use anyhow::anyhow;
use regex::Regex;
use std::{
    io::Write,
    net::Ipv4Addr,
    process::{Command, Stdio},
};

mod preload;

#[derive(serde::Deserialize)]
pub(crate) struct Config {
    interface: InterfaceConfig,
    network: NetworkConfig,
    server: ServerConfig,
}

#[derive(serde::Deserialize)]
struct InterfaceConfig {
    external: String,
    internal: Vec<String>,
}

#[derive(serde::Deserialize)]
#[serde(rename_all = "kebab-case")]
struct NetworkConfig {
    shared_internal: bool,
}

#[derive(serde::Deserialize)]
struct ServerConfig {
    debug: bool,
    secret: String,
}

pub(crate) struct Interfaces {
    pub(crate) external: InterfaceInfo,
    pub(crate) internal: Vec<InterfaceInfo>,
    shared_internal: bool,
}

pub(crate) struct InterfaceInfo {
    pub(crate) interface: String,
    pub(crate) ip: Ipv4Addr,
    pub(crate) mask: u8,
}

pub(crate) struct ServerState {
    pub(crate) debug: bool,
    pub(crate) secret: Vec<u8>,
}

impl ServerState {
    pub(crate) fn init(config: &Config) -> Result<Self, anyhow::Error> {
        let secret = base64::decode(&config.server.secret)?;

        Ok(ServerState {
            debug: config.server.debug,
            secret,
        })
    }
}

impl Config {
    pub(crate) fn read() -> Result<Self, anyhow::Error> {
        let mut config = config::Config::new();
        config.merge(config::File::with_name("config.toml"))?;

        Ok(config.try_into()?)
    }
}

impl Interfaces {
    pub(crate) fn init_blocking(config: &Config) -> Result<Self, anyhow::Error> {
        if config.server.debug {
            // Fake Data from Fake Things for Faking :tm:
            return Ok(Interfaces {
                external: InterfaceInfo {
                    interface: String::from("eth0"),
                    ip: "123.123.123.123".parse()?,
                    mask: 20,
                },
                internal: vec![InterfaceInfo {
                    interface: String::from("enp1s0"),
                    ip: "192.168.6.1".parse()?,
                    mask: 24,
                }],
                shared_internal: false,
            });
        }

        let output = Command::new("ip").arg("addr").output()?;
        let output = String::from_utf8_lossy(&output.stdout);

        let external = parse_interface_info(&output, &config.interface.external)?
            .next()
            .ok_or(anyhow!(
                "Failed to parse IP for interface {}",
                config.interface.external,
            ))?;

        let mut internal = Vec::new();

        for iface in &config.interface.internal {
            internal.extend(parse_interface_info(&output, &iface)?);
        }

        if internal.len() == 0 {
            return Err(anyhow!(
                "No internal interfaces found for {:?}",
                config.interface.internal
            ));
        }

        Ok(Interfaces {
            external,
            internal,
            shared_internal: config.network.shared_internal,
        })
    }

    pub(crate) fn reset_blocking(&self) -> Result<(), anyhow::Error> {
        let firewall_rules = self::preload::firewall_rules(self);

        println!("LOADING RULES");
        println!("{}", firewall_rules);

        let mut child = Command::new("iptables-restore")
            .stdin(Stdio::piped())
            .spawn()?;

        let stdin = child
            .stdin
            .as_mut()
            .expect("Failed to open STDIN (shouldn't happen)");
        stdin.write_all(firewall_rules.as_bytes())?;

        child.wait()?;

        Ok(())
    }
}

fn parse_interface_info<'a>(
    output: &'a str,
    interface: &str,
) -> Result<impl Iterator<Item = InterfaceInfo> + 'a, anyhow::Error> {
    let iface_regx = Regex::new(interface)?;
    let ip_regex = Regex::new(r"([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3})/([0-9]+)")?;

    let iter = output.split('\n').filter_map(move |line| {
        let iface_capture = iface_regx.captures_iter(line).next()?;
        let iface_match = iface_capture.get(0)?;

        let ip_capture = ip_regex.captures_iter(line).next()?;
        let ip_match = ip_capture.get(1)?;
        let mask_match = ip_capture.get(2)?;

        let ip = ip_match.as_str().parse().ok()?;
        let mask = mask_match.as_str().parse().ok()?;

        Some(InterfaceInfo {
            interface: iface_match.as_str().to_owned(),
            mask,
            ip,
        })
    });

    Ok(iter)
}

#[cfg(test)]
mod tests {
    use super::parse_interface_info;

    const OUTPUT: &'static str = r#"1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 24:4b:fe:37:ad:b1 brd ff:ff:ff:ff:ff:ff
    inet 192.168.6.1/24 brd 192.168.5.255 scope global enp1s0
       valid_lft forever preferred_lft forever
    inet6 fe80::264b:feff:fe37:adb1/64 scope link 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether ca:b8:a7:51:07:3d brd ff:ff:ff:ff:ff:ff
    inet 136.49.5.58/20 brd 136.49.15.255 scope global dynamic eth1
       valid_lft 85973sec preferred_lft 85973sec
    inet6 fe80::c8b8:a7ff:fe51:73d/64 scope link 
       valid_lft forever preferred_lft forever
4: wg0: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1420 qdisc noqueue state UNKNOWN group default qlen 1000
    link/none 
    inet 192.168.5.0/24 scope global wg0
       valid_lft forever preferred_lft forever
"#;

    #[test]
    fn parses_external_interface() {
        let info = parse_interface_info(OUTPUT, "eth[0-9]+")
            .unwrap()
            .next()
            .unwrap();

        assert_eq!(info.interface, "eth1");
        assert_eq!(info.ip.to_string(), "136.49.5.58");
        assert_eq!(info.mask, 20);
    }

    #[test]
    fn parses_internal_interface() {
        let info = parse_interface_info(OUTPUT, "enp1s0")
            .unwrap()
            .next()
            .unwrap();

        assert_eq!(info.interface, "enp1s0");
        assert_eq!(info.ip.to_string(), "192.168.6.1");
        assert_eq!(info.mask, 24);
    }
}