use std::fs;
use std::io::{Read, Write};
use std::time::Duration;

const TARGET: &str = "gpu-screen-recorder";
const POLL_INTERVAL: Duration = Duration::from_secs(2);

/// Scans /proc for a process whose argv[0] basename matches the target.
/// Reads cmdline (not the truncated `comm`) to avoid false positives
/// from the 15-char comm truncation matching an unrelated binary.
fn is_recording() -> bool {
    let entries = match fs::read_dir("/proc") {
        Ok(d) => d,
        Err(_) => return false,
    };

    for entry in entries.flatten() {
        let name = entry.file_name();
        let Some(pid_str) = name.to_str() else {
            continue;
        };
        if !pid_str.bytes().all(|b| b.is_ascii_digit()) {
            continue;
        }

        let mut buf = Vec::with_capacity(64);
        if fs::File::open(format!("/proc/{pid_str}/cmdline"))
            .and_then(|mut f| f.read_to_end(&mut buf))
            .is_err()
        {
            continue;
        }

        // cmdline is NUL-separated; argv[0] is everything before the first NUL
        let argv0 = buf.split(|&b| b == 0).next().unwrap_or(&[]);
        let argv0 = String::from_utf8_lossy(argv0);
        let basename = argv0.rsplit('/').next().unwrap_or(&argv0);

        if basename == TARGET {
            return true;
        }
    }
    false
}

fn emit(recording: bool) {
    let json = if recording {
        r#"{"text":"󰑊 <span color='#aaaaaa'>Recording</span>","class":"recording","alt":"recording","tooltip":"gpu-screen-recorder is running"}"#
    } else {
        r#"{"text":"","class":"idle","alt":"idle","tooltip":""}"#
    };
    println!("{json}");
    let _ = std::io::stdout().flush();
}

fn main() {
    let mut last: Option<bool> = None;
    loop {
        let now = is_recording();
        if last != Some(now) {
            emit(now);
            last = Some(now);
        }
        std::thread::sleep(POLL_INTERVAL);
    }
}