#![feature(file_buffered)]
use std::env;
use std::fs::File;
use std::io::BufRead;
use std::io::Write;
use std::io::Seek;
use std::io::SeekFrom;

fn main() {
    println!("Reading kernel messages...");

    let mut kmsg_file =
        File::open_buffered(env::var("PHENIX_KMSG").unwrap_or(String::from("/dev/kmsg")))
            .expect("Failed to open /dev/kmsg");


    kmsg_file.seek(SeekFrom::End(0)).expect("Failed to seek to end");
    let lines = kmsg_file.lines();
    for line in lines {
        match line {
            Err(e) => println!("Error reading line: {e}"),
            Ok(line) => manage_line(line),
        }
    }
}

fn manage_line(line: String) {
    if let Some((prefix, line)) = line.split_once(";") {
        if line.ends_with("PCIe link lost") {
            println!("PCIe link lost {prefix}");

            let id = line.splitn(3, " ").nth(1);
            match id {
                Some(id) => reset_device(id),
                None => println!("No device id found in message {line}"),
            }
        }
    }
}

fn reset_device(id: &str) {
    println!("Resetting {id}");
    echo1(rm_file_path(&id));
    echo1(String::from("/sys/bus/pci/rescan"));
    println!("Rescanned PCI bus");
}

fn echo1(path: String) {
    let rm_file = File::create(&path);
    match rm_file {
        Err(e) => println!("Failed to open remove file at {path}: {e}"),
        Ok(mut file) => {
            file.write_all(b"1")
                .expect("Failed to write to remove file");
            println!("Removed device {path}");
        }
    }
}

fn rm_file_path(id: &str) -> String {
    format!("/sys/bus/pci/devices/{id}/remove")
}