xmpd/src/process_manager.rs

use std::{collections::HashMap, sync::{atomic::{AtomicUsize, Ordering}, Mutex, RwLock}};

use tokio::process::Command;



#[allow(dead_code)]
#[derive(Debug, Clone)]
struct Proc {
    msg: String,
    finished: bool
}

lazy_static::lazy_static!(
    static ref PROCESSES: Mutex<RwLock<HashMap<usize, Proc>>> = Mutex::new(RwLock::new(HashMap::new()));
);

static PROC_INC: AtomicUsize = AtomicUsize::new(0);


pub fn add_proc(mut cmd: Command, msg: String) -> anyhow::Result<()> {
    let mut proc = cmd.spawn()?;
    let id = PROC_INC.fetch_add(1, Ordering::AcqRel);
    
    tokio::spawn(async move {
        let id = id;
        proc.wait().await
            .expect("child process encountered an error");
        PROCESSES.lock().unwrap().write().unwrap().get_mut(&id).unwrap().finished = true;
    });
    
    PROCESSES.lock().unwrap().write().unwrap().insert(id, Proc {
        finished: false,
        msg,
    });

    Ok(())
}

pub fn proc_count() -> usize {
    PROCESSES.lock().unwrap().read().unwrap().len()
}

pub fn is_proc_queue_full(max: usize) -> bool {
    let proc_cnt = PROCESSES.lock().unwrap().read().unwrap().len();
    proc_cnt >= max
}

pub fn purge_done_procs() -> usize {
    let mut finish_count = 0;
    let procs = {
        PROCESSES.lock().unwrap().read().unwrap().clone()
    };

    for (idx, proc) in procs {
        if proc.finished {
            {
                PROCESSES.lock().unwrap().write().unwrap().remove(&idx);
            }
            log::info!("{}", proc.msg);
            finish_count += 1;
        }
    }
    finish_count
}

/// Waits for processes to finish until the proc count is lower or equal to `max`
pub fn wait_for_procs_until(max: usize) -> anyhow::Result<usize> {
    // NOTE: This looks really fucked because i dont want to deadlock the processes so i lock PROCESSES for as little as possible
    // NOTE: So its also kinda really slow
    let mut finish_count = 0;
    loop {
        if !is_proc_queue_full(max) {
            return Ok(finish_count);
        }
        finish_count += purge_done_procs();
    }
}