use std::fs::File;
use std::io::Read;
use std::net::{Ipv4Addr, SocketAddr, ToSocketAddrs};
use std::time::Duration;

use anyhow::{anyhow, bail, Context, Result};

use crate::config::{ConfigOpts, ConfigOptsBase, ConfigOptsConsul};

// This code is inspired by the Trunk crate (https://github.com/thedodd/trunk)

// In this file, we take ConfigOpts and transform them into ready-to-use
// RuntimeConfig. We apply default values and business logic.

#[derive(Debug)]
pub struct RuntimeConfigConsul {
    pub node_name: String,
    pub url: String,
    pub tls: Option<(Option<reqwest::Certificate>, bool, reqwest::Identity)>,
}

#[derive(Debug)]
pub struct RuntimeConfigFirewall {
    pub ipv6_only: bool,
    pub refresh_time: Duration,
}

#[derive(Debug)]
pub struct RuntimeConfigIgd {
    pub private_ip: Option<Ipv4Addr>,
    pub expiration_time: Duration,
    pub refresh_time: Duration,
}

#[derive(Debug)]
pub struct RuntimeConfigStun {
    pub stun_server_v4: Option<SocketAddr>,
    pub stun_server_v6: SocketAddr,
    pub refresh_time: Duration,
}

#[derive(Debug)]
pub struct RuntimeConfig {
    pub consul: RuntimeConfigConsul,
    pub firewall: RuntimeConfigFirewall,
    pub igd: Option<RuntimeConfigIgd>,
    pub stun: RuntimeConfigStun,
}

impl RuntimeConfig {
    pub fn new(opts: ConfigOpts) -> Result<Self> {
        let consul = RuntimeConfigConsul::new(opts.consul)?;
        let firewall = RuntimeConfigFirewall::new(&opts.base)?;
        let igd = match opts.base.ipv6_only {
            false => Some(RuntimeConfigIgd::new(&opts.base)?),
            true => None,
        };
        let stun = RuntimeConfigStun::new(&opts.base)?;

        Ok(Self {
            consul,
            firewall,
            igd,
            stun,
        })
    }
}

impl RuntimeConfigConsul {
    pub(super) fn new(opts: ConfigOptsConsul) -> Result<Self> {
        let node_name = opts
            .node_name
            .expect("'DIPLONAT_CONSUL_NODE_NAME' environment variable is required");
        let url = opts.url.unwrap_or(super::CONSUL_URL.to_string());

        let tls = match (&opts.client_cert, &opts.client_key) {
            (Some(client_cert), Some(client_key)) => {
                let cert = match &opts.ca_cert {
                    Some(ca_cert) => {
                        let mut ca_cert_buf = vec![];
                        File::open(ca_cert)?.read_to_end(&mut ca_cert_buf)?;
                        Some(reqwest::Certificate::from_pem(&ca_cert_buf[..])?)
                    }
                    None => None,
                };

                let mut client_cert_buf = vec![];
                File::open(client_cert)?.read_to_end(&mut client_cert_buf)?;

                let mut client_key_buf = vec![];
                File::open(client_key)?.read_to_end(&mut client_key_buf)?;

                let ident = reqwest::Identity::from_pem(
                    &[&client_cert_buf[..], &client_key_buf[..]].concat()[..],
                )?;

                Some((cert, opts.tls_skip_verify, ident))
            }
            (None, None) => None,
            _ => bail!("Incomplete TLS configuration parameters"),
        };

        Ok(Self {
            node_name,
            url,
            tls,
        })
    }
}

impl RuntimeConfigFirewall {
    pub(super) fn new(opts: &ConfigOptsBase) -> Result<Self> {
        let refresh_time =
            Duration::from_secs(opts.refresh_time.unwrap_or(super::REFRESH_TIME).into());

        Ok(Self {
            refresh_time,
            ipv6_only: opts.ipv6_only,
        })
    }
}

impl RuntimeConfigIgd {
    pub(super) fn new(opts: &ConfigOptsBase) -> Result<Self> {
        let private_ip = opts
            .private_ip
            .as_ref()
            .map(|x| x.parse())
            .transpose()
            .context("parse private_ip")?;
        let expiration_time = Duration::from_secs(
            opts.expiration_time
                .unwrap_or(super::EXPIRATION_TIME)
                .into(),
        );
        let refresh_time =
            Duration::from_secs(opts.refresh_time.unwrap_or(super::REFRESH_TIME).into());

        if refresh_time.as_secs() * 2 > expiration_time.as_secs() {
            return Err(anyhow!(
        "IGD expiration time (currently: {}s) must be at least twice bigger than refresh time \
         (currently: {}s)",
        expiration_time.as_secs(),
        refresh_time.as_secs()
      ));
        }

        Ok(Self {
            private_ip,
            expiration_time,
            refresh_time,
        })
    }
}

impl RuntimeConfigStun {
    pub(super) fn new(opts: &ConfigOptsBase) -> Result<Self> {
        let mut stun_server_v4 = None;
        let mut stun_server_v6 = None;
        for addr in opts
            .stun_server
            .as_deref()
            .unwrap_or(super::STUN_SERVER)
            .to_socket_addrs()?
        {
            if addr.is_ipv4() {
                stun_server_v4 = Some(addr);
            }
            if addr.is_ipv6() {
                stun_server_v6 = Some(addr);
            }
        }

        let refresh_time =
            Duration::from_secs(opts.refresh_time.unwrap_or(super::REFRESH_TIME).into());

        let stun_server_v4 = match opts.ipv6_only {
            false => Some(
                stun_server_v4.ok_or(anyhow!("Unable to resolve STUN server's IPv4 address"))?,
            ),
            true => None,
        };

        Ok(Self {
            stun_server_v4,
            stun_server_v6: stun_server_v6
                .ok_or(anyhow!("Unable to resolve STUN server's IPv6 address"))?,
            refresh_time,
        })
    }
}