use std::ffi::OsString;
use std::io::Write;
use std::os::unix::ffi::OsStrExt;
use std::os::unix::net::UnixListener;
use std::process::ExitCode;
use std::sync::Arc;

use toolkit::egress::{Allow, Proxy, SystemDial};

fn main() -> ExitCode {
    let args: Vec<OsString> = std::env::args_os().skip(1).collect();
    match parse_egress_proxy(&args) {
        Some(code) => code,
        None => run_tool(&args),
    }
}

/// The `egress-proxy --socket <path> --allow <list>` form. Anything else, including a program name
/// that is not `egress-proxy`, returns `None` so the tool form handles it.
fn parse_egress_proxy(args: &[OsString]) -> Option<ExitCode> {
    // Exactly five words: a longer list is not this form, and goes to the tool form (exit 2).
    if args.len() != 5 || args.first()?.as_bytes() != b"egress-proxy" {
        return None;
    }
    // The form is `egress-proxy --socket <path> --allow <list>`, in that order.
    let socket = match (args.get(1), args.get(2)) {
        (Some(flag), Some(path)) if flag.as_bytes() == b"--socket" => path,
        _ => return None,
    };
    let list = match (args.get(3), args.get(4)) {
        (Some(flag), Some(value)) if flag.as_bytes() == b"--allow" => value,
        _ => return None,
    };

    let list = match list.to_str() {
        Some(s) => s,
        None => {
            eprint!("toolkit: egress-proxy: --allow: not valid UTF-8");
            return Some(ExitCode::from(2));
        }
    };
    let allow = match Allow::parse(list) {
        Ok(a) => a,
        Err(e) => {
            eprint!("toolkit: egress-proxy: --allow: {e}");
            return Some(ExitCode::from(2));
        }
    };
    // The directory is fresh for each call, so a file already at the path is a mistake; do not
    // remove it first.
    let listener = match UnixListener::bind(socket) {
        Ok(l) => l,
        Err(e) => {
            eprint!(
                "toolkit: egress-proxy: cannot listen on {path}: {e}",
                path = display(socket)
            );
            return Some(ExitCode::from(2));
        }
    };
    let proxy = Arc::new(Proxy::new(allow, Arc::new(SystemDial)));
    if let Err(e) = proxy.serve(listener) {
        eprint!("toolkit: egress-proxy: {e}");
        return Some(ExitCode::from(2));
    }
    Some(ExitCode::SUCCESS)
}

fn run_tool(args: &[OsString]) -> ExitCode {
    let mut rest = args.iter();
    let name = match (rest.next(), rest.next()) {
        (Some(arg), None) => arg.to_str().unwrap_or("").to_string(),
        _ => String::new(),
    };

    let outcome = toolkit::run(&name, &mut std::io::stdin().lock());
    let _ = std::io::stdout().write_all(outcome.stdout.as_bytes());
    let _ = std::io::stderr().write_all(outcome.stderr.as_bytes());
    ExitCode::from(outcome.exit.code())
}

fn display(o: &OsString) -> String {
    String::from_utf8_lossy(o.as_bytes()).into_owned()
}