use std::io;
use std::path::Path;
use std::process::exit;

use clap::Parser;
use tokio::net::TcpListener;
use tracing::{debug, error, info};

use crate::arguments::Mode;
use crate::server::SharedConfig;

mod arguments;
mod client;
mod config;
mod server;

fn load_config<P: AsRef<Path>>(file_path: P) -> config::Root {
    let content = match std::fs::read_to_string(file_path) {
        Ok(s) => s,
        Err(why) => {
            error!("Failed to read config file: {}", why);
            exit(1);
        }
    };
    let cfg: config::Root = match toml::from_str(content.as_str()) {
        Ok(c) => c,
        Err(why) => {
            error!("Failed to parse config file: {}", why);
            exit(1);
        }
    };
    cfg
}

fn validate_config(cfg: &config::Root) {
    for s in &cfg.service {
        if s.name.contains("\r\n") {
            error!("Service name contains CRLF: `{}`", &s.name);
            exit(1);
        }
    }
}

#[tokio::main]
async fn main() -> io::Result<()> {
    tracing_subscriber::fmt::init();

    let args = arguments::Args::parse();
    info!("args: {:?}", args);
    let cfg = load_config(&args.config);

    validate_config(&cfg);

    match args.mode {
        Mode::SERVER => {
            if cfg.server == None {
                error!("Config `server` is required in current mode");
                exit(1);
            }
            if cfg.service.is_empty() {
                error!("No service is defined");
                exit(1);
            }
            server_main(cfg).await
        }
        Mode::CLIENT => {
            if cfg.client == None {
                error!("Config `client` is required in current mode");
                exit(1);
            }
            client_main(cfg).await
        }
    }
}

async fn server_main(cfg: config::Root) -> io::Result<()> {
    let listener = TcpListener::bind(cfg.server.unwrap().listen).await?;
    info!("Server listening on {:?}", listener);
    let max_srv_name_length = cfg
        .service
        .iter()
        .map(|s| s.name.len())
        .max()
        .expect("No service was defined in config");
    debug!("Max service name length: {}", max_srv_name_length);
    // this immutable object lives throughout the entire process lifetime,
    // so we use 'static here for simplicity
    let shared_config: &'static SharedConfig = Box::leak(Box::new(SharedConfig {
        max_srv_name_length,
        services: cfg.service,
        allow_help: cfg.allow_help,
    }));
    loop {
        let (sock, addr) = listener.accept().await?;
        tokio::spawn(server::handle_client(shared_config, sock, addr));
    }
}

async fn client_server_main(
    upstream_addr: &'static String,
    listener: TcpListener,
    service_name: &'static String,
) -> io::Result<()> {
    loop {
        let (sock, addr) = listener.accept().await?;
        info!("Client connected: {}", addr);
        tokio::spawn(client::handle_client(sock, upstream_addr, service_name));
    }
}

async fn client_main(cfg: config::Root) -> io::Result<()> {
    let mut fut_servers = Vec::new();

    let upstream_addr = Box::leak(Box::new(cfg.client.unwrap().addr));

    for s in cfg.service {
        let listener = TcpListener::bind(&s.addr).await?;
        info!("Server listening on {:?} (service {})", listener, &s.name);
        let service_name = Box::leak(Box::new(s.name));
        fut_servers.push(tokio::spawn(client_server_main(
            upstream_addr,
            listener,
            service_name,
        )));
    }

    for fut in fut_servers {
        if let Err(why) = fut.await {
            error!("Failed to join server future: {}", why);
        }
    }
    Ok(())
}