use std::collections::HashSet;

use anyhow::Result;
use iptables;
use log::*;
use tokio::{
  select,
  sync::watch,
  time::{self, Duration},
};

use crate::{config::RuntimeConfigFirewall, fw, messages};

pub struct FirewallActor {
  pub ipt: iptables::IPTables,

  last_ports: messages::PublicExposedPorts,
  refresh: Duration,

  rx_ports: watch::Receiver<messages::PublicExposedPorts>,
}

impl FirewallActor {
  pub fn new(
    config: Option<RuntimeConfigFirewall>,
    rxp: &watch::Receiver<messages::PublicExposedPorts>,
  ) -> Result<Option<Self>> {
    match config {
      None => Ok(None),
      Some(c) => {
        let ctx = Self {
          ipt: iptables::new(false)?,
          last_ports: messages::PublicExposedPorts::new(),
          refresh: c.refresh_time,
          rx_ports: rxp.clone(),
        };
        fw::setup(&ctx.ipt)?;

        Ok(Some(ctx))
      }
    }
  }

  pub async fn listen(&mut self) -> Result<()> {
    let mut interval = time::interval(self.refresh);
    loop {
      // 1. Wait for an event
      let new_ports = select! {
        Some(ports) = self.rx_ports.recv() => Some(ports),
        _ = interval.tick() => None,
        else => return Ok(()) // Sender dropped, terminate loop.
      };

      // 2. Update last ports if needed
      if let Some(p) = new_ports {
        self.last_ports = p;
      }

      // 3. Update firewall rules
      match self.do_fw_update().await {
        Ok(()) => debug!("Successfully updated firewall rules"),
        Err(e) => error!("An error occured while updating firewall rules. {}", e),
      }
    }
  }

  pub async fn do_fw_update(&self) -> Result<()> {
    let curr_opened_ports = fw::get_opened_ports(&self.ipt)?;

    let diff_tcp = self
      .last_ports
      .tcp_ports
      .difference(&curr_opened_ports.tcp_ports)
      .copied()
      .collect::<HashSet<u16>>();
    let diff_udp = self
      .last_ports
      .udp_ports
      .difference(&curr_opened_ports.udp_ports)
      .copied()
      .collect::<HashSet<u16>>();

    let ports_to_open = messages::PublicExposedPorts {
      tcp_ports: diff_tcp,
      udp_ports: diff_udp,
    };

    fw::open_ports(&self.ipt, ports_to_open)?;

    return Ok(())
  }
}