use serde_yaml::{Mapping, Value};

macro_rules! revise {
  ($map: expr, $key: expr, $val: expr) => {
    let ret_key = Value::String($key.into());
    $map.insert(ret_key, Value::from($val));
  };
}

// if key not exists then append value
macro_rules! append {
  ($map: expr, $key: expr, $val: expr) => {
    let ret_key = Value::String($key.into());
    if !$map.contains_key(&ret_key) {
      $map.insert(ret_key, Value::from($val));
    }
  };
}

pub fn use_tun(mut config: Mapping, enable: bool) -> Mapping {
  let tun_key = Value::from("tun");
  let tun_val = config.get(&tun_key);

  if !enable && tun_val.is_none() {
    return config;
  }

  let mut tun_val = tun_val.map_or(Mapping::new(), |val| {
    val.as_mapping().cloned().unwrap_or(Mapping::new())
  });

  revise!(tun_val, "enable", enable);
  if enable {
    append!(tun_val, "stack", "gvisor");
    append!(tun_val, "dns-hijack", vec!["198.18.0.2:53"]);
    append!(tun_val, "auto-route", true);
    append!(tun_val, "auto-detect-interface", true);
  }

  revise!(config, "tun", tun_val);

  if enable {
    use_dns_for_tun(config)
  } else {
    config
  }
}

fn use_dns_for_tun(mut config: Mapping) -> Mapping {
  let dns_key = Value::from("dns");
  let dns_val = config.get(&dns_key);

  let mut dns_val = dns_val.map_or(Mapping::new(), |val| {
    val.as_mapping().cloned().unwrap_or(Mapping::new())
  });

  // 开启tun将同时开启dns
  revise!(dns_val, "enable", true);

  // 借鉴cfw的默认配置
  append!(dns_val, "enhanced-mode", "fake-ip");
  append!(
    dns_val,
    "nameserver",
    vec!["114.114.114.114", "223.5.5.5", "8.8.8.8"]
  );
  append!(dns_val, "fallback", vec![] as Vec<&str>);

  #[cfg(target_os = "windows")]
  append!(
    dns_val,
    "fake-ip-filter",
    vec![
      "dns.msftncsi.com",
      "www.msftncsi.com",
      "www.msftconnecttest.com"
    ]
  );
  revise!(config, "dns", dns_val);
  config
}