use crate::DResult;
use log::info;
use nix::{
    sys::signal::{kill, Signal},
    unistd::{getpid, Pid},
};
use std::error::Error;
use std::fs::{read_to_string, write};
use std::path::Path;

pub fn replace_old_gameserver(pidfile: &str) -> DResult<()> {
    match read_to_string(pidfile) {
        Err(e) => {
            if e.kind() == std::io::ErrorKind::NotFound {
                info!("pidfile not found, assuming not already running");
                Ok(())
            } else {
                info!("Error reading pidfile (other than NotFound): {}", e);
                Err(Box::new(e) as Box<dyn Error + Send + Sync>)
            }
        }
        Ok(f) => {
            let pid: Pid = Pid::from_raw(
                f.parse()
                    .map_err(|e| Box::new(e) as Box<dyn Error + Send + Sync>)?,
            );
            if pid == getpid() {
                info!("Pid in pidfile is me - ignoring");
                return Ok(());
            }
            match read_to_string(format!("/proc/{}/cmdline", pid)) {
                Ok(content) => {
                    if content.contains("blastmud_game") {
                        info!("pid in pidfile references blastmud_game; starting cutover");
                        kill(pid, Signal::SIGUSR1)
                            .map_err(|e| Box::new(e) as Box<dyn Error + Send + Sync>)
                    } else {
                        info!("Pid in pidfile is for process not including blastmud_game - ignoring pidfile");
                        Ok(())
                    }
                }
                Err(_) => {
                    info!("Pid in pidfile is gone - ignoring pidfile");
                    Ok(())
                }
            }
        }
    }?;
    info!("Writing new pidfile");
    write(Path::new(pidfile), format!("{}", std::process::id()))
        .map_err(|e| Box::new(e) as Box<dyn Error + Send + Sync>)
}