = ClientConfig::<5, _>::new(
            rust_mqtt::client::client_config::MqttVersion::MQTTv5,
            CountingRng(rng.next_u64()),
        );

        if let (Some(user), Some(pass)) = (option_env!("MQTT_USER"), option_env!("MQTT_PASSWORD")) {
            mqtt_config.add_username(user);
            mqtt_config.add_password(pass);
            debug!("{user}:{pass}");
        }

        // TLS layer
        const TLS_BUF_LEN: usize = (1 << 11) + TLS_RECORD_OVERHEAD;
        let mut tls_read_record_buffer = [0; TLS_BUF_LEN];
        let mut tls_write_record_buffer = [0; TLS_BUF_LEN];

        #[cfg(feature = "tls")]
        let tls = {
            let mut config = TlsConfig::new();
            #[cfg(feature = "tls-sni")]
            config
                .with_max_fragment_length(embedded_tls::MaxFragmentLength::Bits11)
                .with_server_name(MQTT_SERVER_HOSTNAME);
            let mut tls = TlsConnection::new(
                socket,
                &mut tls_read_record_buffer,
                &mut tls_write_record_buffer,
            );

            tls.open(TlsContext::<UnsecureProvider<Aes128GcmSha256, _>>::new(
                &config,
                UnsecureProvider::new(&mut rng),
            ))
            .await?;
            tls.flush().await?;
            tls
        };
        #[cfg(feature = "tls")]
        let mqtt_backend = tls;
        #[cfg(not(feature = "tls"))]
        let mut mqtt_backend = socket;
        let after_tls = Instant::now();
        #[cfg(feature = "tls")]
        debug!(
            "tls handshake succeeded: +{}ms",
            (after_tls - after_tcp).as_millis()
        );

        mqtt_config.max_packet_size = 100;
        const BUF_LEN: usize = 80;
        let mut recv_buffer = [0; BUF_LEN];
        let mut buffer = [0; BUF_LEN];

        // MQTT Layer
        let mut mqtt_client = MqttClient::new(
            mqtt_backend,
            &mut buffer,
            BUF_LEN,
            &mut recv_buffer,
            BUF_LEN,
            mqtt_config,
        );
        mqtt_client.connect_to_broker().await?;
        let after_mqtt = Instant::now();
        debug!("connected to broker");
        for (topic, message) in messages {
            mqtt_client
                .send_message(
                    topic,
                    message,
                    rust_mqtt::packet::v5::publish_packet::QualityOfService::QoS1,
                    true,
                )
                .await
                .map_err(SendError::MqttPublish)?;
        }
        let after_mqtt_pub = Instant::now();
        info!(
            "{:?} {:?} {:?} {:?} {:?}",
            after_dns - begin,
            after_tcp - begin,
            after_tls - begin,
            after_mqtt - begin,
            after_mqtt_pub - begin
        );
        Ok(())
    }
    with_timeout(Duration::from_secs(120), inner(stack, messages, rng)).await?
}

#[embassy_executor::task]
pub async fn publish_data(
    stack: NetworkStack,
    rng_seed: [u8; 32],
    interval: Duration,
    wifi: WifiHandle<'static>,
) {
    let mut rng = StdRng::from_seed(rng_seed);
    loop {
        {
            let wifi_guard = wifi.configured().await;
            Timer::after(Duration::from_millis(10)).await;
            let mut data = DATA.lock().await;
            let res = send_message(
                stack,
                data.iter()
                    .map(|(topic, message)| (topic.as_ref(), message.as_bytes())),
                &mut rng,
            )
            .await;
            if let Err(e) = res {
                error!("Oh no: {e:?}");
            };
            drop(wifi_guard);
            data.clear();
        }
        Timer::after(interval).await;
    }
}