use std::ffi::{CStr, CString};
use std::io::{stdin, stdout, Read, Write};

use clap::Parser as _;

mod arguments;
mod cmd;
mod error;
mod pb3;
mod rfc822;

use arguments::{Arguments, Mode};
use error::{Error, Result};

fn switch_to_user(sys_user: &str) -> Result<()> {
    unsafe {
        *libc::__errno_location() = 0;
    }
    let c_sys_user =
        CString::new(sys_user).map_err(|e| Error::Setuid(format!("nul char in user, {}", e)))?;
    let user_info: *const libc::passwd = unsafe { libc::getpwnam(c_sys_user.as_ptr()) };
    let err = unsafe { *libc::__errno_location() };
    if err != 0 {
        return Err(Error::Setuid(format!(
            "error calling getpwnam {:?}",
            unsafe { libc::strerror(err) }
        )));
    };
    if user_info.is_null() {
        return Err(Error::Setuid(format!("user {:?} does not exist", sys_user)));
    };
    let rc = unsafe { libc::setuid((*user_info).pw_uid) };
    if rc != 0 {
        let err = unsafe { *libc::__errno_location() };
        return Err(Error::Setuid(format!(
            "error calling setuid {:?}",
            unsafe { CStr::from_ptr(libc::strerror(err)) }
        )));
    }
    Ok(())
}

fn main() -> Result<()> {
    simplelog::TermLogger::init(
        simplelog::LevelFilter::Info,
        simplelog::Config::default(),
        simplelog::TerminalMode::Stderr,
        simplelog::ColorChoice::Never,
    )
    .unwrap();

    let args = Arguments::parse();

    switch_to_user(&args.sys_user)?;

    let path = args.maildir_path.join(args.mail_user);

    stdout().write_all(b"OPEN\n")?;
    stdout().flush()?;
    let mut req = Vec::with_capacity(2048);
    stdin().read_to_end(&mut req)?;

    let res = match args.mode {
        Mode::Read => cmd::read(path, &req),
        Mode::Raw => cmd::raw(path, &req),
        Mode::List => cmd::list(path, &req),
        Mode::Folders => cmd::folders(path, &req),
        Mode::Count => cmd::count(path, &req),
        //Mode::Search => cmd::search(&path, &req),
        Mode::Move => cmd::move_mail(path, &req),
        Mode::Remove => cmd::remove(path, &req),
        Mode::AddFolder => cmd::add_folder(path, &req),
        _ => todo!(),
    }?;

    stdout().write_all(&res).map_err(|e| e.into())
}